Selection for resistance to fungal diseases and other desirable traits in kikuyu grass (Cenchrus clandestinus)

Abstract

While kikuyu (Cenchrus clandestinus) is an important grass for dairy and beef production in the subtropical region of Australia and the world, the most common cultivar, Whittet, is seriously affected by the fungal diseases, kikuyu yellows (Verrucalvus flavofaciens) and black spot (Bipolaris spp.). Thus resistance to these diseases is a priority in selecting a better kikuyu cultivar, along with higher herbage quality and yield and better winter growth. A study was conducted to identify suitable candidates from kikuyu ecotypes collected along the east coast of Australia plus lines obtained by subjecting Whittet to a mutagenic agent. Initial glasshouse studies identified 19 lines that were resistant to the KY1A strain of kikuyu yellows and 4 of these, with forage quality and yield superior to Whittet, were further evaluated in the field at 2 sites using Whittet as the control. At Site 1, line 12A demonstrated a much higher level of resistance to kikuyu yellows than Whittet, with 85% of plants resisting infection compared with only 15% of Whittet plants. At Site 2, the numbers of 12A and Whittet plants infected were similar. Further tests, using kikuyu yellows inoculum collected from 11 sites along the east coast of Australia, found that only 15% of 12A plants became infected compared with 61% of Whittet plants. Thus, kikuyu line 12A was resistant to most, but not all, strains of the kikuyu yellows pathogen. Annual yield of 12A (19,008 kg DM/ha) was 24% higher than that of Whittet and 12% higher than Acacia, but the difference was significant only for Whittet. During summer, 12A produced 10,212 kg DM/ha (24% higher than Whittet), was more active in early spring, had slightly higher dry organic matter digestibility (66.7 vs. 64.0%) and was resistant to black spot infection.