Polyploidy and sexual polyploidization in the genus Vaccinium |
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Authors: | PM Lyrene N Vorsa JR Ballington |
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Institution: | (1) Horticultural Sciences Department, University of Florida, P.O. Box 110690, Gainesville, FL, 32611, U.S.A;(2) P.E. Marucci Center, Rutgers University, Chatsworth, NJ, 08019, U.S.A |
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Abstract: | Genus Vaccinium,consisting of blueberries, cranberries, lingonberries and many related wild species, includes diploid, tetraploid, and hexaploid
species. Most evidence indicates that the tetraploid species are autotetraploids, with non-preferential bivalent chromosome
pairing. Although homoploid interspecific crosses usually produce numerous fertile hybrids if the parents are from the same
section of the genus, inter sectional crosses at the diploid level normally produce no seedlings, weak seedlings, or seedlings
that are very low in fertility. There is a strong but not complete triploid block within Vaccinium. Even with insections, tetraploid × diploid (and the reciprocal) crosses normally give only a few tetraploid and a few triploid
hybrids. Hexaploid × diploid crosses within sections are very hard to make, and the few hybrids that have been obtained are
pentaploid. The frequency of 2n gametes varies,both among genotypes within species and among species. Vaccinium pollen is normally shed in tetrads, and the frequency of large pollen grains shed in dyads can be used to estimate 2n gamete
frequency. Cultivated blueberries occur at both the tetraploid and the hexaploid levels, and there are important genetic resources
in the diploids. Unreduced gamete production has permitted transfer of genetic material from the diploid to the tetraploid
level and from the diploids and tetraploids to the hexaploid level via triploid hybrids. Intersectional crosses can occasionally
produce tetraploid Vaccinium hybrids that appear to behave as amphidiploids and have medium to high fertility. CommercialVaccinium cultivars are normally propagated by cuttings. Intersectional hybridization, chromosome doubling, and asexual propagation
could permit the production of novel hybrid combinations with value as ornamentals or in fruit production.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | autopolyploidy amphidiploidy blueberry hybridization plant breeding triploid block unreduced gametes 2ngametes |
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