RELATIONSHIP OF SPIKE NODDING ANGLE AND KERNEL BRIGHTNESS UNDER SIMULATED RAINFALL IN BARLEY
The purpose of this research was to study the relationship between spike nodding angle and kernel brightness under simulated rainfall in barley (Hordeum vulgare L.). Five genotypes, selected for differences in kernel brightness and spike nodding angle in the field, were grown in the greenhouse. At approximately 10 days after heading, spike nodding angles of 0, 60, 120, and 180° from a completely upright position were established for each genotype. Spikes were sprinkled with water three times daily until they were ripe. After harvest, kernel brightness and yellowness were measured with a Hunter Color Difference Meter (HCDM). Kernels from spikes nodded at angles of 120 and 180° were significantly brighter than kernels from spikes nodded at angles of 0 and 60°, but there were no significant differences among the four angles for degree of yellowness. A nonsignificant genotype × spike nodding angle interaction for kernel brightness indicated that the barley genotypes responded similarly to nodding angle treatments regardless of their natural kernel brightness. Results of this research indicate that the spike nodding angle should be greater than 90° from vertical in order to contribute to kernel brightness in moist conditions. It is suggested that the barley breeder consider both natural kernel brightness and spike nodding angle as selection criteria for developing varieties with improved kernel brightness.