Some Physiological and Control Studies on Septoria pisi, the Causal Pathogen of Pea Leaf and Pod Spots

Document Type : Original Article

Authors

Plant Pathol. Dept., Fac. Agric., Minia Univ., Egypt

Abstract

Leaf and pod spot disease of pea (Pisum sativum L.) caused by Septoria pisi Westend is considered as a common factor that reduces yield production. Three isolates of Septoria pisi were isolated from naturally infected leaves and pods of pea showing spots collected from Minia and Matai Provinces, Minia Governorate. Pathogenicity test indicated that these isolates were differed in their virulence; isolate S1 was the most virulent one. Master B, Qena 1 and Qena 3 pea cultivars were susceptible to infection, whereas Jaguar and Palmoral cvs were more resistant. Pycnidia formation and sporulation of S. pisi, which are frequently used as propagules for infection and also are necessary to identify the species, can be scarce and are often reduced when the fungus is cultivated in vitro. A series of experiments were conducted to assess the effect of temperature, culture media, carbon and nitrogen sources on S. pisi growth and pycnidial production. Best results were obtained when fungal colonies were grown at 22±2oC on oat meal, malt and pea dextrose of natural media and Czapek’s medium from the synthetic media, in 12 hours-photoperiod at pH 6.5. The lowest growth and sporulation was recorded on basil and garlic extracts media. The best growth and spore formation were obtained when fructose, glucose, maltose and sucrose represented as the sole carbon sources, followed by raffinose, dextrin and starch. Pectin, sorbitol, manitol and sodium citrate proved to be poor sources of carbon for the growth of the tested fungus. Ammonium nitrate and ammonium sulphate mostly favored fungal growth. Minimum growth was observed when each of urea or asparagine was used as a sole nitrogen source. Peptone and the amino acid threonine were the best nitrogen sources for sporulation and forming pycnidia of S. pisi. Whereas, no spores or pycnidia were formed when each of sodium nitrite, cystine or cysteine was used as a sole nitrogen sources.

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