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Disease Note.

First Report of Alternaria padwickii on Rice Seeds in Italy. A. Porta-Puglia, Istituto Sperimentale per la Patologia Vegetale (ISPaVe), via C.G. Bertero 22, I-00156 Rome, Italy . G. Di Giambattista, and A. Infantine Istituto Sperimentale per la Patologia Vegetale (ISPaVe), via C.G. Bertero 22, I-00156 Rome, Italy; and M. L. Giudici, Centro di Ricerche sul Riso-ENR, Strada per Ceretto 4, 1-27030 Castello d'Agogna (PV) Italy. Plant Dis. 80:1208. Accepted for publication 22 July 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-1208D.

In the spring of 1996, a seed sample of paddy rice (Oryza sativa L.) cv. Ariete produced in 1995 in Pavia (northern Italy), was taken from a lot showing kernel discolorations and sent to the ISPaVe laboratory for my-coflora analysis. Four hundred seeds were plated on watersoaked paper in petri plates (25 seeds per plate) and incubated at 22 1C under near-UV light (wavelength peak 360 nm ) 12 h daily. Alternaria padwickii (Ganguly) M. B. Ellis, the incitant of stackburn disease of rice, was detected on 6% of the seeds. The species was identified by colony appearance on incubated seeds and on potato dextrose agar, and by morphology of conidia and sclerotia. Pathogenicity tests were carried out in the greenhouse on potted seedlings of the rice cvs. Ariete, Volano, and Se-lenio, using an isolate of the fungus obtained from the Ariete seed sample under study. This isolate is now maintained in the ISPaVe collection (No. ER 820). The seedlings were inoculated by placing 2 µl of a conidial suspension in water (2 x 104 conidia/ml-1) on an area of the second leaf that had been gently scraped with a sterile needle. Sterile water drops were used for the controls. Following inoculation, the seedlings were covered with plastic bags and kept at 26 4C under natural light conditions. Three to 4 days after inoculation, circular and oval spots with a pale center and dark margins that matched (he disease description appeared on the inoculated leaves. A. padwickii was consistently reisolated from all inoculated plants of the three cultivars. Control plants remained free of symptoms. A. padwickii is widespread in several rice-growing countries in the world. In the Mediterranean region, it occurs in Egypt and has been reported on seed from Portugal (l).This is the first report of the presence of the pathogen on rice in Italy and it is of concern because this country is the major rice producer and exporter in the European Union.

Reference: (1) S. B. Mathur et al Proc. Int. Seed Test. Assoc. 37:803, 1972.