INHERITANCE OF EARLY MATURITY AND NONSENESCENCE IN SOME LOCAL AND EXOTIC CULTIVARS OF SORGHUM (SORGHUM BICOLOR L) MOENCH IN POTHWAR TRACT OF PAKISTAN

Abstract

A study on inheritance of early maturity and nonsenescence in sorghum (Sorghum bicolor L) Moench was conducted to determine the mode of inheritance for efficient and effective selection of the desired traits. The study was carried out in two parts: 1) Generation means analysis for early maturity and nonsenecence traits in sorghum and 2) Combining ability estimates for early maturity and nonsenecence traits in sorghum. In the first study two high yielding ICRISAT type cultivars viz: ICSV 107 and ICSV 219 were crossed with an early maturing local type Pot.3 -9. A field trial with eight generations namely P1, P2, F1, F2, BC1, BC2, BC1 (S) and BC2 (S) for each cross was conducted at two locations i. e. National Agricultural Research Centre (NARC) Islamabad and Maize & Millet Research Institute (MMRI) Yousafwala during kharif season 1992. Analysis of generation means indicated that addi ti ve genetic effects were important for yield per plant, head length, seeds per head, 1000-grain weight, threshing percentage, maturity index, leaves per plant, leaf area of upper six leaves (LAUSL), percent green leaves area per plant fifty days after flowering (%GLA SODAF) and sugar percentage, in both the crosses. Dominance effects were also important for yield per plant, 1000-grain weight, maturity index and %GLA SODAF in cross 1 and yield per plant, maturity index, leaves per plant, LAUSL, %GLA SODAF and sugar percentage in cross 2 which indicated that cross 2 (ICSV 219 X Pot.3-9) was more nonsenescent (stay-green ) . Epistasis was not important for the desired traits in either population. Significant additive effects suggest that effective selection for early maturity, head length, seeds per head, 1000-grain weight and yield, is possible in cross 1 and selection for leaves per plant, LAUSL, %GLA SODAF and sugar percentage is possible in cross 2. Selection fOr early maturity would be more effective in later generations. In cross 2, selection for yield could also be practised in early generations. Narrowsense heritability estimates from variance components ranged from low to high in both populations. Low heritability for yield suggested that selection in cross 1 should be practised in later generations. Low correlation between yield and early maturity in both crosses indicated that selection for early and favourable recombinants could be possible from these crosses. Estimates of general and specific combining ability effects as well as the variances for yield, and stay-green associated components were obtained for a set of 12 straight crosses made in a factorial mating design among seven pure lines of sorghum. The parental material consisted of three pure lines from ICRISAT, viz: ICSV 107, ICSV 112, ICSV 219 and four early local type lines viz: Pot.3-9, Red Janpur, Bagdar and DS-7S . All these lines had been maintained for more than six years. The FI and F2 generations were evaluated in the field to determine the combining ability of the parents for maturity and stay-green traits such as yield per plant, head length, seeds per head, 1000 -grain weight, threshing percentage, maturity index, plant height, leaves per plant, LAUSL, %GLA 50DAF and sugar percentage. The trials were conducted on Fl and F2 generations in randomized complete block design with three replications at the two locations during 1993 and 1994, respectively. General combining ability estimates were non - significant for all the traits except plant height in Fl. Specific combining ability estimates were significant for head length, seeds per head, 1 000 -grain weight, threshing percentage, plant height, LAUSL and %GLA 50DAF in F2 generation. The magnitude of GCA was much greater than SCA for majority of the traits in both Fl and F2 generations indicating that additive genetic variance was more important than nonaddi tive genetic variance. Among male parents, Bagdar gave highest GCA for yield per plant, head length and 1000 -grain weight, whereas Pot.3 - 9 gave highest GCA for maturity index and threshing percentage. Among the female parents, ICSV 107, as expected for being adapted to the Pothwar tract agro-climatic conditions, gave the best GCA . for yield per plant, head length, seeds per head, 1000-grain weight , threshing percentage and maturity index. ICSV 219 gave the highest GCA effects for LAUSL, %GLA 50DAF and sugar percentage among the female parents, indicating its superiority in stay-green character. There was a highly significant positive correlation of maturity with plant height and %GLA 50DAF and significantly negative correlation with yield per plant and head length. Selection for early maturity and high yield in Pothwar area should be practised among progeny of ICSV 107 X Pot . 3-9, while selection for the stay-green associated characters be practised in progeny of ICSV 219 X Pot.3-9. F3 progenies will be planted and evaluated at NARC to identify the best crosses under local agro - climatic