Derivatives of Vaccinium arboreum × Vaccinium Section Cyanococcus. II. Fertility and Fertility Parameters

Abstract

<jats:p>Fertility of F<jats:sub>1</jats:sub> hybrids and their open-pollinated progeny was studied for the intersectional cross <jats:italic>Vaccinium darrowi</jats:italic> Camp × <jats:italic>V. arboreum</jats:italic> Marsh as part of a project to determine the feasibility of using <jats:italic>V. arboreum</jats:italic> to breed vigorous, drought-tolerant southern highbush blueberry cultivars. The 16 F<jats:sub>1</jats:sub> hybrids that were studied were vigorous but very low in fertility. Second generation hybrids [MIKs (mother is known) obtained by open-pollination of the F<jats:sub>1</jats:sub>s] and MIK derivatives were extremely variable in vigor and fertility, but averaged far higher in fertility than the F<jats:sub>1</jats:sub>s as evidenced by pollen stainability and amount of pollen produced. F<jats:sub>1</jats:sub>s produced an average of 0.4 seedlings per 100 pollinated flowers when hand-pollinated in a greenhouse with pollen from <jats:italic>V. darrowi</jats:italic>, 0.2 when pollinated by <jats:italic>V. arboreum</jats:italic> and 3.4 when pollinated by cultivated highbush. Some MIKs that were crossed with other MIKs and with cultivated southern highbush were very high in male and female fertility. Female fertility was estimated in greenhouse crosses from fruit set, berry weight, number and weight of seeds, number of plump seeds per berry, and number of seedlings obtained. Male fertility was estimated by pollen stainability with acetocarmine and amount of pollen shed. Chromosome counts showed that three F<jats:sub>1</jats:sub>s were diploid and that four fertile MIKs were tetraploid. One MIK appeared to be aneuploid. Aneuploidy may explain much of the low fertility found in MIK populations. These results indicate that good progress is being made in returning the hybrid plants to cultivar quality in only a few generations of backcrossing.</jats:p>

Production of Intersectional Hybrids between Colchicine-induced Tetraploid Shashanbo (Vaccinium bracteatum) and Highbush Blueberry ‘Spartan’

“…Variation of pollen stainability was found in the intersectional hybrids in this study and this is consistent with other studies. Chavez and Lyrene (2010) found pollen stainability of intersectional hybrids was much lower (5.8%) than those of parents V. darrowii (95.8%) and V. arboreum (92.2%) and Brooks and Lyrene (1998) also found that pollen stainability of F 1 (V. darrowi · V. arboreum) hybrids averaged only 0.9%. Low pollen fertility of these intersectional hybrids was the result of the infrequency of normal bivalent pairing between the two chromosome sets and numerous meiotic abnormalities from chromosome structural differentiation between the two sections of the genus Lyrene, 1995, 1998;Chavez and Lyrene, 2010;Lyrene, 1991).…”

Hybridization of Cultivated Highbush Blueberry with Vaccinium stamineum: Phenotype and Fertility of Backcross1 Populations

“…With respect to fertility of F 1 hybrids, V. arboreum and V. stamineum crosses differed little. Diploid Cyanococcus hybrids with both V. arboreum and V. stamineum were highly sterile, except that V darrowii • V. arboreum F 1 hybrids produced a few viable unreduced gametes, and a few seedlings were obtained after F 1 flowers were pollinated with pollen from tetraploid highbush cultivars (Brooks and Lyrene, 1998). Diploid V. darrowii • V. stamineum hybrids have so far been too weak to permit backcrosses to tetraploids.…”

Hybridization of two diploid Vaccinium section Cyanococcus species with diploid Vaccinium arboreum in section Batodendron

“…Seed from V. darrowii 9 V. arboreum crosses made in 2007, planted in the first week of November 2007, started to germinate in the second week of March 2008, almost 6 weeks later than V. arboreum 9 V. darrowii crosses. Vaccinium arboreum has larger seeds than V. darrowii and southern highbush cultivars (Brooks and Lyrene 1998b). It is not known whether this is related to the rate of germination.…”