Seed borne infection of wheat seeds by Pyricularia oryzae and its transmission to seedlings: Preliminary studies in Argentina.

SANABRIA, ANALIA; CONSOLO, FABIANA; SALERNO,G.; MARTINEZ, SERGIO IVAN; PERELLO, ANALIA EDITH

Santa Catarina Florianopolis

Congreso; 5th International Symposium on Fusarium Head Blight and 2nd International Workshop on Wheat Blast; 2016

Universidade de Passo Fundo

The effect of Pyricularia oryzae on wheat seed infection and germination is little know in Argentina. Thus, the aim of this study was to examine the seed borne infection and transmission of P. oryzae, in different wheat cultivars currently grown in Argentina. Seeds of BioInta 3004, Baguette 18 and Klein Proteo were inoculated (1,5x105 spores/ml) with isolates PyArg22, PyBol, PyBra and PyPG1 collected from wheat plants, and isolate PyAZ1 collected from rice plants. The effect of the pathogen was studied in laboratory conditions by standard blotter test method. Seeds were kept in three layers of moistened white blotting paper, in plastic trays. Two hundred seeds per each isolate?cultivar combination were analyzed in four replicated experiments. Evaluation of seed germination and infection symptoms was registered at the seventh day, through visual emergence of germ tube. After 7 and 14 days, each seed was examined microscopically to detect sporulation of P. oryzae and a total number of infected seeds was counted. Data analyzed by Kruskal-Wallis non-parametrical test shown differences among wheat cultivars and isolates tested. Klein Proteo germination was not affected by any of the isolates of the fungus tested; in Baguette 18, isolates PyBra and PyBol caused a significant reduction of germination of 15%. All the four isolates tested affected significantly the germination of BioInta 3004 causing a reduction between 50-66%. Symptoms observed were total or partial rot of the seeds, and necrotic symptoms with brown dots and brown or grey spot discoloration. Presence of fungal mycelium was observed and recovered under microscope. Incidence of symptoms indicated that cultivar BioInta 3004 was the most severely infected (64.16% of seeds with presence of the fungus). Seedlings emerged from BioInta 3004 infected with isolate PyArg22 shown symptoms of the disease (necrotic spots on coleoptile and first leaf emerged). A preliminary screening of seed transmission was evaluated on superficially disinfected and then liophyllized BioInta 3004 seeds by PCR technique. These results showed a positive result confirming the presence of P. oryzae in wheat seeds. Given the importance of the seed as a major source of diseases transmission and origin of primary inoculum of infection in wheat seeds, this fungal disease could be considered and evaluated on young seedlings. In this way, the use of pathogen-free seeds will be an important component of integrated wheat blast management in Argentina. Moreover, the reduction in germination and symptoms of rot and discolored seed are considered as indicator for negative characters of seedlings regarding the high cost of their production.