Abstract:

Rice mesocotyl refers to the structure between radicel and coleoptile of seedlings. The mesocotyl length is related directly to the emerging ability of seedlings from soil in direct sowing rice. The rice direct sowing technique with simple and labor-saving characteristics has increasingly become attractive in recent years in China, but many breeders pay little attention to the rice mesocotyl character, one of the most important agricultural characters for rice direct sowing, in the current rice breeding programs, so there are little direct sowing rice cultivars with elongated mesocotyl in production. The emergence of seedlings is affected by the elongation of mesocotyl. In general, the length of mesocotyl is correlated to the depth of the seeds in soil, but it varies depend upon rice cultivars. Although some cultivars with long mesocotyl have been screened, the inheritance on the rice mesocotyl elongation is little known up to now. In the present study, the combinations between a long mesocotyl cultivar H10 and two short mesocotyl cultivars Xiushui 110 and Chunjiangxiangjing and their parents were used to study the inheritance on mesocotyl elongation of rice under the treatment of darkness during germination, and determine the internodeⅠ length, internodeⅡ length, internodeⅢ length, internodeⅣ length, internodeⅤ length, internodeⅥ length, panicle length, internode thickness, flag leaf length, flag leaf width, panicles per plant, grains per panicle, seed setting rate, 1000-grain weight and yield per plant of F₂ plants with long mesocotyl and with short mesocotyl so as to understand the relationship between mesocotyl elongation and the agronomic traits of rice. The results indicated that the mesocotyl elongation of rice was mainly controlled by two recessive genes. The internode length, panicle length, plant height and flag leaf length of F₂ plants with long mesocotyl were larger than those with short mesocotyl, but there were no obvious differences in internode thickness, flag leaf width, panicles per plant, grains per panicle, seed setting rate, 1000-grain weight and yield per plant. The improvement for the elongation character of rice mesocotyl and the utilization of long mesocotyl germplasm in direct sowing rice breeding were also discussed.

Key words: Rice, Mesocotyl, Elongation, Inheritance, Agronomic traits