Cultivar and environmental effects on growth and development of peanuts ( Arachis hypogaea L.). I. Emergence and flowering

Abstract

Phenological development of 16 cultivars of peanut ( Arachis hypogaea L.) representing Virginia, Valencia and Spanish botanical types, was studied using eleven sowing dates at 14-day intervals in subtropical Australia. Changes in phenology were related to environmental parameters, with functional relationships established to allow application of results to other environments. The rate of emergence in all cultivars was positively associated with mean air temperature, with all sowing dates characterized by sub-optimum temperature for this development stage. For all cultivars, the rate of development from emergence to flowering was positively associated with mean air temperature during that period. Temperatures experienced in all sowings were also in the sub-optimal range for this developmental stage. A subset of six cultivars showed an additional positive response in the rate of preflowering development to mean daylength during the same period, although temperature remained the dominant factor. Cultivars in this subset were not characterized by particular places of origin or botanical type. Base temperatures ( T b) and thermal times ( Q f; °C d) required for emergence and flowering were derived for all cultivars from the linear relationship between 100/ s or 100/ f and mean air temperature, where s and f represent the number of days from sowing to emergence, or emergence to flowering, respectively. Although all cultivars had similar T b values for emergence (13.2°C), the four Spanish cultivars were characterized by higher T b values than the 12 Virginia cultivars and the single Valencia cultivar for flowering. The T b values for emergence and flowering did not differ for the Spanish types (12.4 and 12.7°C, respectively) but the Virginia and single Valencia cultivars showed lower T b for flowering (8.2°C) than for emergence (13.4°C). Thermal times for flowering were significantly ( P < 0.01) lower for the Spanish than for the Virginia and single Valencia types. No differences in the response of 100/ f to temperature existed among botanical types. When 100/ f data for each cultivar and sowing data were standardized to remove scale effects caused by differing times from emergence to flowering (i.e. differences in f), all cultivars showed similar temperature sensitivity. This indicated similar quantitative responses to temperature for all cultivars tested in terms of the rate of preflowering development.