Cultivar by environment interaction of coconut under different water and heat regimes at their early stage of growth

摘要

Four coconut hybrids (brown dwarf x Sri Lanka tall, Sri Lanka tall x brown dwarf, green dwarf x San Ramon and greendwarf x Sri Lanka tall) arising with two parental dwarf coconut varieties; green dwarf and brown dwarf were evaluated fortheir early vegetative growth and for duration to reproduction at two sites; Raddegoda and Wanathawilluwa. At Raddegoda,a site with optimum condition for growth of coconut, the overall leaf production rate was 9.4 leaves per palm per yearduring the first 3 year period. In contrast, at Wanathawilluwa, a site subject to severe and prolong drought and heat stressproduced 11.3 leaves per palm per year. Moreover, at Wanathawilluwa crosses made with green dwarf produced aremarkably higher number of leaves compared to crosses made with brown dwarf. However, this trend was not noticeablefor stem girth indicating that the higher photosynthetic assimilates in green dwarf crosses resulting from higher leaf areawere not used for stem growth. When time to attain reproduction is considered, the crosses made with green and browndwarfs were similar at Raddegoda (43.2 Vs 43.8 months). However, green dwarf crosses at Wanathawilluwa were markedlyprecocious attaining early maturity (33.25 Vs 41.9 months), but resulting in a large number of stunted palms. This situationwas severe in green dwarf x San Ramon. The overall results suggested that early vegetative phase of coconut hybridsresulting from green dwarf parent is more susceptible to drought and heat stress conditions. This phenomenon indicated adifferential physiological response of different coconut cultivars under moisture and heat stress.