Phenology studies of wheat in the Thailand tropics - do they offer clues about field adaptation to heat?
1991
Briggs, K.G. (University of Alberta, Alberta (Canada). Faculty of Agriculture and Forestry, Departament of Plant Science)
Ten wheat cultivars with a range of adaptation to rainfed paddy production were grown in 1988 at Chiang Mai University and Samoeng, North Thailand. Characters measured included establishment, leaf and tiller development rates, heat units to double ridge (DR) and terminal spikelet (TS), and dry weight accumulation. Shallower seeding was advantageous for emergence of plants where flooding and crusting stress occurred. Cultivar variation was found for all traits. Rawson (1987) suggested that key traits for heat adaptation would include a reduced time to DR, a long phyllocron interval, and an oligoculm habit. The 'well adapted' cultivar Samoeng 2 best fit this ideotype, but was not the best accumulator of dry matter. Cultivar phyllocron intervals did not vary significantly, nor did they change at DR. Phyllocron heat units were higher than reported in growthroom studies for the 25-32 deg C range, but agreed with prior data from Thailand. Dry matter accumulation was uncorrelated with DR-TS duration. For cultivars, the number of mainstem leaves at DR completion ranged from 3.8 to 5.7, and for TS from 5.4 to 7.1. Days elapsed from DR completion to TS completion ranged from 7 to 12. The 'best adapted' cultivars accumulated higher dry matter at earlier Haun mainstem leaf stages
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