Abstract:Wheat pre-harvest sprouting significantly reduces yield production and flour quality. It has been gradually aggravated in recent years， and destabilize the safety of wheat production in China， particularly in the Huanghuai region. Identification of pre-harvest sprouting resistant germplasm and functional molecular markers are of importance to accelerate pre-harvest sprouting resistant breeding. In this study， 77 pre-harvest sprouting resistant germplasms observed from field experiments and 128 advanced breeding lines from a rotational population introduced with six resistant germplasms were used. These genotypes were tested for pre-harvest sprouting resistance using the whole-split germination and seed germination methods， as well as genotyped by functional markers Vp1B3， Dorm-B1， and PM19. 49.35% （38 of 77） of germplasm resources showed intermediate resistance， and 57.90%（22） of them contained functional resistance alleles of Vp1Ba or（and） Dorm-B1b. The germplasm resources Xinong 172， Kalango， Huaimai 40 and Yunong 186 were detected carrying both two functional alleles. 36.72% （47） of the advanced breeding lines showed intermediate resistance， of which 87.23% contained resistance alleles and 17.02% （8） contained two functional alleles. Stacking resistance loci can increase the level of pre-harvest sprouting resistance. In the germplasm resources， the whole-split germination and seed germination decreased from 36.65% and 34.99% in non-resistant individuals， respectively， to 18.17 % and 23.87 % in individuals with two resistance loci. The same pattern has been observed in advanced lines. There was a significant difference in the number of resistant loci between advanced materials and others. Among them， 17.02% of the materials with medium resistance level contained two resistance loci， while only 4.94% of the other materials without medium resistance level contained two resistance loci. This study deployed molecular markers and phenotypic characterization techniques to identify pre-harvest sprouting resistance germplasm， followed by germplasm innovation using dwarf failing rotation selection， which provided a basis for future improvement of wheat spike germination resistance in the Huanghuai region in China.

Abstract:This study aims to identify the pre-harvest sprouting resistance in wheat germplasm resources and molecular markers for marker-assisted selection， ultimately obtaining excellent white grain wheat germplasm resources applicable in wheat breeding. These spikes of 222 wheat germplasm resources were tested for pre-harvest sprouting resistance， and the functional markers of eight anti-pre-harvest sprouting genes， including myb10D， DFR-B， Vp1B3， PM19-A1， MFT-3A， MFT-A2， MKK3-A， QSD1， were used for genotyping. Phenotypic identification results showed that there were significant differences in the relative sprouting percentage of 222 wheat germplasm resources. The relative sprouting percentage ranged from 0 to 1.15， and the average relative sprouting percentage was 0.73. 38 wheat materials were identified to be resistant to pre-harvest sprouting， including 9 white wheat， 27 red wheat and 2 black wheat. Correlation analysis between allele types and relative sprouting percentage showed that the relative sprouting percentage was significantly correlated with functional markers myb10D， DFR-B， Vp1B3， MFT-3A and MFT-A2， but not with PM19-A1， MKK3-A and QSD1. These results indicated that molecular markers myb10D， DFR-B， Vp1B3， MFT-3A and MFT-A2 could be used for detection of pre-harvest sprouting resistance and marker-assisted breeding. Based on the phenotype and genotype results， nine white wheat germplasm resources with pre-harvest sprouting resistance were selected， including Yunong 914， Yunong 946， Fengdecunmai 30， Fangmai 5， Xumai 029， Lianmai 1901， Baofeng 1903， Zhengmai 829 and 13wang27-8， which could be used for genetic breeding and layout of wheat varieties with pre-harvest sprouting resistance.

Abstract:Pre-harvest sprouting (PHS) is one of the most serious problems in indica rice production. Generating new germplasm with elevated PHS resistance is applicable by editing dormancy-related gene. Taifeng B (TB) is a maintainer line of indica hybrid rice showing high eating quality, whereas this line shows higher PHS. Two genes MPK7 and MPK14 negatively regulates seed dormancy in japonica rice, but whether both result in elevated PHS resistance in indica rice remains unclear. In this study, in order to generate the germplasms with PHS resistance, we deployed CRISPR/Cas9 technology to edit MPK7 and MPK14 in TB via Agrobacterium-guided transformation. Six lines harboring modified target sequences were screened from the transgenic offspring by sequencing, and two were selected for analyzing the seed dormancy. The results showed that the homozygous mutant significantly delayed the seed germination, rather than heterozygous mutants which also exhibited improved PHS resistance if compared to the wild type TB. No significant difference in plant height, number of tillers and grains per spike between the homozygous mutant and TB was observed. As a result, this study generated PHS resistant lines by CRISPR/Cas9 strategy, which provided theoretical technology and material support for the PHS resistance research and rice breeding.

Abstract:Pre-harvest sprouting (PHS) is a frequently-occurring disaster that results in a serious economic loss in rice production. Breeding for PHS-resistant rice varieties has limited worldwide due to the mechanism of PHS that remains unclear. Here, nine independent mutants conferring PHS were identified by screening of an EMS (Ethylmethylsulfone) mutant library, and two of them were subjected for further study. By taking use of whole genome resequencing, SIMM method and HRM technology, two PHS mutant genes (LOC_Os03g08570 and LOC_Os07g10490) were molecularly cloned. LOC_Os03g08570 codes a phytoene desaturase (OsPDS), and LOC_Os07g10490 codes a ζ-carotene desaturase (ζ-carotene desaturase). Both were reported to be involved in the biosynthesis of carotenoid as the precursor of ABA. In summary, our data highlights the critical role of carotenoid that participates in rice dormancy. Further studies of these PHS mutants would allow revealing the mechanism of PHS and breeding for PHS-resistant rice varieties.

Abstract:Pre-harvest sprouting is the devastating disaster of wheat, but varieties resistant to the disaster is rare in common wheat. Germination rate of 35 Ae. tauschii accessions from the middle reaches of the Yellow River, 14 Ae. tauschii accessions from abroad, and 2 wheat cultivars were tested. Meanwhile，diversification analysis classfied the materials into several categories. The results indicated that all Ae. tauschii accessions have stronger pre-harvest sprouting resistance than common wheat, and those from the middle reaches of the Yellow River have stronger pre-harvest sprouting resistance than those from abroad. Among those from the middle reaches of the Yellow River, T005, T007, T008, T016, T030, T062, T065, T068, T069, T072 and T085 were identfied to have strongest resistance to pre-harvest sprouting, and could be applied in wheat breeding.

Abstract:穗发芽严重影响小麦品质和产量。种子自身休眠特性、α-淀粉酶活性、α-淀粉酶抑制剂、迟熟α-淀粉酶活性、种皮颜色、颖壳抑制物以及穗部形态等,均是影响小麦穗发芽的重要因素,其中对子粒休眠特性和α-淀粉酶活性的研究较为深入。位于第3染色体组上的R基因、休眠基因以及4AL上的Phs基因均与小麦穗发芽密切相关。已开发出一些与穗发芽抗性相关的分子标记,其中位于第3部分同源群的三重R基因和位于3B染色体的STS标记Vp1B3,以及位于3A染色体的主效QTL位点QPhs.ccsu-3A.1均可直接用于穗发芽抗性的筛选。本文对以上内容进行了详细论述,并就今后如何提高小麦穗发芽抗性进行了讨论。

Abstract:Resistances to pre-harvest sprouting (PHS) in eight different early indica rice varieties were investigated after their panicles were sampled from 16 days after pollination (DAP) onwards and treated in wetting condition. The result indicated that there was great variation in resistance to PHS among the varieties, which could be reasonably reflected by the treatment of 6d panicle-wetting for the panicles of 22 DAP. The exogenous hormone treatments to panicles, applying gibberellin acid (GA 3) and abscisin acid (ABA) solutions in 3 different concentrations, showed that 30 mg/kg concentration of GA3 could obviously promote the panicle germination and that ABA could restrain panicle germination even though the effect varied considerably for the different varieties.