ABSTRACT
The present investigation was focussed on regeneration, evaluation and screening of somaclones for yellow leaf disease(YLD) resistance using in vitro mutagenesis from a popular susceptible sugarcane variety Co86032 using four chemicalmutagens at three levels of concentration (sodium azide (SA) at 0.5 mg L-1, 1.0 mg L-1, 1.5 mg L-1; sodium nitrite (SN)at 3 mg L-1, 5 mg L-1, 7 mg L-1; ethyl methane sulphonate (EMS) at 0.6 lM L-1, 0.8 lM L-1, 1.0 lM L-1 and 2,4 D at 4mg L-1, 5 mg L-1, 6 mg L-1). A total of 1138 tissue culture seedlings obtained were evaluated for virus resistance both innatural field conditions and in controlled greenhouse condition after aphid vector transmission and presence or absence ofvirus was observed by visual screening and reverse transcription-polymerase chain reaction method. Four out of 207asymptomatic plants (16T22, 16T23, 16T29 and 16T31) were devoid of virus coat protein band and were considered to beYLD resistant. The obtained resistance somaclones showed inferior yield traits so they have to be exploited as parents inhybridization programmes with commercial varieties to impart YLD resistance ultimately yielding agronomically superiorYLD-resistant varieties in sugarcane.
ABSTRACT
The combining abilities for physiological traits in peanut were examined to understand the type of gene action governing these traits, and to identify peanut genotypes suitable for use as parents in breeding for improvement in physiological traits. Substantial genetic variability was observed among the hybrids for the traits studied. The genotypes, TPT-4 and ICGV-91114 were found to be good combiners for developing early flowering types, while ICGV-91114, TCGS- 584, TPT-4 and JL-220 were good combiners for developing early maturing. For SPAD chlorophyll meter reading was K-1375 was best general combiner. Among the parents K-1375, TIR-25 and TCGS-647 were found to be superior as evident from its highest significant positive general combining ability effects for specific leaf area. The best good combiner for transpiration rate was ICGV-91114 and for photosynthetic rate was TIR-25. For water use efficiency only the genotype, TPT-4 was the best combiner. Best performing parents for harvest index were JL-220 and TPT-4. The hybrid, TPT-4 x TIR-25 was the specific hybrid for high water use efficiency. For SPAD chlorophyll meter reading only one cross, K-1375 x TCGS647 was considered to be the good performing hybrid. Two hybrids viz., TIR-25 x TCGS- 647 and ICGV-91114 x JL-220 were found to be good specific combiners for harvest index. A perusal of results of combining ability analysis indicated considerable non-additive gene action in the inheritance of majority of the attributes studied. The non-fixable dominance deviation and epistatic effects are likely to hinder improvement through simple pedigree selection, which is commonly followed in groundnut. Alternatively intermating of the F2 segregants followed by recurrent selection and pedigree breeding can harness the different kinds of gene - effects. Repeated selection and inter-mating of segregating materials for two or three cycles, makes it possible to achieve simultaneously improvement in physiological attributes.
ABSTRACT
Twenty eight F2 populations were evaluated for genetic parameters of 23 characters of morphological, physiological, yield and yield attributes during rabi 2009. TPT-4 x ICGV-91114 was distinct for its lowest mean value for days to maturity and highest mean values for number of well-filled and mature pods per plant, shelling per cent, 100- kernel weight. The F2 involving JL-220 as one of the parents viz., JL-220 x ICGV-99029 for SCMR, JL-220 x TCGS- 647 for SMK per cent, protein per cent, kernel yield per plant and pod yield per plant showed the highest per se performance High genotypic coefficient of variation was observed for number of secondary branches per plant. High heritability and high GAM was recorded for number of secondary branches per plant, high heritability and moderate GAM observed for days to 50% flowering. Moderate heritability and high GAM was showed for leaf area index, number of wellfilled and mature pods per plant, dry haulms yield per plant and harvest index. This indicates that these characters are under additive genetic control and selection for genetic improvement will be worthwhile and may rapidly contribute yield.