Excessive nitrogen application predisposed biometric traits of heat tolerant tomato (solanum lycopersicum) genotypes to environmental interaction

This study assesses the effects of Nitorgen (N) application on growth, genetic variability on yield, and environmental interactions in heat-tolerant tomato genotypes in Savannah of Nigeria. Three tomato genotypes; Icrixina, Roma VF, and UC82 were tested across four N levels: 0, 50, 100, and 150 kg ha⁻¹ at two agro-ecologically distinct sites: Bayero University Kano (BUK) and the National Institute for Horticulture, Bagauda Research Station. Analysis of variance (ANOVA) showed significant effects (p < 0.05) of N levels on biometric traits: plant height, leaf area retention, and chlorophyll stability index (CSI) with Icrixina exhibited a 38.10% increase in height growth rate at 150 kg N ha⁻¹ (BUK), while leaf area loss decreased from 198.96 cm² at 0 kg N ha⁻¹ to 48.60 cm² at 150 kg N ha⁻¹ higher than RomaVF that saw a decrease in LA loss from 198.96 to 44.40 and a reduction in senescence rate from 99.50% to 22.20% as N increased from 0 to 150 kg/ha. The UC82B genotype exhibited high flower abortion and senescence rates, with values significantly reducing only at higher N levels. Yield analysis revealed significant genotype-environment (GxE) interactions, with the highest yield of 15,300 kg ha⁻¹ recorded for Icrixina at Bagauda under 150 kg N ha⁻¹ (p < 0.01) while UC82B possessed the least. Genotypic variance (σ²g = 0.2667) and phenotypic variance (σ²p = 0.4) estimates indicate high heritability (H² = 0.67) for yield traits, suggesting strong selection potential for N use efficiency (NUE). Genetic advance as a percentage of mean (GAM) was 17.44% at BUK and 18.31% at Bagauda, underscoring the potential for genetic improvement in NUE and heat resilience. This study highlights Icrixina and Roma VF as high-yielding, N-efficient genotypes suitable for heat-stressed environments, reinforcing the need for breeding programs focused on NUE and heat tolerance to ensure tomato productivity under climate change pressures.