Investigations of wheat blast fungus (Magnaporthe oryzae pathotype Triticum) on alternative hosts and extent of cross-infection

A study was conducted to investigate the potential alternative hosts of the wheat blast pathogen, Magnaporthe oryzae pathotype Triticum (MoT), among different cereals and weed species prevailing in farmers' fields in Bangladesh. M. oryzae was detected on the leaves/heads/panicles of some winter cereals such as rice (Oryza sativa), triticale (xTriticosecale), barley (Hordeum vulgare), foxtail millet (Setaria italica), and durum wheat (Triticum durum), as well as four weed species: goose grass (Eleusine indica), crab grass (Digitaria sanguinalis), torpedo grass (Panicum repens), and basket grass (Oplismenus burmannii). The extracted isolates were tested with the MoT-specific marker MoT3 and, together with pathogenicity assays on susceptible wheat, confirmed that isolates from wheat, triticale, barley, and durum were MoT. Thereafter, a cross-infection experiment was conducted under controlled conditions using the isolated M. oryzae isolates to inoculate potential alternative hosts to investigate the host spectrum of MoT and other pathotypes. MoT was able to infect and produce blast symptoms on leaves of triticale, barley, and durum, and the isolates from these three crops could infect wheat as well, implying that the four crops share the same blast pathotype MoT. It is noteworthy that MoT was also able to infect the weed species goose grass, producing minor blast symptoms; in contrast, the isolates from goose grass could not produce any symptoms on wheat leaves. Apart from the above-mentioned isolates, no other studied isolates could produce any symptoms on wheat leaves. The fact that MoT is able to infect goose grass makes this grass species a potential alternative host of MoT in the off season.