Date of Graduation

2015

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Biochemistry

Committee Chair

William L MacDonald

Committee Co-Chair

John R Brooks

Committee Member

Daniel G Panaccione

Abstract

Colonization and sporulation (stroma production) of virulent (V) and hypovirulent (HV) Cryphonectria parasitica, were evaluated on two hosts to better understand the saprophytic stage of the fungus and its ability to produce HV inoculum. Both the V and HV C. parasitica strains were isolated from an existing chestnut orchard at the test site. Castanea dentata (American chestnut) and Quercus coccinea (scarlet oak) were used as test hosts. Sixty centimeter long stems of both species were cut from saplings and placed as pairs in three-layer, triangular stacks. Each stack was wound inoculated with either V, HV or water agar (control) inoculum. Five groups of three inoculated stacks were placed on a wooded, upper-slope terrace at the Bunner's Ridge, WV experimental chestnut site. The stems were cut the week of May 15th, 2011 and three inoculations were made starting on May 20th [Inoculation Period-1 (IP-1)], August 4th (IP-2) and October 4th (IP-3). Lesions resulting from each IP was measured for colonization in cm2 from the point of inoculation and the colonized area was visually ranked for sporulation. The infected area was then sampled for fungi at monthly intervals following the date of inoculation until December 8th, 2011. The total colonization and stroma production were analyzed along with the effect of stack layers and stack placement at the site. Results indicated that colonization and sporulation of C. parasitica generally were not significantly different between C. dentata and Q. coccinea and declined propotionally with time for each subsequent inoculation period. With each successive IP, the area C. parasitica was able to colonize decreased, while the colonization and recovery of other fungi increased. Though V grew and sporulated significantly more than HV for IP-1 on both hosts, the differences were not significant for IP's 2 and 3. The analysis of layer and location effects did not conclusively indicate trends that better colonization or sporulation for any specific layer or group of stacks occurred. Isolations showed that HV isolates were able to occasionally colonize V and Control piles and that non-inoculated stems became naturally HV infected up to six months after the initial inoculations. Results also indicate that V and HV are able to be successfully inoculated up to four months following the death of their host. However, colonization during successive IP's was greatly diminished when compared to IP-1. V and HV colonized and sporulated similarly to each other on both hosts and better, but generally not significantly so, on scarlet oak. Also, HV competed nearly as well as V as a saprophyte on both hosts. Initial colonization during IP-1 may have occurred readily and maintained a high recovery rate for V and HV because stems were cut and active host resistance was eliminated. Also, colonization and recovery of C. parasitica during subsequent IP's clearly was diminished by the aggressive colonization by other organisms that accompanied bark deterioration. The time of year stems were cut and bark thickness also may have played important roles in the results.

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