Wheat Information Service
Number 96: 5-10 (2003)
Research article

Genetic analysis of flag leaf area in durum wheat over environments

S.N. Sharma*, R.S. Sain and R.K. Sharma

All India Coordinated Wheat and Barley Improvement Project, Rajasthan Agriculture University, Agricultural Research Station, Durgapura, Jaipur 302 018, Rajasthan, India

Summary

Parental, F₁, F₂, BC₁, BC₂, BC₁₁, BC₁₂, BC₂₁, BC₂₂, BC₁ self and BC₂ self generations of three crosses involving six cultivars of durum wheat (Triticum durum Desf.) were studied for flag leaf area under normal and late sown environments to analyze the nature of gene effects. Various models i.e. 3-parameter model in the cross Cocorit-71 x A-9-30-1 and Raj 911 x DWL 5002 in late sown; 6-parameter model in the cross HI 8062 x JNK- 4W-128 and Raj 911 x DWL 5002 and 10-parameter model in the cross Cocorit-71 x A-9-30-1 and HI 8062 x JNK-4W-128 were found adequate to account for the variability in generation means. Of the epistatic interactions, dominance x dominance (l) and dominance x dominance x dominance (z) played significantly greater role in controlling the inheritance of this trait. Absolute totals of non-fixable gene effects were much higher than the fixable gene effects in all the crosses in both the environments, indicating the greater role of non-additive effects in controlling the inheritance of flag leaf area in durum. Significant heterosis was attributed by the major combined effects of dominance (h) effect and dominance x dominance (l), additive x dominance x dominance (y) and dominance x dominance x dominance (z) epistatic interactions in the cross HI 8062 x JNK-4W- 128 under late sown environment only. Restricted recurrent selection by the way of intermating the most desirable segregates followed by selection and diallel selective mating, which exploit both fixable and non-fixable components, have been suggested for the improvement of this trait.

Introduction

Grain yield is the ultimate aim for cereal breeders. The flag leaf makes a major contribution towards the grain yield of cereals. It contributes 41 to 43 percent to kernel weight and is the major photosynthetic site during the grain filling stage (Athwal 1968; Berdhal et al. 1972; Ibrahim and Abo Elenein 1977). In wheat grain yield is the end product of the interaction of a large number of physiological and biochemical processes in the plants and therefore, is genetically complex. Physiological studies in wheat have indicated that flag leaf contributes to the formation of about 60 percent of dry matter in the kernel at maturity. It is also the only leaf, together with a small contribution from the penultimate one, to carry out an activity essential to grain filling during the period from anthesis to maturity. Since the flag leaf plays a predominant role, its size likely to be important. The leaves being the major site of photosynthetic activity appears to have an obvious relation to the plant grain yield ability. Compared to other leaves the flag leaf contributes most photosynthetic assimilates in wheat and thus it assumes the greatest importance from the grain yield point of view (Lupton 1973). Monyo and Whittington (1973) have shown that leaf area is an indicator of potential grain yield in wheat. Vogele and Grossman (1985) found that flag leaf removal after ear emergence caused a 7 to 9% reduction in kernel weight. Similarly, grain yield and number of kernels /spike were reduced by 10.7 and 11.1%, respectively (Duwayri 1984), number of endosperm cells by 6 and 11%, single kernel weight by 10 to 29%, and grain yield by 15 to 25% (Natt and Hofner 1987). These results indicate the association of flag leaf with yield and its components in the positive sense. Many researchers (Briggs and Aytenfisu 1980; Mahmood et al. 1991; Adnan et al. 1994; Chowdhry et al. 1999) have reported a positive correlation of flag leaf with grain yield, number of grains/spike and kernel weight. These data justify the particular attention devoted by the breeder to this structure. Apart from the direct approach, the problem of yield increase may, in certain situations, be more effectively tackled on the basis of the performance of yield components and other closely associated characters. Therefore, this character would be of great importance as a criterion for selection to enhance the yield potential in durum.

Genetical studies for the inheritance of such an important trait was mostly based on diallel analysis (Ilyhchenko 1977; Hsu and Walton 1970; Jain and Singh 1976; Bariga 1980), which does not provide the estimates of different non-allelic interactions, could inflate the measure of additive and dominance components. To evolve a physiologically efficient and productive genotype in durum wheat, the knowledge of the different non-allelic gene actions, operating in the inheritance of the physiological traits like flag leaf area would be helpful. Information on the nature of the genetic control of flag leaf area is lacking in durum wheat (Triticum durum Desf.), which is the second important wheat species of India. However, scope of such studies is limited if these are not carried over environments. Keeping this in view, the present investigation was conducted to obtain information on the genetic control of flag leaf area under different environments through generation mean analysis.

*Corresponding author, FAX: 91-141-550229, E-mail: ars-jpr@raj.nic.in