Evaluation of Pathogenicity for a Newly Discovered Summer Patch Causal Pathogen.

A new Magnaporthiopsis species, M. meyer-festucae, was uncovered from the diseased roots of fine fescue turfgrasses. It is described and illustrated based on phenotypic characteristics and DNA sequences of SSU, ITS, LSU, MCM7, RPB1 and TEF1genes.

Inoculation procedures for fulfillment of Koch’s postulates were performed. Inoculations were carried out in conetainers, which were filled with sterilized sand, five inoculated oat seeds to provide an inoculum layer in soil profile. Each conetainer was seeded with hard fescue or Kentucky bluegrass seed. The control units were constructed in the same manner; however, the oat seed in those was not inoculated with the fungus. The prepared conetainers were placed growth chambers for 11 weeks. After 11 weeks, plants were removed from the growth chambers and evaluated for foliar and root characteristics. Four turfgrass cultivar's (‘Beacon’ ,and ‘Predator’ hard fescue, ‘Baron’ ,and ‘Midnight’ Kentucky bluegrass) were used. The treatments were positioned as a 2 × 4 factorial in a completely randomized design with three replicates of each treatment combination. Evaluation parameters included foliar and root health, root length, and shoot and root dry weight.

Foliar health of the plants in this study ranged from 1 to 4, and the overall average foliar health was 2.6. Midnight (mean = 3.3), Predator (mean = 2.8), and Beacon (mean = 2.8) had significantly greater foliar health than Baron (mean = 1.8). With respect to the main effect of fungal inoculation, foliar health was significantly reduced in inoculated samples compared to uninoculated. Root health ranged from 2 to 6, and the overall average root health was 4.3. As with foliar health, Midnight (mean = 5.0) was the best, Baron (mean = 4.1) and Predator (mean = 3.8) were the worst, and Beacon (mean = 4.3) was similar to all cultivars. Inoculated samples had significantly lower root health than uninoculated samples.