1Botany Department, Bharathidasan University, Tiruchirappalli, Tamil Nadu-620 024.
2Central Potato Research Station, Shillong-9, Meghalaya State-793 009.
In part fulfilment of Ph.D degree in Botany in the Bharathidasan University, Tiruchirappalli-24.
Twelve isolates representing diverse G. pallida natural populations of virulent pathotypes were studied by rearing them on two highly resistant potato diffemntials. The isolates were different from each other and the virulence was steeply increasing in level with clone VTn2 62. 33.3 than with clone 69–13377/94. With clone 62. 33.3 the isolates spread into two groups while with the other clone they formed one group. It was found that in heterogenous field populations virulence occurred after many generations. Virulence increase was significantly high in soils of bad management by nematicide use. Elevation created variation in virulence build up.
Virulence, Globodera pallida, isolates
