Abstract:Grain weight, as one of the three components, directly associates to the wheat yield production. Grain weight is recognized as a complex quantitative trait which is largely controlled by multiple functional genes/loci and which is also affected by genotype-environment interaction. The genes controlling the grain weight and its components are found to be distributed on each chromosome of three wheat sub-genomes. Many molecular markers in wheat grain weight assisted selection have become applicable.The advances on the genetic characteristics, gene location, molecular mechanism and external factors affecting the grain weight formation have made with the contributions of national and international scholars. In this paper, the composing factors and influencing factors of wheat grain weight have been reviewed. The genetic localization, molecular cloning and allelic variation mining of the underlying genes are described, and the development of gene-based functional markers as well as the application in marker assisted breeding are summarized, as well as the future research prospects of wheat grain weight are proposed.

Abstract:Plant microRNA (miRNA) is a group of endogenous non-coding RNAs that participate in regulating gene expression during the processes of plant growth, development and metabolism. Recent studies indicated that miRNAs play important roles in plant adaptation to low phosphorus stress by regulating phosphorus absorption and utilization. This review summarizes the molecular mechanisms of phosphorus absorption and transport by plants, and introduces the transcriptional patterns of miRNAs under low phosphorus stress. Especially, this focuses on plant miRNAs responding to low phosphorus stress, including structure modification of root system, improvement of the efficiency of phosphorus transport and reuse, as well as anthocyanin and anti-oxidant biosynthesis. It is expected to provide insights for unlocking the molecular mechanisms of plant responses to low phosphorus stress and improving the efficiency of plant phosphorus absorption.

Abstract:In order to find out the geographical distribution characteristics of the collected agricultural biological germplasm resources in Guizhou, the external geographical environment and the internal spatial performance of the collected resources were analyzed with the methods of spatial statistical analysis and diversity analysis. Firstly, the characteristics of elevation, temperature, precipitation and other basic geographic environment of germplasm resources are determined by spatial superposition and statistics. Secondly, the spatial distribution, the orientation and difference as well as heterosexuality, density and richness of germplasm resources are analyzed using the optimizing hotspot analysis, the geographic distribution center analysis and spatial diversity analysis.. The results show that the interval of elevation and meteorological factors in the area where the resources are located is large, but most of them are distributed in relatively concentrated geographical environment. 68.7% of the germplasm resources were found to be distributed between 600 and 1400 m of altitude, 65.1% were distributed between 15 and 17 degrees centigrade of average annual temperature, and 61.7% were distributed from 1250 to 1350 mm of annual precipitation. In addition, the 21 selected counties can basically reflect the spatial distribution characteristics of agricultural biological resources in Guizhou from the perspective of geographic space. Germplasm resources of different topics are cross-distributed, with the exception of edible fungi concentrated in the southwest. The resources of food crops, economical crops, vegetables, fruit trees and medicinal plants, which were provided by 14 ethnic group, are relatively evenly distributed in the province. Among them, the Miao ethnic group provided the highest amount (37%) of resources, followed by the Han (16%) and Buyi (15%) ethnic groups. The proportion of resources provided is less than 1% of the total. Thus, this study described the distribution status and characteristics of agricultural biological resources in Guizhou Province, which will provide reference for the formulation of relevant policies for effective protection and efficient utilization of biological resources in Guizhou Province.

Abstract:China is the origin center of genus Cerasus Mill. with the most abundant wild germplasm resources. In order to clarify its current distribution, conservation status and risks, we investigated the wild Cerasus germplasm resources from 31 survey administrative towns of six provinces in west area of China from 2010 to 2015. Wild Cerasus germplasm trees were found to be widely distributed in various topographies and landforms with diversified phenotype. Unfortunately, the majority of wild Cerasus resources were distributed sporadically except the trees in 13 surveyed sites, which are growing in nature reservation protection areas and places away from cities. The quantity of genetic resources is continuously decreasing, and in-situ habituation areas are under risk due to the human activities. The trees at ca. 84% of the surveyed sites are without artificial management, and the distribution scales are also decreasing. Furthermore, a total of 408 leaf samples were collected in drying in-silica gel and deposited in our laboratory. Moreover, some factors possibly associating with the endangered status of wild Cerasus resources were discussed, and solutions for the conservation and utilization of these resources were proposed.

Abstract:Plenty of leading varieties and backbone parents have been bred in Zhejiang Province, even though the rice planting area is relatively small compared to many other provinces in China. Summarizing the rice breeding experience and results in Zhejiang will not only help to understand the breeding history, but also have important reference values for breeders in selecting breeding parents. Based on the VBA programming, the algorithm is compiled to analyze the variety records for Zhejiang included in the Database for Chinese Rice Varieties and their Genealogy. From 1980 to 2019, 655 rice varieties were bred in the province, among which 514 varieties were certified, and 291 varieties have been grown in large areas. Our analysis shows that the yield per unit area and the edibility quality, chalkiness and transparency of the certified varieties have been raised, while the resistance to bacterial leaf blight of rice has remained roughly the same, and the resistance to rice blast has been somewhat lowered but still higher than the average level of resistance to rice blast of nationally certified varieties in the same rice-growing area in the same time period.

Abstract:By taking use of 481 mungbean germplasms that were collected from 21 countries (or regions), the phenotypic variations at nine qualitative traits and 12 quantitative traits were evaluated at four locations in a frame of three years. The abundant phenotypic variations were observed in these mungbean germplasms. The coefficient of variations of 12 quantitative traits ranged from 5.32% to 76.18% under different environmental conditions, of which, the grain yield per plot and the number of pods per plant had higher coefficient of variation; the genetic diversity index ranged from 1.573 to 2.078, and the plant height and 100-seed weight had the higher genetic diversity index. The growth period was observed to be significant or extremely significant positive correlated with other traits such as plant height, number of stem node and number of branches on main stem, thus implying an important role in mungbean morphogenesis. The cluster analysis suggested four major groups of which the first group included the germplasms showing dwarf, erect, large seeds and early-maturation. These germplasm resources might show a potential as excellent parent materials for breeding. For example, the 100-seed weight of a few accessions (e.g. C06287, Taolv 3, VC4059A and Sulv 1) were higher than 6.50g, which could be used as materials for improving the seed size of mungbean. The growth period of accessions C01075, C01234, and C01249 were shorter, which might carry functional genes causing early-maturation; Liaolv 28, VC1562A and Wei 9002-341 could be used as parent materials for lodging resistance breeding; C05199, C05202 and C05528 could be used as parent materials for mungbean bruchid-resistance breeding. Finally, the principal component analysis (PCA) of quantitative traits suggested that six principal component factors might contribute 83.41% of phenotypic variation. In summary, this article aims to provide a theoretical basis for genetic breeding and germplasm innovation of mung bean by comprehensively evaluating the genetic diversity of 481 mung bean germplasm resources.

Abstract:The genetic diversity analysis of 137 wild soybean accessions from three populations of Shandong province were analyzed by allele-special DNA markers. One dominant allele was detected at E1 and E4 loci, respectively, while the haplotypes E2-in and E3-Ha were found to be predominant at E2 and E3 loci, respectively. Out of five genotypic combinations, the genotype carrying E1E2-dlE3-HaE4 was predominant. By further analyzing the diversity among the three populations, four genotypic combinations were detected in Linyi population. The genotypes carrying E1E2-inE3-MiE4 were often detected, while E2-in and E3-Mi were major alleles at E2 and E3 loci, respectively. Three genotypic combinations were observed in both Penglai and Rongcheng populations, while E1E2-dlE3-HaE4 was often detected. The alleles E2-dl and E3-Ha were superiority allele on E2 and E3 loci, respectively. A similarity on genetic diversity was found between Rongcheng and Penglai populations, while both were differing with Linyi population that represented a highest genetic diversity. Taken together, the results gained from this study might provide insights for the utilization of wild soybean germplasm resources in Shandong Province.

Abstract:In order to investigate the genetic diversity of melon accessions, of 191 melon accessions including thick-skinned, thin-skinned, and wild types, which were collected from the National Mid-term Genebank for Watermelon and Melon (Zhengzhou, China) and USDA-ARS GRIN database, were analyzed with 43 chromosomally-distributed SSR markers. Furthermore, chilling tolerance was evaluated using the chilling-injury indices of melon seedlings under the constant temperature 4 ℃ as well as the leaf-ultrastructure changes before and after the low-temperature treatment. Totally, 366 alleles were detected by the SSR markers, with an average of 8.512 alleles per marker. Mean of observed and expected heterozygosity were 0.074 and 0.704, respectively, while mean of the polymorphism information index was 0.668. The method of UPGMA clustered all the accessions into four groups (I, II, III,and IV). Group I had only two genetically diverse Indian accessions. Group II included 34 wild accessions and 15 think-skinned accessions, all of which were originated from India. Group III comprised of 51 thick-skinned accessions and one wild accessions, which were collected from a wide geographic distribution. The remained 75 thin-skinned accessions, 7 thick-skinned accessions and 6 wild accessions were clustered into group IV, most of which were from East Asia. Furthermore, the Bayesian algorithm assigned the whole accession panel into three subpopulations (P1, P2 and P3), mostly correlated to the three germplasm types, i.e., thick-skinned, wild, and thin-skinned accessions. The coefficient of differentiation and Nei’ genetic distance among the three germplasm types indicated the highest level of genetic differentiation (FST) between the thick-skinned and thin-skinned accessions, following by FST values between wild accessions and thick-skinned accessions or thin-skinned accessions. The rank of the diversity level among the germplasm types were: wild accessions > thick-skinned accessions > thin-skinned accessions. The chilling-injury indices of the three germplasm types tended to follow normal distribution; the chilling tolerance of thin-skinned accessions was largely superior to that of wild or thick-skinned accessions. Leaf ultrastructure showed a slight change observed with the seedlings of the thin-skinned accession ‘Hamasu5’, indicating a high level of chilling tolerance. In contrast, the thick-skinned accession ‘Fenghuang’ presented a heavy chloroplast destruction and an aggravated damage in cell ultrastructure, indicating a high sensitivity to chilling temperature.

Abstract:Four non-coding region, trnH-psbA 、 trnS-trnG spacer + intron 、 trnT-5'trnL and 5'trnL-trnF of 242 germplasm accessions of Malus sieversii from 3 sources of Gongliu, Huocheng and Xinyuan of Xinjiang Uygur Autonomous Region of China were amplified by four primers. Based on the genetic variation of the four chloroplast intergenic regions, the genetic variation and evolution of Malus sieversii populations were explored from the perspective of maternal inheritance. The results showed that the length of the four non-coding regions of chloroplast DNA was 3812 bp after sequencing, splicing, alignment and merging, and 171 variable sites were detected, including 6 singleton variable sites, 16 parsimony informative sites and 149 insertion-deletion gaps. Among the 242 accessions of Malus sieversii the number of variable sites of the regions trnH-psbA, trnS-trnG spacer + intron, trnT-5'trnL and 5'trnL-trnF were 68, 25, 77 and 1. The number of haplotypes for the four regions were 36, 6, 6 and 2, and after the four regions merged the haplotypes of chloroplast DNA fragments were 52. The region with the highest nucleotide and haplotype diversity was trnH-psbA (Hd=0.773 ， Pi=0.01982), and the nucleotide and haplotype diversity of 5'trnL-trnF was the lowest (Hd=0.025 ， Pi=0.00002). The cpDNA diversity of Malus sieversii with the four chloroplast DNA regions merged was high (Hd=0.806，Pi=0.00291). Tajima’s test showed that all the Tajima’s D values are statistically significant at P＜0.05, indicating that the overall variation of the four chloroplast regions had not followed the neutral theory of molecular evolution, and the pressure of natural selection is the main driving force of genetic evolution of Malus sieversii. The genetic variation of Malus sieversii mainly existed within populations. The distance between populations from Gongliu and Xinyuan of Xinjiang was closer than that between populations from Huocheng and Gongliu or from Huocheng and Xinyuan of Xinjiang. The genetic differentiation correlated with the geographical distances. Malus sieversii from the 3 sources were experiencing genetic differentiation, but also having frequent gene exchanges among different populations, and had a tendency to evolve to Xinyuan population in Xinjiang.

Abstract:The tillering stage is the key period for the transition of rice from nursey to paddy. The salt tolerance at the tillering stage becomes of importance when planting rice in salinized soil. Establishment of an optimal strategy is thus of interest in order to identify the rice germplasms that show salt tolerant. This study attempted to determine the optimal salt concentration and the duration of treatment at the tillering stage. By using 26 rice varieties with the levels of salt tolerance, we conducted the experiments with the gradients of salt concentration (10 and 7 in 2015 and 2016, respectively). The salt injury score was deployed as an index for evaluating salt tolerance at the tillering stage. The results showed that, when applied with the salt concentration of 0.5%, salt injury score between varieties showed the largest difference after salt treatment about 4-6 weeks. This pipeline was considered to be optimal in order to examine for rice salt tolerance. On the contrast to the evaluation standard of salt tolerance of rice at the tillering stage that was proposed by international rice research institute (IRRI), this study proposed a updated method for evaluating the salt tolerance of rice at the tillering stage, especially by using a single plant as a unit and deploying the average salt injury score to evaluate the salt tolerance. By taking use of the aforementioned pipeline, this study carried out a three-year evaluation (2017 to 2019) in 2886 rice accessions that were collected from different ecological regions. As a result, 137 rice accessions showing salt-tolerant were identified, which might provide elite resource to support the genetic improvement and breeding research for rice salt tolerance.

Abstract:One-hundred twenty-one wheat germplasm accessions derived from distant hybridization were tested for salt-tolerance, in order to provide insight for salt-tolerant physiology, genetics and breeding in wheat. Based on D value, these materials were classified into five categories: highly salt-tolerant (five genotypes including P13, C1009, 1710, 1713 and 082-1, D value from 0.5877 to 0.6616); salt-tolerant (nine genotypes such as 1706, 081, 0819-1, PSR3628, TB1, D value ranged from 0.4222 to 0.5331); moderate salt-tolerant (41 genotypes such as 1707, 1805, TPF8, 1704, 1712, with a D value of 0.2684 to 0.3940); salt-sensitive (45 genotypes, with a D value of 0.1922 to 0.2640) ; highly salt-sensitive (21 genotypes, with a D value of 0.0504-0.1848). Especially, the D values of P13, 082-1, 081 and 082-2 lines derived from the cross Aegilops ventricosa × durum wheat ranged from 0.4231 to 0.6616, which showed high salt-tolerance or salt-tolerance. The average D values of the derivatives from einkorn wheat × Avena Fatua L．Var．Portugal, and T. timopheevii × Avena Fatua L. Var. Portugal were 0.4145 and 0.4106, which were significantly higher than that of common wheat accessions. The average D values of 8 progeny populations from wheat distant crosses were higher than that of common wheat. Finally, a few of new salt-tolerant germplasm accessions (i.e. P13, 1713, 082-1, 1706, 081) were identified.

Abstract:Grouping germplasm lines and assisting plant breeding using large number of SNP marker have become well accepted due to constant price drops of SNP markers brought about by the advance at high-throughput sequencing technology. How to handle the large SNP datasets becomes an increasing interest, and the user-friendly statistical methodologies are in demand. In this study, four grouping procedures (NJ, SNPhylo , ADMIXTURE + SNPs, and the ADMIXTURE + TagSNPs which we modified from ADMIXTURE + SNPs), were deployed to group 490 corn inbreds into 3 and 6 subgroups using 525,141 SNP markers and their performance were evaluated with four criteria (PCA Scatter Plot, GD, PIC, and BIC). The result showed that PCA Scatter Plot and BIC （BICBW, SBIC）among the four criteria are more powerful in revealing between-subgroup variation, whereas GD and PIC showed less powerful. All four grouping procedures were effective and could be adopted in grouping germplasm. Particularly, ADMIXTURE+TagSNPs was the most effective in delineating subgroups with clear boundary and very little between-group mixing, while SNPhylo was the least effective. ADMIXTURE + TagSNPs required fewer SNP markers thus would cost less than other three procedures, and therefore was highly recommended for germplasm study and marker-assisted breeding.

Abstract:Elite germplasm resources are the basis and prerequisite for breeding new crop varieties of high yield and quality. Creating sweet maize mutant library is of great significance to the breeding of new varieties and molecular breeding research of maize. In this study, ethyl methylsulfonate (EMS) was used to mutagenize the pollen of sweet maize inbred line ‘Hua-tian-xuan H-16-2-2-3’ for artificial pollination and construction of the first sweet maize EMS-mutagenized mutant library in China. Through field screening and phenotypic investigation, we obtained 24363 mutant plants of M2 generation with important agronomic traits of growth period, anthesis-silking interval, angle between stem and upper leaves, leaf size, tassel posture, male fertility, plant height, ear height, ear row number, grain color, grain size, grain shrinkage affected. Preliminary phenotypic screening of 2000 M2 mutants was carried out in the field, and gene mapping of some mutants caused by single recessive nuclear gene mutation was analyzed by high throughput sequencing. On the basis of the above work, the first domestic sweet corn germplasm resource sharing database was proposed to provide valuable experimental materials and genetic resources for sweet corn breeding and gene function research, and to promote the sharing of sweet corn breeding related resources.

Abstract:In order to identify the drought tolerance and high yield germplasm of upland cotton, data of fifteen morphological and yield traits of 102 varieties with two treatments (drought stress and normal irrigation) were determined with direct evaluation and comprehensive identification methods in Dunhuang City, Gansu Province, where the annual rainfall is below 40 mm. Correlational analysis showed that seven indices that are less fluctuating between years should be selected in the comprehensive evaluation of drought tolerance of cotton, which include single boll weight, plant height, length between fruit branches and main stem, fruit branch number, effective boll number, yield per plant and stem dry weight. Comprehensive drought tolerance evaluation based on these indices are highly correlated and can be used to evaluate the drought tolerance of cotton varieties. When screening drought-tolerance and high-yielding performance of cotton germplasm, the influence of many factors should be considered comprehensively. On the basis of comprehensive evaluation of drought tolerance of the varieties, combined with the improved drought tolerance indices and drought tolerance coefficient calculated by the yield per plant of seed cotton, and by way of comprehensive analysis, drought-tolerant and high-yielding cotton varieties Jinken 1 Hao and Jinken 108 were screened out, and cotton varieties Zhong 21371, Brazil 012, Shiyuan 321, Jifeng 1056 and Xinluzao 33 Hao were identified as not being drought-tolerant high-yielding. The drought-tolerant high-yielding cotton varieties were stable in performance through the two-year test, are suitable for cultivation in the northwest inland cotton region, and can be used as standard varieties for drought tolerance identification.

Abstract:Through two consecutive years evaluation of lettuce grown in summer greenhouse, the diversity of 28 traits of 253 lettuce materials introduced from United States Department of Agriculture, World Vegetable Center, and Shanghai Agrobiological Gene Center was analyzed.The result showed that leaf attitude, leaf lobes, undulation of leaf margin, showiness of leaf pustules, leaf color, leaf shape and some other traits had highly genetic diversity. The coefficient of variation of the 28 character ranged from 0.0315 (glossiness of leaf) to 2.7366 (intensity of leaf anthocyanin coloration), with the mean value of 0.7444. The diversity index of 28 characters ranged from 0.0258 (glossiness of leaf) to 1.9700 (fresh weight of aerial parts). According to the cluster analysis, the 253 materials were divided into 6 groups, with group I containing 99 materials, group II 38 materials, group III 84 materials, group IV 5 materials, group V 9 materials, and group VI 18 materials. In this study, the 253 materials were synthetically evaluated in the field under high temperature in summer and 14 excellent materials with strong heat tolerance and late bolting were preliminarily screened based on the investigation of heat damage and bolting time. The identification and evaluation of heat tolerance of lettuce germplasm resources provide variety materials for resource innovation, gene cloning, and mechanism research for lettuce heat tolerance in the future.

Abstract:Vegetables of the genus Allium L. with high diversity are very important in the vegetable production. The viability of the short-lived seed of Allium is easily reduced or even lost during storage. A total of 610 accessions of 6 species of allium vegetables in the National Medium-term Genebank of Vegetable Germplasm Resources, including 267 accessions of A. tuberosum Rottler ex Spreng., 226 accessions of A. fistulosum L., 40 accessions of A. ascalonicum L., 67 accessions of A. cepa L., 8 accessions of A. porrum L., and 2 accessions of A. ampeloprasum L. were evaluated for seed germination. The results indicated that the seed viability of the 6 species of allium vegetable resources declined significantly after 21-30 years storage, with A. ascalonicum and A. cepa the most seriously, that the initial germination percentage of the seeds put in storage heavily affected the viability of the seeds during storage, and that the different genotypes of the same species of allium vegetables also showed difference in longevity.

Abstract:The acquisition of Apocynum venetum mutant library is an effective way to innovate germplasm resources artificially, and it is also the basis of varieties breeding and functional genome research. In this study, wild A. venetum seeds collected in Dongying were used to construct mutant library. Pre-experiment results indicated that 0.7% ethylmethylsulfone (EMS) solution was the LD50 for seeds of A. venetum treated for 13 h. A mutant library of 1452 individual plants was constructed with the treatment in this concentration and duration. The agronomic traits and total flavonoid contents of the M1 population were screened. A total of 125 plants with abnormal agronomic traits were obtained, including 8 albinos, 23 leaf form variants, 16 yellow-striped leaf variants, 32 branching seedling variants, and 46 leaf position variants. The mutation frequencies were 0.55%, 1.6%, 1.1%, 2.2% and 3.2%, respectively.Moreover, the total flavonoids in two plants were significantly higher and in one plant was lower than that in the wild type. The flavanone 3-hydroxylase gene (F3H) involved in the flavone metabolism pathway was sequenced in the mutant library. The results showed that one in every 6.7 plants appeared as an F3H gene mutant. The mutant library of A. venetum constructed in this study showed abundant phenotypic variations, which provided good materials for selection of new germplasm, varieties breeding and gene function research in A. venetum.

Abstract:Flag leaf, which is a major sink organ of rice plant, was reported to significantly positive correlate with the grain yield. Illustrating the genetic basis of flag leaf related traits and the grain yield is of significance in breeding for high-yield varieties with ideal plant type. In the present study, a diverse panel of 1016 rice accessions was evaluated for flag leaf related traits including flag leaf length (FLL), flag leaf width (FLW), flag leaf area (FLA), as well as the grain yield per plant (GY) in Jingzhou of Hubei province in two calendar years (2015 and 2016). The abundant variations at four traits were observed within this population, but the phenotypic variations were found to be largely environmental-dependent. The correlations between GY and each of FLL, FLW, FLA were low.Using genome-wide association analysis based on 4.8M high throughput SNP datasets, a total of 31 QTL for flag leaf related traits and GY were identified. Especially, one QTL (qFLW4) for FLW was detected in both two calendar years. Three regions were found to be associated with two traits including qFLW4 and qFLA4 for FLW and FLA, qFLL6 and qFLA6 for FLL and FLA, and qFLL10 and qFLA10 for FLL and FLA. Using haplotype and bioinformatic analyses in QTL regions, seven candidate genes and 10 favorable alleles were identified. Taken together, our results provided a preliminary base in order to clone the functional genes underlying rice flag leaf related traits, and breed for elite rice varieties with an ideal plant type by deploying different favorable genes by marker-assisted selection.

Abstract:Oryza rufipogon served as an important rice germplasm which harbors excellent yield and stress tolerance genes that have been lost or weakened in cultivated rice. Within this study, a set of introgression lines with chromosome segments derived from Chaling wild rice were used for genetic analysis and QTL identification. Two-hundred sixteen polymorphic markers evenly distributed across the 12 chromosomes were deployed for genotyping. 87.89% of the Chaling wild rice genomes were detected. Averagely, 24 introgression segments were found in each introgression line, and the genetic distance of each segment was accounting for about 16.1 cM. By taking use of phenotypic datasets from two environments, eighteen QTLs on six yield traits were identified. Especially, a QTL associating with grain width on chromosome 6 was found in two environments. Furthermore, five QTLs related to cold tolerance at the germination stage were detected. Taken together, these introgression lines served as elite gene resources with a potential for rice breeding.

Abstract:Powdery mildew, which is caused by biotrophic fungus Blumeria graminis f. sp. tritici (Bgt), is an important epidemic disease threating the wheat production in Hebei province of China. Identification of disease-resistance genes in the commercially authorized varieties and breeding lines is of great significance for efficient utilization and regional distribution of known resistance sources and effective managing of wheat powdery mildew. In this study, 371 wheat accessions (including 256 commercial varieties from 1956 to 2018 and 115 breeding lines) from Hebei province were tested for resistance to powdery mildew at seedling stage with independent inoculation with two isolates of E09 and E20, as well as marker-assisted classification of eight genetically-mapped Pm genes. The results showed that 6.2% and 11.9% of accessions were tested to be resistant to E09 and E20, respectively, while only 4.9% were resistant to both isolates. Marker-assisted selection showed that resistance genes Pm1c, Pm2, Pm4b, Pm21, Pm24 and Pm35 were found in some accessions, while Pm12 was not detected. Almost half of the accessions were found to carry Pm8. It was shown that resistance carrying accessions of resistant authorized varieties were found to be much higher than that of breeding lines, indicating that genetic germplasm improvement enhancement for powdery mildew resistance is an urgent task at present and should be paid more attention. When using linkage or co-segregation markers for Pm gene detection, by means of the method that the number of materials that the resistant reaction type consistent with result of the marker detection occupies the total number of materials detected by the linkage marker of the gene, finding markers linked to Pm12, Pm21 and Pm35 is highly effective. Taking advantage of the user-friendly markers targeting these resistance genes, marker-assisted selection for resistance-carrying lines can be conducted in advance in contrast to a test for resistance.

Abstract:F-box protein is responsible for the recognition of substrates to be degraded in the process of ubiquitin-mediated protein degradation. In recent years, the role of F-box protein in plant resistance to stresses has attracted more and more attention. In order to understand the expression profile and molecular mechanism of F-box members in response to biotic/abiotic stresses in wheat, TcLr15 - a near isogenic line against leaf rust pathogen, was used as the material to obtain the complete coding region (encoding a polypeptide of 421 aa) of wheat F-box gene TaFKOR23. Wheat TaFKOR23 includes 1 F-box domain at N-terminal and 2 Kelch domains at C-terminal, which means that the wheat TaFKOR23 belongs to F-box/Kelch subfamily. Phylogenetic tree showed that wheat TaFKOR23 had extremely high homology with F-box/Kelch-repeat protein OR23 from Aegilops tauschii, and had high homology with that from Brachypodium distachyon. Expression profiles of the gene in TcLr15 plants after treatment with leaf rust pathogen, 3 hormones (ABA, SA and MeJA) and abiotic stresses (NaCl and PEG) were analyzed by qRT-PCR in the present study. No significant difference was observed for TaFKOR23 transcripts accumulation between compatible and incompatible combinations; TaFKOR23 showed up-regulated expression after treatment with the 3 hormones and NaCl, but less affected by PEG; TaFKOR23 prominently expressed in flag leaves than in other parts of wheat. Target proteins interacting with TaFKOR23 were screened and identified by yeast two-hybrid, 11 kinds of target proteins were obtained by library screening, and further results showed that TaFKOR23 can interact with TaSKP1, TaSLY and TaChitinase. The research results laid a solid foundation for further understanding the function and metabolic network of F-box/Kelch genes in wheat, and broadened the functional knowledge of Kelch like F-box genes in plant.

Abstract:Ear-related traits have an important impact on maize yield and general combining ability (GCA) is an important indicator for assessing maize inbred lines. 248 inbred lines of maize and 400 F1 hybrids derived from combinations with 100 lines selected randomly from the 248 inbred lines as the female parents and four elite inbred lines (‘Mo17’, ‘Chang 7-2’, ‘E28’ and ‘Zheng 58’) as the testers according to the NCII genetic mating design were used to study the ear-related traits. The association analysis of ear-related traits and their GCA was performed using 83057 SNP markers. The results indicated that the ear-related traits were significantly different among the genotypes and the environments. The broad-sense heritability of ear length (EL) and ear diameter (ED) were 81.22% and 87.70%, respectively. Combining ability analysis indicated that there were significant differences among females, males and combinations for the two traits. The contribution rate of special combining ability was greater than general combining ability. 34 significant trait-SNP associations were identified using the data of 4 environments (2 locations in 2 years) respectively, and 7 significant trait-SNP associations were identified using the data of best linear unbiased prediction. Each trait-SNP association can explain phenotypic variation ranged from 0.01% to 19.42% and 5 of them had phenotypic variance explained value greater than 10%. The same SNPs of the ear-related traits and GCA were not identified simultaneously. Based on the LD decay distance, candidate genes were identified in the range of the 120 kb upstream and downstream of significantly associated SNP, and 158 genes were obtained. The putative candidate genes were involved in ubiquitin metabolism (GRMZM2G360374, GRMZM2G049568, GRMZM2G178120), β-galactosidase (GRMZM2G178106), serine/threonine-protein kinase (GRMZM2G127050), lysine and histidine specific transporter (GRMZM2G116004). The study provides a reference for the analysis of the genetic basis and molecular-assisted selection breeding of maize ear-related traits and general combining ability.

Abstract:Fiber quality and lint percentage are the main target trait of cotton breeding improvement. In order to explore the elite genetic resources of fiber quality, a genetic map is constructed and QTLs are detected based on an F2 population of 372 individuals derived from a cross between upland cotton Sealand (Se) (a superior fibre-quality germplasm of Gossypium hirsutum L. with G. barbadense L. introgressions) and upland cotton Lumianyan 37 Hao (L37) (a high-yield G. hirsutum L. cultivar). A total of 9628 primer pairs were used to screen polymorphism between the two parents, and 320 pairs of polymorphic primers were identified. The polymorphic primers accounted for 3.32%. Linkage test (LOD=6.5) indicated that 248 polymorphic loci could be mapped into 26 chromosomes and covered a total genetic distance of 2347.63 cM, which was approximately 52.76% of the cotton genome. The average number of marker loci per chromosome was 9.54, with a mean spanning distance of 9.50 cM. Twenty QTLs for fiber quality traits and lint percentage were identified, including two for fiber upper half length (FL), two for uniformity (FU), five for fiber strength (FS), four for micronaire (FM), four for elongation (FE) and three for lint percentage (LP). These QTLs could explain 3.50%-16.82% of the phenotypic variation. The favorable alleles of 11 QTLs for fiber upper half length, strength and fiber elongation were derived from Se, while the favorable alleles of nine QTLs for micronaire, fiber upper half length, uniformity and lint percentage were derived from L37. A QTL cluster including QTLs for fiber upper half length, strength and micronaire and containing 148 genes was identified on D6 chromosome. Three genes related to fiber development, Gh_D06G0039, Gh_D06G0142 and Gh_D06G0145, were identified by GO enrichment analysis and KEGG enrichment analysis combined with TM-1 transcriptome data. This study laid a foundation for fine mapping QTL of fiber quality and lint percentage of cotton and for identifying related candidate genes.

Abstract:Medicago sativa L. is a perennial legume forage. In order to analyze the function of UFO gene from Medicago sativa, we isolated the full-length coding sequence by PCR amplification in alfalfa variety ‘Zhongmu No. 1’. The plant expression vector 3302-3flag-UFO was constructed by DNA recombination technology, and transgenic alfalfa was obtained by deployment of Agrobacterium tumefaciens mediated transformation method. The transgenic efficiency of alfalfa was improved by changing the ratio of hormone concentrations and improving plant expression vector. The type and ratio of hormones have resulted in a difference on the formation of resistant calli and the degree of vitrification of calli. By taking use of optimal transformation strategy, a total of 67 resistant callus were generated, while 56 young alfalfa regenerated plants were obtained. Finally, 17 mature regenerated plants were obtained for seed propagation. Taking together, this study generated the transgenic plants with UFO overexpressing vector, which might provide materials for further functional study of UFO gene.

Abstract:Lipoxygenase is a key enzyme involved in the pathway of fatty acid metabolism, and plays an important role in the growth and development of plants, responses to environmental stresses and the synthesis of aroma components. In this study, the red callus from the leaves of 'Zihong 3' was used for PCR amplification of the MdLOX1a gene and its partial promoter sequence. Sequencing analysis revealed that MdLOX1a has an open reading frame of 2592 bp encoding for 863 deduced amino acids, with a predicted protein molecular weight of 97.69 KDa and the isoelectric point of 5.14. The MdLOX1a gene was found to be localized on chromosome 9 of the apple genome, consisting of 8 exons and 7 introns. Phylogenetic tree analysis with amino acid sequence indicated that MdLOX1a and Pb9S-LOX5 were assigned within the same branch. In addition, we obtained the MdLOX1a promoter sequence with a length of 1058 bp, which contained several cis-acting elements in response to various stresses. Subcellular localization revealed that MdLOX1a was localized on both the cell membrane and the nucleus. The tissue disparity analysis showed that the expression level of MdLOX1a gene was abundant in the pericarp, followed by flower and pulp. The expression of MdLOX1a gene gradually increased with fruit ripening, and its transcription has been induced under continuous light treatment. The expression of MdLOX1a gene was significantly reduced after low temperature (16 ℃) and exogenous ABA treatment at different concentrations. The overexpression of MdLOX1a showed that the transgenic lines showed the induction of the aromatic components in relative to the control lines, suggesting that MdLOX1a might associate with the synthesis of aroma components.

Abstract:Eukaryotic translation initiation factors 1A (eIF1A) function as important regulatory factors in protein synthesis and play crucial roles in the response to abiotic stresses in plants. In this study, we cloned the translation initiation factor MieIF1A-a (GenBank accession number: KP271044) in mango. Bioinformatic analysis was carried out on the MieIF1A-a, and its function was studied through the expression pattern analysis and Arabidopsis thaliana genetic transformation. Sequences analysis showed that the full length of the MieIF1A-a cDNA was 604 bp with an open reading frame of 435 bp, encoding 144 amino acids, and the molecular weight was 16.45 kDa. MieIF1A-a had the highest similarity with VveIF1A of grapevine, had significantly higher expression level in mature fruit than in other tissues. It was up-regulated under salt and drought stresses, causing transgenic plants to produce more pods, to grow better and to be less adversely affected than wild-type plants. Compared with wild-type plants, the relative water content, chlorophyll and proline contents were higher, SOD, POD and CAT activities were stronger, and MDA content was relatively lower in transgenic plants under drought stress. In summary, this study revealed that the MieIF1A-a gene was involved in the regulation of fruit development and responded to stresses, which laid a foundation for further research on stress resistance of mango.

Abstract:In order to produce the elite germplasm resource for tea breeding, we deployed the artificial hybridization approach to generate the F1 hybrids by crossing six elite tea varieties including Fuding Dabaicha (mother) with another variety Baojing Huangjincha 1, which showed a specific phenotype "golden rhyme" but weak adaptation ability. We found that Baojing Huangjincha 1 pollen exhibited a strong living force whose fresh pollen life force reached to 94.22% by taking researching on Baojing Huangjincha 1 pollen life force, different hybrid combination strong rate, hybrid F1 generation seedling rate, F1 generation excellent single plant selection rate, etc.. Under room temperature, 4℃ and -20℃ conditions, its pollen was able to survive up to 7d, 30d and 40d, respectively. The seed setting rates of six hybrid combinations were variable from 15.25% (Bixiangzao) to 31.32% (Fuding Dabaicha) with the average of 21.88%, while the seedling rates were arranged from 50.77% (Bxiangzao) to 66.65% (Tieguanyin) with a mean value of 59.62%. No significant difference was observed in seed setting rate and seedling rate among different treatments (combinations and years). By taking use of three rounds of selecting excellent strains and identifying asexual reproduction ability, a total of 60 strains were finally accepted with a selection rate of 2.35%. The rate of elite hybrids was much higher than that of naturally-occurring hybridization offspring (0.04%). Furthermore, we conducted a comprehensive evaluation of biochemical composition, yield and quality related traits in selected hybrids. Three new strains, which were subjected for the regional test, showed the growth potential and excellent sensory quality (especially with aroma prominent), much better than the father Baojing Huangjincha 1.

Abstract:This study attempted to explore the suitable liquid nitrogen cryopreservation condition of Murraya exotica L. seed and provided a pipeline for the long-term preservation of the seeds. Using mature seeds of Murraya exotica L. with different water content using rapid drying method, cryopreservation experiments were carried out with three approaches including vitrification method, step freezing and direct freezing method, followed by an observation of the micro-characters with the method of paraffin section and the quantification of the physiological and biochemical activity indexes. The results showed that the water content of the seed decreased from 30% to 7%, and the viability of the control group slowly decreased from 98% to 82%. After being treated by different freezing methods, the viability first decreased and then rised with the decrease of water content. At 7% water content, the viability of each freezing group reached to the highest, and the viability is the closest before and after cryopreservation at this time. The seed vigor after step freezing was generally higher than that of vitrification and direct freezing. Among them, the seed color at the cutting surface were darker than other groups after step freezing, and the seeds with 30% water content had cavity or severe plasmolysis in some cells after step freezing. The vigor and structure of the seeds in the 7% water content group were basically unchanged after the different freezing treatments compared with the control group. After the step freezing treatment, the malondialdehyde content, protein content, catalase activity and peroxidase activity of the seeds decreased and the dehydrogenase activity was found to be elevated. Thus, we concluded that the Murraya exotica L. seeds are able to be stored following the ultralow temperature preservation pipeline in liquid nitrogen, by use of the water content of 7% seed with the method of step freezing.

Abstract:Genetic diversity of 1061 walnut germplasm from 14 prefectures and cities of Yunnan Province was analyzed by SSR molecular marker technique. On the basis of this, a core collection was constructed through least distance stepwise sampling (LDSS) and tested for its diversity. The results showed that 322 alleles were detected by 19 pairs of SSR primers (on average 16.95 per pair of SSR primer). The means of Shannon’s information index (I), expected heterozygosity (He) and Nei’s gene diversity (Nei) were respectively 1.3375, 0.6040 and 0.6043, which indicated a relatively high genetic diversity of the germplasm. The genetic diversity distributed differently among the 14 prefectures and cities. Diqing Prefecture had the highest genetic diversity while Lincang had the lowest. Sampling rates of 30%-5% were taken for construction of the primary core collection, secondary core collection, core collection-1 and core collection-2, on the basis of UPGMA clustering results. With the genetic diversity analysis and t-test, the core collection-1 with 10.84% sampling rate and 115 samples was determined to be the core collection of walnut germplasm in Yunnan.

Abstract:In order to establish an accurate and reliable identification method for dwarf-traits of litchi, and comprehensively evaluate the dwarf degree of part of the litchi germplasm resources, 120 litchi germplasm resources were used as materials to investigate and determine eight candidate dwarfing-related morphological indicators of length of new branch (LNB), diameter of new branch (DNB), length of common petiole (LCP), diameter of common petiole (DCP), length of internode (LI), length of single leaf (LSL), width of single leaf (WSL) and thickness of single leaf (TSL) with correlation analysis, normal distribution test, membership function, and principal component analysis. The results showed that all the 8 morphological indicators had good genetic diversity, fitting or approximating the normal distribution characteristic. Except for TSL, the other seven indicators had significant or extremely significant correlations. With principal component analysis, two principal components were obtained to explain 72.738% of the original data information, and seven indicators (excluding TSL) were preliminarily identified as the main morphological indicators of the comprehensive evaluation of litchi dwarfing, which could be used to effectively evaluate the dwarf traits of litchi germplasms. After comprehensive evaluation of dwarfing, the 120 litchi germplasms were divided into 5 grades, including 9 germplasms in grade I (dwarf), 10 in grade II (semidwarf), 69 in grade III (subarboreous), 25 in grade IV (arboreous), and 7 in grade V (very arboreous). According to this evaluation approach, we screened out a number of dwarf and semi-dwarf germplasm resources such as ‘Nuomici’, ‘Miaozhongnuo’, ‘Ziniangxi’, ‘Yamulong’, ‘Nongmei 12 Hao’, and ‘KOM’. The above results indicated that based on the determination and analysis of the seven major morphological indicators, the comprehensive evaluation method of litchi dwarf degree was accurate and reliable, which would provide the scientific basis for more in-depth exploration and development of litchi dwarf resources.