建立水稻種原(Oryza sativa L.)耐旱性之幼苗篩選方法

Abstract

Lack of accurate screening techniques limits the development of tolerant cultivars to drought, which is the most important constraint in rice productivity. A series of experiments were conducted in three stages to evaluate drought tolerance response of indica type rice genotypes at seedling stage: 1) identification of the drought-tolerance potential through observation of root proliferation at different soil depths; 2) selection of soil:sand mixtures and evaluation of drought tolerance responses of rice seedling in nursery trays, as well as in vitro test using PEG-6000 in MS medium; 3) evaluation of drought-tolerance physiological responses at seedling stage in vitro of four previously selected genotypes. Significant genetic variations among genotypes were found in number of root at depths from 0-5 cm, passing 5 and 10 cm, and in accumulated number of root counted from 0-40 cm. According to the root proliferation under drought stress, the genotypes TCS17, TCS10 and TN1 were identified as drought tolerant; genotypes CSY112, and CSY951042 were identified as susceptible. In the in vivo screening of rice seedling, a rapid screening process through soil:sand mixture for rice seedling was established. Leaf drying score was confirmed as a reliable criterion to evaluate water status of rice genotypes seedling under drought stress. The addition of 5 g l-1 of PEG-6000 was found to reduce seedling survival rate (6.67%, 30% and 36.67% for TCS17, CSY112 and TNGS14, respectively), fresh weight and dry weight in vitro, but the increase of dry matter was not significant. For seedling evaluations, genotypes KHS7 and TCS17 showed the best drought tolerance; TS2, TNGS14, and CSY112 were susceptible. The PEG drought-stressed treatment causes reduction in relative growth rate (RGR) and increase proline (Pro) content. Tolerant genotypes showed lower RGR reduction than susceptible genotypes; no differences among genotypes were found in Pro accumulation. The total amount of proteins increased under stress in susceptible genotypes, while decreased in tolerant genotypes. A rapid, simple, and feasible screening system, which combines the use of nursery trays and polyethylene glycol (PEG) tissue culture test, was developed to select drought tolerant rice genotypes at seedling stage under controlled conditions.