Physiological Response to High Temperature and Simple Sequence Repeat Markers (SSR) in Diverse Okra Abelmoschus esculentus L. (Moench) Germplasm

Okra is an important summer vegetable crop and high temperature has been shown to lower its germination, growth and yield. Genetic diversity is crucial for plant breeding purposes, especially in the context of environmental stress such as high temperature, which damages the plant photosystem, changes the balance between photosynthesis and respiration and impairs cellular function by damaging membranes. We assessed the genetic variability for heat-tolerance among Okra genotypes from Pakistan and the AVRDC (The World Vegetable Center) using phenotypic and genotypic data. One hundred and thirty okra genotypes were exposed to 45°C for 6 hours and chlorophyll fluorescence measured in both control and heat shock treatments. This preliminary screening identified 30 Okra accessions (including tolerant and sensitive types) which were used for more detailed physiological measurements, including fluorescence and electrolyte leakage. Damage of the photosystem was observed in some varieties, and an increase in electrolyte leakage was found in most genotypes with high temperature exposure. DNA extraction was optimized for Okra leaf tissue with high mucilage content and 25 SSR markers were tested for their ability to detect polymorphism in Okra accessions. Eight markers that demonstrated most polymorphism were chosen to test 104 accessions for genetic variability. These markers identified how closely the heat tolerant genotypes were related.