Characterization of Phytophthora species inciting citrus foot rot in Punjab

Foot rot or gummosis is considered one of the most devastating diseases of citrus plants responsible for orchard decline. Disease incidence of 20.50 to 37.27% was recorded in orchards and nurseries of different districts of Punjab. Soil samples were collected from the rhizosphere of orchard plants and nursery seedlings for identification of Phytophthora spp., using morphological and molecular approaches. P. nicotianae was found as the sole causal agent of foot rot/ gummosis in all the 40 isolates collected from different citrus growing regions of Punjab. The 40 isolates were grouped into two different clusters by UPGMA clustering using 17 SSR primer pairs. All the isolates from regions of Sri Muktsar Sahib, a few isolates from Hoshiarpur, Ludhiana and Sangrur were grouped in one cluster while all the isolates of Bathinda, Fazilka, a few isolates from Hoshiarpur and Ludhiana were in the second cluster. The representative isolates of P. nicotianae from these regions should be included in screening of planting material for disease resistance breeding programmes.