Date of Award

Summer 8-10-2018

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

Seanna Annis

Second Committee Member

Frank Drummond

Third Committee Member

Jianjun Hao

Additional Committee Members

Dave Yarborough

Abstract

The primary focus of this research project was to identify factors in the field affecting survival and the environmental conditions affecting carpogenic germination of pseudosclerotia of Monilinia vaccinii-corymbosi (MVC) which is a common fungal pathogen of lowbush blueberry (Vaccinium angustifolium) in Maine. The interactions between biological oranisms, such as fungi and insects with pseudosclerotia prior to and during the overwintering process were investigated in the research outlined below. Fungi from the surfaces of pseudosclerotia were screened as potential antagonists in a co-plate experiment. Most of the potentially antagonistic fungi tested reduced the width of the MVC reference cultures. These potential antagonists should be examined further for their use in biological control. In 2015 and 2016, field experiments investigating possible insect interactions with pseudosclerotia were set up to compare the loss of pseudosclerotia from treatments with no cages to the losses inside cages with varying sizes of mesh (ranging from 1, 4, 7 and 14 mm2). In both years, there were greater numbers of pseudosclerotia remaining inside cages with the smallest mesh compared to larger mesh cages, or treatments with no cages. In 2016, pseudosclerotia density did not affect the disappearance of pseudosclerotia. No-choice laboratory experiments in 2015 and 2016 recorded insect interactions with pseudosclerotia in both years and most insects damaged pseudosclerotia, with some families being more active than others. In the fall season of three years, from 2014 to 2016, pseudosclerotia were collected from three to five fields for use in field and laboratory experiments examining the effects of chill-hours (800 to 3200 hours), post-chill air temperature and soil moisture on carpogenic germination. In all three years, treatments with higher chill-hours accumulation produced greater numbers of apothecia. A model was generated to predict carpogenic germination and illustrated that the number of degree-days needed for 25% of the maximum number of pseudosclerotia to produce apothecia decreased significantly with increasing chillhours. Additional incubation experiments were set up to observe carpogenic germination over different chill-hour levels (1150, 1200, 1500, 1850, 2000 and 3000 chill-hours), incubation temperatures (10, 13 and 16°C) and five percent soil moisture levels (50, 60, 70, 75 and 85%) combined over a two-year period. In both years, the highest chill-hour levels produced the greatest amount of carpogenic germination, significantly more apothecia germinated at 16°C compared to lower temperatures and soil moisture was a significant predictor of the emergence of stipes, but not for apothecia. Pseudosclerotia were collected from lowbush blueberry fields in Maine and all were placed in a common garden experiment to determine if MVC was adapted to field location. In the field and laboratory experiments, field location did not effect carpogenic germination from pseudosclerotia.

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