ADVANCES IN MÉXICO ON BEAN BREEDING FOR TOLERANCE TO HIGH TEMPERATURE AND DROUGHT

Abstract

Dry bean (Phaseolus vulgaris L.) of the ‘Flor de Mayo’ type is an important staple crop in the Mexican highlands because of its high demand for human consumption. The objective of this work was to study a group of ‘Flor de Mayo’ dry bean cultivars regarding their response to drought, high temperatures and breeding advances. Three experiments were established during 2007: Spring-Summer cycle at Celaya, Guanajuato under irrigated conditions, and at Montecillo, Texcoco, State of México under both rainfed and irrigated conditions. Eight ‘Flor de Mayo’ (FM) cultivars, along with ‘Michoacán 128’ dry bean landrace were evaluated, all of them of indeterminate type III growth habit. The modern varieties showed better seed yields and better yield components, as well as final aerial biomass, thus evidencing a considerable advance due to genetic improvement, which was associated to better tolerance to drought mainly in the weight of 100 seeds. On the drought susceptibility index (S) calculated for seed yield (SY), final aerial biomass (FB), number of pods (NP) number of seeds (NS) and weight of 100 seeds (W100S), varieties ‘FM Sol’ and ‘FM M38’ were classified as drought resistant with an S < 1.0 for SY, FB, NS and NP, and significantly lower (P < 0.05) than the other cultivar. Variety ‘FM M38’ showed the highest SY through the three experiments. The temperature (T) depression of the canopy (TDC ºC = air T - canopy T) was higher for ‘FM Bajío’, ‘FM M38’, ‘FM Anita’ and ‘FM Noura’, through the three experiments, with the lowest TDC values observed in varieties ‘FM 2000’ and ‘Michoacán 128’, which showed negative values (canopy temperature above of the air T). TDC was positive and significantly related with SY, FB, NP and NS, with the highest values corresponding to varieties with the best performance. Bean seed yield might be improved by selecting genotypes with higher TDC and lower S under water stress and high temperatures.