| The very strong heterosis demonstrated in cross between indica(0ryza sativa ssp. Indica )and japonica (Oryza sativa ssp. Japonica )rice has generated considerable research in recent decades aimed at exploiting such heterosis by developing indica-japonica hybrids promising significant yield advantage over intra-subspecific hybrids. However, one important problem that fertility of many indica-japonica hybrids is very sensitive to temperature fluctuation has arisen . It has been observed that hybrids containing the S5n allele have normal fertility under high -temperature conditions, but the fertility is greatly reduced under somewhat lower temperature which do not affect the fertility of the parents .It has shown that an average daily temperature falling below 23 掳C at the booting stage can result in a significant fertility reduction in some indica-japonica hybrids . The main objectives of the present study are to determine the genetic mechanism of low-temperature-sensitive pollen sterility in the booting stage in intersubspecific rice hybrids .In the present study, pollen fertility of intersubspecies hybrids in different temperature were detected. Mapping quantitative trait loci (QTLs) controlling low-temperature-sensitive pollen fertility in intersubspecies hybrids has been carried out in the "3037/02428" F2 populations using SSR markers. The possibility of using rice cold tolerance germplasm to improve the low-temperature-sensitive sterility of intersubspecies hybrids has studied .The results were as follows:1 , There existed positive correlation between pollen fertility and seed set on the analysis of the three-cross Fl segregating population, Akichikara//IR36/Dular.2, Eighteen rice cultivars and hybrids in different types (indica, japonica, javanica, indica hybrid, japonica hybrid and inter-subspecies hybrid ) were evaluated to determine the effect of temperature on pollen fertility in subspecies rice hybrids. The result showed that the pollen fertility of inter-subspecies hybrids was greatly reduced in booting stage in early October when the average daily temperature dropped to 22.0-23.0 C, and the extent of pollen fertility reduction varied greatly among them. However, the pollen fertility reduction of indica and japanica hybrids and conventional cultivars was not obviously observed in thesame temperature conditions. The cool conditions (the average daily temperature dropped to 19 C) was an obstacle to pollen developing of all tested rice cultivars and hybrids.3 Identification of QTL controlling pollen strility in intersubspecies hybrid rice using molecular markers.The linkage map of chromosome 1-12 were constructed using "3037/02428" Fa as a mapping population with 88 SSR markers, the distance between two marker is 18.02cM. Using this map, we identified QTL controlling low-temperature-sensitive pollen sterility of intersubspecies hybrids. In Fa population, 7 putative QTLs in chromosome 1 , 2, 4, 5, 6 , 9 were detected by interval mapping. Loci in chromosome 1(LOD=3.69) was between marker RM84 and RM283, loci in chromosome 2(LOD=2.39) was between RM1385 and RM240 , the first loci in chromosome 4(LOD=2.24) was between RM451 and RM348, the second loci in chromosome 4(LOD=2.04) was between RM348 and RM559, loci in chromosome 5(LOD=2.18) was between RM13 and RM507,loci in chromosome 6(LOD=3.64) was between RM527 and RM136, loci in chromosome 9(LOD=2.03) was between RM3533 and OSR28,the phenotypic variation explained by each QTL for pollen sterility is 10.3%,15.6%,8.7%,6.4%,11.9%, 15.3% and 5.9% respectively .. 4. The very strong cold tolerance rice resources from Yunnan Province has been used to verify whether the cold tolerance germplasm can improve the low-temperature-sensitive strerility of intersubspecies hybrid rice, the results showed that the germplasm confering the cold tolerance genes at both seeding and reproductive stage can not improve the the low-temperature-sensitivity of the Fl.So further study need to be done to determine the genetic mechanism of cold tolerance to facilitate the util...
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