Status of potato cyst nematodes, Globodera spp infection on potato at Kodaikanal hills of Tamil Nadu, India and yield loss estimation
A study was conducted to asses the distribution of potato cyst nemtodes (PCN), Globodera rostochiensis and Globoera pallida in potato (Solanus tuberosum L) fields of Kodaikanal hills, Tamil Nadu, India during 2014-2015. Soil and root samples were collected from 75 potato fields and examined for cyst infestation in soil or female infection in roots. Vulval cone of cysts were prepared and species was identified using appropriate taxonomic keys. Results showed that 36% of potato fields in Kodaikanal hills were infested with PCN. The mixed populations of G. rostochiensis and G. pallida was common in all positive fields. Infestation was high (60-90 cysts/ 200 cm3 soil) at Poomparai and Gundupatti villages followed by moderate (30-60 cysts/200 cm3 soil) at Poondi, Kookal, Mannavanur and Shenbananur villages. Low density (0-30 cysts/200 cm3 soil) was observed at Pallangi and Kodaikanal villages. A field study was conducted to estimate the avoidable yield loss due to natural populations of PCN on potato. The 33.0 % tuber yield loss was observed due to natural populations of G. rostochiensis and G. pallida. Pot experiment was also conducted to confirm the yield loss estimation using challenge inoculated populations of G. rostochiensis and G. pallida. Results revealed that inoculum level of 10,000 eggs/pot could cause tuber yield loss of 53.4%. It is concluded that PCN control efforts are needed to increase yield and to check further spread in potato fields at Kodaikanal hills.