Environmental Interactions among Reed Canarygrass Genotypes for Nutritive Value, Height, and Disease Severity

The objective of this study was to determine whether genotypes of reed canarygrass (Phalaris arundinacea L.) that were superior for in vitro digestible dry matter (IVDDM), crude protein content (CP), plant height, and resistance to tawny blotch [Stagonospora foliicola (Bres.) Bubak] without irrigation were also superior under irrigation with municipal wastewater effluent involving two and three cuttings per year. Twenty-five genotypes were established as spaced plantings in central Pennsylvania on a Hagerstown silt loam soil (fine, mixed, mesic Typic Hapludalf). Main blocks were not irrigated or were sprinkler-irrigated with municipal wastewater effluent one or two times weekly from kite May through mid-September. Subblocks in four replications were harvested two or three times per year. Plant height was measured at all harvests, and IVDDM and CP were determined for the first and third harvests. Tawny blotch severity was rated at the second and third harvests. Significant differences as determined by orthogonal contrasts were observed among the 25 genotypes for each trait. The number of genotypes involved in interactions with each environmental variable were: irrigation 16, cutting frequency 13, harvest 24, and year 18. The number of genotypes that contributed to interactions for each trait were: IVDDM 18, CP 16, height 24, and tawny blotch 12. These results indicated wide differences in environmental stability of genotypes. No genotype was superior for all traits over all environments. There were significant phenotypic correlations between irrigated and nonirrigated clonal means for IVDDM and CP in spring but not in fall harvests. In vitro digestible dry matter in fall never correlated with spring IVDDM, but fall CP often correlated with spring CP. In vitro digestible dry matter was correlated with CP in spring but not in fall. Plant height in any environment correlated with height in any other environment. Tawny blotch rating appeared to be independent of IVDDM, CP, and height. Some genotypes that performed well without irrigation also performed well under irrigation.