Physiological testing of cool-season faba bean cultivars to drought stress

The problem of global climate change has several impacts on agricultural production. Environmental factors that impose water-deficit stress, such as drought, place major limits on plant productivity. Faba bean (Vicia faba L.) is considered to be relatively drought-susceptible and various physiological traits have been shown to be useful in screening faba bean material for tolerance to drought stress at the seedling stage and the results correlate well with those obtained in field plots. Seedling tests are time-consuming, requiring 6 weeks of growth and 2 weeks of testing, so a rapid procedure based on detached organs would be useful. Plants of five faba bean cultivars (Aurora, Disco, Jõgeva, Kontu and Mélodie) were grown in greenhouse conditions. Shoots of 3-week-old plants were detached and the cut end immersed in a range of concentrations of polyethylene glycol (PEG) 4000 or in distilled water. A 0.6% solution of PEG was found to be the most informative. Leaf temperature readings were taken and relative water content (RWC%) was determined at 24 and 48 hours after the induction of water stress. Water stress resulted in a rapid and considerable decline in RWC% (from 93% in well-watered plants to 70% in stressed ones). The differences in RWC% among cultivars were significant. Mélodie maintained the highest RWC values even in stressed conditions, while Jõgeva and Kontu had the lowest RWC%. Leaf temperature showed no significant difference among the cultivars under the non-stressed conditions, but significant difference in the stressed condition, where Mélodie and Disco had significantly higher leaf temperatures than the others. The screening has shown genotype diversity for drought-associated physiological traits in cool-season faba bean cultivars. The method will be tested on detached leaves in the near future.