QTL Mapping For Cold Tolerance At Booting Stage Using Chromosome Segment Substitution Lines In Rice(Oryza Sativa L.)

Rice(Oryza sativa L.)is one of the most important crops,providing food for more than half the population in the world.China has a huge population and great demand for rice,but the per capita arable land area is small.Therefore,cultivating rice varieties with stable yield and high quality is not only the target pursued by breeders,but also a powerful measure to ensure food security in China.However,the extreme disasters have occurred frequently in recent years.The great economic losses with serious reduction in yield had emerged in south and northeast China caused by low temperature at booting stage in rice.Therefore,studying the mechanism of cold tolerance at booting stage is especially important.In our previous studies,some low-fertility plants were found in derived population constructed by SL431 and Sasanishiki in Hainan province.We speculated that the plants were sensitive to low temperature at booting stage.SL431 is one of the CSSLs constructed by using japonica Sasanishiki and indica Habataki as recipient and donor.In order to study the mechanism of cold tolerance at booting stage in rice,the derived population was used to screen overlapping lines with smaller substitution segments.Then,they were treated under artificial climate chamber and natural environment with cold stress to identify the possible QTL associated with cold tolerance.In addition,several cold-sensitive rice varieties at booting stage were selected to analysis their cold-tolerance at other growing stages.The main results are shown as follows:1.In this study,15 genotypes with different chromosome substitution segments were screened from the F2 and F3 derived populations crossed by SL431 and Sasanishiki.2.The materials were treated under normal temperature in Yangzhou and low temperature in Lingshui.The seed setting rate was used as cold tolerant index to map the genes preliminarily.Three major QTL were identified in chromosome 10 and named qPF10.1,qPF10.2 and qPF10.3.Among them,qPF10.1 was located in the range of 562 kb between q1-15 and q1-7,qPF10.2 was located in the range of 322 kb between q2-20 and RM5806,and qPF103 was located in the range of 1338 kb between q3-7 and M132.3.It was found that the genetic interaction existed in the three QTL.Rice showed strong tolerance at booting stage when qPF10.3 contained a Sasanishiki gene,qPF10.1 and qPF10.2 contained an Sasanishiki or Habataki gene.Rice was sensitive to cold stress when qPF10.3 contained a Sasanishiki gene,qPF10.1 and qPF10.2 contained different genotypes.However,when qPF103 contained an Habataki gene,rice showed cold tolerance at booting stage.Regardless of the genotypes of qPF10.1 and qPF10.2 were consistent or not.4.The cold tolerance of rice varieties at different growth stages was identified and analysis.In order to study the correlation of cold tolerance between booting stage and other stages in rice,four chilling sensitive varieties were collected.Sasanishiki and SL431 were served as control to identify cold tolerance at budding,seedling and booting stage.The results indicated that rice germplasms with strong cold tolerant at booting stage will also show cold tolerant at seedling stage.There was a significant correlation between the two stages.