Antifungal Proteins during Sorghum Grain Development and Grain Mould Resistance

Proteins potentially inhibitory to the growth of grainmoulding fungi in vitro have been identified from sorghum seeds. However, their role in vivo during fungi infection is still not clear. The objective of the present study was to evaluate the presence of antifungal proteins (AFPs) during grain development. Suren˜o (a grain mould-resistant line), RTx430 (a grain mouldsusceptible) and their F1 hybrid, were planted at two moisture levels. Caryopses were collected from each genotype every 7 days after anthesis (DAA) during development and maturity of the grain. Significant levels of grain mould occurred naturally. Levels of four AFPs (sormatin, chitinases, b-1,3-glucanases and ribosomal- inactivating proteins) were determined using the immunoblotting technique. During grain development (7–35 DAA), Suren˜ o and the F1 hybrid showed higher levels of sormatin and chitinase than RTx430. RIPs levels in Suren˜ o and the F1 hybrid were higher than those in RTx430 after 21 DAA. Sormatin, chitinases, b-1,3-glucanases and RIPs levels in Suren˜ o and in the F1 hybrid were higher than those of RTx430 after grain physiological maturity. AFPs are associated with grain mould resistance because Suren˜ o and the F1 hybrid induce and/or retain higher AFPs levels under grain mould infection pressure than did RTx430.