Cochliobolus sativus (S. Ito & Kurib.) Drechsler ex Dastur causative agent of helminths of durum wheat

Abstract

Helmintosporiosis occurs wherever cereals are grown and can manifest itself in different forms, which is the reason why it has different names: brown spot, black spot, or root rot. A study on the occurrence and development of the fungus Cochliobolus sativus in different varieties of durum wheat was conducted in the experimental field of the FCI – Chirpan, in the period 2020/2023. Phenological observations were conducted annually and the appearance and development of helmintosporiosis during the growing season was monitored in dynamics. Potato dextrose agar (РDA) was used for primary isolations and multiplication of cultures. During the years studied, the pathogen C. sativus was observed in the form of numerous small, dark brown spots on the leaves of durum wheat. At first, the spots are round, and later - oblong with a yellow halo. Symptoms become visible after emergence and most often on the lower leaves. The mycelium of the fungus is septate, dark olive-brown and grows in the intercellular space of the attacked plant tissue. The ascomycete fungus Cochliobolus sativus has been identified in two consecutive years on the leaves of durum wheat varieties Vazhod and Railydur. For accurate diagnosis and identification, the characters with the highest taxonomic value-morphology and size of asexual sporulation were taken into account. Conidiophores emerging through the stomata, bearing conidia that are septate, straight or slightly curved, and dark olive-brown, have been observed. In the conducted study, a different level of pathogen manifestation was observed, depending on the phenophase in which the durum wheat is located.