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A natural strawberry genotype, `Jilin 4', was collected from the Changbai Mountains located in Gongzhuling Region, Jilin Province, Northeast China. It was identified as a pentaploid (2n = 5x = 35) by counting the chromosomes of the root-tip cells. Natural pentaploid strawberries have not been reported as originating in China or outside of California in the U.S. Jilin 4 was the most vigorous genotype among representatives of all 15 wild species of Fragaria and more than 60 cultivars of F. ×ananassa in a common garden. The size of its flowers and anthers were similar to those of cultivars and it produced abundant runners. The pollen was viable, but the pistils were sterile. It appeared to be drought and cold tolerant, but showed symptoms of local virus infection. There are three possible origins of Jilin 4, which are discussed in this report.

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is known to show very high levels of tolerance to dutch elm disease ( Townsend et al., 2005 ). In the course of surveying wild U. americana , a natural pentaploid was found in western Nebraska (discussed subsequently), and this also showed

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Abstract

Three pentaploids produced from hybridizing hexaploid Vaccinium ashei Reade and diploid V. darrowi Camp were analyzed for fruit set, number of seeds/fruit, seedlings/pollination, pollen grains/sporad, 2n gamete production, pollen germination, leaf area and berry weight, color, scar, and firmness. The pentaploids were intermediate between the parental species in fruit size and leaf area. There was high variation in fertility and in fruit quality among the pentaploid hybrids.

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Seedlings from some small seeds of diploid × diploid crosses using `Miyauchi iyokan' (Citrus iyo Hort. ex Tanaka) as the seed parent were found to be pentaploid (2n = 5x = 45). The growth of pentaploid seedlings was extremely weak on their own roots, but was much more vigorous when micrografted on seedlings of tetraploid trifoliate orange [Poncirus trifoliata (L.) Raf.]. Diploid `Miyauchi iyokan' produced hexaploid seedlings from small seeds in addition to triploid and tetraploid seedlings from normal seeds when crossed with tetraploid `Funadoko' (C. funadoko Hort. ex Y. Tanaka) and `Trovita' sweet orange [C. sinensis (L.) Osbeck]. Based on this phenomenon, the origin of pentaploids is discussed.

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breeding lines of L. camara , triploids were found to be the most male sterile of the ploidy levels, followed by hexaploids, pentaploids, tetraploids, and diploids ( Czarnecki et al., 2014 ). In addition, elite cultivars were found to vary widely in male

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Abstract

V. corymbosum L./V. ashei Reade pentaploid blueberry hybrids backcrossed to tetraploid V. corymbosum yield tetraploids and aneuploids. Six BC1 derivatives, a tetraploid (2n = 4x = 48) and five multiple aneuploids (2n = 4x + 3, 4, 5, 8, and 9 = 51, 52, 53, 56, and 57) were selfed, intercrossed, and backcrossed to the V. corymbosum cv. Bluecrop. The fertility parameters measured were percent fruit set (FS), total seeds/berry (TS), developed seeds/berry (DS), percent developed seeds/berry (PDS), percent seed germination (PG), and number of seedlings (NS). Values of all parameters decreased as aneuploidy level of the cross (sum of extra chromosomes, number of chromosomes over 2n = 48, in the seed and pollen parent) increased; the relationship was principally linear. A significant quadratic relationship was noted for PDS. Diallel analysis revealed that reciprocal effects were significant for all parameters except PG and were the second most important factor contributing to variability among crosses for NS. All parameters indicated a high level of self sterility. Although the aneuploids in this study had reduced crossability, they can produce sizable progenies with practical efficiency. Contrary to previous reports, these results suggest that pentaploid hybrids and their BC1 derivatives can be used to facilitate gene transfer from V. ashei into V. corymbosum.

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Abstract

Percent fruit set, fruit size, total seeds/berry, developed seeds/berry, percent developed seeds/berry, and percent pollen stainability were examined in 4x × 5x and 5x × 4x progenies derived from Vaccinium ashei Reade/V. corymbosum L. pentaploid hybrids backcrossed to V. corymbosum. All fertility parameters indicated that the BC1 progenies were more fertile than the pentaploid hybrids. Pollen stainability indicated that the BC1 derivatives were less fertile than the parental species. All fertility parameters were significantly and negatively correlated with chromosome number, which ranged from the tetraploid (2n = 4x = 48) to pentaploid (2n = 5x = 60) levels within these progenies.

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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.

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, tetraploid, pentaploid, hexaploid, and octoploid levels were identified. Variability in ploidy level was confined to series Cyrta . Accessions representing series Styrax were measured as diploids. This survey confirms the published count for S. redivivus

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(‘Sp 1 ’, ‘Sp 2 ’, and ‘Sd 1 ’) ranged from 32 to 42 μm. However, there are no confirming studies and no data on interploid cytotypes, such as pentaploids or hexaploids. Confirming ploidy level in woody plants can be achieved with flow cytometry and

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