Regeneration of plantlets from mature embryo calli of Western Ghats land race cultivar of rice, Oryza sativa L.

The Malnad region located in the Western Ghats of Karnataka is known for the cultivation of indigenous rain fed land race cultivar of rice. The present study was to investigate the callogenic and caulogenic potentialities of the two indigenous rice cultivar namely Karimundaga and Kanadatumba using dehusked mature embryo explants. For callus and shoot bud differentiation, the explants were cultured on Murashige and Skoog (MS) medium supplemented with 2,4-D (1–3 mg/L), IAA (1–2 mg/L), Kn (1–4 mg/L) and BAP (1–4 mg/L). The morphogenic potentialities of the two rice cultivar differed in texture of callus. In both the cultivar callogenic frequency was optimized at 1 mg/L 2,4-D concentration, it was 94% in Karimundaga and 58% in Kanadatumba. Supplementation of IAA either alone (1–2 mg/L) or in combination with Kn or BAP at 1 to 4 mg/L concentration of each induces shoot bud differentiation from the calli. In the cultivar Karimundaga caulogenic frequency was highest (10.60±2.55) at 1.0 mg/L IAA and 4.0 mg/L BAP concentration. While in the cultivar Kanadatumba highest number of shoot buds (7.90±2.69) was differentiated at 1.0 mg/L IAA and 4.0 mg/L Kn concentration. The calli derived regenerants were successfully acclimatized in the greenhouse and agro-morphological variations were evaluated. The growth characteristics and yield related parameters exhibited by in vitro plants were lower than the in vivo plants.

Candidate genes for drought tolerance and improved productivity in rice (Oryza sativa L.).

Candidate genes are sequenced genes of known biological action involved in the development or physiology of a trait. Twenty-one putative candidate genes were designed after an exhaustive search in the public databases along with an elaborate literature survey for candidate gene products and/or regulatory sequences associated with enhanced drought resistance. The downloaded sequences were then used to design primers considering the flanking sequences as well. Polymerase chain reaction (PCR) performed on 10 diverse cultivars that involved Japonica, Indica and local accessions, revealed 12 polymorphic candidate genes. Seven polymorphic candidate genes were then utilized to genotype 148 individuals of CT9993 x IR62266 doubled haploid (DH) mapping population. The segregation data were tested for deviation from the expected Mendelian ratio (1:1) using a Chi-square test (less than 1%). Based on this, four candidate genes were assessed to be significant and the remaining three, as non-significant. All the significant candidate genes were biased towards CT9993, the female parent in the DH mapping population. Single-marker analysis strongly associated (less than 1%) them to different traits under both well-watered and low-moisture stress conditions. Two candidate genes, EXP15 and EXP13, were found to be associated with root number and silicon content in the stem respectively, under both well-watered and low-moisture stress conditions.