Abstract
Patch diseases caused by Thanatephorus cucumeris (Frank) Donk and Waitea circinata Warcup and Talbot varieties (anamorphs: Rhizoctonia species) pose a serious threat to successful maintenance of several important turfgrass species. Reliance on field symptoms to identify Rhizoctonia causal agents can be difficult and misleading. Different Rhizoctonia species and Anastomosis Groups (AGs) vary in sensitivity to commonly applied fungicides and they also have different temperature ranges conducive for causing disease. Thus correct identification of the causal pathogen is important to predict disease progression and make future disease management decisions. Grouping Rhizoctonia species by anastomosis reactions is difficult and time consuming. Identification of Rhizoctonia isolates by sequencing Internal Transcribed Spacer (ITS) region can be cost prohibitive. Some Rhizoctonia isolates are difficult to sequence due to polymorphism of the ITS region. Amplified Fragment Length Polymorphism (AFLP) is a reliable and cost effective fingerprinting method for investigating genetic diversity of many organisms. No detailed analyses have been done to determine the suitability of AFLP for inferring infra-species level of Rhizoctonia isolates. The objective of the present study was to develop AFLP fingerprinting to identify infra-species level of unknown R. solani Kuhn and W. circinata isolates. Seventy-nine previously characterized R. solani (n=55) and W. circinata (n=24) isolates were analyzed with AFLP markers generated by four primer pairs. Unweighted Pair Group Method with Arithmetic Mean (UPGMA) correctly grouped R. solani and W.circinata isolates according to their AG, AG subgroup or W.circinata variety. Principle component analysis (PCA) corroborated UPGMA clusters. To our knowledge this is the first time AFLP analysis has been tested as a method to decipher the AG, AG subgroup or W.circinata variety across a wide range of Rhizoctonia isolates.
Highlights
Patch diseases caused by multiple Rhizoctonia species pose a serious threat to growth and maintenance of several important turfgrass species in the southern and transition zones of the USA [1,2]
A few isolates of Anastomosis Groups (AGs) 2-2IIIB grouped with W. circinata var. zeae (Wcz) group while W. circinata var. circinata (Wcc) cluster consisted of a few W.circinata var. zeae (Wcz) isolates
The present study investigated the applicability of the Amplified Fragment Length Polymorphism (AFLP) technique for grouping R. solani and W. circinata isolates into their infra-species level
Summary
Patch diseases caused by multiple Rhizoctonia species pose a serious threat to growth and maintenance of several important turfgrass species in the southern and transition zones of the USA [1,2]. The transition zone refers to the central part of the country where climatic conditions are not favorable for either cool-season or warmseason turfgrasses. Both turfgrass types are routinely grown and managed in this region. The form-genus Rhizoctonia includes uninucleate, binucleate, and multinucleate species, and of these, multinucleate Thanatephorus cucumeris (Frank) Donk (=R. solani Kühn) and Waitea circinata Warcup and Talbot varieties agrostis, zeae, oryzae, circinata, and prodigus; and binucleate Ceratobasidium cereale Murray and Burpee (=R. cerealis Van der Hoeven, AG-D) have been reported from diseased turf lawns and golf greens [1,2,3,4]. Six AGs have been reported to cause blight in turfgrass with AG 1(–IA and –IB), AG 2 (–2IIIB and –2LP), and AG 4 being more common on infected turfgrasses than other AGs [7,8]
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