Combining ability for some important physiological parameters in sesame were examined to understand the nature of gene action and to identify parents for breeding programme. Seven diverse genotypes of sesame, their 21 F 1 s and 21 F 2 s were grown in summer, 2003, in a randomized complete block design with three replications. Data were collected on leaf area index (LAI) at 30, 45, 60 and 75 days after sowing (DAS), crop growth rate (CGR) estimated between 30-45 DAS, 45-60 DAS and 60-75 DAS, days to peak flowering (DPF)

No abstract

The present work was conducted to study the genotypic variability of rice genotypes at the germination and seedling stages at different levels of salinity (0 M, 0.15 M, 0.2 M and 0.25 M NaCl). The results showed that increasing salinity decreased germination and seedling growth. Significant genotypic variability exists in the germination and seedling stages in response to different NaCl concentrations. Most of the genotypes showed more than 90% germination in the control, indicating good seed vigour. Two genotypes, VBR 638 (93%) and VBR 644 (84%), were selected as being tolerant to salinity at 0.2 M NaCl at the germination stage. Therefore, these could be used as source materials for genetic improvement for salinity tolerance at the germination stage. A considerable amount of genotypic variability was also found under control and saline conditions at the seedling stage with respect to the variables shoot height, root length, shoot and root dry weight. The high heritability observed for these variables offers good scope for genetic improvement for salinity tolerance both at the germination and seedling stages. The genotypes VBR 616, VBR 628, VBR 645, VBR 640, VBR 611, VBR 620, VBR 612, VBR 618, VBR 644, VBR 629, VBR 625 and VBR 630 were selected as being tolerant to salinity at the seedling stage.

Seven parents (CST2002, MT34, OS-Sel-2, TKG22, AAUDT9304-14-4, B67 and Rama), their 21 F 1 s and 21 F 2 s were grown in summer 2003 in a randomized block design with three replications. Heterosis and inbreeding depression were studied for seven important yield-contributing characters (plant height, branch number plant −1 , capsules plant −1 , seeds capsule −1 , 1000-seed weight, stick yield plant −1 and seed yield plant −1 ). Maximum heterosis for seed yield plant −1 over the mid- and better-parent was recorded in CST2002×TKG22 (43.30%) and MT34×B67 (27.22%), respectively. Mid-parent heterosis for seed yield plant −1 was due to cumulative heterosis for various important component traits, such as capsules plant −1 , seeds capsule −1 and 1000-seed weight. Inbreeding depression was highest for seed yield, followed by 1000-seed weight, capsules plant −1 , branch number and plant height, indicating the predominance of non-additive genetic effects. B67×Rama exhibited significant positive heterosis in F 1 , but non-significant inbreeding depression in F 2 for seed yield. This cross can be utilized as basic material for identifying better pure lines. The clustering pattern indicated that in general genetically diverse parents exhibited more heterosis, as evident in the majority of the crosses.