Triticum monococcum L. and T. boeoticum L., diploid wild relatives of bread wheat (T. aestivum L.), possess resistance to leaf rust (also known as brown rust) caused by Puccinia triticina Eriks. Haustorium formation-based resistance mechanisms (i.e. pre-haustorial and post-haustorial resistance) to leaf rust have been studied and reported in various T. monococcum accessions. In the present study, the mechanism of leaf rust resistance in T. monococcum and T. boeoticum accessions was studied using confocal laser scanning microscopy. Components of resistance studied at a histological level against leaf rust pathotypes, a Mexican pathotype (TCB/TD) and a Swiss pathotype (97512-19), indicated different types of resistance mechanism operative in the two accessions. The resistance in T. monococcum ranged from pre-haustorial resistance against 97512-19 to post-haustorial resistance against TCB/TD. The response in T. boeoticum was post-haustorial with necrosis against the two pathotypes. Pre-haustorial resistance observed in T. monococcum could serve as a potential source of durable rust resistance in wheat breeding.
