Small Fruit Plant Pathology Research
Dr. Smith conducts basic and applied research in the broad area of diseases of small fruit crops as part of a long range program designed to develop new and improved cultural and management practices and new and improved small fruit cultivars which are pest resistant and adapted to the Gulf Coast Region. She is responsible for developing and conducting research on plant disease control that is of immediate importance to growers of small fruit crops and also is of long-standing importance (e.g., pathogen identification and physiology, interaction among genotypes of small fruit hosts and their pathogens). Dr. Smith's research assignment to small fruit diseases includes diseases of strawberry, blueberry, blackberry and muscadine grape; their epidemiology and control, and breeding for disease resistance.
Dr. Smith’s major emphasis is on strawberry anthracnose. She developed a screening program to identify anthracnose crown rot resistance in large populations of strawberry seedlings which is used worldwide to identify strawberry germplasm resistant to Colletotrichum acutatum as well as C. fragariae. Dr. Smith was the first in the U. S. to report the occurrence of the destructive anthracnose fruit rot pathogen, C. acutatum, and that three Colletotrichum species caused identical symptoms on strawberry plants, and to identify several important distinguishing characteristics between these species. She studied the epidemiology of strawberry anthracnose and the effect of various cultural practices on the severity and spread of the disease in the field, and determined that strawberries grown in soils with high levels of nitrogen, especially from ammonium sources, are more susceptible to anthracnose than plants grown in soils with lower nitrogen levels or those with high levels of calcium nitrate. Overhead irrigation and plastic mulch resulted in more severe anthracnose than drip irrigation and straw mulch. Dr. Smith identified factors affecting the expression of resistance to C. fragariae by strawberries; age and nutritional status of the plant, method of inoculation and effect of races of the pathogen. Along with a plant geneticist she determined the inheritance of resistance to Colletotrichum species in strawberry and released a cultivar, 'Pelican,' and three strawberry clones resistant to anthracnose crown rot, which have been supplied to plant breeders from throughout the world. She was invited to write three chapters on strawberry anthracnose for the revised edition of the APS Strawberry Compendium.
Dr. Smith studies rosette disease of erect blackberry and through SEM observations the relationship between the casual fungus, Cercosporella rubi, and the blackberry flower buds. Through field studies she established that the infection period began during bloom and continued through the summer. This differed from previous research which had indicated that infection did not occur after mid-May and thus resulted in a change in the fungicide spray schedule which greatly improved the effectiveness of chemical control. She identified cultural practices that reduce disease incidence and used an in vitro assay to screen fungicides for activity against C. rubi. Dr. Smith and a plant geneticist studied the inheritance of rosette resistance in erect blackberry. Dr. Smith wrote the chapter on blackberry rosette in the APS Raspberry and Blackberry Disease Compendium.
Dr. Smith has identified the major berry diseases occurring on rabbiteye blueberries at harvest and the susceptibility of rabbiteye cultivars to these diseases, and was the first to report that C. acutatum was the major causal agent of blueberry ripe rot rather than the more commonly reported C. gloeosporioides. She developed an in vitro assay to identify blueberry germplasm resistant to stem blight and along with the plant geneticist used the assay to screen blueberry germplasm for resistance to stem blight. This information is being used by plant breeders as they select parents for future crosses, by horticulturists as they recommend cultivars to plant and by extension plant pathologists as they develop fungicide spray recommendations. Her other publications on blueberry include reports on botrytis blossom blight and phytophthora root rot.
Dr. Smith and a Ph. D. level graduate student conducted studies on the identification, incidence and epidemiology of diseases on muscadine grape in south Mississippi. They investigated the efficacy of fungicide control of these diseases, and identified a reduced fungicide spray schedule for muscadines grown for the juice market. Dr. Smith identified major diseases occurring on muscadine grapes and cultivar susceptibility to these diseases and collaborated with scientists at Florida A&M who develop a quick and accurate method to detect the bacterial pathogen (Xylella fastidiosa) in grapevines