STUDIES ON GENETIC VARIATIONS IN A SORGHUM VARIETY (Sorghum bicolor (L.). Moench) IRRADIATED WITH COBALT 60 (CO60)

STUDIES ON GENETIC VARIATIONS IN A SORGHUM VARIETY (Sorghum bicolor (L.). Moench) IRRADIATED WITH COBALT 60 (CO60)

Abstract:

Genetic variability was created in a common sorghum variety SK5912 (SAMSORG 17) using gamma-ray irradiation from Cobolt 60 (Co60) source. The M0 seeds were grown in the off-season of 1985/86. This was bulk harvested and planted as M, bulk in 1986. In 1986, 90 M2 single seed selections were made from single plants selected based on height, yield and disease resistance. These were advanced to M3 in 1987, out of which 34 M4 family selections were obtained for evaluation. The 34 M4 family selections were harvested and threshed. The seeds from each family were divided into three equal portions for evaluation. The 34 M4 plant types were evaluated in a randomized complete block design (RCBD) for three years (1989, 1990 and 1991) in the Institute for Agricultural Research (I.A.R) farms. Data were collected on 22 characters, (i) eight (8) panicle characters, (ii) eight (8) leaf characters, and (iii) six (6) stem (culm) characters. Coefficients of variability (C.V%) were high for panicle characters, than for leaf and stem characters. They ranged from 1.65% for days to 50% flowering to 4.15% for grain weight per spikelet. Heritability estimates were high for most panicle characters (>45%) while they were moderate for both the leaf and stem characters (<40%). There were highly significant mean squares for all characters except for grain weight per spikelet in the combined analysis. There were high and significant correlations (r= >0.5) between the lengths of first and second leaf sheaths (r=0.689) and also the lengths of internodes (r=0.652, 0.628 and 0.634). Highly significant but negative correlation was found between length of first leaf shealth and width of spikelet (r = -0.840) in 1991. Variance components from the combine analyses showed that genotypic variancve was high for all characters except for percentage protein and weight of spikelet. All other characters had lower genotypic variances than their respective phenotypic and error variances. Principal components extracted from the combine correlation matrix showed high variability in leaf and stem characters than in the panicle characters. Internode lenth and leaf sheaths length load significantly on the first factor in the individual years as well as in the combined. Ploting the first two factors of all the years (Fl and F2) in a common scale showed that internode length and leaf sheath length were clustered together in one quadrant; grain weight per panicle, grain weight per spikelet, days to 50% flowering and width of spikelet where also clustered together which is indicating the close relationship between these characters. The negative correlation between the leaf and stem characters with days to 50% flowering and some panicle characters might be suggesting that selection for shorter plants which have erect leaf could result in increase in yield and early maturing plant. However, there were low correlations between internodes length, length of leaf blade and length of leaf sheath which were highly variable with most panicle characters (yield components). It might be more effective to select directly for grain weight per panicle, length of panicle, spikelet number per panicle and grain weight per spikelet together with these photosynthetic structures for better improvement in yield in our ‘plant types

STUDIES ON GENETIC VARIATIONS IN A SORGHUM VARIETY (Sorghum bicolor (L.). Moench) IRRADIATED WITH COBALT 60 (CO60)