Two banana cultivars differ in composition of potentially immunomodulatory mannan and arabinogalactan

Banana (Musa acuminata and M. acuminata x M. balbisiana) fruit cell walls are rich in mannans, homogalacturonans and xylogalacturonan, rhamnogalacturonan-I, and arabinogalactans, certain forms of which is considered to have immunomodulatory activity. The cultivars Nanicão and Thap Maeo represent two widely variants with respect to compositional differences in the forms of these polysaccharides. Nanicão has low amounts of mannan in the water-insoluble and water-soluble fraction. Both cultivars have high amounts of water-soluble arabinogalactan. These commelinoid monocots lack the (1→3),(1→4)-β-d-glucans of grasses, but Thap Maeo has higher amounts of non-starch glucans associated with wild species than does Nanicão. High amount of callose was found in both cultivars. As immunomodulatory activity is associated with the fine structure and interaction of these polysaccharides, breeding programs to introgress disease resistance from wild species must account for these special structural features in retaining fruit quality and beneficial properties.