Submitted to: Blueberry Research Extension North American Workers Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/27/1998
Publication Date: N/A
Interpretive Summary: The ability of woody perennial plants to survive freezing winter temperatures is dependent on plants annually entering a state of dormancy and developing cold hardiness (CH). For plants in this dormant state, a chilling period is required for budbreak tooccur the following spring. Together, this chilling requirement(CR) and CH level determine whether temperate-zone woody perennial fruit crops will survive the winter and early spring without frost damage to shoots and flower buds. Despite the critical roles CR and CH play in determining winter and early spring survival, very few genetic studies have been conducted on the inheritance of these traits in woody perennials. We are progressing toward our goal of mapping CR and CH in blueberry. Molecular marker-based genetic maps are being constructed using populations suitable for mapping CH and CR. To date, 27 markers have been assigned to eight chromosomes in one population and 37 markers have been assigned to 12 chromosomes in another population. Based on the inheritance of CR in these populations, a working model has been developed to explain genetic control of CR. In its simplest form, this model assumes that two genes with equal and additive effects control CR. This work will help breeders to develop more effective breeding strategies for shortening or lengthening CRs and ultimately will enable use of marker-assisted breeding approaches.
Technical Abstract: We are progressing toward our goal of mapping quantitative trait loci (QTLs) controlling chilling requirement and cold hardiness in blueberry. Randomly amplified polymorphic DNA (RAPD)-based genetic linkage maps are being constructed using two testcross populations segregating for chilling requirement and cold hardiness. Testcross populations were derived from interspecific hybrids of wild diploid blueberry species, Vaccinium darrowi Camp x V. caesariense Mackenz. Twenty-seven RAPD markers were assigned to eight linkage groups in the V. darrowi testcross and 37 RAPD markers were assigned to 12 linkage groups in the V. caesariense testcross. Chilling requirement data was used in a generation means analysis to evaluate different genetic models to explain the gene action of chilling requirement. This analysis, which assumes that parental populations are homozygous for all genes controlling chilling requirement, failed to identify any models which accurately described the chilling requirement gene action for the populations analyzed. Based on the observed segregation ratios of chilling requirement in the F1 and testcross populations, we were able to evaluate single and digenic models for the inheritance of chilling requirement. A two gene model was developed which fairly accurately predicted the observed ratios in the testcross populations. In its simplest form, this model assumes that two genes with equal and additive effects control chilling requirement.