Forage Yields and Plant Character Correlations in 30 Digitaria Selections

Abstract

The total green forage, dry matter, and protein yields per acre were determined for 30 Digitarias at the Río Piedras Experiment Station for a period of one year. All grasses were harvested at 60-day intervals; prior to each cutting all plots were evaluated using visual ratings of one to nine, nine being the best condition. The following plant characters: ground cover ability and/or vigor (X₁); resistance to the attack of rust caused by Puccinia oahuensis Ell. and Ev. (X₂); and resistance to yellow aphid infestation Sipha flava Forbes (X₃), were correlated with total green forage (Y₁), total dry matter (Y₂) and total pounds protein (Y₃). Significant positive correlations were obtained for Y₁X₁ (r = 0.34), Y₁X₃ (r = 0.12), Y₂X₁ (r = 0.29), Y₂X₃ (r = 0.10) and Y₃X₁ (r = 0.25). Significant negative correlations were obtained between total green forage and resistance to rust attack, Y₁X₂ (r = —0.16); total dry matter yield and resistance to rust attack, Y₂X₂ (r = —0.12); and total protein yield and resistance to rust attack Y₃X₂ (r = —0.14).  When the grasses were rated after each 60-day interval, the more vigorous grasses also were the most susceptible to the rust disease. None of the Digitarias exhibited complete resistance to either rust or to yellow aphid attack. The findings show that rust resistance is not as important in a Digitaria breeding program as ground cover ability and/or vigor and resistance to yellow aphid infestation. Dry matter yields ranged from 15,841 to 40,484 pounds per acre yearly. One selection, D. eriantha (P.R.P.I. 5277), produced greater yields than the other Digitarias at the 5-percent level, including Pangolagrass.