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Wheat Information Service
Number 87: 31-38 (1998)
Research article

Combining ability analysis of scab resistance for F1 and F2 in 4 x 5 factorial, cross of common wheat

Guo-Liang Jiang

Wheat, Research Laboratory, Department of Agronomy, Nanjing Agricultural University, Nanjing 210095, China


Summary

Nine genotypes with different levels of resistance and genetic backgrounds were crossed in a 4 x 5 factorial cross to make a choice and effective use of excellent parents in wheat breeding program for resistance to scab. A field trial including parents, F1's and F2's was conducted in a 3-replicate randomized block design at Nanjing. The number of diseased spikelets was observed to assess the fungal-spread resistance by single-floret inoculation with Fusarium graminearum. Average numbers of diseased spikelets of F1 and F2 were less than midparent values for most combinations, indicating dominance effects of the resistance genes. The parent versus F1' effects and average degree of dominance showed that the midparent heterosis in F1 was mainly attributed to overdominance. General and specific combining ability effects were significant for both F1 and F2. For inheritance of the resistance, the additive effects of resistance genes in F2 played a more important role than those in F1. Hence, parent selection in breeding pure lines should be mainly based on combining ability analysis for F2 rather than for F1. The effects of resistance levels of parents and their interaction on the performance of offsprings should be considered. It is suggested that two new resistant resources could be used in breeding program.

Key words: Triticum aestivum, scab resistance, combining ability, factorial cross, breeding


Introduction

Scab or head blight caused by Fusarium graminearum Schwabe with the perfect stage Gibberella zeae (Schw.) is a world-wide disease in common wheat (Triticum aestivum L.) (Mesterhazy 1983; Wu 1990; Wilcoxson et al. 1992; Van Eeuwijk et al. 1995). It occurs frequently in temperate humid and semi-humid regions, and is especially destructive in the middle and lower reaches of the Yangtze River Valley and the South China (King 1996). Development of resistant cultivars is the most economical and effective approach controlling this disease. In general, however, high yielding and semidwarf genotypes tend to be rather susceptible to scab, and most of resistant germplasm resources do not possess desirable agronomic traits (Jiang 1992; Liu et al. 1992). In China, for a long time, very few resistance resources were utilized in wheat breeding, programs and the strategy and methodology of breeding for resistance were not approached quite well (Wu et al. 1984; Liu et al. 1992). Although certain progresses were made inbreeding for scab resistance, the resistance has not been incorporated into superior cultivars and any resistant cultivar has been hardly planted in wheat production up to now (Jiang 1992).

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