Rice seedborne infection in southern Spain

Rice (Oryza sativa) seeds were analysed to determine their potential transmission of pathogenic and saprophytic micro-organisms. In four and three hundred lots (stocks) of seeds, in 1998 and 1999 respectively, proceeding from mechanical drying sheds, none presence of Pyricularia oryzae was detected. It did not happen that way for Drechslera spp., whose presence was detected in 8.3% and 28% of the lots, in 1998 and 1999; within these ones the affected seed average was 1.3% in both years. Fusarium sp. appeared in 41% and 48% of the lots, in 1998 and 1999, respectively; the affected seed percentage, within these lots, oscillated between 1.7 and 2.4%. Regarding Arthrobotris sp. and Curvularia sp. the percentage of both, affected stocks and affected seed within these ones, were lower than 2%. About saprophytic micro-organisms, Alternaria appeared in 51% of the stocks in 1998, and in 38% in 1999, while Nigrospora did it in 39% and 33%. The affected seeds average per stock was about 2%. These low seed infection percentage seems a consequence of the mechanical drying process, that disables parts of the inoculum seed. On the other hand, harvested grain samples from trials established to promote the infection of Pyricularia oryzae in 1998, 1999 and 2000, showed that this pathogen was not present in any of these three years, in line with the seed results mentioned above. However, Pyricularia was present in 55% of the harvested grain samples in 2001 trial, as well as in 40% of the seeds. Seed can be a way of transmission of fungi if proceed from campaigns with a high level of inoculum in field.