ABSTRACT JACOBS, RAYMOND LEO, III. Inheritance of Rate-Limiting Foliar Resistance to Anthracnose Crown Rot and Fruit Rot in Cultivated Strawberry. (Under the direction of Dr. Jeremy A. Pattison and Dr. G. Craig Yencho.) Anthracnose crown rot and fruit rot caused by Colletotrichum gloeosporioides and C. acutatum are two of the most prominent and destructive diseases of cultivated strawberry (Fragaria x ananassa Duchesne). Both species are capable of establishing hemibiotrophic infections (HBI) in leaf tissue, encouraging undetected dissemination of diseased nursery plants to fruit production fields and inciting subsequent crown- and fruit-rotting epidemics. The purpose of this research was to explore a novel mechanism in strawberry foliage, which may confer rate-limiting resistance to multiple Colletotrichum species in that tissue. Germplasm from the NC State strawberry breeding program were screened for resistance to C. gloeosporioides HBI. Preliminary variation in resistance and significant differences among genotypes were observed. Methods were developed to increase the accuracy and precision of percent sporulating leaf area (PSLA) measurements, including the use of imaging software for quantification of PSLA. Direct visual estimates were strongly correlated (r=0.91) to image-based quantification of PSLA, but the accuracy of visual estimation varied with different patterns of sporulation and tended to underestimate higher infection severities. A larger panel of 18 cultivars and NC State selections were screened for resistance to hemibiotrophic foliar infections of both C. gloeosporioides and C. acutatum. Genotype PSLA means were significantly different and ranged from 8.5% to 26.5%, though means separation was poor for moderate genotypes. These 18 genotypes were also evaluated for resistance to anthracnose crown rot (ACR) by applying C. gloeosporioides inoculum directly to the crown and observing wilt symptoms over ten weeks. ACR means separated distinctly over a wide range of resistance phenotypes. Findings of moderate correlation of resistance to C. gloeosporioides and C. acutatum HBI in leaf tissue suggested resistance to these Colletotrichum species may be shared in this common tissue type. However, weak correlation of resistance to C. gloeosporioides HBI and ACR in leaf and crown tissue, respectively, suggested that resistance to a single Colletotrichum species may operate independently between tissue types. A population was constructed to examine the inheritance of rate-limiting resistance to C. gloeosporioides and C. acutatum HBI in strawberry leaf tissue as well as the inheritance of resistance to ACR in crown tissue. Low dominance to additive variance ratios for C. acutatum HBI and C. gloeosporioides ACR indicate strong additive genetic control of resistance to these traits. C. gloeosporioides HBI had a much higher dominance to additive variance ratio which suggested this trait was under nearly equal dominance and additive genetic control. Heritability estimates were low for C. acutatum HBI (0.25) and C. gloeosporioides HBI (0.16) but were moderate for C. gloeosporioides ACR (0.61). Resistance gains from selection were predicted to be high for ACR, moderate for C. acutatum HBI, and low for C. gloeosporioides HBI. A strong genetic correlation (rA = 0.98) between resistance to C. acutatum HBI and C. gloeosporioides HBI suggested that resistance to these two Colletotrichum species was controlled by the expression of common genes in strawberry leaf tissue. Selecting for increased resistance to HBI for one Colletotrichum species should produce gains in resistance to the other. Negative genetic correlations between ACR and both HBI traits (rA = -0.85 and -0.61) suggested that resistance in crown tissue is inherited independently of resistance in leaf tissue in the examined population. These results recommend independent evaluation and advancement of resistance to HBI and ACR within breeding programs. © Copyright 2015 Raymond Jacobs All Rights Reserved Inheritance of Rate-Limiting Foliar Resistance to Anthracnose Crown Rot and Fruit Rot in Cultivated Strawberry by Raymond Leo Jacobs III A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the Degree of Doctor of Philosophy Horticultural Science Raleigh, North Carolina 2015 APPROVED BY: _______________________________ _______________________________ G. Craig Yencho, Ph.D. Jason A. Osborne, Ph.D. Chair, Advisory Committee Statistics Minor Representative _______________________________ _______________________________ Frank J. Louws, Ph.D. Dennis J. Werner, Ph.D. DEDICATION To my closest friend, who braved all of the emotions that graduate school brings. You stood by my side every step of the way and for that I will always be grateful. To my sister, for her unconditional love and support. You never failed to keep my outlook positive and spirits high. To my grandparents, for always letting me know how proud they were of me. Finally, to my parents, who taught me to be humble and kind. You urged me to seize every opportunity, encouraged excellence in my work, and provided the freedom to forge my own path in the world. ii BIOGRAPHY Raymond Leo Jacobs III was born in Green Pond, South Carolina on December 24, 1986 to Ray and Paula Jacobs. Just 13 months later his sister and lifelong friend Rebecca Jacobs was born. He spent his childhood roaming the expansive forests and wetlands of White Hall Plantation where his family lived and his father served as property manager. Raymond was curious, mischievous, and had a talent for getting into trouble. During his childhood, Raymond’s favorite time of year was spring. His morning ritual included an inspection of his parents’ garden to see what progress had been made from the day before. He learned the magic of pollination at an early age and could be seen pulling cotton swabs out of his pockets on spring and summer mornings, competing with the bees to set a good crop. Raymond’s first foray into the world of plant breeding occurred in his mother’s daylily garden where there were an amazing diversity of daylily shapes, sizes, and colorations. He discovered that he could make controlled crosses among these plants, collect the seed, and within a year could grow the plants to flowering size and view his new creations. Many beautiful and hideous daylilies resulted from these crosses. Regardless, he was fascinated and a career was born. His mother still grows the daylilies from these first crosses – even the ugly ones. Raymond whizzed through Colleton County High School where he was honored to graduate valedictorian of his class and to accept an offer to study at Cornell University. Going from Zone 8b in South Carolina to 5b in upstate New York wasn’t the only shock of heading to college at Cornell. Raymond (now Ray) was met and welcomed by a diversity of cultures and ideas completely new to him. Ray majored in Plant Biology with a focus in iii Plant Breeding and Genetics and minored in Business. He taught himself how to study at a college level and excelled at his coursework. Some of Ray’s most influential experiences, however, were outside of the classroom. He was an active member and president of Hortus Forum, Cornell’s undergraduate horticulture club. The club grew houseplants on campus that were sold to students and faculty at weekly plant sales to fund educational trips. During his four years at Cornell Ray traveled with the club to six countries to explore agricultural operations around the globe. He also spent a semester abroad studying at the University of Melbourne in Victoria, Australia – a place he fell in love with and hopes to return to someday. Ray graduated with a B.S. under the guidance of Dr. Mark Sorrells in May 2009. Ray then ventured west to Woodland, CA to spend a year working at Seminis Vegetable Seeds and gaining experience in private industry. He picked up many practical skills during his time there and thoroughly enjoyed the experience. He knew he wanted to pursue a career in plant breeding but would first need a graduate-level education to master the subject. Ray enrolled in the Department of Horticultural Science at North Carolina State University in August 2010. iv ACKNOWLEDGMENTS I would like to thank a number of people for helping me during my time in graduate school: Dr. Jeremy Pattison for taking me on as a student, working closely with me to develop this project, teaching me to keep an open mind, and showing me how to “see the trees through the forest”; Elizabeth Clevinger for all of the time and hard work she contributed to seeing this project a success; Megan Bame for her dedicated care of my plants and for going beyond the call of duty to help me when I needed it most; Dr. Craig Yencho for his excellent breeding advice and willingness to step into the role of committee chair; Dr. Frank Louws and Dr. Tika Adhikari for their help in developing this project and understanding the complex nature of these pathogens; Dr. Dennis Werner for showing me how much fun teaching can be as well as his encouragement and willingness to join my committee; Dr. Jason Osborne for his continued statistical advice during this project; the crew at the Piedmont Research Station in Salisbury, NC for their hard work and dedication to the strawberry breeding program; and finally to all of the faculty and staff at the Plants for Human Health Institute at the NC Research Campus in Kannapolis, NC for being a pleasure to work with and always coming to my aid.