Heterosis studies in bread wheat (Triticum aestivum L.) for yield and its component traits over the environments

Introduction

Bread wheat (Triticum aestivum L.) is the most important food grain crop among the cereals and stands next to rice in India. It is one of the ancient grain crops consumed as primary food by human beings since the dawn of civilization and is known as the protector of man from hunger. It is a self-pollinated crop belonging to the family Poaceae. It is a hexaploid species (2n=6x=42: AABBDD genomes) with 21 pairs of chromosomes. It significantly contributed towards the success of the "Green Revolution" and has greatly helped to transform our country from a situation of ship to mouth to become a self-sufficient. In India, it is the second most important crop after rice and occupies 318.33 lakh hectares with a total production of 1132.92 lakh tonnes and productivity of 3560 kg/ha during 2024-25 crop season (USDA Report, 2024-25). It is third ranking cereal crop in the world in terms of area and production followed by maize and rice. Major wheat growing states in India are Uttar Pradesh, Punjab, Haryana, Madhya Pradesh, Rajasthan, Bihar and Gujarat. The term ''heterosis'', which is now widely used in crop breeding, was coined by Shull (1908) [15] . It refers to the process in which the F1 hybrid obtained by crossing two individuals having dissimilar genetic constitution that shows either increased or decreased vigour over the better or mid parental value. The commercial utilization of the hybrid primarily is based on its performance that need to be compared with the best commercial variety of the region. Therefore, the term "useful heterosis or standard heterosis" suggested for comparing the yields of hybrids with that of the highest yielding and widely adopted commercial variety of

Estimation of Heterosis, Heterobeltiosis and Economic Heterosis:

The per cent increase or decrease of F1 over the mid parent, better parent and best check variety has been referred as relative or average heterosis, heterobeltiosis and economic heterosis, respectively. Heterosis over mid parent and best standard check was calculated as per the usual procedure whereas; heterobeltiosis was calculated as per procedure suggested by Fonesca and Paterson (1968). They were calculated as follows. or 1% level of significance.

Negative direction of heterosis has been considered desirable for the traits days to heading, days to maturity, plant height. Whereas, positive direction was considered desirable for rest of the characters.

Results and Discussion

The range of heterosis, heterobeltiosis and useful heterosis over check variety MACS-6478 and the number of direct and reciprocal crosses that exhibited significant desirable heterosis for days to heading, days to maturity and plant height in negative direction and for other traits viz, number of effective tillers plant-1, spike length, number of spikelets spike-1, number of grains spike-1, grain weight spike-1, 1000 grain weight and grain yield plant-1 in positive direction is given in Table -1. It revealed that the number of crosses exhibited significant heterosis over mid parent are more followed by useful heterosis and heterobeltiosis. However, in plant breeding for commercialization of hybrids, its performance is tested over the check variety, so here useful heterosis is important criteria to select the promising crosses that performed better over the check variety for grain yield and other component traits. [8,9,10,12,14,19] [2,3,6,7,8,9,12,13,14,16,17,19] .

At Akola the useful heterosis for grain yield plant-1 was ranged from -53.51 percent to 60.40 percent. [1,7,8,12,13,14,18,19] .

The crosses exhibited heterosis for grain yield plant-1 was not heterotic for all the traits (Table -3). The character plant height was independently associated with grain yield plant-1. However, the traits viz, no. of grains spike-1, grain wt. spike-1 and 1000 grain wt. was closely associated with grain yield plant-1 on pooled environment basis. The study on heterosis reveals a good scope for isolation of superior genotypes from the subsequent segregating generations of these potential crosses for improvement of the grain yield and other yield component traits in wheat.

Conclusion

Overall results on analysis of three types of heterosis i.e average heterosis (H1) over mid parent value, heterobeltiosis (H2) over the better parent and Useful heterosis (H3) over the check variety MACS-6478 at two locations viz, Akola and Niphad and also on pooled data revealed that the following two direct crosses viz