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Dactuliophora Leaf Spot of Pearl Millet in Niger and Mali

Pearl millet (Pennisetum glaucum (L.) R. Br.) fields and cultivar trials in Sadoré, Niger, and Samanko, Mali, were surveyed in late August 1999 Most plants were in the late stem elongation to panicle exertion stage Local open-pollinated cultivars, experimental hybrids, and inbreds had disease severities of up to 10% of foliage diseased, with most severe disease on lower leaves. Individual, young, brown necrotic lesions averaged 2 × 1 mm and were surrounded by circular to irregular purple watersoaked margins 1 to 7 mm wide. Lesions expanded in irregular concentric rings, with zones of necrosis often separated by zones of green tissue Mature, individual lesions averaged 4.3 × 1.9 cm. Entire leaves could be blighted by coalescing lesions. No sclerotia were observed in young lesions, but sclerotia consistently developed and were macroscopically visible in necrotic tissues of older lesions. Sclerotia were oblong to pyriform (averaging 178 × 124 mm) and borne on erumpent, cup-shaped sclerotiophores. When incubated under high humidity, sterile gray mycelia grew rapidly from necrotic lesions up to a distance of ≈5 mm on the lower leaf surface, which likely resulted in the large concentric zones necrosis. Fungal characteristics and symptoms were consistent with disease caused by Dactuliophora elongata Leakey (1,2). Based on observations at the International Pearl Millet Downy Mildew Virulence Nursery in Mali, it is likely that resistance to D. elongata exists. Leaf spot of pearl millet caused by D. elongata has been reported only in Nigeria (1,2). Our observations confirm that the pathogen also is present on pearl millet Niger and Mali.

References: (1) C. L. A. Leakey. Trans. Br. Mycol. Soc. 47:341, 1964. (2) P. D. Tyagi Proc. Ind. Acad. Sci. (Plant Sci.) 94:407, 1985.