Impact of drought and temperature constraints on development and growth of faba bean (Vicia faba L.)

Faba bean (Vicia faba L.) is an important traditional pulse crop in many parts of Asia and the Mediterranean region. However, water deficit and temperature, two of the key variables associated with climate variability, can have major negative influences on the development and growth of faba bean. A series of experiments were conducted to study the potential impact of temperature and water deficit on several physiological processes among faba bean genotypes. Development of node number was determined to be dependent on temperature and was found to be essentially constant among genotypes with a value of 56 degrees C accumulated temperature required for appearance of each node. Plant leaf area, which is important in crop carbon accumulation, was estimated by developing allometric relationships between plant leaf area and number of nodes. The coefficients of these relationships varied among genotypes. Water deficit was found to be critical in impacting plant transpiration and nitrogen fixation rates. The threshold for the decrease in transpiration rate with soil drying was found to range from a fraction of transpirable soil water (FTSW) from 0.22 to 0.60 among 12 genotypes, indicating a genetic resource for improving drought resilience. Results in comparing symbiotic nitrogen fixation on drying soil among genotypes also indicated genetic variation, with one genotype (WW4403/H) being especially drought tolerant. The results of these experiments identified important genotypic differences in sensitivity of specific physiological processes to temperature and water deficit, which can be exploited to improve faba bean resilience to these environmental variables.