The First Glimpse at the Timing of Flower Initiation in Carya illinoinensis Using Gene Expression Studies

Pecan (Carya illinoinensis) is the most economically important nut producing tree species native to North America and is being planted in several areas throughout the world. The most important constraint in pecan production is alternate bearing which is defined as high yields of lower quality pecan nuts in one year and low production of high quality pecan nuts the next year. Flower initiation is directly related to alternate bearing in pecan. Flowering initiation is based on genetic signals within the plant but the timing in pecan is unknown. In other species, including apple, grape, and persimmon, flower initiation occurs during the previous growing season before flowering. We hypothesize that flowering signals in pecan may occur the growing season before flowering occurs and carbohydrate status and phytohormones play a pivotal role. Experiments including RNASeq studies of the complete gene expression profile and qRT-PCR to validate specific pecan flowering genes will characterize the signals responsible for flower induction in pecan and elucidate the timing of these signals. In this study bud and leaf tissue of the fruiting and non-fruiting shoots of four ‘Wichita’ and four ‘Western’ cultivar pecan trees were collected during the growing season and bulked appropriately to construct transcriptome libraries. The RNASeq analyses of these primary transcriptome libraries should elucidate differences in gene expression patterns of these two genotypes and gene expression data will be presented.