Little is known regarding the genetic control of yield components of forage grasses. We conducted four experiments to determine if genotypes of tall rescue (Festuca arundinacea Schreb.) differed in number of tillers and weight/tiller. The relationship between those traits and yield/plant was also investigated under low‐competition conditions.Genotypes selected for high number of tillers exhibited lower yield/tiller, and often a lower yield/plant than those with a low number of tillers, when cut following 18 to 24 days of regrowth. Among 225 plants from a 6×6 diallel series diallel series, tillers/plant was negatively correlated (r = —0.55) with yield/tiller. Path coefficient analyses revealed that the direct effect of tillers/plant on yield/plant was about 1.5 times greater than that of yield/tiller.Rate of leaf area expansion was related closely to yield/tiller among genotypes that were selected to represent a broad range in number of tillers/plant. The relationship was not as close (r = 0.43) among progenies of the diallel. Path coefficient analysis of the diallel progeny indicated that leaf elongation rate had 1.6 to 1.8 times more influence than did leaf width on leaf area expansion rate. Leaf area expansion rate may be an acceptable criterion for selection for yield/tiller. Concentration of water‐soluble carbohydrates in leaves and CO2 exchange rate of leaves were not related to number of tillers/plant, yield/tiller, or leaf area expansion rate.

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Genetic variation exists for leaf photosynthesis in tall rescue (Festuca arundinacea, Schreb.), but little information exists on its relationship to forage yield. Therefore, net carbon exchange (NCE) of leaves of tall rescue genotypes was measured in the field during regrowth stages and compared to forage yield of the swards in the subsequeut harvest. Genetic variation existed for both yield and NCE on a leaf area basis, but no consistent relationship between these characters was found. Both NCE and forage yield were increased by irrigation during drought. Correlations between NCE and yield also tended to change from positive to negative with irrigation. Although NCE on a single leaf basis is a primary component of forage yield, other factors such as a environmental stress, canopy shape, and dry matter distribution will need to be considered if NCE is to be included in an effective selection index for improvement of forage yield.

Twenty clonal lines of reed canarygrass, Phalaris arundinacea L., and their topcross progenies were evaluated under two clipping management systems designed primarily to compare forage harvested in the fall after two‐month and three‐month regrowth periods. Objectives were to investigate the genetic variability in forage yield, crude protein percentage, and palatability to rabbits and sheep.The differences among the clonal and progeny lines in forage yield and crude protein percentage were similar under the two management systems; however, the entry ✕ year and entry ✕ cutting interactions generally were statistically significant. Broad‐sense heritabilities (mean basis) ranged from .77 to .88 for forage yield and from .44 to .70 for percentage crude protein. Narrow‐sense heritabilities ranged from .33 to .44 for forage yield and from .19 to .41 for crude protein. The additive genetic variance (2CovPC) constituted from 40 to 59% of the total genetic variance.Significant differences among clones and among topcross progenies in palatability of dried fall‐cut forage were obtained in most cafeteria trials. When differences among the lines were significant, the parent‐progeny correlations and the correlations between rabbit and sheep trials were usually significant.

Diseases such as hypomagnesaemia (grass tetany) have been associated with deficiencies of certain minerals in tall fescue (Festuca arundinacea Schreb.) and in other forage species. To overcome these deficiencies through breeding, information is needed on the inheritance of accumulation of these minerals. Objectives of our investigation were to measure the heritability of the accumulation of Mg, Ca, K, P, and a ratio, K/(Ca+Mg), and their interrelationships in tall fescue. Two diallel mating sets, each with six parents, were randomized and planted in one experiment. Forage was analyzed for Mg, Ca, K, P, and K/(Ca+Mg) for three harvest dates in 1974 and in 1975. Parents and progenies differed significantly for all minerals studied except that progenies were not significantly different for K in one of the diallel sets for the first harvest date. Estimates of general combining ability were more important than estimates of specific combining ability in the inherited uptake of these minerals. Heritability values calculated by the progeny‐parent regression and standard unit method indicated that progress can be made in breeding for higher mineral levels of most minerals at most harvest dates. Since the K/(Ca+Mg) ratio was highly heritable, progress in breeding a tall fescue with low hypomagnesaemia potential should be possible. Correlation of Mg between years was highly significant in one diallel but not in the other. Correlation of K/(Ca+Mg) between years was highly significant at all sampling dates for both diallels. Correlations coefficients between years for Ca, K, and P were more erratic.