HETEROTIC STUDIES AND INBREEDING DEPRESSION IN F2 POPULATIONS OF UPLAND COTTON

Abstract

To study the genetic potential, heterotic effects and inbreeding depression, 8 × 8 F2 diallel populations with parental lines of upland cotton were grown during crop season 2010 in a randomized complete block design at Khyber Pakhtunkhwa Agricultural University Peshawar, Pakistan. Highly significant (p≤0.01) variations were noticed among parental lines and F2 populations for all the traits. According to genotypes mean performance for various traits, plant height varied from 101.60 to 126.30 cm and 98.60 to 140.60 cm, bolls plant-1 (12.87 to 19.53; 12.13 to 22.60), boll weight (3.80 to 5.01 g; 3.04 to 5.38 g) and seed cotton yield plant-1 varied from 55.74 to 85.47 g and 45.57 to 96.05 g in parental cultivars and their F2 populations, respectively. However, 12 and 7 F2 populations manifested significant heterosis over mid and better parents for plant height, 7 and 3 for bolls plant-1, 13 and 9 for boll weight and 13 and 5 F2 populations for seed cotton yield plant-1, respectively. F2 populations i.e. CIM-554 × CIM-473, CIM-554 × CIM-499, CIM-496 × SLH-284, CIM-473 × CIM-446 and CIM-554 × SLH-284 with low mean values for plant height performed better and manifested highly significant heterotic values over mid and better parents for bolls per plant, boll weight and seed cotton yield. By comparing F2 mean values with F1s, inbreeding depression was observed for plant height (0.66 to 23.99%), bolls per plant (5.00 to 63.16%), boll weight (0.20 to 23.24%) and seed cotton yield (0.44 to 75.52%). However, 62% of F2 populations revealed negative values for inbreeding depression, 14% for bolls per plant, 77% for boll weight and 21% for yield, revealed that these F2 populations were more stable and performed better than F1s even after segregation. Although, F2 populations may display less heterosis as compared to F1s, but still better than high parents and can be used as hybrid cotton to skip the expensive F1 hybrid seed production.