Spot blotch disease of wheat as influenced by foliar trichome and stomata density.

Spot blotch, caused by Bipolaris sorokiniana, is a potent biotic constraint to wheat crop leading to substantial yield abatement in warm humid South Asia (e.g. India, Nepal and Bangladesh) and other major wheat-growing countries such as Canada, the United States, Brazil and Australia. A set of 98 bread wheat genotypes were evaluated over two growing seasons to investigate the relationship among foliar trichome, stomata density, and susceptibility to the spot blotch pathogen. The higher density of trichomes (90-140 mm^-2) on the adaxial surface of flag leaves entrapped 32-74 mm^-2 pathogen spores. It restricted the dew droplets size (0.15-0.3 mm²) on the flag leaves and thus prevented direct contact between the spores and the leaf epidermis. Trichome density was negatively associated with the disease development and spore germination but positively associated with grain size and the number of spores entrapped on trichomes per mm²....