Abstract:Throughout thousands of years，successfully domesticated crop plants have gone through longtime courses of continuous cultivation and selection. This principal has been validated in earlier domesticated crops such as wheat，corn，rice，apple，plum and grape，and in kiwifruit，blueberry and strawberry which were domesticated in a relative duration. By history as reference，this paper briefly outlines and analyzes the processes of domestication and genetic improvement of plant crops. Meanwhile，we focuses on cases of the fruit trees that are domesticated last century，and discusses the principal and strategy for domesticating wild fruit species in the 21th century.

Abstract:Some interspecific hybrids and allopolyploids show morphological, physiological and molecular traits biased to one progenitor, which is referred to as genome asymmetry or genome dominance, in spite of the inclusion of the genomes of the two or more progenitors in the same nucleus. Besides the occurrence of the expression dominance of the rRNA genes with the B>A>C hierarchy in three cultivated Brassica allotetraploids, the genome asymmetry for their phenotypic features is also obvious, for some traits of Brassica oleracea are strongly expressed and are dominant over those of B. nigra and B. rapa, while those of B. nigra are dominant over those of B. rapa, with the C>B>A hierarchy. As to the phenotypic performance in the intergeneric hybrids and allopolyploids of Brassica species with several relatives including Raphanus sativus, Orychophragmus violaceus and Isatis indigotica, Raphanus sativus and Orychophragmus violaceus are dominant, particularly with their basal serrated leaves being persistently expressed. Notably, these dominant traits are controlled by one or several chromosomes. The phenotypic dominance is possibly related to the structure and nature of the parental genome and gene(s) involved and the interaction between divergent genomes, but the regulation mechanisms remain largely to be elucidated.

Abstract:Xinjiang is one of the origin and diversity center of deciduous fruit trees and the gene bank for quality breeding. In recent years，important progresses have been made in the evaluation，mining and innovative utilization of germplasm resources of wild fruit forests and deciduous fruit trees in Xinjiang，such as Malus sieversii（Ledeb.）M. Roem.（wild apple）and korle pear. The significant achievements are listed as follows：（1）Studies have clarified that Malus sieversii is the ancestral species of cultivated apples，and its evaluation，mining and innovative utilization have achieved important results，（2）The Xinjiang korle pear，which originated from the hybrids of Eastern and Western pears，has strong heritability of high quality and storability，and is an important parent resource for pear quality breeding，（3）Yili wild apricots and southern Xinjiang cultivated apricots have played an important role in domestication of cultivated apricots. The hybridization and breeding of superior lines broke down the genetic isolation among the three natural apricot groups in Kuqa，Kashgar and Hotan，providing support for the good seeding of more than 200，000 hectares of southern Xinjiang apricots，（4）Xinjiang Wild Cherry Plum is one of most important species in genus Prunus L.. The ex-situ planting of wild cherry plum resources resulted in breeding for the plum varieties.

Abstract:The significant advance on crop breeding largely relies on exploration and utilization of excellent germplasm resources. Sugarcane (Saccharum spp.) is the major sugar crop in the world, but for a long time limited progress in sugarcane breeding has been made. Saccharum Spontaneum L. is a wild species in Saccharum L, and this species as the most successful example has been used in sugarcane breeding. Optimal use of this wild species Saccharum Spontaneum L. in sugarcane breeding is of interest to overcome this limitation. In this review, we summarized the progress on the genetic diversity analysis and innovative utilization of Saccharum Spontaneum L, analyzed the limitations restricting its innovative utilization, and ultimately raised prospective for future innovation and utilization in sugarcane breeding.

Abstract:Under the frame of the Third National Survey and Collection Action on Crop Germplasm Resources, 201 sweetpotato landraces were collected from 57 counties in Guangdong province from 2016 to 2018. These sweetpotato landraces were mainly distributed in the junction areas of northern Guangdong, eastern Guangdong and Pearl River Delta, and most of them were found from counties including Jiexi, Conghua and Yangxi. Analysis of the phenotypic variations showed that, a majority of the landraces were qualified for fresh-edible sweetpotato varieties. These elite landraces including 76 high-yield and 29 high-dry-matter-content sweetpotato landraces have been identified. Especially, five sweetpotato landraces with high yield, good quality, and excellent taste have been clarified, including Shipai hong ganci, Yidianhong, Jiguxiang, Huangsha gaoshan hongshu, and Shijiao hongshu.

Abstract:There are few systematic studies on finger millet germplasm resources in China. In order to further explore the utilization value of finger millet，breeding high-quality millet varieties，the phenotypic diversity of 69 finger millet germplasms collected from 40 counties and cities in Hunan, Jiangxi, Guangxi and Tibet was evaluated. in the study.The results showed that the 69 local resources were mainly distributed in the low and medium altitude of 400-600 m. The diversity analysis based on 19 phenotypic traits revealed a rich genetic diversity in this collection. The correlation analysis and principal component analysis suggested 7 principal components including weight per plant, number of branches on main spike, leaf color, whole growth period, seed coat color, 1000-grain weight and glutinousness. The cumulative contribution rate was 75.525%. Two main categories were suggested for the 69 accessions. The first group included 44 germplasms with small plant, low biomass and low grain yield, and was further divided into two subgroups: compared with subgroup I-1, subgroup I-2 had even smaller plant, lower biomass and lower grain yield. The second group included 25 germplasms with relatively large plant, high biomass and high grain yield, and was further divided into two subgroups: compared with subgroup II-1, subgroup II-2 had lower biomass and lower grain yield. A core collection containing 12 finger millet accessions were identified, by cluster analysis results and extreme-values of quantitative traits and variation types of qualitative traits, as representative resources of the following four types: forage accessions with large biomass, grain accessions with long spikes, glutinous grain accessions, and dual-purpose grain and forage accessions with high grain yield and high biomass.

Abstract:In this study, 14 phenotypic traits of 160 wild apple (Malus sieversii) germplasm resources in Tianshan area of Ili were evaluated, from which elite germplasms were screened. The results showed that the variation coefficients of the 14 phenotypic traits ranged from 5.75% to 38.44%, with an average of 21.78%, the variation coefficient of fruit hardness was the highest, and the fruit shape index was the lowest. The Shannon-Weiner diversity index ranged from 1.95 to 2.06, with an average of 2.01, and most of the traits were rich in genetic diversity. The membership function of the 160 germplasm resources ranged from 0.202 to 0.681, with a mean value of 0.514, among which 20 resources had the value greater than 0.6, with obvious advantages in fruit weight, fruit hardness and fruit size. Correlation analysis showed that the fruit weight was significantly positively correlated with fruit length, fruit diameter, stalk diameter and fruit hardness, and significantly negatively correlated with soluble solids content and stalk length. The results of principal component analysis showed that the cumulative contribution rate of 5 principal component factors was 79.258%, among which the first principal component was related to fruit traits, the second principal component was related to leaf traits, the third principal component was related to branch traits, the fourth principal component was related to fruit traits and branch traits, and the fifth principal component was related to fruit stalk traits. Based on the 14 phenotypic traits, the 160 germplasm resources were divided into 6 groups, among which group II had the highest fruit weight, group III had the highest fruit hardness, and group V had the highest soluble solids content. The results of this study would provide important references for conservation and utilization of the wild apple germplasm resources.

Abstract:Larix principis-rupprechtii Mayr is an important ecological and afforestation tree species that is distributed in North China. Unlocking the phenotypic variation of its cone is of great significance to provide insights on the production of improved varieties and the study of ecological adaptability. In this study, 12 phenotypic traits of 7,800 cones, which were collected from 13 natural populations in the entire distribution area of Larix principis-rupprechtii, were analyzed. Extensive genetic variation was observed, while the intra-population variation (45.3%) was higher than that among the populations (12.38%). The coefficient of variation on cone weight was highest with broad variation range in population, whereas the coefficient of variation on breeding scale rate was lowest. The cone weight showed very significantly negative correlation with longitude, the length of cones, the number of scales and the ratio of height to diameter were significantly negatively correlated with longitude, and the weight was also significantly negatively correlated with latitude. Principal component analysis showed that the first four principal components contributed to 84.7% of phenotypic variations. Thirteen natural populations were classified into three clusters based on Euclidean distance using cluster analysis. No significant correlation was detected between phenotypic distance and geographic distance. Collectively, this work provided information valuable on collection and utilization of excellent genetic resources of Larix principis-rupprechtii, which has implications for the production of improved varieties in the future.

Abstract:Potato is ranking the world's fourth largest food crop on yield production, with an important role in ensuring global food crisis and malnutrition. Potatoes are shallow-rooted crops and sensitive to drought stress in arid and semi-arid areas. Cultivating drought-resistant varieties is thus of great significance to ensure potato yield in arid areas via improving water resource utilization. In this study, two treatments of normal irrigation and water deficit were set up, and the yield of each genotype of diploid potato population under different treatment was measured at harvest and the drought resistance coefficient was calculated. After quantifying the yield production under three environmental conditions and calculating the drought stress index using statistical analysis, significant difference analysis, correlation analysis, variance analysis and bioplot analysis, we found that the field experiment in 2020 and the drought-resistant greenhouse experiment in 2020 were suitable to reveal the drought resistance by mimicking mild drought stress conditions; the net greenhouse experiment in 2019 was suitable to mimick severe drought stress environmental condition. There were 58 genotypes with the same drought resistance level under the two different drought stress levels, accounting for 47.93% of the total population. Collectively, this study identified drought-resistant potato materials which laid a foundation for future research on isolation of important genes and dissection of drought resistance mechanisms.

Abstract:In order to make full use of local peanut germplasm resources and expand the genetic breeding parent database of peanut, 134 local peanut germplasm resources in Jiangxi Province collected in the Third National Survey and Collection of Crop Germplasm Resources were identified and evaluated by variance analysis, correlation analysis, principal component analysis and cluster analysis, in order to screen the special germplasm resources. The results showed that pod mass per plant had the highest coefficient of variation (49.13%), followed by total number of branches, main stem height, 100-pod mass, and 100-kernel mass, while growth duration, and kernel percentage had low coefficient of variation. Correlation analysis showed that pod mass per plant was significantly positively correlated with total number of branches and growth duration, so an appropriate increase of the total number of branches could improve the yield per plant. The nine main agronomic traits were classified into 3 principal components, and the cumulative contribution rate reached 71.454%, which could comprehensively summarize the information of the nine main agronomic traits. Based on cluster analysis, 134 resources were divided into four groups, with the same botanical types separated into different groups. Group I was intermediary-fruit peanut resources with medium pod mass per plant, Group II was small-fruit peanut resources with low pod mass per plant, Group III was high-yield peanut resources, and Group IV was large-fruit peanut resources. Nine peanut germplasms with high pod mass per plant, three with small fruit, and five with large fruit were screened.

Abstract:High temperature seriously threatens the yield, quality and fertility of middle rice varieties in Jianghan Plain. In order to identify rice varieties with high-temperature tolerance, this study analyzed the heat resistance at heading and flowering stages regarding new rice varieties in Hubei Province in the past three years, under natural high temperature environment (daily average temperature above 32 °C, the highest temperature above 35 °C and the duration above 5 days) and high temperature stress in glass greenhouse. Out of the varieties showing strong high-temperature resistance, the proportion of conventional varieties (lines) was equivalent to that of two-line hybrid rice combinations, and the proportion of three-line hybrid rice combinations was the second. A total of 20 varieties with strong heat resistance and better heat resistance were screened out in 3 year, among which 5 conventional varieties (lines) were Yuehesimiao, Runzhuxiangzhan, S532, Chunuo 3 and Lifengzhan. They can be used as heat-resistant germplasm resources for breeding and utilization, and can also be used as heat-resistant varieties after priority approval in the heat-damaged common areas. Quanyou 133, Quanyou Jingzhan and Quanyou Jinhe are three-line hybrid rice varieties, Cliangyou 300, Quanliangyou 5 and Enliangyou 454 are two-line hybrid rice varieties, which can be popularized and applied as heat-resistant varieties in heat-damaged common rice areas after the approval of the same conditions. The germplasm resources with excellent heat resistance may be screened out by further identification of their parents or one of their parents. A total of 102 heat-resistant varieties were identified and screened. The materials can be selected and approved according to the comprehensive performance of other traits, and then used as heat-resistant varieties in common rice areas. Among them, Enuo98, Hongnuo 1 and Longwangnuo 81 were conventional varieties ( lines ). Although their heat resistance is not too strong, most of them have excellent comprehensive agronomic traits, which can be used in the case of lack of heat-resistant breeding germplasm. 32 sub-varieties, such as Teyou 559, Huazheyou 1534 and Zhongguangyou 2, were sensitive upon heat treatment. It is suggested that priority should be eliminated at the time of approval, and special caution should be taken even in the promotion and application of approval.

Abstract:Through analyzing the phenotypic differences at agronomic traits under salt stress and control growth conditions, the rice cultivars showing salt-tolerant have been obtained valuable in breeding for new rice varieties adapting to the saline-alkali fields. In this study, we conducted a screening for salt-tolerant elite rice genotypes using 120 rice genotypes in China. This experiment was performed using hydroponic culture using five treatments (salt concentration: 0‰, 1.5‰, 3‰, 4.5‰ and 6‰) in the whole growth period. Dozens of phenotypic traits (Plant height, main stem thickness, root length, the length of top first leaf, the width of top first leaf, the length of top second leaf, the width of top second leaf, green leaf number, spike length of the main stem, stem dry weight, leaf dry weight, panicle dry weight, root dry weight, ground dry weight, root shoot ratio, spike number, spike grain number, thousands seeds weight, seed setting rate and theoretical yield of each rice variety) were quantified at the maturity stage. First, the optimal salt concentration was determined by the quartile difference method. Secondly, principal component analysis was carried out for each salt-tolerant coefficient under the optimal screening salt concentration. Based on the principal component analysis, membership function value and comprehensive evaluation value (D value) was obtained by using fuzzy function method. Stepwise regression analysis and correlation analysis were carried out with D value and salt-tolerant coefficient value of each variety. Finally, the D values of each rice variety were systematically analyzed by the Euclidean distance and Ward method. The results showed that 6‰ salt concentration was the best salt concentration for screening. The regression equation was obtained through principal component analysis, membership function analysis and stepwise regression analysis: D value = 0.152 + 0.004*LT1 + 0.005*GDW + 0.007*SL - 0.027*MST + 0.047*WT1.The results of systematic cluster analysis showed that 11 rice varieties with highly salt-tolerant, 19 salt-tolerant, 24 medium salt-tolerant, 45 salt-sensitive, and 21 highly salt-sensitive were classified (Euclidean distance 5).The optimal salt concentration was 6‰ during the whole growth period of hydroponics. The salt-tolerant of rice could be quickly identified by using the regression equation by measuring the length of top first leaf, the width of top first leaf, main stem spike length, ground dry weight and main stem thickness of rice at maturity. Collectively, this study identified highly salt-tolerant rice germplasm resource which laid a foundation for future exploring salt-tolerant genes and breeding for rice varieties.

Abstract:Soybean is a globally-important crop plant that supplies edible oil and plant protein. Drought is one of the most important abiotic stresses decreasing the growth and yield in soybean. In order to study the response under drought stress conditions, evaluation of drought resistance at multiple growth stages (germination, seedlings, whole growth period) was conducted in 253 soybean germplasm resources. Morphological indicators such as root length, plant height, 100-seed weight were measured, and stressful indicators such as germination rate, repeated drought survival rate, and enhanced drought resistance coefficient were calculated. The drought resistance evaluation index, which reflected the drought resistance of soybean germplasm resources, had been identified through correlation analysis and regression analysis. The drought stress treatment resulted in dramatic decrease on the measured index value (10.27%-96.62%), and significant difference if compared with that of the normal irrigation treatment (P<1.6E-09) was observed. No significant correlation between the values of drought resistance at multiple growth periods was detected. These germplasm accessions showing late maturity showed better performance on drought resistance to that of late maturing accessions. The drought resistance indexes qualified for the germination period (germination rate), the seedling period (survival rate of repeated drought) and the whole growth period (the number of pods per plant, the number of seeds per plant, the grain weight per plant and the biomass per plant) have been identified. Seven elite accessions, which showed extremely strong or strong drought resistant under three treatment conditions were obtained, and fifty accessions at two treatment conditions were obtained. Collectively, this study provided theoretical guidance and germplasm resource for deciphering drought resistance basis and identifying the elite parental lines used for soybean breeding.

Abstract:Forty-three maize inbred lines in different heterosis groups were used to analyze the difference on grain filling and dehydration rate, in order to provide insights in breeding for maize varieties with high grain filling and dehydration rate. The results showed that: (1) the average yield of maize inbred lines was 4504.29 kg hm-2, while Jing724 showed the highest yield performance (7140.60 kg hm-2). The performance among different heterosis groups was revealed (X group > Reid group > Improved Reid > Huangzaosi improved lines > Reid group > Iodent group > P group> Lüda red cob group). (2) The average grain filling rate was 0.68 g-100 grain d-1. Jing2416 showed the highest grain filling rate (0.88 g-100 grain d-1), representing 0.28 and 0.19 g-100 grain d-1 higher than Zheng58 and PH4CV. Among different heterosis groups, X group was observed to higher than hat of Reid group, followed by Iodent group, Huangzaosi improved lines, Improved Reid, Lüda red cob and P group. (3) The average grain moisture content at harvest was 22.44%, and that of Jing2416 was 18.91%, which was 6.34% and 3.18% lower than that of Zheng58 (25.25%) and PH6WC (22.09%); the average grain dehydration rate after physiological maturity was 0.65% d-1, among which Jing2416 was the highest (0.82% d-1), 78.26% and 17.14% higher than that of Zheng58 (0.46% d-1) and PH6WC (0.70% d-1). The dehydration rate of different types of maize inbred lines was as follows: X group and Iodent group>Huangzaosi improved lines>Reid group>Improved Reid>Lüda red cob>P group. (4) Four inbred lines including Jing2416, JingB547, JingMC01 and Jing72464 showed higher grain filling rate and dehydration rate. (5) The grain yield was significantly positively correlated with grain filling rate and dry matter transport rate. A significant negative correlation between grain moisture content at harvest and grain dehydration rate after physiological maturity was detected, whereas a significant positive correlation between grain dehydration rate and grain filling rate after physiological maturity was observed. The results showed that the grain filling and dehydration rates of X group were higher than those of other genetic groups; Jing2416, the Huangzaosi improved lines, had the earliest maturity and the highest grain filling and dehydration rates, which had important breeding value for breeding new maize varieties with early maturity and suitable grain yield

Abstract:Using maize haploid embryogenic callus as genetic transformation receptor and combining with chemical doubling method, homozygous individuals whenever hosting a transgenic element might be obtained in a short time. This study attempted to obtain haploid callus from maize using diploid embryogenic callus induction method, followed by analyzing the detection rate of haploid callus, browning rate and mortality after different subculture times, as well as diploid callus and haploid callus growth rate and other important indicators. The haploid callus was treated with 0.005%-0.03% colchicine, and the mortality rate of haploid callus, powder dispersal rate after adult, ratio of large anther (strong pollen vigor), seed setting rate and plant ratio of more than 5 seeds were analyzed. The results showed that induction of haploid embryogenic callus was applicable using the improved method of diploid callus induction. The detection rate of haploid callus is 4.2%, similar to the induction rate of 18-599(red) by MT-1 lines. Both the browning rate and mortality of haploid callus were significantly higher than diploid callusof the same time of subculture, and both the browning rate and mortality rate of haploid callus reached the highest level after three inductions. With callus diameter as reference, the growth rate of haploid callus was lower than t diploid,. , which could be used as an key reference indicator to distinguishhaploid and diploid callus in the early growth period. After being treated with colchicine of different concentrationsfor different period of time, the pollinating rate, rate of large anther, seed setting rate and ratio of plants with more than 5 seeds of haploid callus increased as the concentration increases and the time prolongs, and survival rate and small anther (of poor or no viability), on the other hand, drops as the concentration increases and the time prolongs.. The results showed that colchicine treatment could enhance the pollinating rate and seed setting rate of maize callus in adult plants where higher seed setting rate was dependent on higher rate of large anther.. Collectively, this paper includes analysis of multiple factors in the process of callus induction and doubling of maize haploid. And screened out 0.01% colchicine treatment for 12h and 0.02% colchicine treatment for 3h) as better modesfor doubling of maize haploid callus.

Abstract:Maize rough dwarf disease (MRDD) is a severe virus-conferring disease in multiple maize cultivation areas in China. Exploration of resistant germplasm resource and application in resistance breeding is the most economical and effective measure. In this paper, 201 maize germplasm accessions were subjected upon natural inoculation over two years in a high incidence area for MRDD. Out of them, 25 accessions were tested by artificial inoculation. Under field condition, one accession “Shen 137” turned to be highly resistant; 12 inbred lines (P138, Dan 3130, Liao 68, Qi 318, Huangyesi, CA339, H191, Qi 319, X178, SH15, Jinhuang 59 and R18) were resistant; nine accessions (835, Zhongzi 01, 9046, Duohuang 29, CA335, Jinhuang 96B, Hai 9-21, Jinhuang 55 and Shen 136) showed moderate resistance. Notably, the phenotypic datasets gained from two years showed significant different (F = 69.999, P < 0.01). Moreover, by tests for disease resistance by deployment of artificial inoculation, two accessions P138 and R18 which turned to be moderately resistant, whereas Huangyesi and Jinhuang 55 were highly susceptible with disease index of 46.15 and 82.14, respectively. The germplasms showing resistant, except Jinhuang 96B, were selected from the hybrid P78599. Collectively, this study identified several maize inbred lines with rough dwarf disease resistance, valuable in maize breeding for MRDD resistant varieties.

Abstract:Evaluation of the edible quality of sweetpotato is being conducted with the traditional sensory evaluation method. However, lack of a standard protocol makes the traditional evaluation method to be subjective and unprecise. To address this problem, this study intended to establish a new sensory evaluation model by using fuzzy mathematics. Firstly, five criteria indices were screened for evaluating the sweetpotato quality, including color, odour, sweetness, stickiness (flour-like taste) and fibrous taste. Each of these criteria indices was seperated and definded for five-point scores. The analytic hierarchy process (AHP) was used to construct a weight set and the industry experts were invited to score each pair of criteria indices of pairwise comparison. The sensory scores of various criteria indices of all tested varieties marked by valuators were used as the rank elements to construct fuzzy relationship matrix. The matrix was built and then used to calculate the result vector of fuzzy comprehensive evaluation. Lastly, the calculation rule of the integrated score of sweetpotato edible quality was formulated and edible quality grading standard of sweetpotato was proposed. To test the accuracy of the new evaluation system, 11 sweetpotato varieties with confirmed quality definitions (evaluating in the sweetpotato of China agricultural research system in 2019) were re-evaluated by the new built evaluation system. The result showed that the fuzzy comprehensive evaluation was more stable than that reveled with the tranditional method. The outcome gained from the new evaluation method is coincidence with the current universal recognition by the sweetpotato of China agricultural research system. Furthermore, the scoring was more accurate because there was a detailed scoring rubric for evaluators to mark. Difference in the tested varieties could be quantified with the integrated score via a fuzzy comprehensive evaluation rather than an expert direct scoring method.

Abstract:Heat tolerance of wheat is a complex quantitative trait controlled by multiple genes. Molecular markers related to heat tolerance can be acquired by correlation analysis. With these tolerant markers，the accuracy of molecular marker-assisted selection breeding may be improved，and the process of breeding for heat tolerant wheat may be accelerated. In this study，heat sensitivity indexes (HI) of five grain traits，including 1000-kernel weight，kernel length，kernel width，kernel surface area，and kernel circumference were identified in 190 wheat varieties (lines). Molecular markers Xwmc622 and Xwmc707 related to heat sensitivity indexes were obtained by simple correlation analysis. Polyacrylamide gel electrophoresis analysis showed that Xwmc622 and Xwmc707 each had three allelic types: I，II and III. Type I allelic loci of Xwmc622 were extremely significantly negatively correlated with HI of 1000-kernel weight，of kernel width，and of kernel circumference (all P < 0.01)，and significantly negatively correlated with HI of kernel length and of kernel surface area (all P < 0.05). The average values of HI in wheat varieties (lines) with type I allelic variation were less than 1. Type II allelic loci of Xwmc622 were extremely significantly positively correlated with HI of 1000-kernel weight (P < 0.01)，and significantly positively correlated with HI of kernel length，of kernel surface area，and of kernel circumference (all P < 0.05). The average values of HI in wheat varieties (lines) with type II allelic variation were greater than 1. Type III allelic loci of Xwmc622 were not correlated with HI of grain traits. Type I allelic loci of Xwmc707 were not correlated with HI of wheat grain traits. Type II allelic loci of Xwmc707 were significantly negatively correlated with HI of 1000-kernel (P < 0.05). The average values of HI in wheat varieties (lines) with type II allelic variation were less than 1. Type III allelic loci of Xwmc707 were significantly positively correlated with HI of 1000-kernel weight，of kernel width，and of kernel circumference (all P < 0.05). The average values of HI of the grain traits in wheat varieties (lines) with type III allelic variation were greater than 1. The results showed that allele I of Xwmc622 and allele II of Xwmc707 were superior alleles of wheat heat tolerance，which provided reference information for molecular marker-assisted breeding for wheat heat resistance.

Abstract:The objective of the study is to dissect genetic basis and identify QTL related to Anaerobic germination related traits in rice, and to detect the elite rice lines carrying favorable alleles, therefore providing excellent germplasm for molecular marker-assisted (MAS）breeding. The seeds of 318 rice lines were germinated for measuring coleoptile length under normal and anaerobic conditions. QTL associated with anaerobic germination (AG）tolerance was determined by GWAS and candidate genes were analyzed. The broad variation of AG tolerance was observed among rice accessions ranged from -0.923 to 3.069, with an average of -0.238, a median of -0.342. A total of 27 QTL revealed by 83 SNPs were detected associating with AG tolerance. The QTL locus qAG4-2 was selected for analyzed and 20 candidate genes in the target interval were annotated. Among them, three genes were detected with elevated transcripts induced by anaerobic stress. The excellent germplasm resources and the QTL loci associating with anaerobic germination were valuable in rice breeding.

Abstract:Southern rice black-streaked dwarf virus disease (SRBSDVD) is one of the most serious viral diseases. Exploration of resistant germplasm resource and identification of resistance-conferring gene become of interest in rice breeding. Here, by testing for SRBSDVD resistance in a breeding population by artificial inoculation under both field and greenhouse conditions followed by RT-PCR detection, individual plants showing a segregation on resistance and susceptibility were observed implying the presence of a new recessive virus resistance locus. We assembled the resistance and susceptibility bulks by pooling the resistant and susceptible plants, respectively. By genotyping using the whole genome breeding gene chip (GSR 40K) technology, this resistance gene against southern rice black-streaked dwarf virus disease was delimited in a lower resolution. Collectively, this study provided a resistance resource/gene valuable in resistance breeding against southern black streaked dwarf disease.

Abstract:Maize ear rot is a worldwide serious fungal disease, and at present has become one of the main problems in maize growing areas. However, the measure against this disease remains difficult. In this study, a RIL population comprising 233 lines and a natural population comprising 452 backbone inbred lines were used for evaluating ear rot resistance. The cobs were inoculated with Fusarium verticillioides to observe their kernel resistance and cob resistance; while the kernels were inoculated with F. verticillioides to observe their cob resistance and kernel resistance. By comparing the kernel resistance observed by inoculating cob and kernel resistance observed by inoculating kernel, it was found that the kernel resistance observed by inoculating cobs of 114 lines in RIL population and 230 inbred lines in associated population was not consistent with their kernel resistance observed by inoculating kernel. By comparing cob resistance observed by inoculating kernel with cob resistance observed by inoculating cob, it was found that the cob resistance observed by inoculating kernel of 138 families in RIL population and 247 inbred lines in associated population was not consistent with their cob resistance observed by inoculating cob. Collectively, the interaction between kernel resistance and cob resistance may involve a new disease resistance mechanism, which deepened the understanding of the resistance mechanism of maize ear rot from a new perspective.

Abstract:Hosta plants have high value in landscape and pharmacology. Hosta plants in the wild are vulnerable to natural disasters, viruses, diseases and insect pests, and the normal tissue culture is faced with high maintenance costs, and chances of pollution. Considering the need for breeding new varieties and maintaining the genetic stability, it is of great significance to establish a preservation technique with safety, low maintenance and low consumption. This research was conducted to obtain the optimal in vitro preservation protocol for Hosta plantaginea by using the orthogonal design and to study the effects of different concentrations of sucrose, mannitol, abscisic acid and CCC (chlormequat chloride) in the culture medium on the survival percentages and stability during the slow growth of in vitro plantlets of Hosta plantaginea. The results showed that 100% survival of in vitro Hosta plantaginea plantlets was obtained after six-month storage at 20-25℃, which were cultured in the MS medium supplemented with 50 g/L sucrose, 20 g/L mannitol, 1mg/L ABA, 20 mg/L CCC and 0.7% agar (pH 5.8), and the storage life without subculture was twice as much as that of the control of 3 months on normal medium. The activities of SOD, POD and CAT in preserved in vitro plantlets were higher than those of the control group, and the content of MDA was lower than that of the control group, which indicated that the activity of antioxidant enzymes increased, the degree of lipid oxidation decreased, the senescence process was delayed, and the storage life was prolonged.

Abstract:New materials are the basis and premise of breeding elite maize hybrids. This study was based on the scanning with MaizeSNP50 BeadChip (containing 60,000 SNPs) of the whole genome of 104 test materials that included tropical/subtropical germplasms, temperate-tropical lines (SI, PB, etc.), Reid, Lancaster and Tangsipingtou groups, and on the analysis with R language package GAPIT of the population genetic structure. Improved lines QB5721, QB5722, QB5744, QB5725, QB5775, QB5785 from SI (Suwan-Iodent) populations, representative line HCL645 of Iodent germplasm, and tropical Suwan germplasms QR273, ZH908 were chosen as the materials, with Iodent and 6 improved lines paired with 7 test materials from different groups to obtain 49 cross combinations, according to NCII design. Heterosis of the 6 SI lines was evaluated by RGCA (relative effect of general combining ability) of grain weight per spike. Analysis of genetic structure based on MaizeSNP50 BeadChip scanning divided the 104 materials into four types: tropical germplasm, Tangsipingtou (TSPT), Reid-Lancaster, and Iodent germplasm. The genetic distance was large between Iodent group and other five types of germplasm, and SI germplasm improved lines were clearly superior to Reid, Lancaster, and PB groups in heterosis. Phenotypic analysis indicated that the range of RGCA of the 6 SI improved lines was between ?1.62% and 5.67%, and the range of RSCA (relative effect of specific combining ability) of the 49 cross combinations was between ?2.64% and 2.98%. The RGCA of QB5725 was 5.67%, higher than that of QB5775 (4.39%), QB5721 (2.42%), QB5722 (1.68%), QB5744 (2.29%) and HCL645 (2.38%). These results may provide new research ideas for the creation and application of tropical maize germplasm resources in temperate regions in China.

Abstract:Genetic improvement of root traits in soybean largely relied on exploring the elite loci that associated with beneficial root traits. In this study, 242 northern spring cultivars and 102 landraces were subjected for analyzing phenotypic variation in root under laboratory conditions in 2018 and 2019. 175 pairs of SSR primers were applied for genotyping, followed by the genetic linkage disequilibrium analysis, the population structure analysis, and association analysis using general linear model (GLM). The results show that both collinear combination and non-collinear combination groups have different degree of linkage disequilibrium. The cultivars were clustered into two subpopulations. Seventeen genetic loci associated with six root traits were detected showing the phenotypic variation ranged from 1.35% to 7.83%. The landraces were assigned into two subgroups. Twelve genetic loci were found to be associated with five root traits, which contributed to 3.89% to 16.64% on phenotypic variation. Two genetic loci Satt309 and Sat_358, which were simultaneously detected in the two cultivar and landrace populations, were associated with main root length and root average diameter, respectively. A total of 38 alleles with positive effect were present in 29 cultivars. Out of them, the alleles of main root length (MRL), root length (RL), root average diameter (RAD), root volume (RV), root surface area (RSA), root tip number (RTN) with the greatest synergistic effect were Satt309-122bp (Hefeng35), Sat_272-254bp (Heihe16), Sat_358-236bp (Jilin12), Sat_381-193bp (Suinong26), Sat_381-193bp (Kendou18), and Sat_381-224bp (Hefeng51), respectively. A total of 33 alleles with synergistic effect were found from 31 landraces. For example, the alleles governing MRL, RL, RAD, RV, RSA, RTN which had the greatest synergistic effects, were Satt220-242bp (Xiaobaiqi), Satt683-206bp (Wangqingshenxiandong), Sat_160-174bp (Pingdingxiang-2), Satt239-200bp (Linjiangdahuangdou), Satt247-245bp (Bailudou-1), and Satt156-227bp (Xiaobaiqi), respectively. Collectively, this study identified the superior alleles and donor lines which could be used in breeding for soybean varieties with superior root traits.

Abstract:GmILPA1 (Glyma.11g026400) is an important gene that controls petiole angle by modulating the formation of leaf pillow by promoting cell growth and division in soybean. The mutation of gmilpa1 can cause abnormal development of leaf pillow and increase petiole angle. However, whether the polymorphic variations of this gene in Soybean Germplasm determines the petiole angle remains unknown. In this study, re-sequencing data derived from 783 soybean germplasm accessions was used to analyze the haplotype variation of the GmILPA1 gene. Thirty-two polymorphic loci including 13 SNPs and 19 indels were detected, with a frequency of 1 SNP / 285 bp and 1 indel / 195 bp, respectively. Out of nine haplotypes, Hap1 was found to be predominant and Hap3 showed two non-synonymous mutations. The results showed that there were four α - helix differences in the secondary structure between Hap1 and Hap3, whereas there was not detected difference on the stimulated crystal structure. No significant difference in petiole angle among different haplotypes was observed. The number of polymorphic loci and haplotype diversity of GmILPA1 were decreased in varieties in relative to the landraces. Collectively, gained from the genetic diversity analysis, this study revealed a fixation (bottleneck) of GmILPA1 elite allele in varieties due to positive selection in the process of soybean breeding.

Abstract:Maize ear cob diameter (CD) and kernel ratio (KR) are controlled by multiple quantitative loci and both traits associate with the yield production. The genomic selection in conjugation with information identified by genome-wide association study (GWAS) is an effective method to improve the prediction accuracy. By taking use of the phenotypic datasets of CD and KR and the genotypic data derived from genotyping-by-sequencing in 309 maize inbred lines, here we investigated the genomic prediction accuracy using three GS models (genomic best linear unbiased prediction, GBLUP; Bayes A; reproducing kernel Hilbert space, RKHS) and different marker subsets (GWAS-derived markers: fixed and random model circulating probability unification, FarmCPU; compressed mixed linear model, CMLM; randomly selected markers, and all markers). By taking use of FarmCPU- and CMLM-derived markers at both traits, only slight difference (0 to 0.03) on the prediction accuracy using three prediction models was observed. For random markers, GS using RKHS model represented higher prediction accuracy of CD (3.57-15.91%) if compared to two other models, whereas no difference for KR was detected. Except for 50 and 100 markers, the prediction accuracy of CMLM-derived marker using three models were higher than that of FarmCPU-derived markers. Compared to random markers, GWAS-derived markers were able to increase the prediction accuracy (15.52%-88.37% for CD; 1 to 5.89-fold for KR). The prediction accuracy by deployment of GWAS-derived marker subsets was higher than that of all markers. Collectively, these results indicated that genomic selection using GWAS-derived markers could improve the prediction accuracy of CD and KR in maize.

Abstract:Seed yield is the most important trait for genetic improvement in rapeseed, and it is controlled by quantitative loci/genes. In the present study, QTL mapping for seed yield in rapeseed were conducted at multiple environmental conditions, using a doubled haploid (DH) population derived from a cross between a winter-type cultivar ‘EXPRESS’ and semi-winter-type line ‘SWU07’, and an immortalized F2 population generated by randomly intermating among DH lines. A total of 18 putative QTL were identified in China across two years and 15 putative QTLs were identified in one year in Germany environment. These loci were located on 13 linkage groups including A1, A2, A3.1, A3.2, A7.1, A7.2, A9, C1, C3, C4, C5, C8 and C9, respectively, each of which could explain phenotypic variation ranging from 2.27% to 16.93%. Out of the identified QTL, six loci on linkage groups A2, A3.1, A7.1, A9 and C5 have been detected across environments or populations, thus becoming of interest in controlling seed yield in rapeseed. Collectively, these QTLs provided useful information for future improving seed yield in rapeseed breeding.

Abstract:Lint percentage is an important index affecting cotton fiber yield. In this study, an F2 segregation population containing 2403 individual plants was constructed derived from chromosome introgression line MBI 7747-14 (Gossypium barbadense x Gossypium hirsutum) with high lint percentage crossing with CCRI 45. The BSA-seq was conducted using two bulked samples by pooling individual plants showing higher and lower lint percentage, respectively. As a result, four candidate physical regions showing confidence indices higher than 95% were obtained in a total length of 5.47 Mb on chromosome D02, which contained 236 annotated genes. Out of them, 200 genes contain SNPs, 190 genes contain Indel, and 70 genes contain non-synonymous mutation sites. Through gene expression pattern analysis of transcriptome data, 19 candidate genes possibly associating with lint percentage were identified. GO functional enrichment analysis showed that the 19 candidate genes were enriched in NADP+ activity, aldol metabolism, carbon utilization and regulation of cell development. KEGG analysis showed that the 19 candidate genes were mainly involved in pathway such as ABC transport and phenylpropane biosynthesis. Collectively, this study laid a foundation for further analyzing the genetic mechanism of cotton fiber lint percentage formation.

Abstract:Peanut (Arachis hypogaea L.) is an important oil crop with economical interest. Peanut testa showed difference in colors, such as white, red, purple, pink and variegated. The molecular mechanism of the anthocyanin synthesis in variegated testa merit further in-depth research. In this study, the variegated testa peanut VG-02 was analyzed using Liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis, in order to detect the relative changes in content of anthocyanins in variegated testa at different developmental stages. Twelve metabolites associating with the testa color were detected. In the comparison of F2-B2 at DAF45 (45 days after flowering and needling) stage the highest number of differential metabolites was revealed. The relative contents of cyanidin 3-O-galactoside and cyanidin O-syringic acid were lower by 0.63 and 2.35 fold in the pigmented area than that in the non-pigmented area, respectively. The relative contents of rosinidin O-hexoside, procyanidin A1, A2, B2, B3, cyanidin, delphinidin, delphinidin 3-O glucoside and cyanidin 3-O-galactoside were higher by 1.05 to 11.55 fold in the pigmented area than that in the non-pigmented area, respectively. Cyanidin and delphinidin were the main metabolites that caused the difference in color between the pigmented area and the non-pigmented area. RNA-seq analysis revealed 1,050 differentially-expressed genes (DEGs), which included 27 DEGs highly related to the synthesis of variegated testa color. Thirteen were up-regulated and 14 were down-regulated, including 3 PALs, 1 C4H, 2 CHSs, 1 F3H, 1 F3'H, 2 DFRs, 2 LARs, 2 IAAs, 4 bHLHs, and 9 MYBs. KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis suggested that the metabolic pathways related to anthocyanin biosynthesis included phenylalanine metabolism, phenylpropanoid biosynthesis, flavone and flavonol biosynthesis, flavonoid biosynthesis, plant hormone signal transduction and circadian rhythm plant, among which flavonoid biosynthesis was proposed to be relevant with the testa variegation. Moreover, twenty DEGs were subjected for qPCR analysis. The similarity on transcriptional pattern revealed by qPCR and RNA-seq was observed. Collectively, the results of this study should help to further reveal the molecular regulatory mechanism of anthocyanin synthesis of the variegated testa in peanut.

Abstract:MYB family transcription factors have been proved to play an important role in biological process, such as plant growth and development, flavonoid synthesis, environmental stress, lignin biosynthesis. To explore if the MYB family members are involved in the lignin biosynthesis in Averrhoa carambola, a genome-wide bioinformatics analysis of R2R3-MYB transcription factor has been conducted, followed by the RT-qPCR analysis to valid the expression levels of the eight R2R3-MYB genes in twigs (T1, T3, T6), fruits and leaves at different stages. Fifty-seven 1R-MYB, 100 R2R3-MYB and four 3R-MYB have been identified. Out of them, 100 R2R3-MYB (AcMYBs) were detected to be unevenly distributed on 11 chromosomes and they were divided into 24 subclades (A1–A24; the genes from the same subclade present similarity on gene structures and functional motifs). The family gene expansion might associated to the segmental and tandem duplications, and the duplicated genes were undergone purifying selection. The sequence homology of R2R3-MYB gene family was observed in A. carambola, Arabidopsis thaliana and Populus trichocarpa. RT-qPCR showed that except for AcMYB05, the genes AcMYB41, AcMYB65, AcMYB84, AcMYB87, AcMYB92, AcMYB97 and AcMYB100 were found with higher expression in T3 and T6 and rare transcripts in T1, fruit and leaves. Collectively, the transcriptional profiles suggested the tissue-specific expression of seven AcMYBs, which possibly participate in the lignin biosynthesis pathway of A. carambola, therefore providing reference for further analyzing the MYB family members that interplay with the lignin biosynthesis.