Physiologic Races of Bunt of Wheat

Inheritance of resistance to common bunt in spelt and common wheat

“…1). Past studies indicate that common bunt reaction could easily be affected by environmental conditions, such as soil temperature and moisture, soil type and seeding depth, etc., and by the amount of inoculum load on seeds (Reed 1928;Gaudet and Puchalski 1989b;He 1999), which made it difficult to obtain discrete segregation especially when tested in the field. In addition, all the parents except Genesis in three populations had a higher disease incidence in 1996 than in 1995 (Tables 3 and 4).…”

“…Based on the computer simulation that we did, this method of classification can be affected, to a great extent, by the value of σ (He 1994, unpublished data). Especially, for common bunt, the disease reaction can vary substantially, resulting in a large σ, under different environmental conditions (Reed 1928;Gaudet and Puchalski 1989b;He 1999). Accordingly, we classified the segregating progenies using the actual distribution of the susceptible parent and tested the extreme observations, prior to the phenotypic grouping, within the susceptible parent distribution to ascertain the correctness of the classification for all the experiments of disease evaluation for resistance to three bunt races.…”

“…The cause of these inconsistencies in bunt incidence between the parental generations is not clear. However, genotype × environment interaction could change the relative degree of disease infection among the different genotypes (Reed 1928;Gaudet and Puchalski 1989b) or differences in inoculum load could affect the chances of exposure of seeds to disease infection. The inconsistent results in different generations could also result from misclassification of genotypes (Clarke et al 1994).…”