High-temperature-tolerant wheat: A description of variation and a search for some limitations to productivity

Abstract

Abstract The hypothesis was examined that rapid phenology, poor biomass production and sterility are major factors leading to the poor yields of wheat grown from sowing to maturity at high temperatures. Twenty-four genotypes which were chosen for their differences in growth and floral development at moderate temperatures were compared in a glasshouse study of minicanopies planted and grown at 30/25°C, and exposed to high radiation, long days, and near-optimal water and nutrient availability. Absolute differences among genotypes in growth and floral development became small at these high temperatures, with most genotypes reaching floral initiation by 2 weeks after sowing and anthesis by 50 days. However, a short vegetative period did not prevent rapid rates of biomass production (which averaged 22 g m −2 during tillering) and the emergence of at least six ears per plant. Furthermore, there was little evidence that high temperature resulted in floret sterility except in two of the genotypes and consequently harvest index was generally very high. The range in grain yields among genotypes was 0–10 g plant −1 which converts to 0–800 g m −2 ; more than 70% of genotypes bettered 7 g plant −1 . It is suggested that ‘high-temperature-tolerance’ already exists in many common wheats. A major boost to yields in countries with a hot start to the season would come with the appreciation that the potential of the crop is very largely set in the first 2–3 weeks after sowing, during which all aspects of agronomy must be optimized. Failure to do this could account for a reduction in potential yields from 6 down to less than 1 t ha −1 . Factors in this period likely to affect potential yield are discussed.