Methods for Detection of Alternaria padwickii in Rice Seeds

The fungus Alternaria padwickii has been frequently detected in seed tests of rice collected from commercial crops in Corrientes Province, Argentina. This pathogen causes germination inhibition, seedling death or spotted grains and is the causal agent of Alternaria leaf spot. The pathogen survives as mycelia and sclerotia on seeds, plant debris and soil. Four detection methods were compared in laboratory tests, to select the best for a quick identification of the fungus in seeds. The methods were (i) Blotter Test (ii) Potato glucose agar, (iii) Bean agar (BA) and (iv) Malt extract agar. Twenty seed samples of different varieties of rice collected from Empedrado, Goya, Ita Ibate, La Cruz, Mercedes, Paso de los Libres and Perugorria localities (Corrientes, Argentina), were analyzed in the assays. The ANOVA test and the Tukey multiple range test were applied on the data to compare the A. padwickii incidence among the varieties and detection methods. BA method was found more sensitive than other methods for A. padwickii. The incidence values ranged from 3.6 to 76%. The statistical analysis demonstrated that the BA method was the most efficient for the detection of seed pathogens, and it could be useful in studies of transmission and chemical control.