Evaluating spot blotch resistance of wheat: Improving disease assessment under controlled conditions and in the field
1998
Duveiller, E. | Garcia A., I. | Franco, J. | Toledo B., J. | Crossa, J. | Lopez F., F.
Studies were conducted on spot blotch resistance of wheat at these edling stage. Results showed that plants inoculated with Bipolaris sorokiniana, causal agent of spot blotch, should be exposed to conditions of 25oC and 100 percent relative humidity (RH)for 24 h and then incubated at 24oC and 85 percent RH for 144 h to allow the detection of statistically significant differences in resistance between genotypes. Among the components of resistance studied, lesion density was difficult to assess. Standardization of experimental conditions was critical for the correct appraisal of genetic resistance at the seedling stage and differences between genotypes tended to be obscured as a result of high data variation. In the field, comparison of AUDPC (area under disease progress curve) was the best approach to separate genotypes based on disease scores repeated over time. Differences in spot blotch resistance observed among genotypes in Poza Rica, Mexico, were generally in agreement with data observed elsewhere; however, the relationship between disease severity, yield loss, plant size, and earliness appeared to be complex. Due to high disease pressure, early genotypes such as NL297, harboring some level of spot blotch resistance, appeared susceptible. Studies on spot blotch resistance under climatic conditions more favorable for the wheat crop are needed in order to detect moderate resistance levels and to better assess the effect of disease on yield.
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