Identification of seedling root morphological traits associated with economic yield and yield components of cowpea (Vigna unguiculateL.)

Abstract

Cowpea (Vigna unguiculata L.) is well adapted to relatively dry and less fertile environments hence root system characteristics are very important for water and nutrient acquisition. The present study was conducted to identify the relationship between economic yield and yield components with seedling root traits of recommended cowpea varieties in Sri Lanka. Three experiments under controlled environment conditions were conducted at Faculty of Agriculture, University of Ruhuna. Eight cowpea varieties (Var. Dawala, Waruni, Vijaya, Bombay, MI35, MICP1, ANKCP1 and ANKCP2) were used. A pot experiment was conducted in protected house and set up according to randomized complete block design with three replicates while two lab experiments were arranged to evaluate seedling root traits by using completely randomized design with five replicates. Number of branches per plant, number of pods per plant, average pod length, number of seeds per plant, 100 seed dry weight, total number of active nodules per plant and root dry weight at maturity were measured. Length of the taproot, total root length, number of lateral roots per plant and root dry weight was recorded in seedlings. All yield parameters and root traits measured were significantly different among cowpea varieties (P < 0.001). Seedling taproot length and number of lateral roots per plant varied significantly with the growth condition where var. Waruni and Bombay recorded the highest tap root length in sand media and var. Dawala and ANKCP2 in wet cotton wool media.Number of lateral roots per plant was always high in wet cotton wool media when compared to sand media. A great number of active nodules per plant were observed in var. Bombay and ANKCP2. Seedling root traits were positively correlated with the yield components namely average pod length, number of seeds per pod and 100 seeds dry weight.