Genome-wide identification and analysis of the MLO gene families in three Cucurbita species

Powdery mildew (PM) is a major fungal disease in the Cucurbita species in the world, which can cause significant yield loss. The Mildew Locus O (MLO) family genes play important roles in the PM stress response. In this paper, twenty, twenty-one, and eighteen candidate MLO genes in Cucurbita moschata, Cucurbita maxima and Cucurbita pepo, respectively, were identified and designated as CmoMLO, CmaMLO and CpeMLO, respectively. The phylogenetic analysis indicated that these MLOs were divided into five clades and the number of MLOs belonging to clade V in the Cucurbita species was more than that in other crops. Furthermore, the expression analysis in the susceptibility (S) and resistance (R) lines showed that CpeMLO1, CpeMLO2 and CpeMLO5 might be involved in the susceptibility response. CpeMLO4 and CpeMLO6 showing opposite expression patterns in the R/S lines might be involved in the resistance response. All these data would be beneficial for future functional analysis of MLOs in the Cucurbita species.