Primary Mapping Of QTLs For Heading Date And Plant Height, And Fine-mapping Of QPH6.2in Indica Rice

Plant height is one of the most important traits related to yield potential of rice. Heading date is a major determinant of the regional and seasonal adaption of rice varieties. Thus, understanding the genetic bases underlying the inheritance of the two traits and their relationship with the genetic control of yield traits has significant implications for rice improvement.Two recombinant inbred line populations of indica rice were constructed using restorer line Milyang46as the common male parent and maintainer lines Xieqingzao B and Zhenshan97B as the female parents, respectively. The two populations were planted in a trial site in multiple years for the detection of QTLs for heading date and plant height. In comparison with QTLs for yield traits previously detected in the two populations, the effects of those QTL on yield trait were investigated. Four BC2F6populations and four BC2F7populations were constructed using Zhenshan97B as recurrent parent. They were used to fine map qPH6.2, a QTL for plant height locating on the short arm of chromosome6detected in Zhenshan97B/Milyang46RIL. The pleiotropic effect of qPH6.2on heading date was also analyzed using these populations. Four NIL sets were developed from four BC2F7populations to validate the effects of qPH6.2on plant height and heading date and to investigate the effect on yield traits. The main results are summarized as follows:A total of12QTLs for heading date and11QTLs for plant height were detected in the two RILs populations, among which only two QTLs for heading date locating on the short arm of chromosome6and pericentromeric region of chromosome7were found in both populations. It was indicated that in related to the common parent Milyang46, the maintainer lines Xieqingzao B for dwarf-abortive cytoplasmic male sterility and Zhenshan97B for wild-abortive cytoplasmic male sterility differ greatly on the genetic control of heading date and plant height, especially on plant height. In comparison with QTLs for yield traits previously detected in the two populations, six QTL regions showing pleiotropic effects were found. Included are one controlling heading date, plant height and yield traits, three controlling heading date and yield traits, and two controlling plant height and yield traits. qPH6.2was delimited to a103.4kb region flanked by Si9291and Si9396using four BC2F6populations and four BC2F7populations. The pleiotropic effects of qPH6.2on heading date and yield traits were also detected in all advanced backcross inbre population and/or NILs showing allelic variation at qPH6.2, the enhancing alleles are always derived from the donor parent Milyang46. The allele from Milyang46increased plant height by3.55-8.17cm, delayed heading by3.99-6.14d, produced10.82-11.54more number of spikelets per panicle and6.82-8.16more number of grains per panicle, improved grain yield per plant by2.16-2.51g.The103.4kb region including qPH6.2covered the gene Hdl controlling heading date in rice, which suggested that qPH6.2and Hdl are same gene. It was indicated that Hdl has pleiotropic effects on heading date, plant height and yield traits. Pervious studies show that Milyang46carried photoperiod insensitive allele Se-1e at Hdl locus which confers a long basic vegetative growth. On the basic of the results, Se-1e not only delays heading, but increases plant height and grain yield as well, it will be quite useful in rice breeding to develop suitable cultivars in the low latitudes where short photoperiods persist throughout the year.