Pedigree breeding in early segregating generations of cowpea (Vigna unguiculata (L.) Walp)

Abstract

Pulses represent an essential component of agricultural food crops and considered as an important crop to meet food and nutritional security. They complement cereal crops in terms of dietary requirement as a source of protein and minerals. In several countries of the tropics and sub-tropics, cowpea serves as an important food legume. It plays an essential role in enrichment of daily diet, mainly as a grain and green pods. In general, cowpea seeds contain 23.4 per cent protein, 60.3 per cent carbohydrates and 1.8 per cent fat. It also provides considerable amount of vitamins and phosphorus. The protein availability in cowpea seeds and green pods is almost double/ triple the amount of available cereal protein. The average grain yield of cowpea is still low and no single variety is adaptable for all growing conditions. Exploiting genetic variability is an essential method, to overcome the complex nature of cowpea breeding and to identify an elite high yielding genotype. Selection of best lines with high yield and other associated characters, in segregating generations paves a way to develop new varieties. The present study aimed to evaluate the F2 and F3 generations for high yield and protein content in two crosses (H 10 and H 11), involving Anaswara, PKB 3 and PKB 4 as parents. In general, the F2 families of both the crosses showed high mean performance and variance over the parents. Grain yield showed very low phenotypic coefficient variation (PCV) and genotypic coefficient variation (GCV). All other characters showed a moderate PCV and GCV values in segregating generation expect for days to first flowering, days to first harvest and days to last harvest. Most of the characters showed high heritability (h2) in F2 generation. In F2, the lowest value for h2 was observed for single pod weight in H 10 family and for grain yield in H 11 family. Similarly, High genetic advance over mean (GAM) was exhibited by 100-seed weight in H 10 family and number of pods per plant in H 11 family. Selection based on characters with high h2 and high GAM will be highly effective.

In F2 generation of H 10 family, single pod weight showed significant and positive correlation with hundred seed weight and grain yield per plant. Days to first harvest and days to last harvest had a significant negative correlation with grain yield per plant. Days to first flowering, days to last harvest and single pod weight had significant negative correlation with protein content. In F2 generation of H 11 family, days to last harvest and number of pods per plant showed significant and positive correlation with grain yield per plant. Number of pods per plant showed a significant positive correlation with protein content. Days to first harvest showed significant negative correlation with grain yield per plant and days to first flowering with protein content. On path analysis, plant height, days to first harvest, pod length and hundred seed weight showed a positive direct effect on grain yield. Negative direct effect was exerted by protein content towards grain yield. A selection criteria was fixed based on number of pods per plant, grain yield per plant and protein content for selecting best lines to be forwarded to F3 generations. Eight lines from F2’s of H 10 family and fifteen lines from F2’s of H 11 family were identified to be the best and forwarded to next generation. F3 family of both H 10 and H 11 followed a general trend for mean, variance, GCV, PCV, h2 and GAM. Mean and variance were high for most of the characters and GCV and PCV values were moderate except for days to first flowering, days to first harvest, days to last harvest, 100-seed weight and grain yield, where it was low. F3 families showed high heritability and moderate GAM, for most of the characters. In F3 generation of cross H 10, days to last harvest had significant positive correlation with grain yield per plant. There was no significant positive correlation with the characters towards grain yield, in the F3 generation of cross H 11. Significant and negative correlation, showed by days to first harvest with grain yield per plant and days to first flowering with protein content in family H 10. Whereas, in family H 11 hundred seed weight showed significant negative correlation with protein content. On path analysis, days to first flowering showed very high positive direct effect followed by single pod weight, plant height and 111 number of pods per plant. Very high negative direct effect showed by days to first harvest through days to first flowering towards grain yield. Nine lines each from F3’s of H 10 and H 11 with high yield and protein content was selected and shall be forwarded for next generation evaluation