1 State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, China; 2 Institute of Lianyungang Agricultural Science of Xuhuai Area, Lianyungang 222006, China; 3 Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China; # These authors contributed equally to this paper; *Corresponding author, E-mail: email@example.com
Heading dates of 26 japonica rice cultivars native to Southwest China were investigated, and their basic vegetative growth(BVG), photoperiodsensitivities(PS) and temperaturesensitivities(TS) were analyzed under artificially shortday and natural longday conditions in Nanjing of Jiangsu Province, China, as well as artificially high temperature and natural low temperature conditions in winter in Hainan Province, China. The results showed that the PS and TS varied with different cultivars. The BVGs of all the japonica cultivars were well situated, but differed in cultivars. Regression analysis showed a significant correlation between heading date and PS, indicating that PS was the main factor affecting heading date of japonica cultivar in Southwest China. Genetic analyses were conducted on these 26 cultivars using a set of heading date near isogenic lines as tester lines. The results showed that all these japonica cultivars carried the dominant earlyheading gene Ef1 or Ef1t, and most of these cultivars carried the dominant photoperiod sensitivity allele E1 or E1t, the PS of which was slightly weaker than E1. For the Se1 locus, these japonica cultivars mainly carried recessive photoperiod insensitivity gene Se1e. In addition, the recessive allele hd2 could repress or weaken the PS of 22 japonica cultivars by inhibiting the expression of E1 and Se1. These results indicate that the heading date genotypes determined different PS and well situated BVG in japonica rice cultivars of Southwest China. The above results would be useful for breeding and expanding new japonica cultivars with well adaptability in Southwest China.
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