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Meiling Yang, Fang Li, Hong Long, Weiwei Yu, Xiuna Yan, Bin Liu, Yunxiu Zhang, Guorong Yan and Wenqin Song

Malus sieversii (Ledeb.) Roem. is a wild apple species native to Central Asia. Its provenance includes the region of the Tienshan Mountains, extending from China to Kyrgyzstan and Kazakhstan. It has been recognized as one of the major progenitors

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Christopher M. Richards, Gayle M. Volk, Patrick A. Reeves, Ann A. Reilley, Adam D. Henk, Philip L. Forsline and Herb S. Aldwinckle

exploration teams collected Malus sieversii seeds and clones from Kazakhstan between 1989 and 1996 ( Dzhangaliev, 2003 ; Forsline et al., 2003 ; Hokanson et al., 1997 ; Luby et al., 2001 ). Over one thousand trees derived from seeds collected during these

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Gayle M. Volk, Adam D. Henk, Christopher M. Richards, Philip L. Forsline and C. Thomas Chao

The mountains of Central Asia have forest species that include Malus sieversii (Ledeb.) M. Roem., a highly diverse apple crop wild relative. The Russian scientist Vavilov explored the forests of Central Asia in the 1920s and made note of the wide

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Carole L. Bassett, D. Michael Glenn, Philip L. Forsline, Michael E. Wisniewski and Robert E. Farrell Jr

., 2002 ). Although there has been some confusion regarding the taxonomy of the cultivated apple (summarized in Harris et al., 2002 ), most taxonomists agree that Malus sieversii is the most closely related species ( Mabberley et al., 2001 ; Robinson

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M.T. Momol, W.F. Lamboy, P.L. Forsline and H.S. Aldwinckle

Malus sieversii is one of the primary progenitors of the cultivated apple. Since 1989, several collecting trips have been made to central Asia by personnel of the USDA and Cornell Univ. to collect seeds of wild Malus sieversii from many diverse ecosystems. In 1992, an ex situ plot in Geneva, N.Y., was established with trees grown from seed that was collected in three different habitats in Kazakstan, Tajikistan, and Uzbekistan in 1989. In 1995, trees grown from seed that was collected in five additional habitats in Kazakstan and Kyrgyzstan in 1993 were added to the ex situ plot. In the summers of 1995 and 1996, tips of vigorously growing shoots of 1135 seedlings from 79 different populations were inoculated by hypodermic syringe with 5 × 108 cfu/ml of Erwinia amylovora strain Ea273. Seedlings from the 1989 collection were in the fourth and fifth field-growing seasons, with some beginning to bear fruit. Seedlings from the 1993 collection were in first and second field-growing seasons. Results from both seasons indicated that individuals within each of the 79 populations of M. sieversii are resistant to fire blight (defined as ≤20% shoot length infected). Resistance differed among populations, with some populations having no resistant individuals and others having >80% of the seedlings resistant. The range of resistance is quite similar to that seen among apple cultivars from North America and Europe. In another test, some accessions from 1989 collection had sufficient bloom for inoculation in 1995 and 1996. At full bloom, blossoms on these trees were inoculated with the E. amylovora suspensions (5 × 107 cfu/ml) using a backpack sprayer. These also gave diverse resistant reactions.

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Warren F. Lamboy, Jing Yu, Phil L. Forsline and Norman F. Weeden

One of the primary progenitors of the cultivated apple is Malus sieversii L., a species native to the forested regions of central Asia. Despite the horticultural importance of M. sieversii, little is known about genetic variation in this species. In this study, allozyme diversity at 18 loci was determined for 259 seedlings belonging to 31 sib families, each consisting of the set of offspring from a different open-pollinated maternal (seed) parent. Maternal parents belonged to 14 populations from four geographic regions. Genetic diversity statistics were computed from the resulting allele and phenotype frequencies. Cluster analysis of sib families showed that there was some grouping based on geographic region, but 16 of the sib families were most closely related to sib families from other regions. Analysis of molecular variance (AMOVA) indicated that 85% of the enzyme variability was due to differences among sib families within populations and 15% was due to differences among regions. No variability could be assigned to differences among populations within regions. In addition, no alleles were found that were fixed in a region and unique to that region. These results suggest that plants belonging to M. sieversii effectively form a panmictic population. Consequently, a thorough sampling of a few large populations will efficiently capture most of the genetic diversity present in wild M. sieversii.

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Gayle M. Volk, Christopher M. Richards, Ann A. Reilley, Adam D. Henk, Philip L. Forsline and Herb S. Aldwinckle

Seeds and scionwood of Malus sieversii Lebed. have been collected from wild populations of apple trees in Kazakhstan. Seedlings and grafted trees were planted in the orchards at the U.S. Dept. of Agriculture Plant Genetic Resources Unit in Geneva, N.Y. We developed core collections to capture the genetic and phenotypic diversity represented in the trees from each of two of the Kazakhstan collection sites. These core collections capture more than 90% of the genetic diversity of the original populations, as determined using seven unlinked simple sequence repeat markers and 19 quantitative traits. Since phenotypic evaluations of these materials have been completed, the 35 trees within each population will be used as parents in crosses so that the genetic diversity in the orchard populations can be captured as seed for long-term ex situ conservation. This strategy of storing seeds, rather than maintaining costly field collections, could be applied to other collections of wild plant materials in the National Plant Germplasm System.

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D. Michael Glenn and Carole Bassett

population of Malus sieversii . Materials and Methods Irrigated ‘Empire’/‘M.7A'were planted at a density of 500 trees/ha in 1992 at the USDA/ARS Appalachian Fruit Research Station, Kearneysville, WV (lat. 39.3 N, long. 77.9 W, elevation 175 m). In all years

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James Luby, Philip Forsline, Herb Aldwinckle, Vincent Bus and Martin Geibel

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Warren F. Lamboy, Jing Yu, Phil L. Forsline and Norman F. Weeden

One of the primary progenitors of the cultivated apple (Malus ×domestica) is M. sieversii, a species native to the forested regions of Central Asia. Despite the horticultural importance of M. sieversii, little is known about its genetic variation. In this study, isozyme diversity at 18 loci was determined for 259 open-pollinated offspring belonging to 31 different maternal half-sib families collected from 14 different populations in 4 regions of central Asia. Genetic diversity statistics were computed from the resulting allele and phenotype frequencies. Cluster analysis of half-sib families showed that there was some grouping based on geographic region, but 16 of the half-sib families were most closely related to half-sib families from other regions. AMOVA, the analysis of molecular variance, indicated that most of the enzyme variability (85%) was attributable to differences among half-sib families within populations, none could be assigned to populations within regions, and 15% was due to differences among regions. In addition, no alleles were found that were both fixed in a region and unique to that region. These results suggest that plants belonging to M. sieversii effectively form a single panmictic population. Thus, a thorough sampling of a few large populations will efficiently capture most of the genetic diversity present in wild M. sieversii.