2012 Annual Report
1a.Objectives (from AD-416):
The objective of this cooperative agreement is to survey and identify pathogenic and non-pathogenic Rhizoctonia spp. associated with turfgrasses with molecular pathological, cytological, ecological, and epidemiological criteria with a view to manage Rhizoctonia diseases. Another component of this objective is to molecularly characterize pathogenicity/virulence-associated factors at genome, gene or protein level.
1b.Approach (from AD-416):
To identify Rhizoctonia infecting turfgrasses, a survey will be conducted to collect Rhizoctonia isolates from major golf clubs in Virginia, Maryland, and possibly a few North Eastern States. Rhizoctonia isolates will be classified to major groups (anastomosis groups (AGs), species, etc.), based on morphological, biochemical, and molecular biological characters. For molecular characterization, we may check the usefulness of rDNA PCR and sequencing, AFLP, RAPD, UP-PCR etc. We may also use non-turf Rhizoctonia isolates for comparative and disease control purposes. Molecular techniques like CHEF-gel electrophoresis, Northern, Southern and Western hybridizations, gene cloning, gene transformation may also be applied to study Rhizoctonia pathogenicity. For ecological and epidemiological studies, we may study climatic adaptation and prevalence of Rhizoctonia; susceptibility of various grass species and sensitivity of Rhizoctonia isolates to commonly used fungicides in turfgrasses.
ARS scientists in Beltsville, MD and the University of Tennessee carried out a project on accurate molecular identification of brown patch-causing Rhizoctonia species in turfgrasses from Virginia and Maryland. It was demonstrated that (1) ribosomal DNA internal transcriber spacer (ITS) region analyses is a reliable approach for Rhizoctonia identification from turfgrasses, (2) Universally Primed Polymerase chain reaction (UP-PCR) followed by cross-hybridization could identify Rhizoctonia isolates into their respective AG subgroup level, (3) UP-PCR cross hybridization distinguishes closely related Rhizoctonia isolates to their infra-species level, and (4) sequence characterized amplified region (SCAR) markers generated from the UP-PCR products successfully distinguish Rhizoctonia isolates of two anastomosis subgroups (i.e., AG 1-IB and AG 2-2IIIB) from isolates of other anastomosis groups and subgroups.