1a. Objectives (from AD-416)
Identify factors that explain differences in yield among lowbush blueberry clones. Compare high yielding clones to low yielding clones for several factors. Factors include average genetic similarity with neighbors and effects of relationship of parents in controlled crosses on fruit set, synchrony of flowering time with neighbors, freezing tolerance of closed flower buds and open flowers, floral morphological and physiological differences (nectar amounts) that might be more attractive to bees, signs of disease, etc.
1b. Approach (from AD-416)
Studies will focus on comparing high yielding clones to low yielding clones for several factors. Because V. angustifolium is predominantly outcrossing and self-fertility is poor due to early- acting inbreeding depression, one of the factors that will be investigated is genetic relationship with neighboring clones. EST-PCR markers will be used to genotype clones and determine relationship (genetic similarity) to other clones. Crosses will be made between high yielding clones and other clones in the field that have clearly different similarity values. The same will be done with low yielding clones. In this way, it will be determined if genetic relationship affects yield. In addition, 4-5 clones in the immediate vicinity of each high and low yielder will be genotyped. The average similarity value between each focal high and low yielder and its neighbors will be determined and compared. Other factors will be compared between high and low yielding clones including synchrony of flowering time with neighbors, freezing tolerance of closed flower buds and open flowers, flower morphology, signs of disease, etc.
3. Progress Report
About 1/3 of commercial blueberry production is from managed, wild stands of lowbush blueberry (V. angustifolium). Lowbush blueberry grows in a patchwork or mosaic pattern of individual plants referred to as clones. Variation among clones is very high with adjacent clones showing as much as 12-15 fold differences in berry yield. The focus of this research is to use DNA markers to identify genetic factors responsible for these yield differences. Lowbush blueberry is pollinated by rented honey bees which tend to fly short distances, thus plants tend to be pollinated by themselves or by near neighbors. Crosses between individual blueberry plants that are too closely related may result in low yields due to inbreeding. Therefore, one hypothesis for the yield differences between clones is that certain clones may be too closely related to neighboring clones to yield high amounts of fruit because of inbreeding depression. Molecular markers were used to examine genetic relatedness of individuals within two wild blueberry fields in Maine, in combination with genetic crosses, to determine if relationship of parents involved in crosses affects yield. No evidence of yield being affected by genetic relationship was found except in the case of self crosses (where the same parent was used as both male and female parent), which generally resulted in lower yields. Importantly, it was found that the better selfers generally yielded more in outcrosses, as well. This information will help scientists make recommendations to growers on ways to improve yields in lowbush blueberry. Progress was monitored by the ADODR through meetings, phone calls, and e-mails to exchange data and discuss research plans.