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Oral Technical Session: Host Resistance


Effect of waxy (low amylose) on fungal infection of sorghum grain
D. L. FUNNELL-HARRIS (1), S. E. Sattler (2), P. M. O'Neill (2), K. M. Eskridge (3)
(1) USDA ARS, Lincoln, NE, U.S.A.; (2) USDA-ARS; Grain, Forage and Bioenergy Research Unit, Lincoln, NE, U.S.A.; (3) Department of Statistics; University of Nebraska, Lincoln, NE, U.S.A.

Loss of function mutations in the Waxy (Wx) gene, encoding Granule Bound Starch Synthase (GBSS) that synthesizes amylose, results in starch granules containing mostly amylopectin. Grain with this trait has increased usability for feed, food and grain-based ethanol, due to altered starch properties. In sorghum, two classes of waxy (wx) alleles had been previously characterized for absence or presence of GBSS: wxa (GBSS-) and wxb (GBSS+, with reduced activity). Field-grown grain of wild-type; waxy, GBSS-; and waxy, GBSS+ Plant Introduction accessions, were screened for fungal infection. Overall, results showed that waxy grains were not more susceptible than wild-type. GBSS- and wild-type grain had similar infection levels. However, height was a factor with waxy, GBSS+ lines: wxb accessions, which were short, were more susceptible than tall waxy accessions, with an undescribed allele. In greenhouse experiments, grain from accessions and near-isogenic wxa, wxb and wild-type lines, were inoculated with Alternaria sp., Fusarium thapsinum and Curvularia sorghina, to analyze germination and seedling fitness. As a group, waxy lines were not more susceptible to grain pathogens than wild-type, supporting field evaluations. Amongst most waxy and wild-type lines, reduced emergence, survival and seedling weights were observed after C. sorghina and F. thapsinum inoculations. These results are valuable for developing waxy hybrids with resistance to grain-infecting fungi.