1. Using real-time PCR to survey frequency of azoxystrobin-resistant allele G143A in Alternaria populations from almond and pistachio orchards in California
- Author
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Luo, Yong, Ma, Zhonghua, Reyes, Heraclio C., Morgan, Dave P., and Michailides, Themis J.
- Subjects
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FRUIT trees , *PLANT diseases , *LEAF diseases & pests , *NUCLEIC acids - Abstract
Abstract: Alternaria spp. cause leaf spot of almond and Alternaria late blight of pistachio in California, and azoxystrobin is a strobilurin fungicide that has been registered for the control of these diseases. To date, only a single point mutation of G143A in cytochrome b resulting to azoxystrobin resistance in Alternaria spp. was found in California. Based on this single point mutation, a real-time PCR assay was developed to quantify the frequency of the resistant allele G143A (FA) in pathogen samples taken from orchards. Forty-one almond and pistachio orchards were arbitrarily selected in eight counties of California. Fifty leaf lesions caused by Alternaria spp. per orchard were cut to extract the fungal DNA for a real-time PCR assay to determine the FA. About 88% of 41 surveyed orchards had Alternaria spp. with FA>0.90, while six pistachio orchards showed a FA<0.90. Therefore, azoxystrobin-resistant Alternaria populations are predominant in almond and pistachio orchards in California, and sprays of azoxystrobin to control Alternaria diseases are not recommended in these orchards. This study shows a potential use of a real-time PCR assay to efficiently quantify the frequency of azoxystrobin-resistant Alternaria spp. from large number of samples. [Copyright &y& Elsevier]
- Published
- 2007
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