Studies On Seed Dormancy Of Hybrid Offsprings Of Chaling Wild Rice

Cultivated rice has lost many excellent genes during long-term artificial breeding.In recent years,the situation of pre-harvest sprouting?PHS?is frequent.Especially in South China pre-harvest sprouting of rice seeds can occur easily in higher temperature and rainy weather of rice harvest season,which seriously affect rice grain and seed quality,resulting in a huge loss of rice production.It is of great significance to explore and utilize the strong dormancy characteristics?or genes?of wild rice to improve the dormancy characteristics of rice varieties.In this study,we obtained several advanced backcross populations and substitution lines by using Chaling wild rice?Oryza rufipogon Griff.?as the donor parent and indica cultivar 9311 as the recurrent parent.Seed dormancy was evaluated through germination tests.Whole genome SNP microarray analysis was performed in this study to locate the position of dormancy genes and predict the candidate genes.The main results are as follows:?1?Among the 425 individuals of the BC₃F₂ population,the germination rates of three plants were 40%or less and showed strong dormancy;Among the 387 individuals of the BC₄F₁ population,the germination rates of two plants were 40%or less and showed strong dormancy;The germination rate of the parent 9311 was 89.54%,and the dormancy was very weak.?2?By identifying dormancy for three BC₃F₃ lines with strong dormancy and two BC₄F₂ lines with strong dormancy,we have found that the germination rates of these lines were below 20%,The germination rate of the parent 9311 in the same period was 68%;Those further indicated that those five substitution lines have strong dormancy.Among those five substitution lines,there were 33 individuals whose germination rates were 10%or less.Responses of those individuals to a dormancy-broken with a dry heat treatment were further detected.The results showed that the germination rate of the parent 9311 reached100%,and the germination rates of those five substitution lines were also significantly increased,reaching 78%-93%.And it indicated that dry heat treatment can effectively relieve seed dormancy and may be applied to rice genetic improvement.?3?The background purification rates of five strong dormancy substitution lines were studied by using 60k SNP gene chip.It was found that the background recovery rates of 9311 in the five substitution lines was 73.32%-94.98%.The background purification rate of SL445?BC₄F₂?was the highest,which was 94.98%;SL853?BC₃F₃?and SL812?BC₃F₃?were 93.04%and 75.66%,respectively.The background of SL108?BC₄F₂?was the lowest,only 73.32%,followed by 75.19%of SL851?BC₃F₃?.?4?SNP gene chip analysis was performed on two extreme phenotypic pools in the BC₄F₂ population of SL812.The results showed that there was a 823.3 kb region on chromosome 5 with the dormancy gene Sdr5.The genotypes of the five substitution lines in the Sdr5 region were analyzed,and the effective region of the gene was reduced to 55.1kb and determined that Sdr5 was a dominant inheritance from the donor Chaling wild rice.The accuracy of SNP results was further verified by the design of six polymorphic Indel primers in this 55.1 kb region,which could be applied to molecular assisted breeding.Bioinformatics analysis of 55.1 kb on chromosome 5 predicted that there were 14 candidate genes in this segment.