Ultrastructural changes during early infection of Vigna unguiculata and Phaseolus vulgaris leaves by Xanthomonas axonopodis pv. phaseoli and an unexpected association between chloroplast and mitochondrion

Common bacterial blight, caused by Xanthomonas axonopodis pv. phaseoli, is an important disease affecting beans causing considerable yield losses in many producing areas. Our aim was to investigate Xap–beans interactions in the first 48 h after infection analyzing structurally relevant changes by electron microscopy. Scanning electron microscopy analysis demonstrated morphological changes on leaf surfaces of both species. Transmission electron microscopy showed different types of chloroplast structural disorganization in both parenchyma and bundle sheath cells of Vigna unguiculata which were only observed in parenchyma cells of Phaseolus vulgaris. Additionally, we report an unexpected physical association between the chloroplasts and mitochondria observed only to P. vulgaris-infected plants.