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 F2 population for studying mean performance, heterotic effects and inbreeding depression in upland cotton for polygenic traits. Parental genotypes and their F2s 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 F2 hybrids. Mean performance for parents and their F2 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. F2 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 F2 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 F2 mean values with F1s, 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 F2 population like 96.66% (seeds locule-1 & seeds boll-1), 60% (lint%) and 90% (seed cotton yield-1), respectively meant F2 population has shown more stability even after segregation and have exceeded the check cultivars and better parents in performance.
Highlights
Cotton (Gossypium hirsutum L.) is a major cash crop, often cross-pollinated, long day plant belonging to the family Malvacae
It is expected that F2 populations express only 50% of the economic heterosis shown by F1 hybrids, and even less when heterosis is defined in terms of the higher yielding parent
Genetic material: Breeding material used during the study of genetic potential, heterotic effects and inbreeding depression for yield related traits in 6 × 6 F2 populations of upland cotton were consisted of six different Gossypium hirsutum L. genotypes i.e. CIM-446, CIM-496, CIM-499, CIM-506, CIM-554 and CIM-707 and their 30 F2 cross combinations in a complete diallel fashion
Summary
Cotton (Gossypium hirsutum L.) is a major cash crop, often cross-pollinated, long day plant belonging to the family Malvacae. It is a sixth largest source of vegetable oil in the world and can boost up the economy of any country by producing edible oil for human consumption, feed (seed cake) for animals and local consumption in textile industries. Heterosis (over better parent) is a best source for improvement of F1 and F2 hybrids for production It has ability which can lead breeders for commercial utilization of valuable hybrid combinations in breeding program. Hybrid cotton has been produced successfully on primary basis since 1960s in countries like China and India due to availability of cheaper labor
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