Studies of alternaria black spot disease of pomegranate caused by Alternaria alternata in Punjab

Abstract

Alternaria black spot of pomegranate caused by Alternaria alternata pose significant economic losses in India as it reduce the crop yield. Farm survey was undertaken at Punjab Agricultural University, Pomegranate Research Block, Fruit Research Station, Jallowal- Lesriwal Jalandhar during 2015. Among all the five cultivars highest disease incidence (70%) and severity (30%) was registered in cultivar Bhagwa. Twenty two isolates of A. alternata were recovered from infected fruits and clustered using UPGMA (unweighted pair group method with arithmetic averages) on the basis of disease score produced in five cultivars (Ganesh, Ruby, Bhagwa, Jyoti and Mridula). It was revealed that five isolates namely AL14, AL15, AL20, AL21 and AL22 were highly virulent on almost all the pomegranate cultivars. Two cultivars viz. Bhagwa and Mridula were found to be most susceptible as 45.45 % isolates were found to be highly virulent on them.Thein vitro antifungal effects of the six fungicides on mycelial growth were investigated. Based on the inhibition of mycelial growth, all the fungicides showed most toxic reaction with 50% effective concentrations (EC50) of < 1 ppm. However, they varied in EC90 values. 10 ppm cocentration of Tilt (azole group) showed 90% effective concentration (EC90). Folicur also showed approximately same results as Tilt while EC90 value of Natio and SAAF was <25 ppm and > 20 ppm. However, two fungicides namely Dithane Z-78 and Bavistin showed less toxicity against Alternaria alternata as compared to other with EC90 value at concentrations <50 ppm and > 25 ppm. Azole group fungicides (Tilt and Folicur) were found most effective to inhibit the pathogen growth.