Characterization and Selection of Advanced Tomato Inbred Lines for Hybrid Breeding under upland Conditions of Balochistan, Pakistan

Development of locally adapted tomato parental resources is essential for improving hybrid breeding programs in highland production environments. This study aimed to characterize advanced tomato inbred lines and identify promising parental candidates under the highland agro-ecological conditions of Balochistan, Pakistan. Sixteen S₆-generation tomato lines were evaluated during Kharif 2025 at the Agriculture Research Institute (ARI) Sariab, Quetta, using a randomized complete block design with three replications. Eight morphological, agronomic, and disease-response traits, including plant height, branches per plant, fruit size, fruit weight, days to flowering, fruits per plant, yield, and field response to late blight and Fusarium wilt under natural infection pressure, were recorded. Analysis of variance revealed significant differences among lines for all quantitative traits, demonstrating genetic variation within the evaluated germplasm. Yield ranged from 2.45 to 4.12 t ha⁻¹, with L-14 showing the highest yield, superior fruit weight, maximum fruits per plant, early flowering, and strong field disease response. Fruits per plant and fruit weight exhibited strong positive associations with yield, indicating their potential value as indirect selection traits. Based on combined agronomic performance, fruit characteristics, and disease response, L-14, L-5, L-12, and L-8 were identified as promising parental candidates, whereas L-6 represented a potential disease tolerance donor. These findings provide valuable genetic resources for future tomato hybrid breeding programs in Balochistan; however, multi-location evaluation, combining ability studies, and molecular characterization are required for further validation.