Fertility and cytogenetics of Vaccinium darrowi Camp times Vaccinium arboreum Marsh F-1 hybrids and their open-pollinated derivatives.

摘要

Fertility, unreduced gamete production, cytogenetics, and ability to cross with tetraploid (2n = 4x = 48) V. corymbosum L. were studied in two taxa: (1) diploid intersectional F-1 hybrids between V. darrowi Camp (2n = 2x = 24, section Cyanococcus) and V. arboreum Marsh (2n = 2x = 24, section Batodendron) and (2) seedlings, termed Mother is Known (MIK), obtained by open pollinating the F-1's in a field where pollen from section Cyanococcus species V. corymbosum (4x) and V. ashei Reade (6x) were available. Female and male fertility was very low in the diploid F-1 hybrids, but were much higher (although variable) in the MIKs. Cytogenetic analysis showed low levels of chromosome pairing at metaphase I in the F-1 hybrids and in the least-fertile MIKs, which led to lagging chromosomes at anaphase I and anaphase II and aneuploid gametes at telophase II. In the most fertile MIKs, most pairing at metaphase I was bivalent and most disjunction at anaphase I and anaphase II was normal. The more frequent bivalent pairing in the MIKs compared to the F-1 hybrids was probably due to the fact that most of the MIK chromosomes were derived from section Cyanococcus and fewer from V. arboreum. About one quarter of the F-1 hybrid population produced some unreduced gametes, an ability possibly derived from their V. darrowi parent. Unreduced gametes allowed the F-1 diploid hybrids to produce tetraploid hybrids when pollinated with pollen from V. corymbosum, and at least one pentaploid hybrid was produced, apparently from pollination of the diploid F-1 hybrids by hexaploid V. ashei. The high frequency of univalents in most of the diploid intersectional hybrids indicates that V. darrowi and V. arboreum have diverged genetically. However, their hybrids can be used as a bridge to obtain tetraploid hybrids with V. corymbosum in which fertility is medium to high and V. arboreum genes and characteristics are present.