Diallel Analysis of Gene Effects Conditioning Resistance to Stagonospora nodorum (Berk.) in Wheat

Stagonospora nodorum (Berk.) blotch (SNB) is a fungal disease that affects all aboveground parts of wheat (Triticum aestivum L.) plants. Stagonospora nodorum blotch causes serious losses in grain yield and seed quality of wheat grown in the southeastern USA. The objective of this study was to conduct a genetic analysis of components of partial resistance to SNB in wheat. Ten lines of soft and hard winter wheats that varied in resistance to SNB were used in two sets of intrawheat-class half-diallel matings. Seedling plants of parents, [F.sub.1] crosses, and [F.sub.2] populations were inoculated at the two-leaf stage with spores of SNB in a humidity chamber to determine incubation period (IP), latent period (LP), and necrosis percentage (NP). The analysis of variance (ANOVA) showed highly significant differences for IP and NP among hard wheat crosses in both [F.sub.1] and [F.sub.2] generations. Highly significant differences for IP were noted among soft wheat [F.sub.1] crosses. Significant differences for NP were observed among soft wheat [F.sub.1] and [F.sub.2] crosses. General combining ability (GCA) was found to be the major component of variation among crosses. For hard wheats, both IP and NP of partial resistance had significant GCA effects, but none had significant specific combining ability (SCA) effects. The results from soft wheat also indicated that GCA was more important than SCA in the inheritance of resistance to SNB. Two hard wheat patents, TX84V344 and SWM14240, and one soft wheat parent, 18NT should be very useful as SNB-resistant breeding lines.
Foliar and head blight diseases of wheat cause losses in yield and seed quality throughout most areas of the world. Stagonospora nodorum blotch previously call Septoria nodorum blotch, [caused by [...]