Mung bean (Vigna radiata L.) is one of the most important legumes in the world. This nitrogen-stabilizing plant has rapid growth and a short growth period, leading to improved soil fertility. Mung bean is widely cultivated in tropical and subtropical regions of Asia due to its high adaptation range. Plants are obligate aerobic organisms and thus depend on O2 to grow and compete successfully with neighbouring plants in natural environments. Waterlogging stress is one of the most important factors limiting the planting of mung bean under Ahvaz conditions.
Materials and Methods
In order to study the effects of waterlogging stress on some agronomic and physiological characteristics of two Mung bean cultivars, a pot experiment was conducted as split factorial in a completely randomized block design with three replications in the field. The main plots were different growth stages consisted of vegetative growth stage, the beginning of flowering, grain filling stage, and three growth stages. The combination of stress levels (control and waterlogging stress) and two Mung bean cultivars (Hindi and Omrani) were as subplots.
Results and Discussion
Waterlogging was caused to decrease significantly dry matter and grain yield in both cultivars at each growth stages, In Hindi cultivar, the highest grain yield reduction was observed at flowering stage and the least difference was observed in waterlogging stress at all three growth stages. In Omrani cultivar, the highest grain yield reduction was observed in waterlogging stress at all three growth stages, and the least grain yield decrease at flowering stage. Overall, the reductions in dry weight and grain yield were higher in Omrani than Hindi cultivar at three growth stages. Therefore, in stress-prone areas such as Ahvaz where summer plants such as Mung bean are exposed to waterlogging stress at different growth stages, Hindi cultivar is suggested for cultivation. Waterlogging stress did not show a significant effect on grain weight and grain number per pod, but significantly reduced the number of pods per plant. The number of pods per plant was significantly more important in determining yield and had a positive and significant correlation (r = 0.846 **) with grain yield. The reason of difference between two cultivars was the better physiological compatibility of Hindi cultivar under stress conditions, including higher levels of photosynthesis and photosynthetic pigments contents. When plants were treated only with waterlogging stress in one growth stage, the Omrani cultivar could compensate some damages due to its indeterminate growth and phenological flexibility, as the period of pod formation was longer in this cultivar. SPAD value had the highest correlation with grain yield (r=0.707**) compared to other photosynthesis-related traits and could be used as a marker trait for selection of tolerant cultivars because of its ease, speed, cheapness and the possibility to measure this trait in the field.
The results indicated that mung bean yield decrease in response to waterlogging stress, depending on growth stages, and experimental duration. The reductions in grain yield was impacted by the growth stage subjected to waterlogging stress. Moreover, the Hindi cultivar seems to be more tolerant to waterlogging in Khuzestan region