Identification of QTL Combinations that Cause Spikelet Sterility in Rice Derived from Interspecific Crosses

Chang-Min Lee,Hyun-Su Park,Man-Kee Baek,Suk-Man Kim,Jung-Pil Suh,Young-Chan Cho,O-Young Jeong,Song-Joong Yun

doi:10.1186/s12284-021-00540-6

Chang-Min Lee, Hyun-Su Park + Show 6 more

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https://doi.org/10.1186/s12284-021-00540-6

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Abstract

BackgroundThe exploitation of useful genes through interspecific and intersubspecific crosses has been an important strategy for the genetic improvement of rice. Postzygotic reproductive isolation routinely occurs to hinder the growth of pollen or embryo sacs during the reproductive development of the wide crosses.ResultIn this study, we investigated the genetic relationship between the hybrid breakdown of the population and transferred resistance genes derived from wide crosses using a near-isogenic population composed of 225 lines. Five loci (qSS12, qSS8, qSS11, ePS6-1, and ePS6-2) associated with spikelet fertility (SF) were identified by QTL and epistatic analysis, and two out of five epistasis interactions were found between the three QTLs (qSS12, qSS8 and qSS11) and background marker loci (ePS6-1 and ePS6-2) on chromosome 6. The results of the QTL combinations suggested a genetic model that explains most of the interactions between spikelet fertility and the detected loci with positive or negative effects. Moreover, the major-effect QTLs, qSS12 and qSS8, which exhibited additive gene effects, were narrowed down to 82- and 200-kb regions on chromosomes 12 and 8, respectively. Of the 13 ORFs present in the target regions, Os12g0589400 and Os12g0589898 for qSS12 and OS8g0298700 for qSS8 induced significantly different expression levels of the candidate genes in rice at the young panicle stage.ConclusionThe results will be useful for obtaining a further understanding of the mechanism causing the hybrid breakdown of a wide cross and will provide new information for developing rice cultivars with wide compatibility.

Highlights

The exploitation of useful genes through interspecific and intersubspecific crosses has been an impor‐ tant strategy for the genetic improvement of rice
Evaluation of spikelet fertility (SF) Using the near-isogenic line (NIL) Population Development of the Population Gene-pyramided line (GPL; a backcrossed line with the genetic background of Jinbu) is a NIL with the japonica background obtained from a marker-assisted backcross (MAB) based on an inter(sub)specific cross
Because the SF of both parents was higher than 75%, the inheritance pattern of the NIL population suggested that multiple genes and not a single gene would dominate the SF

Summary

Introduction

The exploitation of useful genes through interspecific and intersubspecific crosses has been an impor‐ tant strategy for the genetic improvement of rice. Postzygotic reproductive isolation (RI) occurring after mating is known to drive speciation and maintain species identity, which blocks or reduces the gene flow among species (Kubo et al 2016). A common form of postzygotic RI appears to be abnormal in offspring generations, as demonstrated by hybrid breakdown/weakness, hybrid sterility, and necrosis in the F 1, F2, or backcross generations (Jiang et al 2008; Yamamoto et al 2010; Ichitani et al 2012; Ouyang and Zhang 2013). Molecular genetic studies have revealed more than 50 loci that cause the fertility of inter(sub)specific crosses in rice, and these loci include loci with major effects and quantitative trait loci (QTL) with minor effects (Ouyang and Zhang 2013; Fang et al 2019)

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