Heterosis and Inbreeding Depression in F₂ Populations of Upland Cotton (<i>Gossypium hirsutum</i> L.)

Abstract

Hybrid cotton production through exploitation of heterosis is the only way for having vertical improvement and betterment in seed cotton yield which has been stagnated in the recent years. The current study was conducted to evaluate the performance of F 2 population for studying mean performance, heterotic effects and inbreeding depression in upland cotton for polygenic traits. Parental genotypes and their F 2 s were sown at Khyber Pakhtunkhwa Agricultural University, Peshawar during 2010, manually. All the traits revealed highly significant (p ≤ 0.01) variations for both parents and their F 2 hybrids. Mean performance for parents and their F 2 hybrids is: (5.26 to 7.12 & 4.43 to 6.60) seeds locule -1 , (21.10 to 28.03 & 20.40 to 28.50) seed boll -1 , (32.20 to 34.80 & 32.22 to 35.05) lint% and (62.87 to 85.47 & 45.94 to 92.04) seed cotton yield plant -1 , respectively. Heterotic effects found over mid parent and better parent were: 66.66% & 46.66% (seeds locule -1 ), 60% & 30% (seed boll -1 ), 43.33% & 30% (lint %) and 36.66% & 16.66% (seed cotton yield plant -1 ), respectively. For the parameters: seeds locule -1 (11 & 10), seeds boll -1 (2 & 1) and seed cotton yield plant -1 (3 & 1) showed positive highly significant heterosis for both mid and better parent, respectively while lint% did not reveal any positive significant heterosis. F 2 populations i.e. CIM-499 × CIM-554 and CIM-554 × CIM-499 revealed highly significant heterotic effects over mid and better parent for all the traits except lint % while CIM-554 × CIM-707 showed highly significant heterotic effects for seeds locule -1 and seed cotton yield palnt -1 . Positive economic heterotic effects were also exhibited by more than 50% of the F 2 population i.e., 76.66% for seed locule -1 , 50% for seeds boll -1 , 3.33% for lint% and 20% for seed cotton yield plant -1 , respectively. By comparing F 2 mean values with F 1 s, only lint % showed (0.00% to 15.55%) maximum inbreeding depression while negligible amount of inbreeding depression was observed for the remaining traits. However, negative inbreeding depression was revealed by majority of the F 2 population like 96.66% (seeds locule -1 & seeds boll -1 ), 60% (lint%) and 90% (seed cotton yield -1 ), respectively meant F 2 population has shown more stability even after segregation and have exceeded the check cultivars and better parents in performance.