Variations in host preference among and within populations of Heterodera trifolii and related species

Seven populations of Heterodera trifolii from Arkansas, Kentucky, Pennsylva nia, and Australia plus 3 or 4 single-cyst isolates (SCI) from each populat ion were tested for reproduction on seven species of plants to compare the host preferences among and within populations. Common lespedeza, Kummerowia striata cv. Kobe, was a good host for all populations and isolates. Theref ore, a plant was considered to be a host if the number of females produced on it was 10% or more of the number on Kobe. All seven populations reproduc ed on Trifolium repens and T. pratense. None reproduced on Beta vulgaris or Glycine max. One single-cyst isolate from the Australian population produc ed a few females on T. pratense. The Australian population maintained on ca rnation, Dianthus caryophyllus, produced, females on carnation but not on c urly dock, Rumex crispus. However, its subpopulation maintained on T. repen s produced females on R. crispus but not on carnation. Four of the other si x populations produced females on R. crispus, and four produced females on carnation. Differences in host range were observed among seven of the mothe r populations and their SCI, and among isolates within each population. Fiv e host range patterns were found in populations and SCI of H. trifolii. Sig nificant quantitative differences occurred among populations in the numbers of females on most hosts, between isolates and their original populations, and among isolates from the same population. SCI selected from white clove r produced fewer females on a series of test hosts and had host ranges the same as or narrower than those of the original populations. However, SCI se lected from Kobe lespedeza had more females on some hosts and had host rang es the same as or wider than those of the original populations. The host ra nges of all populations and SCI of H. trifolii were different from those of populations and SCI of race 3 of H. glycines and H. lespedezae.