FIELD SCREENING FOR RHIZOME NUMBER IN TALL FESCUE

Rhizomes can enhance competitiveness and persistence of tall fescue, Festuca arundinacea Schreber., but reliable field screening techniques need to be developed for the rhizome trait. We investigated the effects of plant age and infection with the endophyte Acremonium coenophialum (Morgan-Jones & W. Gams) [previously Epichloe typhina (Fries.) Tulasne] on number of rhizomes. Six, endophyte-infected (EI) genotypes varying in ability to produce rhizomes and their endophyte-free (EF) clones were compared in a split-split plot design with plant age (about 3, 6, 9, and 12 mo after transplanting) as main plots, genotypes as subplots, and infection status as sub-subplots. The experiment was planted twice and rhizomes counted on each treatment in the field at the time of digging and after washing. Number of rhizomes was highest 1 yr after transplanting. More rhizomes were counted on washed than field-counted plants, but correlations between the two were high (r = 0.95), indicating that either would accurately rank genotypes. There was no endophyte effect on number of rhizomes, but a significant genotype x infection status interaction was found in March. Screening within a closed El or EF population and counting rhizomes on freshly dug 1-yr-old plants at one location is projected to be a good procedure. When this procedure was used estimate heritability for number of rhizomes within EF 'Kentucky 31', a broad-sense estimate of 0.76 and narrow-sense estimates ranging from 0.38 to 0.88 were calculated.