Heterosis and inbreeding depression for seed yield and yield traits in Indian mustard (Brassica juncea L. Czern & Coss.)

Introduction

Brassica juncea is one of the most important oilseed crops cultivated in India and several other countries of the world. The crop belongs to the family Brassicaceae and occupies a significant place among edible oilseed crops because of its adaptability under diverse climatic conditions. Rapeseed-mustard group ranks third among global oilseed crops after soybean and palm. Vegetable oils obtained from oilseed crops are essential for human nutrition and also serve as raw materials for industrial products such as biodiesel, lubricants and pharmaceuticals. Increasing population, urbanization and changing dietary habits have continuously increased the global demand for edible oils. India is one of the major consumers and importers of edible oils. Countries like Indonesia and Malaysia dominate palm oil trade, whereas Argentina is well known for soybean oil export. During 2024-25, global oilseed production was estimated to exceed 690 million tonnes due to expansion in soybean, rapeseed and sunflower cultivation. In India, rapeseedmustard is cultivated mainly during the Rabi season and contributes substantially to the national oilseed economy. The crop covers more than 9 million hectares with productivity around 1.4 tonnes per hectare. Rajasthan occupies the leading position in production followed by Madhya Pradesh, Uttar Pradesh and Haryana. In eastern Uttar Pradesh, Ballia district has emerged as an important mustard-growing region because of suitable agroclimatic conditions. Mustard seed contains approximately 30-42 percent oil and the residual cake is rich in protein. Besides its nutritional importance, mustard possesses medicinal value due to the presence of vitamins, minerals and antioxidants. However, traditional Indian mustard genotypes often contain high levels of erucic acid and glucosinolates, which adversely affect oil quality and meal suitability. Therefore, improving seed quality along with enhancement of yield has become a major objective in mustard breeding programmes. The yield potential of presently cultivated varieties remains comparatively low because of their susceptibility to diseases, insect pests and environmental stresses. Development of high-yielding and stable varieties with better oil quality is therefore essential for achieving selfsufficiency in edible oil production. Understanding the nature of gene action controlling yield and its components is necessary for effective crop improvement. The principles of quantitative inheritance proposed by Ronald A. Fisher, J. B. S. Haldane and Sewall Wright later provided the basis for combining ability and heterosis studies. Combining ability analysis helps in identifying desirable parents and superior cross combinations for breeding programmes. Therefore, the present investigation was undertaken to study combining ability and heterosis for yield and related traits in Indian mustard.

Materials and Methods

The present investigation was conducted during Rabi seasons of 2021-22 to 2023-24 at the Nidharia Agricultural Farm of Shri Murli Manohar Town Post Graduate College. The experimental material comprised eight diverse parents of Brassica juncea namely Maya, Aashirvaad, Azad-Mahak, Kranti, Basanti, Rohini, Varuna and Urvashi collected from the Department of Genetics and Plant Breeding, Chandra Shekhar Azad University of Agriculture and Technology. These genotypes differed for flowering, maturity, plant height, branching pattern, siliqua formation, oil content and seed yield. The crossing programme was carried out in a full diallel design including reciprocal crosses following the method of Singh and Chaudhary (1985) based on Hayman's approach. The parents were sown on 17 November and 24 November 2021 to synchronize flowering and to obtain 28 F₁s along with 28 reciprocal crosses. During 2022-23, parents and hybrids were again planted for maintenance and development of F₂ populations through selfing. The final experimental material consisting of eight parents, 56 F₁s including reciprocals and their corresponding 56 F₂s was evaluated during Rabi 2023-24 in a Randomized Block Design with three replications. Sowing was done on 18 November 2023 in two rows of four metre length with spacing of 50 cm × 25 cm. Recommended agronomic practices were followed throughout the experiment. Observations were recorded on days to flowering, plant height (cm), number of primary branches per plant, number of secondary branches per plant, number of siliquae per plant on main raceme, days to maturity, biological yield per plant (g), number of seeds per siliqua, test weight (g), harvest index (%), oil content (%) and seed yield per plant (g). Heterobeltiosis was estimated as the superiority of F₁ over the better parent using the following formula:

The significance of heterosis was tested using standard error and critical difference values calculated as:

Inbreeding depression was estimated by comparing F₂ performance with F₁ using the formula:

The genetic components of heterobeltiosis were partitioned according to Jinks and Jones (1958) as:

The variance associated with heterobeltiosis was estimated as:

Results and Discussion

The present investigation was conducted at the Nidharia Farm of Shri Murli Manohar Town Post Graduate College using eight diverse genotypes of Brassica juncea in a full diallel mating design including direct and reciprocal crosses.

The parents along with their F₁ hybrids were evaluated in a Randomized Block Design with replications under field conditions. Observations were recorded on twelve important agronomic traits related to flowering, maturity, yield and oil content.

The study revealed considerable heterosis and inbreeding depression for all the characters, indicating the involvement of both additive and non-additive gene actions.

References

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