Thermotolerance of various Jatropha curcas accessions to seasonal variations in the South East Botswana - A semi-arid country

Thermotolerance is the ability of an organism to survive high temperatures. An organism’s natural tolerance of heat is their basal thermotolerance. High temperatures are a common phenomenon in arid and semi -arid regions. Botswana is a semi-arid region where Jatropha curcas a plant well known for its medicinal and seed rich in oil for biodiesel uses. The study aimed to compare various J. curcas accessions’ thermotolerance in this semi-arid region with a wide range of diurnal leaf temperatures throughout the year. Four accessions located in a field in the Department of Agricultural Research, Sebele, Botswana were studied. Measurements of photosynthetic rates, stomatal conduction, leaf temperatures, internal carbon dioxide, and vapour pressure deficit were performed diurnally in spring summer and autumn from 2015 to 2017 on various J. curcas accessions. Despite the interplay of the various parameters that influenced the photosynthetic performance of the accessions the impact of temperature was greatest. As a result of their higher photosynthetic activity the Ghana and Tlokweng accessions surfaced as more thermotolerant than the Tsamaya and Thabala accessions. In conclusion, as the Ghana and Tlokweng accessions appeared more thermotolerant than the Tsamaya and Thabala accessions the study recommends them to be incorporated into breeding programmes alongside other accessions with the ultimate objective of continuing to improve their photosynthetic activity.