Genetic Variability in Root and Shoot Growth Characteristics of Peanut1,2

Abstract

Abstract The shape and extent of root systems influence the rate and pattern of nutrient and water uptake from the soil. In dicotyledons such as peanut (Arachis hypogaea L.), the primary root and its laterals constitute the main root system. Rooting trait differences in some crops have been associated with drought tolerance. Our objective in this study was to determine if variation in root length and number occurs among peanut genotypes. In one test, shoot and root growth of 23 genotypes (12 spanish and 11 virginia types) were compared in the greenhouse at 55 days after planting using clear acrylic tubes 7.5 cm in diameter and 2.2 m in length. Shoot dry weight, leaf area, tap root length, and root number at 1 m depth ranged for spanish-type entries from 1.23 to 2.65 g, 214 to 409 cm2, 95.0 to 186.8 cm, and 1.0 to 3.1, respectively. Similarly, ranges for virginia-type entries were 1.35 to 3.23 g, 135 to 460 cm2, 122.4 to 192.6 cm, and 1.0 to 7.1. Correlations between shoot and root parameters indicated strong positive association between aerial and subterranean growth. However, the relationship of leaf area to root length was stronger for virginia- than for spanish-type entries. Root length and numbers were highly correlated for spanish, but not for virginia entries. In other tests that included two each of virginia-, spanish-, and valencia-type entries, similar results were found for plants at 34 and 47 days after planting. Significant differences in both root (length and numbers) and shoot growth (dry weight and leaf area) were found among the genotypes tested. Inherent differences in root growth rate were evident at early stages of seedling growth. The results from this sample of peanut germplasm indicate that there is considerable diversity in root growth and there is high shoot/root growth association.