Evaluation of Early Generation Testing in Chickpea¹)

Abstract

Inter-generation correlations between F2-F3, F2-F4 and F3-F4 in six crosses of chickpea were calculated by using individual plant/progeny means. In general, correlation values in case of plant height, seeds per pod and 100-seed weight were higher between F3 and F4 than those between F2 and F3 and F2 and F4, However, inter-generation correlations were mostly nonsignificant in case of pods per plant and grain yield. These results clearly show that selection in F3 can be fruitful for seeds per pod and 100-seed weight. However, selection for pods per plant and grain yield in early generations may not show any relationship with later generation performance for these traits.To achieve maximum efficiency and progress in breeding for any character, effective selection carried out in early generations would be advantageous. SHEBESKI (1967) suggested yield testing in early generations when most of the variability is present, assuming that there is a positive relationship of the yield of the genotypes in the early generations with the yielding ability of the later generation derivatives of such genotypes. MAHMUD and KRAMER (1951) observed in soybean that F3 lines provided good estimates of the average yield potentials of F4 segregates if genotype-environment interaction can be kept under control.Results using the yields of F2 derived lines to predict the lines of later generations have been inconsistent (FREY 1954, MCKENZIE and LAMBERT 1961, BRIGGS and SHEBESKI 1971and KNOTT and KUMAR 1975 and often poor correlations were obtained. In some of these experiments, the generations were grown in different years, so the interaction between geriotype and environment could have affected the correlations. Often heterozygosity and variability within an F2 derived line is the cause of poor relationship between it and the ') Part of Ph, D, thesis submitted by the senior author to IARI,

Response to selection for grain yield and correlated response for grain size and earliness in cowpea based on early generation testing

“…In other studies where decisions on the effectiveness of early generation selection were based on parentoffspring correlations, significant correlations have been observed for only the most heritable traits including 100 seed weight and days to flowering (Rahman & Bahl, 1986;Thurling & Ratinam, 1989). In other studies where decisions on the effectiveness of early generation selection were based on parentoffspring correlations, significant correlations have been observed for only the most heritable traits including 100 seed weight and days to flowering (Rahman & Bahl, 1986;Thurling & Ratinam, 1989).…”

“…Heritability estimates determined by parent-offspring correlations were generally low and could arise from gene segregation and/or genotype  environment interaction because generations were evaluated in different years. In other studies where decisions on the effectiveness of early generation selection were based on parentoffspring correlations, significant correlations have been observed for only the most heritable traits including 100 seed weight and days to flowering (Rahman & Bahl, 1986;Thurling & Ratinam, 1989). Changes in the relative magnitude of the population mean to that of the mean of the parent for grain yield and number of pods/plant across generations suggest that at least for these two traits, gene segregation may be an important cause of the low heritability estimates.…”

“…Theory (Cockerham, 1963) suggests that the expected genetic correlation (r g ) between line performance at an early generation and its descendant line at homozygosity is r g = 0.667-0.707 for F 2 -derived lines and r g = 0.840-0.866 for F 3 -derived lines, depending on the role of dominance (Bernardo, 2003). Martin & Geraldi, 2002) and ineffective in some situations (Rahman & Bahl, 1986;Quail et al, 1989;Borghi et al, 1998). In practice, early generation selection has been found to be effective in some situations (N'tare et al, 1984;Hegstad et al, 1999;St.…”

“…In practice, early generation selection has been found to be effective in some situations (N'tare et al, 1984;Hegstad et al, 1999;St. Martin & Geraldi, 2002) and ineffective in some situations (Rahman & Bahl, 1986;Quail et al, 1989;Borghi et al, 1998). Padi (2007a) observed that early generation selection for grain yield in a large cowpea population under additive series intercropping with sorghum was effective at 40% selection intensity.…”

Effectiveness of selection, parent-offspring correlation and regression in bacterial blight resistance genes introgressed rice segregating population

“…Selection pressure in rice based on grain yield, total tillers and grain per panicle could be advantageous (TALWAR, 1976). Effectiveness of early generation selection could be reduced by genotype and environment interaction (WHAN et al, 1981;RAHMAN & BAHL, 1986). Direct selection may not be effective in segregating population for improvement of grain yield (BARTLEY & WEBER, 1952;JOHNSON et al, 1955).…”