An organ-specific view on non-host resistance

Non-host resistance (NHR) is the resistance of plants to a plethora of non-adapted pathogens and is considered as one of the most robust resistance mechanisms of plants. Studies have shown that the efficiency of resistance in general and NHR in particular could vary in different plant organs, thus pointing to tissue-specific determinants. This was exemplified by research on host and non-host interactions of the fungal plant pathogen Magnaporthe oryzae with rice and Arabidopsis, respectively. Thus, rice roots were shown to be impaired in resistance to M. oryzae isolates to which leaves of the same rice cultivar are highly resistant. Moreover, roots of Arabidopsis are also accessible to penetration by M. oryzae while leaves of this non-host plant cannot be infected. We addressed the question whether or not other plant tissues such as the reproductive system also differ in NHR compared to leaves. Inoculation experiments on wheat with different Magnaporthe species forming either a host or non-host type of interaction revealed that NHR was as effective on spikes as on leaves. This finding might pave the way for combatting M. oryzae disease on wheat spikes which has become a serious threat especially in South America.