Population Parameters and Path-Coefficient Analysis of Tomato Grown under Heat Stress

Abstract

Development of genetically improved heat-tolerant varieties is one of the most important approaches for minimizing the negative effects of heat stress. Although there are many factors causing similar negative effects of high temperature, screening of heat tolerance using fruit set percentage as a direct selection for promising genotypes is the common approach. This study aimed to enhancement of selection capacity for heat stress through dual trends; analysis the genetic and phenotypic information derived from generation analysis in tomato and study the causes and effects of indirect selection for heat stress by path coefficient analysis. Homogenous and heterogeneous generations (P 1 , P 2 , F 1 and F 2 ) were used for estimation the following traits; fruit weight (g), fruit set %, total yield per plant (kg), fruit firmness (inch/cm 2 ), chlorophyll a/b ratio, total chlorophyll/carotenoids ratio and electrolytes leakage at vegetative (ELV) and fruiting (ELF) stages. High genetic variability (GCV, 37.24) with moderate value of heritability (72.02%) was recorded by total chlorophyll/carotenoids followed by electrolytes leakage at vegetative stage (ELV) with genotypic coefficient of variance of 25.89% along with high heritability that estimated by 82.20%. Results of the path analysis along with heritability and selection gain showed that fruit set % and electrolytes leakage are the two most critical component traits for fruit yield under heat stress condition. On the other hand, the average fruit weight had low indirect effect but highly significant with fruit yield per plant. The electrolytes leakage showed high ability to distinguish the sensitive and tolerant tomato plants at early stage of plant development which can be relied upon in the selection of heat tolerant genotypes. Among the evaluated materials, ten genotypes; 130, 129, 127, 08, 11, 10, 131, 155, 161 and 124 that possessing better heat tolerance performance with high yield that could be incorporated in further tomato improvement programs.