Population Structure and Management of Podosphaera pannosa Associated with Peach Powdery Mildew in Oman |
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Authors: | Abdullah M. Al‐Sadi Ibtihal J. Al‐Raisi Masood Al‐Azri Hamoud Al‐Hasani Mohammed S. Al‐Shukaili Saif M. Al‐Shuraiqi Khater O. Al‐Fahdi Mike L. Deadman |
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Affiliation: | 1. Department of Crop Sciences, College of Agricultural and Marine Sciences, Sultan Qaboos University, , PO Box 34 Al Khoud, 123 Oman;2. Directorate General of Agriculture and Livestock research, Ministry of Agriculture and Fisheries, , Barka, Oman |
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Abstract: | In 2004, severe powdery mildew infection on peach occurred in Al‐Jabal Al‐Akdhar, Oman, and resulted in substantial yield losses to growers. This study was conducted to investigate occurrence, causal agents, genetic diversity and efficacy of azoxystrobin in management of this disease. Powdery mildew was observed on all farms and peach trees in Al‐Jabal Al‐Akdhar. Disease symptoms were first observed on shoots in April, followed by appearance on fruits. Disease severity reached its peak between May and June. Morphological and molecular identification of 22 powdery mildew isolates indicated that all belong to Podosphaera pannosa. Podosphaera pannosa reproduced the same symptoms upon inoculation on peach leaves. Amplified fragment length polymorphisms analysis of 35 isolates of P. pannosa from five different villages using four primer pair combinations produced 688 polymorphic loci and 35 different genotypes. Populations of P. pannosa were found to have low levels of gene diversity (H = 0.1858), which suggests that P. pannosa has been recently introduced into Al‐Jabal Al‐Akdhar. Analysis of molecular variance showed low levels of genetic differentiation among populations from the different villages, implying the introduction of P. pannosa into the different villages via common sources as well as frequent movement of pathogen inoculum among the different villages. Evaluating the efficacy of azoxystrobin showed that azoxystrobin is as efficacious as thiophanate‐methyl in managing the disease, with sulphur being the least efficacious. The study is the first to report the presence of P. pannosa in Oman. Also reported are its genetic diversity and its management under commercial conditions. |
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Keywords: |
Sphaerotheca pannosa
ITS rDNA rose topsin Ortiva |
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