YIA-PGR: Genetic, Molecular and Developmental Analysis of Variation in Tomato Fruit Morphology

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Breeding and mutation analysis in tomato have resulted in a diverse germplasm collection, providing a rich resource for studies on fruit morphology. Often, fruit morphological changes occur during growth and maturation of the ovary prior to pollination and/or during maturation of the fruit after pollination and successful fertilization. Therefore, tomato varieties displaying altered fruit shape may provide unique insights into developmental processes controlling ovary and fruit growth and maturation. Understanding the molecular-genetic basis of diversity in fruit form will allow insights into evolutionary processes in tomato as well as other fruit-bearing crops, and modification of developmental processes regulating ovary and fruit formation. The first goal is to identify and fine-map novel genetic loci to obtain a global view of key loci and developmental pathways controlling variation in tomato fruit shape. Populations derived from crosses between cultivated tomato exhibiting extreme fruit shapes and a round-fruited wild relative will be phenotypically and genotypically analyzed to identify quantitative trait loci (QTL) controlling fruit shape. These loci will be introgressed into a homogenous background to permit future genomic analyses and map-based cloning of genes underlying fruit morphology QTL. The second goal is to identify changes in gene expression profiles during tomato ovary and fruit growth, and to correlate these to developmental changes in morphology. Results from the analyses will provide insights into molecular events regulating ovary and fruit development. In addition, genes will be identified whose transcript levels change as a consequence of allelic substitution at fruit shape loci resulting in changes in fruit morphology. This information will allow insights into networks of genes and biochemical processes potentially downstream from fruit shape loci, and how fruit morphology is regulated. The third goal is to integrate fruit shape characteristics with gene expression and genotype information becoming available during the course of the project, and to develop a searchable database containing this information. In addition, a software package will be developed to semi-automatically analyze variation in fruit shape in tomato varieties and in mapping populations.