Final Abstract

Finemapping of Chlorophyll Content Locus in Tomato (S. lycopersicum)

Katie Toomey, Yasin Topcu, & Ester van der Knaap

Chlorophyll are the color-capturing pigments found in plants that allow them to photosynthesize. Chlorophyll A is considered the main pigment that absorbs UV in the orange-red and violet-blue range (430-660 nm) while the accessory pigment, chlorophyll B, absorbs orange-red UV (470 nm). To map chlorophyll B content genes in tomato, we worked with tomatoes of a known genetic background: BGV007900 and BGV007936 which are known to have high and low chlorophyll B contents respectively. Using with these two accessions from the sol genomics varitome project, one F4 and three F7 populations were created and F3:4 and F6:7 plants were selected using marker assistant selection using Kompetitive Allele Specific PCR (KASP). Populations along with parental checks were grown in a greenhouse and plants were phenotyped weekly for chlorophyll content index (CCI) using an apogee chlorophyll meter. The genetic interval responsible for chlorophyll B was narrowed from 69.8 kb to 31.5 kb pair interval that includes only four genes. Based on their expression patterns and blasting results, only two genes were identified as candidate genes, Solyc04g010290 and Solyc04g010300.

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Florida and DNA extraction

This week, my lab took a trip to Florida to harvest some tomatoes we had in Floridian fields. I learned some tomato terms like "breaker" (a tomato in between green/red) and "inflorescence" (a flowering group) while getting my field experience. The project works with the University of Florida which was kind enough to let us use some lab space while we were there. We chopped up tomatoes to observe their volatiles in GCMS for a Ph.D. student in our lab. I enjoyed the experience because it gave me another opportunity to explore a lab space dedicated to plant science and I was able to see interesting Floridian wildlife. We arrived at the fields in the early morning; these are the fields we harvested. Above is a bug that was blended into a plant in Florida that we saw on our trip. After returning to Georgia, we set to work to extract DNA from the F6 generation from the greenhouse in addition to the parental lines. By extracting one cotyledon from each plant, we had enoug

Selection of Plants for Transplanting

At this point, we have just confirmed our plant selection using marker-assisted KASP PCR genotyping. Using the DNA extracted earlier, we ran a KASP PCR. The then amplified DNA is read by the Teacan machine which works by reading the specific fluorescent dye in a FAM marker which will bind to the reference allele (determined by the Sol Genomics Network available for free on their website) while the HEX marker will bind to the alternative/SNP allele. The program, Klustercaller, is then able to interpret the Teacan reads which allows us to genotype the plants as either X:X(reference homozygous/FAM dye), X:Y(heterozygous/FAM & HEX), or Y:Y(alternative homozygous/HEX dye). Whether the BGV007900 or BGV007936 parental line has the reference or alternative allele depends on the location. For example, at locus "1", BGV007900 may have the same genotype as the reference genome, then at that location, X:X would correlate to having the BGV007900 allele. However, maybe at locus "2

Explaining the Project

For the general public: Leaf Color Genetics in Tomato Blossom-end rot (BER) is a physiological disorder in tomatoes that reduces the bottom end of the fruit to brown mush. My mentor studies BER, but the research involved takes many months. So to compensate for a lack of time, I am working with a simplified project involving leaf color/chlorophyll content. This project should mimic the process of BER trait testing on a smaller scale. This summer, I will aid in breeding projects aimed to confirm the location of the gene that controls leaf color/chlorophyll content. To do this, we will observe the genetic and expressed (color, incidence, etc.) traits of progeny that resulted from crosses between dark-leafed and light-leafed plants. By comparing the genetic and expressed traits, we should elucidate the gene's location. A picture of the greenhouse with my mentor's plants. The bottom left seed tray has my F2 generation. A picture of the greenhouse with my mentor's plants. The

HORT 484 Blog: UGA Crop Genetics and Genomics REEU

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