Screening for heat tolerance in common bean (Phaseolus vulgaris L.) lines and cultivars using JIP-test

The changes in chlorophyll a fluorescence, caused by high temperature (HT), have been used to study heat-tolerance in nine common bean (Phaseolus vulgaris L.) accessions (3 cultivars and 6 lines) available in the gene banks of Maritsa Vegetable Crops Research Institute and Institute for Plant Genetic Resources. The plants were grown in controlled greenhouse conditions until the blossoming stage, treated with HT (45° C) for 2 h and returned for recovery for 4 h at 23° C. The obtained results allowed us to differentiate four groups, among the studied bean plants, by their response to HT. The first group, includes a single cultivar – ‘Secuntsa’. The accession was considered heat sensitive, because it showed a decrease of its total performance index (PItotal), calculated by JIP-test, during HT stress and did not recover to the initial values. The second group, comprised of lines RH13, BBSR17, BBSR28, and ‘Starozagorski cher’, expressed an increase in PItotal during heat stress, which however was followed by a decline in PItotal values during recovery after HT treatment. The third group – RRR46 displayed a decrease in various JIP-test parameters during HT treatment followed by full recovery after returning the plants to 23° C. The accessions from the fourth group RH26D, ‘Ranit’, similarly to the control heat tolerant line 83201007 did not show significant alteration in PItotal. We assumed that the accessions from the fourth group are heat-tolerant. The line RRR46 is also promising in terms of heat tolerance because of its flexible response to HT treatment. These genotypes will be used in our further breeding program.

Research highlights▶ Plant photosynthetic apparatus suffers serious damages, while exposed to heat stress. ▶ Plants differ in they ability to tolerate and recover after heat stress. ▶ This can be easily studied by means of JIP-test and used to select heat tolerant genotypes ▶ The JIP-test is a new method to analyze the OJIP part of in vivo chlorophyll fluorescence. ▶ We are using JIP-test to find heat-tolerant bean genotypes.