Abstract:
Cowpea is an important grain legume crop and inexpensive plant protein source cultivated year around in Sri
Lanka. Tolerance to moisture stress is a critical factor for getting high production of cowpea growing in the Dry
Zone (mean annual rainfall < 1,750mm). The present study consisting of three experiments was conducted in a
protected house and laboratory conditions to determine the relationship of root traits with plant morphology and
yield among eight cowpea varieties grown in Sri Lanka under moisture stress conditions. The eight cowpea
varieties and two moisture stress levels were used as experimental factors and set up as a two-factor factorial
completely randomized design. The interaction effect between the two factors were not significant for
morphological traits such as the number of branches, plant height, number of leaves and basal stem diameter, but
some of those traits significantly influenced by the main factors. The yield and root attributes such as the pod
length, 100 seed dry weight and root dry weight at maturity were significantly influenced by the interaction while
the number of flowers per plant, the number of pods per plant, the number of seeds per pod and the above ground biomass per plant were not significantly affected by the interaction. However, those parameters varied
significantly with variety and moisture stress levels. Furthermore, the interaction effect was significant for the
water use efficiency of the mature plants. The basal root growth angle, taproot diameter at 5cm level and length of
the taproot at maturity were significantly affected by the interaction. Additionally, seedlings grown in cotton wool
culture reported a significant interaction effect of main factors on the length of the taproot, the total root length
and root dry weight except for the number of lateral roots. However, the Interaction effect of variety and moisture
stress was significant for the majority of root attributes such as length of the taproot, total root length and the
number of lateral roots of the seedlings grown in sand media. A positive correlation found between the total root
length of the mature plant and the above-ground biomass. All seedling root traits measured in cotton wool culture
showed a negative correlation with the above-ground biomass of mature plants while none of the seedling root
traits in sand media had an association with above-ground biomass. All root traits recorded in mature plants
showed a significant negative and positive correlation with important yield attributes of cowpea. Therefore,
identified favourable root attributes related to morphology and yield components of cowpea could be used as
screening parameters of cowpea populations at the seedling stage to identify efficient genotypes under moisture
stress levels and introduce them to breeding programs.
