Production of hyphopodia by wild-type and three transformants of Gaeumannomyces graminis var. graminis

Abstract

Gaeumannomyces graminis var. graminis causes root and crown disease of rice and turf grasses. Its hyphae produce melanized hyphopodia (= appressoria) on aerial plant surfaces and on plastic; the hyphopodia presumably serve both in surviving the epiphytic portion of the life cycle and in penetrating the host. As a first step in characterizing putative genes and gene products associated with the induction of hyphopodia, three transformants of G. graminis var. graminis with altered hyphopodium formation were identified. According to DNA hybridization analyses, all had single insertion sites of the transforming DNA that encodes either benomyl (JH1113 and JH849) or phleomycin (JH2982) resistance. Wild-type strain JH2033 hyphopodia were pigmented and lobed. Transformant JH1113 hyphopodia were lobed, but more frequently produced and not as pigmented as the wild-type. Transformant JH2982 hyphopodia were pigmented, but were less lobed and less frequently produced than in the wild-type. Transformant JH849 only rarely produced hyphopodial-like structures; they were pigmented but essentially lobeless. The selected strains also were affected pleiotropically in growth habit and in hyphal branching.

Key Words:

• appressoria
• development
• Gaeumannomyces graminis var. graminis
• hyphopodia
• morphogenesis
• thigmodifferentiation