Response of anthers in in vitro culture was examined in the indica-japonica hybrids of rice (Oryza sativa L.). Significant genotypic differences were observed for callus induction and regeneration among the different interracial hybrids of indica-japonica races. Induction frequency of haploids ranged from 57.7 to 72.9 per cent and doubled haploid androgenic lines ranged from 27.1 to 42.3 per cent in the anther culture of the different hybrids. The indica-japonica hybrids recorded partial pollen grain and spikelet fertility in F1 (29.9 to 41.5% and 19.4 to 48.7% respectively) as well as in F2 (42.7 to 50.6% and 37.1 to 54.4% respectively). In contrast, the androgenic doubled haploid lines recorded significant increase and the pollen grain and spikelet fertility was 76.3 and 78.6 per cent respectively. The results suggested that the sterility barriers for realising genetic recombinants and fixation of fertile homozygous lines in indica-japonica hybridization programme could be overcome through F1 anther culture technique.
Three parents with three different durations were crossed in full diallel fashion. The resultant six hybrids were selfed along with their three parents to get six F 2 's. The F 2 's were selfed to obtain six F 3 's. The aforementioned five generations of the six crosses were studied for days to flowering, number of productive tillers per plant, number of filled grains per panicle, 100 seed weight, grain L/B ratio, grain yield per plant and harvest index. The distribution pattern of the segregating generations revealed that, the F 3 's of the cross ADT 38 x ADT 37 for hundred seed weight and the F 3 's the cross ADT 38 x ADT 44 for grain yield per plant showed normal symmetrical distribution. The kurtosis value was almost negligible indicating mesocurtic nature of the distribution. The F 3 's of ADT 38 x ADT 44 recorded high mean coupled with higher coefficient of variation, indicating the presence of additive genetic control. The higher mean performance in F 3 may be due to accumulation of favourable genes. All the other crosses and generations showed asymmetric distribution in positive as well as negative direction, for almost all the characters of interest. The mean was comparatively higher but the coefficients of variation were comparatively lower, indicating the preponderance of non-additive genetic control in the expression of the traits of interest. It is better to resort to intermating of segregants followed by recurrent selection for further improvement. The F 3 's unique cross ADT 38 x ADT 44 had taken less number of days to first flowering, higher grain L/B ratio coupled with higher grain yield. A simple selection among the F 3 progenies of the cross ADT 38 x ADT 44 may yield some useful segregants with earliness, desirable grain quality and higher grain yield.
Relationship between carliness and other yield components were analyzed in 20 crosses involving four early and five very early lines in indica rice. Earliness (days to flowering) had significant and positive correlation with most of the characters studied. Positive significant association was observed among the yield components. Correlation studies revealed that selection for very early types obviously resulted in reductin in panicle length, number of grains and 100 grain weight which in turn reduced the yield.
P 2412, a medium duration, high yielding medium slender rice culture was released as PY 6 (Subramania Bharathi) in January, 2000 for general cultivation in Pondicherry and Karaikal regions of the Union Territory of Pondicherry. It matures in 135 to 140 days. It has recorded a mean yield of 5852 kg ha in station trails and 5570 kg ha' in the adaptive research trials/on farm trails. Its overall mean yield in 74 locations (1993 to 1999) was 5534 kg har with 4 (ADT 38) to 19 per cent (Co 43/ I White Ponni) increased yield over checks. It is medium to tall in stature with compact panicle and medium size white boy grain. This variety is moderately resistant to blast and gall midge. PY 6 can be sown in September and is the best alternative to I White Ponni
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