Detection of metalaxyl resistance in phytophthora infestans isolates at pantnagar

Results of the studies revealed that resistance to metalaxyl gave positive results as they exhibited met-resistance up to both 5 and 100 ppm having ≥ 40% growth as compared to 0 ppm (control) in all P. infestans isolates of potato cultivars. Among the four P. infestans isolates, potato cultivar K. Bahar showed the race 1.2.3.4.5.6.7.8.9 with 10 gene complex, while other three potato cultivars (K. Badshah, K. Jawahar and K. Sutlej) showed race 1.2.3.4.5.7.8.10 with 8 gene complex. No oospores were formed in pairings of any of the P. infestans isolates of four potato cultivars for identification of mating type, indicating that all the isolates belonged to A₁ mating type and at Pantnagar, A₂ mating type was not encountered till 2007.