Grouping of populations of Heterodera trifolii by host preference and AFLP pattern

Eight populations of clover cyst nematode, Heterodera trifolii, collected from Arkansas, Kentucky, Pennsylvania, USA and from Australia, were compared for host preference and genomic differences. Reproduction of each population on curly dock (Rumex crispus L.), mixed carnation cv. Chaubaud (Dianthus caryophyllus L.) and 14 cultivars of carnation were evaluated according to the numbers of females produced in glasshouse tests. On curly dock, five populations (1 to 5) of H. trifolii consistently reproduced abundantly, while the other three populations (6 to 8) consistently produced significantly fewer females. On cv. Chaubaud, reproduction by each population varied from test to test, and no apparent population groups could be identified. However, on 14 cultivars of carnation, populations 1 to 5 and 6 to 8 could be separated into two distinct groups on six of the cultivars (Blueboy, Peach Majestic, Tasman, Pallas, IMP White Sim and Dart) on which populations 1 to 5 did not reproduce but populations 6 to 8 did. Populations 1 to 5 apparently had more affinity for curly dock than for these six carnation cultivars, which separated these five from populations 6 to 8. DNA analysis with amplified fragment length polymorphism (AFLP) consistently revealed that populations 1 to 5 were similar and populations 6 to 8 were similar. These two groups always showed distinctly different AFLP patterns when multiple selective primer pairs were used. These results indicated that populations 1 to 5 and 6 to 8 represent two putative host races in clover cyst nematode that can be separated either by host preference test or by AFLP analysis.