Diallel Analysis of Fusarium Head Blight Resistance in Wheat
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abstract
Fusarium head blight (FHB) negatively impacts grain yield and quality of wheat (Triticum aestivum L. em. Thell) worldwide, especially when warm, humid weather prevails during flowering and grain filling. Our objective was to determine the mechanism of genetic control of FHB resistance in selected winter and spring wheat germplasm. Six genotypes, 'Nekota' (A), '2137' (B), 'Harding' (C), 'Ning7840' (D), 'ND2710' (E) and 'BacUp' (F), were included in a modified diallel. The F1 and F2 populations were evaluated in a greenhouse, whereas only F2 populations were evaluated in a mist-irrigated field nursery. Plants were artificially inoculated with Fusarium graminearum Schwabe isolates in both environments. Additive gene effects were more important than non-additive gene effects. General combining ability (GCA) effects were significant in both F1 and F2 populations in both environments. Specific combining ability (SCA) effects were significant only in the greenhouse environment for F2. Combining ability ratio (0.66 to 0.89) was high, and narrow-sense heritability (0.40 to 0.64) was moderate. Parents D and E had large positive GCA effects for resistance to FHB. Parent B had the largest negative GCA effect for susceptibility to FHB. Graphical analysis of data based on the biplot method was also used to visualize the data and showed that the D/E cross had the lowest percentages of uninfected kernels. Lines D and E had the best resistance to deoxynivalenol (DON) accumulation. Percentages of uninfected kernels and DON content were negatively and significantly correlated in the F1 (r = -0.71, P< 0.01) and F2 (r = -0.84, P< 0.01) greenhouse environments. Multiple field tests across years and locations are needed to confirm whether or not selecting for low disease index will identify genotypes with low DON content. Parents D and E, both 'Sumai3' derivatives, contributed resistance to FHB and were better than F, which is a 'Nuy Bay' derivative. Parent B must be avoided in FHB resistance breeding programs because of its susceptibility and undesirable negative GCA effect.
