Of the fungal pathogens of cereal crops in Hungary, Drechslera and Bipolaris species have recently increased in importance. Until 1988, B. sorokiniana was considered the most frequently occurring wheat pathogen of the Helminthosporium sensu lato genus. The pathogen was found at a frequency of 5- 8% in fields, infecting all parts of the wheat plant. During the past few years, the fungus has often been identified on wheat seeds displaying black point disease. In 1988, D. tritici-repentis was first reported on winter wheat and rye in Hungary. The pathogen caused a serious epidemic 011 rye hybrids, whose cultivation was consequently discontinued in some regions. Later the fungus was also isolated from barley and millet. In the early 1990s, the spread of D. tritici-repentis decreased to a few percent but has increased again in the past two years. In the autumn seasons of 1991-1994, hundreds of monocotyledonous samples were collected to examine the occurrence and host range of Bipolaris, Drechslera, and Exserohilum species. Bipolaris sorokiniana and D. tritici- repentis were collected from 18 and 2 plant species, representing 12 and 2 genera, respectively. The pathogens infected both cultivated and wild plants. Grasses, especially those growing in non-cultivated fields, may act as fungal hosts during overwintering. Susceptibility of 76 wheat genotypes to B. sorokiniana and D. tritici-repentis at the seedling stage was tested based on sporulation intensity on detached leaves. Types and degree of chlorotic/necrotic symptoms and intensity of mycelium formation were recorded. Plant response to inoculation differed between the two pathogens. In general, an agar plug of B. sorokiniana produced higher sporulation levels than that of D. tritici-repentis. Inoculation with D. tritici-repentis, however, resulted in the formation of more abundant mycelia and necrosis.

English

9806|AGRIS 9802

Jose Juan Caballero

CIMMYT Publications Collection