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Title: AFLP fingerprinting for identification of infra-species groups of Rhizoctonia solani and Waitea circinata

Author
item AMARADASA, BIMAL - University Of Nebraska
item Lakshman, Dilip
item AMUNDSEN, KEENAN - University Of Nebraska

Submitted to: Journal of Plant Pathology & Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2015
Publication Date: 4/26/2015
Citation: Amaradasa, B.S., Lakshman, D.K., Amundsen, K. 2015. AFLP fingerprinting for identification of infra-species groups of Rhizoctonia solani and Waitea circinata. Journal of Plant Pathology & Microbiology. 6:262.

Interpretive Summary: Patch diseases caused by fungal species Thanatephorus cucumeris and Waitea circinata (also called Rhizoctonia) pose a serious threat to successful maintenance of several important turfgrass species. However, it is difficult to identify Rhizoctonia causal agents based on field symptoms. 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, cost prohibitive, and time consuming. In this investigation, we have developed a molecular fingerprint-based approach (AFLP) to identify unknown isolates of R. solani and W. circinata. 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.

Technical Abstract: Patch diseases caused by Thanatephorus cucumeris and Waitea circinata 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 the 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. Some reports suggest AFLP is suitable only for deriving genetic diversity at the individual level but not at the AG or AG subgroup level. The objective of our study was to develop AFLP fingerprinting to identify infra-species level of unknown R. solani and W. circinata isolates. Seventy-nine previously characterized R. solani (n = 55) and W. circinata (n = 24) isolates were analysed with AFLP markers generated by four primer pairs. Separate analysis of R. solani and W. circinata isolates based on unweighted pair group method with arithmetic mean (UPGMA) correctly grouped them according to their AG, AG subgroup, or W. circinata variety. Principle component analysis (PCA) corroborated UPGMA clusters. When both W. circinata and R. solani isolates were analyzed together, AFLP markers did not result in an acceptable dendrogram, probably due to the co-migration of DNA fragments of W. circinata and R. solani species. 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 varieties across a wide range of Rhizoctonia isolates.