Scanning electron microscopy of the establishment of compatible and incompatible Xanthomonas campestris pathovars on the leaf surface of Italian ryegrass and maize¹

Scanning electron‐microscopy observations made on the leaves of Italian ryegrass and maize, inoculated with Xanthomonas campestris pvs graminis, oryzae and oryzicola clearly showed a difference in the distribution pattern among the different pathovars tested. Pvs oryzae and oryzicola could be detected on the leaf trichomes of ryegrass, while pv. graminis was not. On maize leaves, the attachment of pvs oryzae and oryzicola to trichomes was much more pronounced than on ryegrass. In addition, pv. oryzae spread further into leaves of maize than did pvs graminis and oryzicola and could be detected in masses until at least the sixth day after inoculation. These observations suggest that non‐host plants such as maize could function as alternate inoculum sources of pv. oryzae for nearby rice plants.