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Fine fescues (Festuca spp.) are being bred for low-maintenance turfgrass applications. One of the major limitations to the widespread use of fine fescue is summer patch susceptibility and traffic tolerance. Magnaporthiopsis poae (Landschoot & Jackson), is the long known causal organism of summer patch, however recent research has found a new species, Magnaporthiopsis meyeri-festucae (Luo & Zhang) from the diseased roots of fine fescue turfgrasses exhibiting summer patch symptoms. Breeding for improved tolerance to summer patch is critical but in order to do so a better understanding of the pathogen(s) is necessary. During 2017 and 2018, isolates of M. meyeri-festucae were compared to isolates of M. poae through plant-fungal interaction in growth chamber experiments and in vitro fungicide sensitivity assays with penthiopyrad, azoxystrobin, and metconazole. In the plant-fungal interaction experiments, M. poae was shown to exhibit higher levels of virulence than M. meyeri-festucae; however, certain isolates of the two species were ranked equal. In the fungicide sensitivity assays, an isolate of M. meyeri-festucae was shown to be 9.5 times more tolerant to azoxystrobin than a M. poae isolate. These results indicate that M. meyeri-festucae may be involved with summer patch symptoms of fine fescue under field conditions and should be considered along with M. poae when breeding for tolerance and developing best management strategies for controlling summer patch disease in fine fescue.
Genetic resistance is an important control strategy and could reduce fungicide use. This study determined narrow-sense heritability of summer patch resistance in hard fescue (F. brevilipa R. Tracey) and evaluated inheritance characteristics of summer patch disease resistance. Inheritance characteristics such as heterosis were determined by evaluating the disease severity of progeny from crosses between resistant and susceptible hard fescue clones. Parental clones and progenies from crosses were established in a field trial in a randomized complete block design and inoculated with an isolate of both M. poae and M. meyeri-festucae applied at a rate of 3 cc per plant of prepared inoculum. Differences in progeny means between crosses were observed. Progeny from resistant × resistant crosses had less disease severity than resistant × susceptible and susceptible × susceptible crosses. Medium narrow-sense heritability estimates support the idea that additive gene action plays a role in disease resistance and that summer patch resistance is possibly quantitatively inherited.
To better understand the tolerance to wear and traffic replicated field studies were established in North Brunswick, NJ and St. Paul, MN, and each included 157 Chewings fescue (F. rubra ssp. commutata Gaudin; syn. F. rubra ssp. fallax (Thuill.) Nyman), 155 hard fescue, and 149 strong creeping red fescue (F. rubra L. rubra Gaudin) genotypes. Wear tolerance was evaluated in North Brunswick and traffic tolerance was evaluated in St. Paul during 2015 and 2016 using different simulators to determine both plant performance and broad-sense heritability estimates for wear and traffic tolerance. Broad sense heritability estimates for the three species when calculated on a clonal basis was between 0.69 and 0.82 for wear tolerance in the North Brunswick location and between 0.49 and 0.60 for traffic tolerance in the St. Paul location. On a single plant basis, broad sense heritability estimates for the three species were between 0.31 and 0.45 for wear tolerance in the North Brunswick location and 0.09 and 0.12 for traffic tolerance in St. Paul. However, this research does indicate that improvement of wear and traffic tolerance in fine fescues is possible through recurrent breeding methods based on selection of replicated clonally propagated genotypes rather than selection of single individual plants of a population. This was the first study to determine the genetic effects of wear and traffic tolerance in any turfgrass species.

ETD_9565

Ph.D.

Includes bibliographical references

doi:10.7282/t3-d1fb-8q95

ETD doctoral

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