OVERWINTERING OF WHEAT BLAST IN BANGLADESH: EVIDENCE OF STUBBLE-BORNE PERSISTENCE WITHOUT ALTERNATIVE HOSTS

Abstract

The fungal disease wheat blast, caused by Magnaporthe oryzae pathotype Triticum (MoT), threatens wheat production in Bangladesh and other South Asian countries, causing substantial yield losses. Identifying its overwintering mechanisms and potential alternative hosts is crucial but information on these aspects remains limited under South Asian conditions. The study investigated potential alternative hosts and assess pathogen survivability in wheat stubble. One study examined five common grass weed species, namely jungle rice (Echinochloa colona), barnyard grass (Echinochloa crus-galli), goose grass (Eleusine indica), crab grass (Digitaria sanguinalis), and Bermuda grass (Cynodon dactylon), along with cereal crops rice (Oryza sativa) and maize (Zea mays) in controlled conditions. A second experiment examined the survivability of the wheat blast pathogen in blast-infected wheat stubble in the laboratory. PCR analysis using the MoT-specific marker MoT3 confirmed infection only in the susceptible wheat cultivar BARI Gom 26, which developed typical blast symptoms with 84% disease severity and produced the expected 361-bp amplicon, whereas no PCR amplification or blast symptoms were detected in the tested grass weed species, rice, or maize. MoT remained detectable in infected wheat stubble for up to six months post-harvest; however, spore abundance progressively declined, and no spores were detected after seven months. While the five grass weed species, rice, and maize were evaluated in the study, they are unlikely to serve as alternative hosts for MoT under the conditions of this study. However, MoT can persist in wheat stubble for up to six months after harvesting. These findings are critical for managing wheat blast effectively in Bangladesh and other wheat-growing regions with similar agroecological conditions.