| The two indica heavy-panicle type rice erect panicle mutants R1338 and R334 of genetic stability, which were generated from indica heavy-panicle type restorer Shuhui 498 by EMS mutagenesis, were used to research systematically phenotype of erect panicle mutants, anatomical structure and population physiological property and to do genetic analysis to erect panicle gene and clone candidate gene. The incomplete diallel cross was used to research application prospect of erect panicle mutants R1338 and R334 in breeding. The detailed results were showed as follows:1. The erect panicle mutants R1338 and R334 were extremely significantly smaller than wild type in plant height, panicle length, grain length and grain thickness, and were extremely significantly greater than wild type in grain width and grain density. There was no difference between mutants and wild type in other agronomic traits, such as 1000-grain weight, number of grain per panicle and panicle weight per panicle.The panicle curves of R1338 and R334 were about 8.48°nd 22° respectively and R1338 and R334 belonged to typical erect panicle type materials.2. The erect panicle mutants R1338 and R334 were significantly higher than Shuhui498 in stem diameter, wall area, cross sectional area, pith area, content ofCellulose and lignin. The shorter internodes in erect panicle mutants R1338 and R334 significantly increased lodging resistance. The primary reasons for erect panicle were that length of the number of primary branches got shorter and the primary branches density increased.3.Leaf length was short and angle of flag leaf was small in erect panicle mutants R1338 and R334. Chlorophyll content of R1338 and R334, including chla, chlb and car, was significantly higher than wild type, which could put off premature senescence. The decline rate of light intensity below canopy in erect panicle population was less than curve panicle population. Photosynthetic efficiency in erect panicle population was higher.4. Genetic analysis indicated that phenotype of erect panicle was both controlled by apair of semi dominant nuclear genes. Resequencing of near-isogenic pool and co-segregation analysis showed that erect panicle character of R1338 was caused by DEP2/EP2 equilocal mutation, but the mutational pattern in R1338 wasn’t same with frameshift mutation in DEP2/EP2. A single A to G nucleotide mutation in the seventh exon in DEP2 led to the 928th arginine (AGG) to glycine (GGG) amino acid substitution, which resulted in erect panicle in mutant R1338, which indicated mutation site might was important protain domain. LOC_Os09g07220 mutation on on chromosome 9 resulted in erect panicle character of R334. LOC_Os09g07220 contained two exons and its length was 1725bp. A single C to T nucleotide mutation in the first exon led to the 56th alkaline arginine to neuter cysteine amino acid substitution. LOC_Os09g07220 might be a new erect panicle gene, named DEP4.5. Yield and related properties analysis of incomplete diallel cross combination between sterile lines of curve panicle, erect panicle containing DEP1 and R498, erect panicle mutants indicated that although erect sterile lines or erect restorers were controlled by different erect genes, the hybrid F1 between erect sterile lines or erect restorers and curve parents showed semi-erect. And the hybrid F1 between erect panicle and erect parents showed erect. In the similar genetic background, the yield of semi-erect panicle hybrid rice combinations was same with or even higher than curve panicle combinations and the yield of erect panicle hybrid rice combinations was lower. Analysis of different character, such as yield components, culms and leaves in hybrid rice combinations of curve panicle, semi-erect panicle and erect panicle which had same or similar genetic background, showed that semi-erect panicle combinations were between curve panicle and erect panicle and its plant height and panicle length decreased. The superior culm characters in semi-erect panicle combination improved population transmission of light and photosynthetic efficiency, but had no effect on other yield traits. Therefore, contraposing the ecological conditions of few sunshine, high humidity, small temperature difference in southwest china, select breeding of indica semi-erect heavy-panicle type hybrid rice varieties and increasing density properly may be optimum selection to improve rice yields in southwest china. |
