Selection for persistence in endophyte-free Kentucky 31 tall fescue

'Kentucky 31', released in 1943, remains the most widely used tall fescue c ultivar (Festuca arundinacea Schreb.). The fungal endophyte, Neotyphodium c oenophialum (Morgan-Jones & Gams.) Glenn, Bacon & Hanlin comb. nov., which naturally infects Kentucky 31, enhances survival and competitiveness of the grass. However, cattle grazing forage from endophyte-infected (E+) Kentuck y 31 suffer from fescue toxicity because of alkaloids in the forage. A poss ible strategy to reduce fescue toxicity is cultivar improvement to develop more persistent endophyte-free (E-) cultivars. The objective of our researc h was to assess the results of selection with different levels of stress (g razing and competition with bermudagrass, Cynodon dactylon L.) to increase persistence and competitiveness within E- Kentucky 31. Populations were sel ected in the following environments: (i) seeded into bermudagrass and graze d with continuously stocked beef cattle, (ii) seeded into bermudagrass and clipped intermittently with a mower, (iii) seeded into tilled soil and graz ed with continuously stocked beef cattle, and (iv) seeded into tilled soil and clipped intermittently with a mower. Populations were developed from th e best surviving plants in each selection condition and tested for grazing persistence and competitiveness with bermudagrass. Grazing, especially when combined with bermudagrass competition, created the greatest reduction of persistence. No selected population was found to survive better than E- Ken tucky 31 even when tested in the same conditions used during its selection. The E+ checks were the most persistent entries in all testing conditions. These experiments indicate that selection within E- Kentucky 31 for improve d persistence will be difficult and may need to be explored on other E- tal l fescue germplasm sources, but another strategy may be reinfection with no n-toxic endophyte strains.