Fruit Quality Measurements in a Segregating Blueberry Population: Plant Breeding Training for Undergraduates

At U.S. institutions, plant breeding is rarely offered as an undergraduate major.  For many undergraduates majoring in plant sciences, plant breeding is a higher level elective, and for those not majoring in plant sciences, plant breeding is often an entirely new concept.  Even when offered as a course, hands-on training in plant breeding is not common.  Our participation in a multi-institutional research project to develop a linkage and quantitative trait locus map for tetraploid highbush blueberry (Vaccinium corymbosum L.) has given the opportunity to offer laboratory and plant breeding training to several undergraduate students.  The cohort of students involved in this project were recruited primarily through guest lectures on blueberry history, culture, and breeding given in introductory horticulture and biology courses at the University of Florida.  Fruit was collected from a segregating tetraploid highbush blueberry F₁ population that was created from an intra-specific cross between the northern-adapted cultivar Draper and southern highbush cultivar Jewel. The population is clonally replicated in several locations including Gainesville, FL, and Homerville, GA, where berries from each genotype were harvested once each plant had 50% fully ripe fruit.  Because many of the fruit quality traits measured in this population required objective measurements, we focused on these as training opportunities.  For fruit size (g) and firmness (g/mm compression force as measured on a FirmTech 2 firmness analyzer), samples were held in a cooler (4 °C) and measured within 48 hours.  For total solids (g dry weight/10 g fresh weight), soluble solids (°Brix measured on a handheld refractometer), titratable acidity (citric acid equivalent), and anthocyanin content (mg/L of cyanidin-3-glucoside equivalents), berry samples were held in a cooler (4 °C) for up to 48 hours, and then frozen (–20 °C) prior to processing.  Students were required to contribute to sample processing, measurement, and analysis.  Mini-experiments were designed to take students from hypothesis to statistical analysis, and illustrate the variation for many fruit quality traits possible through plant breeding.  For example, the correlation between total solids and soluble solids was tested to determine whether soluble solids could predict total solids as in other processed fruits and vegetables. For this population Spearman’s rank correlation indicated total solids and soluble solids were correlated for fruit collected from the Florida (r = 0.34, P = 0.004) and Georgia (r = 0.72, P < 0.0001).