and was not simply the result of parental chromosome differences. In cases in which sterility is incited by improper chromosome pairing, doubling the chromosome complement (polyploidization) of sterile hybrids to produce allotetraploids provides a
Somatic hybridization in citrus using the embryogenic suspension protoplast plus leaf protoplast fusion model can be considered a reliable technique, because hundreds of allotetraploid somatic hybrids have been produced for both scion and
Wide hybridization can potentially lead to the combination of diverse traits, but these hybrids are often sterile as is the case with the inter-subgeneric hybrid Rhododendron `Fragrant Affinity'. Induction of polyploidy can restore chromosome homology and fertility in wide hybrids. In this study we successfully developed an allopolyploid form of R. `Fragrant Affinity' using oryzalin as a mitotic inhibitor and chromosome doubling agent. Approximate genome size (2C), determined using flow cytometry, was 1.6 pg for the diploid and 3.2 pg for the allotetraploid. Pollen viability, determined by staining and germination tests, was 4% and 0%, respectively for the diploid and 68% and 45%, respectively for the allotetraploid. No seeds were produced when the diploid R. `Fragrant Affinity' was crossed with pollen from viable diploid and tetraploid parents. The allotetraploid produced viable seeds and seedlings when crossed with viable pollen from either diploid or tetraploid parents, including self pollination, demonstrating restored fertility. Additional crosses were successfully completed using the allotetraploid as part of an ongoing breeding program to develop new fragrant, cold hardy, evergreen rhododendron.
Markwith, S.H. Stewart, D.J. Dyer, J.L. 2006 TETRASAT: A program for the population analysis of allotetraploid microsatellite data Mol. Ecol. Notes 6 586 589 10.1111/j.1471-8286.2006.01345.x Marquis, D
morphology of Rudbeckia will better enable the development of improved varieties. The objectives of this study were to evaluate fertility, morphology, phenology of flowering, and perennialness for lines of diploid and induced allotetraploids of R
Interploid hybridization was conducted using `Key' lime [Citrus aurantifolia (Cristm.) Swing.], `Lakeland' limequat hybrid [C. aurantifolia × Fortunella japonica (Thumb.) Swing.], Palestine sweet lime (C. limettioides Tan.), `Etrog' citron (C. medica L.), and seven lemon [C. limon (L.) Burm. F.] varieties as female progenitors and five allotetraploid somatic hybrids {`Hamlin' sweet orange [C. sinensis (L.) Osbeck] × `Femminello' lemon (C. limon)]; `Key' lime × `Valencia' sweet orange (C. sinensis); `Valencia' sweet orange × rough lemon (C. jambhiri Lush); Milam lemon (purported C. jambhiri hybrid) × `Femminello' lemon (C. limon); and `Valencia' sweet orange × `Femminello' lemon} and two autotetraploids [`Giant Key' lime (C. aurantifolia) and `Femminello' lemon] as pollen progenitors. A few tetraploid × diploid crosses were also performed. Thirty-five parental cross combinations were accomplished in 2000, 2001, and 2002. The breeding targets were seedlessness, cold-tolerance, and disease resistance. Triploid hybrids were recovered through embryo culture. Generation of triploid citrus hybrids was affected by several factors including sexual compatibility, cross direction, embryo developmental stage, pollen viability, as well as horticultural practices and climatic conditions. Efficiency of triploid hybrid production was higher in diploid × tetraploid crosses than the reciprocal. Many more triploid hybrids were generated from lemon seed progenitors compared to the other acid citrus fruit progenitors. `Todo el Año', `Lisbon', and `Limonero Fino 49' showed the highest sexual compatibility. Embryo germination rate and normal plant recovery were also higher in lemons as compared to the other seed progenitors. Low winter temperatures might have affected the hybrid production efficiency from tropical acid fruit progenitors. A total of 650 hybrids (mostly triploid) were transferred to soil. The novel genetic combinations of these progenies should be valuable for the genetic improvement of acid citrus fruit (lemons and limes).
hybrids present fertility issues, but if hybrids can be made at the tetraploid level, allotetraploid fertility and apparent tetraploid buffering almost surely guarantee some level of success will exist in the backcrossing of intersectional hybrids to
US 1930, a 4 x V. meridionale – V. vitis-idaea clone. The high female fertility of this S 1 V. meridionale – V. vitis-idaea clone allows perhaps the best estimation of potential male fertility. Fertility of F 1 allotetraploids might be expected
been a successful and interesting parent, producing F 1 triploids and both triploids and tetraploids in BC 1 type crosses. Notably, our hybrids, the 4 x particularly, were highly fertile. Fertility of F 1 allotetraploids might be expected because
A study was done to test whether inheritance is tetrasomic or disomic in tetraploid Fl hybrids between 2x Vaccinium elliottii Chapm. and 4x V. corymbosum L. Seventeen Fl hybrids derived from V. elliottii homozygous for recessive anthocyanin deficiency (AD) were confirmed by isozyme analysis and, where V. elliottii was the seed parent, by the presence of anthocyanin. Fertile hybrids with high pollen stainability were assumed to be 4x and duplex for the AD allele, having arisen from 2n gametes in V. elliottii. In nine Fl × Fl crosses, all progeny populations segregated for AD phenotype at or above the expected tetrasomic ratio of 1 AD:35 normal; no AD would be expected with disomic inheritance. Tetraploid AD progeny were used in testcrosses on sixteen Fl hybrids in 1991. Progeny segregated tetrasomically, 1 AD:5 normal. Isozyme loci PGD-2 and PGI-2 also segregated tetrasomically.