TY - JOUR
T1 - Development of resistance to hymexazol among Pythium species in cucumber greenhouses in Oman
AU - Al-Balushi, Zainab M.
AU - Agrama, Hesham
AU - Al-Mahmooli, Issa H.
AU - Maharachchikumbura, Sajeewa S.N.
AU - Al-Sadi, Abdullah M.
N1 - Funding Information:
Previous surveys in Oman conducted by our team over a 10-year period showed the association of P. aphanidermatum, P. spinosum, and P. splendens with diseases in greenhouse cucumber (Al-Sadi et al. 2011b). The occurrence of two new species of Pythium in Oman (P. catenulatum and P. myriotylum) may suggest that these pathogens have been recently introduced into the country. This is supported by their limited distribution in greenhouses in Oman. Previous studies have shown that Pythium spp. can be introduced into greenhouses via potting media, organic fertilizers, wind-driven dust, and other agricultural material (Al-Sadi et al. 2011a; Sanchez et al. 2001). Alternatively, P. catenulatum and P. myriotylum could have been introduced into Oman a long time ago but they could have possess a lower degree of fitness in this part of the world compared with the dominant species (P. aphanidermatum). Assessing the genetic diversity and degree of fitness of a larger population of P. cat-enulatum and P. myriotylum from different areas in Oman may help provide insights about the origin of these species.
Publisher Copyright:
© 2018 The American Phytopathological Society.
PY - 2018/1
Y1 - 2018/1
N2 - A study was conducted to characterize the common Pythium spp. in greenhouses in Oman and their level of resistance to hymexazol, a widely used fungicide in the country. Pythium isolates were obtained from soil samples, cocopeat bags, and cucumber roots collected from seven regions in the country. Identification of 80 Pythium isolates to the species level using sequences of the internal transcribed spacer region of the ribosomal RNA showed that they belong to four species: Pythium aphanidermatum (77 isolates), P. spinosum (1 isolate), P. myriotylum (1 isolate), and P. catenulatum (1 isolate). Investigating the aggressiveness of three Pythium spp. on cucumber showed that P. aphanidermatum, P. myriotylum, and P. spinosum are pathogenic. Phylogenetic analysis of P. aphanidermatum isolates showed that most of the isolates obtained from cocopeat clustered separately from isolates obtained from soil and roots. This may indicate a difference in the origin of the cocopeat isolates. Evaluating the resistance of 27 P. aphanidermatum isolates to hymexazol showed that most isolates were sensitive (0.9 to 31.2 mg liter-1) whereas one isolate was resistant (142.9 mg liter-1). This study is the first to report P. myriotylum and P. catenulatum in Oman. It is also the first to report the development of resistance to hymexazol among P. aphanidermatum populations from greenhouses. Growers should use integrated disease management strategies to avoid further development of resistance to hymexazol.
AB - A study was conducted to characterize the common Pythium spp. in greenhouses in Oman and their level of resistance to hymexazol, a widely used fungicide in the country. Pythium isolates were obtained from soil samples, cocopeat bags, and cucumber roots collected from seven regions in the country. Identification of 80 Pythium isolates to the species level using sequences of the internal transcribed spacer region of the ribosomal RNA showed that they belong to four species: Pythium aphanidermatum (77 isolates), P. spinosum (1 isolate), P. myriotylum (1 isolate), and P. catenulatum (1 isolate). Investigating the aggressiveness of three Pythium spp. on cucumber showed that P. aphanidermatum, P. myriotylum, and P. spinosum are pathogenic. Phylogenetic analysis of P. aphanidermatum isolates showed that most of the isolates obtained from cocopeat clustered separately from isolates obtained from soil and roots. This may indicate a difference in the origin of the cocopeat isolates. Evaluating the resistance of 27 P. aphanidermatum isolates to hymexazol showed that most isolates were sensitive (0.9 to 31.2 mg liter-1) whereas one isolate was resistant (142.9 mg liter-1). This study is the first to report P. myriotylum and P. catenulatum in Oman. It is also the first to report the development of resistance to hymexazol among P. aphanidermatum populations from greenhouses. Growers should use integrated disease management strategies to avoid further development of resistance to hymexazol.
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U2 - 10.1094/PDIS-11-16-1680-RE
DO - 10.1094/PDIS-11-16-1680-RE
M3 - Article
C2 - 30673464
AN - SCOPUS:85038854052
SN - 0191-2917
VL - 102
SP - 202
EP - 208
JO - Plant Disease
JF - Plant Disease
IS - 1
ER -