Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress
Salsomaggiore Terme, Italy - 26/29 September, 2001
PCR-BASED METHODS TO DISTINGUISH BROWN SPOT FROM BLAST DISEASE IN RICE (ORYZA SATIVA L.)
PIOTTI E.*, RIGANO M. M.*, RODINO D.**, RODOLFI M.**, CASTIGLIONE S.*, BILONI M.***, PICCO A.M.**, SALA F.*
* Dipartimento di Biologia, Università di Milano, Via Celoria, 26 - 20133 Milano, Italia
** Dipartimento di Ecologia del Territorio e degli Ambienti Terrestri, Sez. Micologia, Università di Pavia, Via S. Epifanio 14 - 27100 Pavia, Italia
*** Ente Nazionale Risi, Centro di Ricerche sul Riso, Castello d’Agogna (PV)
brown spot, rice blast, Pyricularia grisea, Bipolaris oryzae
Rice blast disease, caused by Pyricularia grisea, and brown spot, caused by Bipolaris oryzae, occur in all major rice growing regions of the world. Both fungi produce lesions on leaves, on nodes, on different parts of the panicle and on the grain of susceptible cultivars. Farmers frequently mistake the symptoms of blast infection with those of brown spot, a disease that usually cause no significant losses. Since preventive spraying with fungicides against blast is widely practiced in Italy, the use of molecular methods to distinguish rice blast from brown spot disease could lead to a more rational use of chemical control. In order to distinguish between the two disease, gene sequences specific for B. oryzae were recovered from the EMBL gene bank. Specific PCR primers were designed to these sequences. A primer pair was selected because of its capacity to amplify B. oryzae DNA but not other parasitic fungi or rice DNA; similarly a primer pair was selected for the P. grisea population.
Because P. grisea is highly variable with respect to its infectivity a collection of different isolates of the fungus is needed in order to select rice cultivar naturally resistant to blast or to produce resistant transgenic plants. As part of a joint scientific study between the Rice Research Centre (Ente Nazionale Risi) and the University of Pavia and Milano, 45 strains of P. grisea were collected in North Italy from different rice cultivars. DNA extracted from the above mentioned strains were submitted to molecular analysis in order to define the level of similarity between them. All the isolates were analysed using rep-PCR (repetitive-element-based polymerase chain reaction). Banding profiles were sufficiently polymorphic to allow the identification of different strains. Statistical analysis of the results allowed the identification of 9 different lineages. Preliminary data show that there exists lineage-cultivar specificity, hence, it is probable that the specific amplification products seen with rep-PCR could be used to distinguish the various lineages of P. grisea that are found in Italy.