Enhancement of Abiotic Stress Tolerance in Rice (Oryza sativa L.) through Androgenesis and Transgenic Approaches

Abstract

The work was mainly focused on in vitro somatic and gametic embryogenesis for crop improvement, application of various stress pre-treatments factors to enhance androgenetic responses and increasing chromosome doubling efficiency in rice. Anther and microspore derived embryoids were used for Agrobacterium-mediated transformation system. For somatic embryogenesis mature seeds of a total number of twenty indica rice genotypes were considered out of twenty three and cultured them in four different media (MS, N6, SK3 and B5). Out of four media, N6 along with 3.0 mg/l 2,4-D + BAP 1.5 mg/l + Kin 1.0 mg/l showed best callusing in BRRI dhan29. The variety BRRI dhan29 showed maximum rooting (64-90.67%) in RRM (rice rooting medium). For anther culture we evaluated twenty three rice cultivars with four induction media where almost genotypes showed more or less callusing in all media but the SK3 showed better than others. An experiment was conducted for suitable regeneration system and reducing albino plant production by early transferring methods. Results indicated that transfer of anthers with or without embryo like structure (ELS) from induction to regeneration medium posed a significant impact on improving regeneration potentiality and reducing albinisms. Another experiment was conducted to evaluate the effect of cold pre-treatment duration (4°C) to harvested spikes (1-15 days). It was observed that three days cold pre-treatment showed highest ELS, GPR (green plant regeneration) and reducing albinisms. Besides cold pre-treatment as physical stress pre-treatment factors drought was applied to excised anthers. Here three hours drought stress pre-treatment proved to be the more suitable for ELS and GRP. It may be concluded that application of drought stress pre-treatment for three hours to excised anthers prior to culture in liquid medium is very effective for embryoids induction as well as green plant regeneration. Combined effects with drought and heat stress pre-treatments were also found and interesting results obtained with 3h drought + 1h heat stress at 27°C anthers that enhanced embryo yield and GRP in rice.---