Appearance and diversity of Phytophthora infestans in Oman in 2013–2015

The purpose of this study was to characterize Phytophthora infestans isolates obtained from diseased tomato tissue in Oman from 2013 to 2015. Late blight caused severe epidemics on tomatoes in Oman in 2013–2014 and 2014–2015. Prior to 2013, late blight had not previously been reported from Oman. Isolates collected from diseased tomato plants in commercial production fields in Oman were assayed for a series of traits. All fifty-five isolates tested for mating type were determined to be A1. A subset of nine isolates analysed for allozymes, sensitivity to mefenoxam, DNA fingerprint as detected with random genome probe fifty-seven (RG57), and microsatellite genotypes revealed a diverse population. A range of sensitivity to mefenoxam was observed and one multi-locus genotype (MLG) was detected in four of the nine isolates. The A2 strain Blue_13, which was recently identified in India and thought to be a possible source of the pathogen, was not detected.