EXTANT OF HETEROSIS FOR SEED YIELD AND YIELD ATTRIBUTING TRAITS IN INDIAN MUSTARD (BRASSICA JUNCEA L. CZERN & COSS.) UNDER TIMELY AND LATE SOWN CONDITIONS

Abstract

Indian mustard (Brassica juncea (L.) Czern & Coss.) is one of the most important oilseed crops, contributing significantly to edible oil production in India. Exploiting heterosis through suitable parental combinations remains an effective strategy for enhancing seed yield and associated agronomic traits. The present investigation was undertaken to assess the magnitude of heterosis and identify promising hybrid combinations for seed yield and its contributing characters under contrasting environmental conditions. A set of ten genetically diverse parental genotypes and their forty-five F₁ hybrids, developed through a half-diallel mating design excluding reciprocals, were evaluated under two sowing environments, namely timely sown (E₁) and late sown (E₂), along with pooled analysis. The experimental material was assessed for seed yield and its component traits, including seeds per siliqua, 1000-seed weight, oil content, and other yield-related parameters. Analysis of variance revealed highly significant differences among treatments, parents, hybrids, and parent versus crosses for all the traits studied under individual as well as pooled environments, indicating the presence of substantial genetic variability and the existence of considerable heterotic potential among the parental lines. The magnitude of heterosis varied considerably among different crosses and traits, demonstrating the influence of parental genetic diversity and environmental conditions on hybrid performance. Significant positive mid-parent heterosis for seeds per siliqua and oil content was recorded in the cross HUJM-05-03 × SKM-0526, suggesting the presence of favourable non-additive gene action for these economically important traits. High and desirable better-parent heterosis (heterobeltiosis) for oil content was observed in the crosses Purple mutant × HUJM-05-03 and HUJM-05-03 × SKM 0526. Similarly, superior heterobeltiosis for seeds per siliqua was exhibited by Purple mutant × RKM-3 and RKM-3 × Varuna across timely sown, late sown, and pooled environments, indicating their stability and consistency under varying sowing conditions. Under the late-sown environment (E₂), where plants are exposed to terminal heat stress, the cross Maya × Varuna expressed significant positive heterosis for 1000-seed weight, reflecting its potential for maintaining seed development under stress conditions. For seed yield per plant, the crosses HUJM-05-03 × RKM-3 and RH-0512 × SKM 0526 emerged as the most promising combinations owing to their superior hybrid performance and desirable heterotic response. Nevertheless, none of the hybrid combinations consistently expressed significant positive heterosis over both the mid-parent and better parent simultaneously for all the traits investigated, highlighting the complex inheritance pattern and trait-specific nature of heterosis in Indian mustard. In present study identified several superior cross combinations possessing favourable heterotic effects for seed yield and its associated traits. These hybrids represent valuable genetic resources for the development of high-yielding and quality mustard cultivars and may serve as potential candidates for future breeding programmes aimed at exploiting hybrid vigour and improving productivity under diverse environmental conditions.