Grain Mold Resistance and Seed Quality Traits in a Sorghum Association Panel.

Tomar, S.S.¹, Perumal, R¹, Morris, G.P.², Tesso, T.², Rooney, W.L.³, and Little, C.R.⁴

¹ Kansas State University, Agricultural Research Center, Hays, KS; ² Department of Agronomy, Kansas State University, Manhattan, KS; ³ Department of Soil and Crop Sciences, Texas A&M University, College Station, TX; ⁴Department of Plant Pathology, Kansas State University, Manhattan, KS

A grain mold screening experiment was conducted using 227 accessions of the sorghum diversity panel and was planted in two replications in Manhattan, Kansas in 2014 using a split-plot design with lines as the whole plot and treatments as subplot. At 50% flowering, nine plants per replication were selected and assigned three treatments: (i) panicles inoculated with Fusarium thapsinum and bagged for seven days, (ii) panicles non-inoculated and bagged for seven days, and (iii) non-inoculated and non-bagged panicles. The same plants were used to collect data on lodging resistance, staygreen, glume coverage, glume length, glume width, lowest primary rachis branch length (LPRL), plant height, panicle length, and 1000-seed weight (TSW). At physiological maturity panicle grain mold ratings (PGMR) on a scale of 1 to 5 (1 = < 1% panicle caryopses molded; 5 = > 50% panicle caryopses molded) were acquired. Panicles were harvested at physiological maturity and evaluated for threshed grain mold rating (TGMR) on the same scale as PGMR. Harvested seed samples were bulked/line /treatment/replication and were analyzed for quality traits (phenolic acids, tannins, protein, moisture, fat, fiber, ash, starch, and 3-deoxyanthocyanin (3-Deo) content) using near-infrared reflectance (NIR) spectroscopy at Texas A&M University, College Station. For PGMR and TGMR a highly significant interaction was recorded for genotype, treatment, and genotype ´ treatment. Correlation studies showed that PGMR had highly significant negative correlations with TSW, lodging resistance, glume length, glume coverage, glume width, LPRL, plant height, and panicle length. But TGMR showed significant negative correlations with lodging resistance, LPRL, TSW and plant height. NIR data revealed that PGMR and TGMR have significant negative correlations with % protein, % fat, phenolic acids, and tannin; and a negative correlation with % moisture, % ash, and 3-Deo content. These results indicate that grain mold has a direct impact on the deterioration of these seed quality traits. Out of 227 accessions only 9 % had mean PGMR scores > 3, 31% had scores between 2 and 3, and 60% had PGMR scores < 2. Last year's limited rainfall in eastern Kansas may have not been sufficient to generate the required environment needed for screening sorghum accessions for grain mold or generate sufficient disease pressure. The same experiment is being repeated in summer 2015 to confirm the results.