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CROP PHYSIOLOGY & METABOLISM

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

Plant Environment Lab., Univ. of Reading, Dep. of Agriculture, Cutbush Lane, Shinfield, Reading RG2 9AD, UK

* Corresponding author (p.q.craufurd{at}reading.ac.uk)

The concept of a linear increase in harvest index, dHI/dt , has proven very useful for crop simulation modeling. The effect of high temperature on the response of dHI/dt of pods and seeds of peanut (Arachis hypogaea L.) has not been described. The objectives of this work were to determine (i) whether dHI/dt was linear at high temperature, (ii) whether high temperature affected dHI/dt and/or the timing of the linear phase of increase in HI, and (iii) whether there was genotypic variation in the response of dHI/dt 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/dt for pods and seeds was linear and varied from 0.0058 to 0.0109 d^-1. At 38/22°C, dHI/dt 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/dt 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/dt 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/dt , 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/dt to high temperature to successfully simulate yields in warmer environments.

Abbreviations: DAP, days after planting • HI, harvest index • dHI/dt, rate of change of harvest index