Vaccinium ashei (6x) /V. corymbosum (4x) pentaploid hybrids backcrossed to V. ashei yield aneuploid progeny ranging in chromosome number from 5x to 6x levels. Six backcross aneuploids having chromosome numbers of 2n = 61, 62, 64, 66, 68, and 70 were selected from this backcross and crossed in a complete diallel mating design and backcrossed (as female parents) to two V. ashei cultivars and an interspecific hexaploid hybrid. Fertility variables measured were percent fruit set, total seed per berry, developed seed per berry, percent developed seed per berry, percent seed germination, developed seed per pollination, and seedlings per pollination. A significant linear and positive relationship was found between chromosome number and all seven fertility variables. However, regression accounted for 30% or less of the variation among crosses. Diallel analysis revealed that general combining ability was the major contributing effect for all seven variables, followed by reciprocal effects. Specific combining ability was not significant. The second backcross to the hexaploid level suggested significant effects due to both the BC1 aneuploid and hexaploid genotypes and to a significant genotype × genotype interaction for three of the variables. All six aneuploids were either fully or partially self-sterile. The findings of this study substantiate earlier suggestions that pentaploids in blueberry can be used to facilitate bilateral transfer of characteristics between the tetraploid and hexaploid levels in blueberry.
N. Vorsa and James R. Ballington
Eight highbush blueberry (V. corymbosum L.) triploids (2n = 3x = 36) were crossed with diploids (2n = 2x = 24), tetraploids (2n = 4x = 48), and hexaploids (2n = 6x = 72). No plants were recovered from 4021 3x × 2x crosses. One triploid was relatively fertile in 3x × 4x and 3x × 6x crosses, which is most likely attributable to 2n gamete production in the triploid. The lack of fertility of triploids, which do not produce 2n gametes, in crosses with diploids and tetraploids suggests that the production of gametes with numerically balanced (n = 12 or 24) chromosome numbers is extremely low. In addition, the inability to recover progeny from 3x × 2x crosses also suggests that aneuploid gametophytes and/or zygotes, including trisomics, are inviable in blueberry. Pollen stainability was also highly reduced in triploids. Frequency distributions of anaphase I pole chromosomal constitutions of three triploids were significantly different from one another. Two of the three distributions were shifted toward the basic chromosome number of 12, with one triploid having 25% poles with 12 chromosomes. However, the sterility of 3x × 2x and 2x × 3x crosses indicates that lagging chromosomes during meiotic anaphases are probably not excluded from gametes, resulting in unbalanced gametes in blueberry. Triploids can be used as a bridge to facilitate gene transfer from the diploid and tetraploid levels to the hexaploid level in blueberry.
R.G. Novy, N. Vorsa, and K. Patten
Highly variable productivity among Vaccinium macrocarpon (Ait.) Pursh `McFarlin' bogs in Washington has been noted by growers. The fruiting habits of 12 Washington `McFarlin' bogs, ranging from 5.7-28.4 t/ha productivity were characterized. Uprights from each bog were characterized using RAPD markers, and then used in a greenhouse pollination experiment to determine if variation in fruiting and fertility phenotypes could be associated with RAPD profiles. Fifteen RAPD profiles were identified, and genetic heterogeneity was high among the 12 bogs. An association between RAPD profiles and reproduction characteristics was observed. The most frequent (30%) RAPD profile appeared to represent the `true' `McFarlin', since it was abundant in higher-yielding bogs and its profile was identical to `McFarlin' samples from other growing regions. A unique RAPD profile was also identified which exhibited high yield characteristics, but did not appear to be related to `McFarlin'. The Washington `McFarlin' bogs examined are composed of a diverse array of genotypes with variable fruiting phenotypes, indicating the variability in production has a genetic component.
Rodomiro Ortiz, D.E. Costich, T.P. Meagher, and N. Vorsa
DNA flow cytometry was used to determine nuclear DNA content in diploid blueberry species, and 3x, 4x, 5x, and 6x ploidy levels. Relative fluorescence intensity of stained nuclei measured by flow cytometry was a function of the number of chromosome sets (X): Y = 3.7X – 2.3 (r2 = 95.1%). DNA flow cytometry should be useful for ploidy level determination in the seedling stage. A significant linear relationship was established between nuclear DNA content and number of chromosomes (x); DNA (pg) = 0.52 x1 (r2 = 99.8%). Based on this equation the haploid genome DNA amount (1C) was calculated as 0.62 ± 0.08 pg, with an approximate haploid genome size of 602 Mbp/1C. The results indicate that conventional polyploid evolution occured in the section Cyanococcus, genus Vaccinium: the increase in DNA was concurrent with increase in chromosome number. DNA content differences among 2x species were correlated with Nei's genetic distance estimates based on 20 isozyme markers. Most of the variation was among species (49%), with 26% between populations within species, and 25% within populations.
M.I. van Heemstra, L.P. Bruederle, and N. Vorsa
Diploid populations and progenies of controlled crosses of blueberry, Vaccinium section Cyanococcus, were analyzed by starch gel electrophoresis for nine enzyme systems, aconitase (ACO), aldolase (ALD), alcohol dehydrogenase (ADH), glyceraldehyde-3 -phosphate dehydrogenase (G-3-PDH), isocitrate dehydrogenase (IDH), leucine aminopeptidase (LAP), malate dehydrogenase (MDH), 6-phosphogluconate dehydrogenase (6-PGD), and phosphoglucose isomerase (PGI). Allozyme variants indicated the existence of three alleles at Ace-1, Ald, G-3-pdh-2, and Mdh-2; four alleles at Mdh-3 and 6-Pgd-2; five alleles at Aco-2, Idh, Lap-1, and 6-Pgd-1; six alleles at Adh-2 and Pgm-2; and nine alleles at Pgi-2. In addition, a null allele was found at Lap-1. In the majority of progenies, the inheritance patterns for each of these loci were consistent with mendelian laws for single gene control. Forty-seven pairs of loci were tested for independent assortment revealing two linked pairs, Pgi-2/Lap-1 and Pgm-2/6-Pgd-2, which appeared to represent two independent linkage groups.
T.R. Roper, A.R. Krueger, C.J. DeMoranville, N. Vorsa, J. Hart, and A.P. Poole
Nitrogen fertilizer application is a universal practice among cranberry growers. Cranberries only use ammonium nitrogen sources. This study was undertaken to discover how quickly cranberries in the field would take up fertilizer-derived ammonium nitrogen. Ammonium sulfate labeled with 15N was applied in field locations in Oregon, Massachusetts, New Jersey, and Wisconsin. Samples of current season growth were collected daily for 7 days beginning 24 hours after fertilizer application. In all cases 15N was detectable in the plants from treated plots by 24 hours following application. Additional nitrogen was taken up for the next 3 to 5 days depending on the location. With the exception of Oregon, the maximum concentration of 15N was found by day 7. Oregon was the coolest of the sites in this research. To determine a temperature response curve for N uptake in cranberry, cranberry roots were exposed to various temperatures in aeroponics chambers while vines were at ambient greenhouse temperatures. The optimum temperature for N uptake by cranberry vines was 18 to 24 °C. This research suggests that ammonium fertilizers applied by growers and irrigated into the soil (solubilized) are taken up by the plant within 1 day following application. Soil and root temperature is involved in the rate of N uptake.
J.F. Hancock, P.W. Callow, S.L. Krebs, D.C. Ramsdell, J.R. Ballington, M.J. Lareau, J.J. Luby, G.P. Pavlis, M.P. Pritts, J.M. Smagula, and N. Vorsa
Flower bud and leaf samples collected from a wide range of native North American Vaccinium populations were tested for the presence of blueberry shoestring virus (BBSSV) using the enzyme-linked immunosorbant assay. The highest disease incidence was found in Michigan (14%), although a few positive samples also were found in Virginia, New Jersey, Maine, Ontario, and Quebec. Of seven species tested, only V. corymbosum L. and V. angustifolium Ait. were infected with BBSSV.