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. One hypothesis is that certain clones may be too closely related to neighboring clones to yield high amounts of fruit because of inbreeding depression. To test this hypothesis, the spatial genetic structure of lowbush blueberry was examined across four fields in Maine. Leaf tissue from seven clones per field, equally spaced apart in a linear pattern, was collected for DNA fingerprinting and genetic relationship determination. Within fields, it was found that there was no correlation between physical distance and genetic distance-that is, those clones that were closer together physically were not more closely related genetically. There was a random structure within fields. At the distances among fields, however, there was a correlation between physical distance and genetic distance. Clones within fields were more closely related to each other than to clones in other fields further away. This suggests that genetic relationship is not responsible for yield differences among clones within fields. This research will ultimately be used by scientists in making recommendations to growers for increasing yields. Progress was monitored by the ADODR through meetings, phone calls, and e-mails to exchange data and discuss research plans.