Studies On The Morphological,Physiological And Genetic Characteristics Of M893, A Rice (Oryza Sativa L.) Mutant With Sheathed Panicle

A rice mutant with sheathed panicle from a restorer line T893 was obtained in tissue culture induction. The mutant, named as M893, kept sheathed panicle characteristics for four generations at two locations in two years, indicating that the character was genetically stable. In this paper, the morphological, physiological and genetic studies were carried out on the character, respectively. And the results are as follows:1. The main morphological, characteristics of M893 were:fully sheathed panicle, dwarf, small panicles, shortened upper 3 leaves. Compared with T893 (Check), the internode number of main stem of M893, which was almost 5, wasn't significantly different. But the length of all the 5 internodes from top first to top fifth, was shortened by 88.40%,83.92%,65.55%,45.04%and 32.79%at extremely significance, respectively. And the shortened length and proportion of top-first internode was the most.2. It showed that, compared with T893, the length of cell in intercalary meristem in top-first culm of M893 wasn't significantly different under microscope. And the cells in intercalary meristem arranged in line, similar to that of T893. However, the longitudinal length of parenchyma cell in top-first internode of M893 was extremely significantly different from that of T893. And the average length of 10 cells of M893 was 205.90μm, but that of T893 was 309.37μm. The result suggested that the cells in top-first internode of M893, which were originated from intercalary meristem by differentiation, didn't extend. Accordingly, the top-first internode didn't elongate effectively. 3. At stageⅣ,ⅥandⅧof panicle differentiation, the contents of hormones in top-first internode and flag leaf of main stem, including GA4,IAA,ABA and Z, were determined, respectively. The result showed that, compared with the check, the content of GA4 and IAA in culm of M893 decreased significantly or extremely significantly, respectively. And the content of ABA decreased significantly at stageⅣand VI of panicle differentiation, but increased extremely significantly atⅦof panicle differentiation. The content of Z wasn't significantly different between M893 and T893. The results of analysis on the content of GA4,ABA and Z in flag leaf were similar to that in the culm.4. At the end of stageⅦof panicle differentiation, a population of M893 had been treated by gibbrellic acid(GA3) solution with different concentrations by 80mg/L,120mg/L,160mg/L and 200mg/L, respectively. The length of internode from top first to top third wasn't significantly different compared with T893, and the internode didn't elongate significantly. It showed that M893 was insensitive to gibberillic acid (GA3) induction.5. The trait of sheathed panicle was stable genetically during four-generation cultivation in Changsha and Hainan. All 6 populations of F1, originated from the crossing between the mutant and Bing5060,Bing4170,Minghui81,T893(wild type),Lunhui422 respectively, headed normally, and it indicated that the trait was genetically recessive. The segregation ratio of 8 populations, including 6 populations of F2 and 2 populations of F3,F4 from the crossing between M893 and Bing5060, fitted the expected ratio of 3:1, which suggested that the trait of sheathed panicle was controlled by a pair of recessive genes. And the mutant gene was named as Shpx.6.The mutant gene shpx was mapped on the rice chromosome 2 by SSR markers. And it located among RM12680,RM6247 and RM12685. The genetic distances from the target gene to the markers RM12680,RM6247,RM12685 were 0.2cM,0cM and 1.2cM, respectively. The co-segregation between the marker RM6247 and the gene shpx indicated that RM6247 was linked tightly with shpx.7. The technology of cDNA chip was used to analyze gene expression difference between M893 and T893. Four candidate genes, including AK063150.1,9630.m04842,AF056027.1 (REH1) and AK070347.1, were selected preliminary, and it suggested that they are related to the mutant probably. Further analysis showed that AK063150.1,9630.m04842,AF056027.1 (REH1), which were classified as the regulatory gene of auxin, expressed very lower in M893, and AK063150.1 was the one expressed lowest. AK070347.1, classified as up-regulated gene, had a function on inhibitting to elongate, which was similar to ABA.