Stand Maintenance and Genetic Diversity of Bermudagrass Pastures under Different Grazing Management Strategies during a 38‐Year Period

Abstract

ABSTRACTStocking rate can affect production and persistence of bermudagrass [Cynodon dactylon (L.) Pers.] pastures. ‘Coastal’ and common bermudagrass pastures were grazed at different stocking rates to maintain specific low, medium, and high herbage mass (HM) during a 38‐yr period. From 1969 to 1984, pastures received identical fertilization, and from 1985 to 2005, regimens of N plus annual ryegrass (Lolium multiflorum Lam.) vs. no N plus clover (Trifolium spp.) were superimposed on each bermudagrass × HM. Stand of both Coastal and common bermudagrass was negatively affected by decreasing HM and no N fertilizer. Bahiagrass (Paspalum notatum Flüggé) was the primary non‐bermudagrass invasive species on no‐N pastures. Invasive bermudagrass ecotypes were more abundant at 73 to 86% on low HM Coastal with clover or ryegrass, respectively. On common bermudagrass, ecotypes were present at about 25 and 40%, respectively, on clover and ryegrass but not affected by HM. During October 2005, 125 whole plant‐root core ecotypes were collected and fingerprinted using amplified fragment length polymorphism (AFLP) markers, analyzed via coefficient of genetic similarity matrix, and clustered in genetically related groups. Four groups were identified in Coastal and five in common bermudagrass. The Coastal and Coastal‐similar ecotypes were different from common bermudagrass and common bermudagrass‐similar ecotypes in plant height, leaf length, leaf width, and leaf coarseness. Plant inflorescence characteristics of ecotype ranked similar to those of growth traits. The bermudagrass were most sustainable under moderate to high HM and with N fertilization.