Potential MLO homologous genes in legume crops

Abstract

Knock-out mutation in one member of the MLO family lead to durable and broad spectrum resistant against powdery mildew in several crops including barley, tomato and pea. Lack-of-function of this MLO has been associated with higher efficiency of papilla formation impeding cell penetration by a wide range of pathogenic isolates of powdery mildew independently of their races. Despite mlo-based resistance is the unique exploited source of resistance so far to confer powdery mildew resistance in pea in the fields, this resistance mechanism have not been exploited in other legume. As a first step to exploit mlo-based resistance in other legumes, we characterised the MLO gene family in eight legume species from different clades of the Papillionoideae sub-family in the frame of the LEGATO EU-project. This study revealed the multiplication of clade IV and V members that regroups all MLO linked to powdery mildew susceptibility. Thus three candidate MLOs were identified in chickpea, barrel medic and lupin while six were identified in common bean and pigeonpea. Based on these results, candidates to confer mlo-based resistance to powdery mildew were also identified in faba bean, grass pea and lentil. Similarly to chickpea, three potential candidate genes were identified in these species that are being mapped on their respective genetic and physical maps. In addition, allelic variation of these genes is being identified in lentil germplasm collections including wild relatives. These studies confirmed the presence of several candidate MLO genes that should allow exploitation of mlo-based powdery mildew resistance in legume crops.