Reproductive incompatibility barriers in crosses between Vaccinium corymbosum and V. elliottii

Abstract

A study was made of barriers to hybridization between tetraploid V. corymbosum L., the cultivated highbush blueberry, and V. elliottii Chapm., a wild diploid blueberry which may be useful in breeding cultivars adapted to the southeastern United States. Both prefertilization and postfertilization barriers were detected. Prefertilization barriers were mainly observed when V. elliottii was the male parent and were manifested as an arrest of pollen tube growth at the base of the style. In cases where fertilization did take place, regardless of which species was used as the female, a strong postfertilization barrier usually prevented development of hybrid zygotes. Zygotes remained in a resting state after fertilization and usually aborted before dividing. Meanwhile, the endosperm underwent four to six cycles of cell division before it started to degenerate. A causal relationship between embryo abortion and endosperm malfunction was not clearly established. Endosperm malfunction and embryo abortion were delayed when V. corymbosum was the female parent.