Effect of waterlogging on growth and development of selected green gram (Vigna radiata L.) varieties

Abstract

In Kenya, green gram is mostly grown in arid and semi-arid areas under rainfed agricultural systems for both subsistence and commercial purposes. KAT 00301, KAT 00308, KAT 00309, KS20, N22 and N26 are grown in Kenya. However, the commonly grown varieties are KAT 00301 (dengu tosha), KAT 00308 (dengu biashara) and KAT 00309 (dengu karembo). Climate change has caused unpredictable rainfall patterns followed by floods which has led to waterlogging, which limits green gram production by affecting morpho-physiological and biochemical parameters hence food insecurity. There is need to fully understand morpho-physiological, biochemical and yield response of selected green gram varieties to waterlogging in order to identify waterlogging-tolerant varieties. The general objective of the study was to determine the effect of waterlogging on growth and development of selected green gram varieties. The specific objectives were to determine the effect of waterlogging on morphological, physiological, chlorophyll content and yield components of selected green gram varieties. The research was carried out under greenhouse set-up at the University Botanic Garden, Maseno. Ten-litre pots were arranged in a completely randomized design and filled with solarised soil obtained from the University Botanic Garden. Five seeds of KAT 00301, KAT 00308 and KAT 00309 were planted in the pots. Each pot was watered with 500 ml of water daily after and before the waterlogging treatment period. This continued throughout the study period. At 14 days after sowing (DAS), seedlings in each pot were thinned to three. Waterlogging treatments were induced at 21 DAS by dipping the 10-litre pots in larger 20-litre pots and maintaining standing water at 3 cm above the soil level for 3 days, 6 days and 9 days. The control treatment was watering each pot daily with 500 ml water throughout the study period. Each treatment had three replications. Collection of data began on 37 DAS and continued after every seven days throughout the study period. Morphological parameters data, i.e., the number of leaves were counted and fresh weight was determined using digital weighing balance. Data on physiological parameters; photosynthesis rate, stomatal conductance and transpiration rate were measured using LI-680 portable photosynthesis systems. Total chlorophyll content was determined using the Arnon method. Number of days to 50% flowering was counted and dry weight of 100 grains was determined using digital weighing balance. The data was subjected to analysis of variance using Statistical Analysis System (SAS) and separation of means done using LSD test at 5% level. Waterlogging significantly (P≤0.05) decreased the number of leaves, fresh weight, stomatal conductance, photosynthesis rate, transpiration rate, chlorophyll content and weight of 100 grains but significantly increased the days to 50 % flowering of the selected green gram varieties. The fresh weight, photosynthesis rate, chlorophyll content and weight of 100 grains were significantly lower in KAT 00308 as compared to KAT 00301 and KAT 00309. The number of days to 50% flowering in KAT 00308 was significantly more as compared to KAT 00301 and KAT 00309. KAT 00301 and KAT 00309 were less sensitive to waterlogging but KAT 00308 was more sensitive to waterlogging. KAT 00301 and KAT 00309 should be improved to waterlogging-tolerant varieties through breeding. Green gram farmers should plant either KAT 00301 or KAT 00309 to minimise losses due to waterlogging.