Dry Matter Production and Rate of Change of Harvest Index at High Temperature in Peanut

The concept of a linear increase in harvest index, dHI/d t , has proven very useful for crop simulation modeling. The effect of high temperature on the response of dHI/d t of pods and seeds of peanut ( Arachis hypogaea L.) has not been described. The objectives of this work were to determine (i) whether dHI/d t was linear at high temperature, (ii) whether high temperature affected dHI/d t and/or the timing of the linear phase of increase in HI, and (iii) whether there was genotypic variation in the response of dHI/d t to high temperature. Four peanut genotypes varying in heat tolerance were grown in pots at either 28/22 or 38/22°C from 21 to 90 d after planting (DAP). Plants were harvested on 10 occasions starting 27 DAP and total dry matter accumulation and partitioning measured. High temperature reduced total dry weight by 20 to 35%, seed HI by 0 to 65%, and seed dry weight by 23 to 78%. At 28/22°C, dHI/d t for pods and seeds was linear and varied from 0.0058 to 0.0109 d −1 At 38/22°C, dHI/d t of pods and seeds was also linear and varied from 0.0028 to 0.0089 d −1 There were genotypic differences in response to temperature. High temperature had no effect on dHI/d t in moderately tolerant genotypes 796 and 47‐16. In susceptible genotypes ICGV 86016 and ICGV 87282, however, the start of pod and seed filling was delayed by 5 to 9 d and dHI/d t reduced by 20 to 65% at 38/22°C. Reductions in pod and seed dry weight at 38/22°C were therefore due to reductions in total dry matter and dHI/d t , depending on the heat tolerance of the genotype. Crop models need to account for genotypic differences in the response of timing and rate of dHI/d t to high temperature to successfully simulate yields in warmer environments.