2011 Annual Report 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 fields 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 identify genetic factors responsible for these yield differences, as the parent project goal is to increase productivity and yield in blueberries. One hypothesis for the yield differences between clones is that certain clones may be either male sterile (not producing much viable pollen) or female sterile (not producing many ovules). An experiment was performed in which average number of ovules per flower and average number of viable pollen grains per flower were determined for each of 56 lowbush clones. About five plants, or 10%, were found that were nearly male sterile, producing very low amounts of viable pollen. No plants were found that produced very low numbers of ovules. 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.