Plant Height Components and Gibberellic Acid Response of Oat Dwarf Lines

The use of oat (Avena sativa L.) dwarfing genes in breeding programs to improve lodging resistance has been limited, mainly because of decreases in yield and grain quality in many environments. The objectives of this study were to evaluate the effects of the dominant Dw6, Dw7, and Dw8 dwarfing genes on plant height components and the gibberellic acid (GA) response of the dwarf lines. Plant height components including internode length, panicle length, and panicle exertion were measured in plants of three nondwarf and nine dwarf lines grown in the field at St. Paul in 1992 and 1993. Five experiments were performed in growth chambers to assay the response of nondwarf and dwarf oat genotypes to exogenous GA applied at the seedling stage. The Dw6 gene in line OT207 caused a 34 to 37% reduction in plant height due to the reduction in the length of the three uppermost internodes but not internode number. The 46% reduction in height caused by the Dw7 gene in line NC2469-3 resulted from decreases in both internode number and elongation. The Dw8 gene present in derivatives of seven Japanese lines shortened all internodes but did not affect internode number, reducing plant height by about 50%. The dwarf lines that carry these dwarfing loci are responsive to exogenously added GA3, GA1 and GA20, and thus the mutations appear not to involve disruptions of the conversion of GA20 to GA1 The results indicate that different strategies may be needed to adjust for the different plant height component effects of each of the three dwarfing genes for their use in oat cultivar development.