SCREENING OF DIFFERENT ONION VARIETIES AGAINST "Alternaria porri" CAUSING PURPLE BLOTCH DISEASE

Abstract

An experiment was conducted in the field of SAU (Sher-e-Bangla Agricultural University) farm, Dhaka to screen out the resistant cultivars of onion against purple blotch disease (Alternaria porn) during the period from October, 2009 to April, 2010. Nine onion cultivars viz. BARI Peas-I, BARl Peas-2, BARl Peas-3, Thakurgaon local, Faridpur local, Indian big, Manikgonj local, Taherpuri and Indian small were used as treatments. The screening of the varieties was done based on different parameters like disease incidence, disease severity and yield performance. The lowest disease incidence at 30 DAP, 45 DAP, 60 DAP, and 90 DAP respectively were found in BARI Peas-3, Indian small and Indian big with some extent. The highest disease incidence at 30 DAP, 45 DAP, 60 DAP, 75 DAP, and 90 DAP, were observed in case of local cultivars Taherpuri, Fridpur local, Thakurgaon local and Manikgonj local. The highest yield 12.67 t/ha was obtained from BARI Peas-3 followed by Indian small 10.33 t/ha and Indian big 9.84 t/ha. The lowest yield 4.34 t/ha was harvested from Taherpuri followed by Faridpur local 4.84 t/ha. In case of disease reaction 8.00% observed in BARI Peas-3 was graded as resistant followed by Indian small 10.00%, Indian big 1I .00%, and 18.67% on BARI Peas-2 this cluster ranked as moderately resistant against Purple blotch . The local cultivars Taherpuri 37.67%, Faridpur local 35.00%, Thakurgaon local 34.33%, Manikgonj local 34.00% and BARI Peas-l (25.00%) were graded as susceptible. BAR! Peas-3 performed best in respect of all the parameters considered against Purple blotch of onion.