QTLs detection and pyramiding for stigma exsertion rate in wild rice species by using the single-segment substitution lines

Seed yield is one of the main limitations in hybrid rice production. The improvement of stigma exsertion rate (SER) of male sterility lines is essential for the higher seed yield in hybrid rice. Wild rice species are valuable germplasms with exserted stigma. It is worthy of mining-related genes for SER in wild rice species, as well as probing the way to use the beneficial genes in rice breeding. In the present study, we identified a total number of 36 stable QTLs for the SER distributing on 11 chromosomes by using a set of single-segment substitution lines (SSSLs) of 3 AA-genome wild rice species, O. barthii , O. meridionalis , and O. rufipogon . The mean genetic effects of these QTLs were ranged from 14.50 to 41.25% during 2016–2017. Twelve QTLs among them were novel by comparing the chromosome intervals with the reported QTLs. Besides, 7 homozygous 2-QTL pyramiding lines (PLs) were developed in BAR-SSSLs and MER-SSSLs to detect QTL interactions on the same background of HJX74. The epistatic effects in 3 out of 7 QTL pairs were positive, including qSERb3-1/qSERb6-1 , qSERb3-1/qSERb8-1 , and qSERb3-1/qSERb12-1 , which mean epistatic effect was 13.56%, 4.76%, and 7.29% in 2018–2019, respectively. The PL of B6/B19 ( qSERb3-1 / qSERb12-1 ) had the highest mean SER of 80.59% and the largest pyramiding effect of 55.51%. The results in the present study demonstrated that SSSLs were the elite materials for SER QTL detection from wild rice species, and elite PLs could be developed among SSSLs for SER improvement in hybrid rice breeding.