Brassica napus includes economically important crops such as oilseed rape, rutabaga, and leaf rape. Other vegetable forms of Brassica napus, namely nabicol and couve-nabiça, are grown in northwestern Spain and north of Portugal, respectively, and their leaves are used for human consumption and fodder. The relationship of nabicol with other Brassica napus leafy crops was studied before, but its origin remained unclear. The aims of this work were to study the genetic relationships among nabicol landraces and other B. napus crops based on microsatellites and to relate the genotypic differences with the use of the crop. The relationship among 35 Brassica napus populations representing different crops was studied based on 16 microsatellite markers. An analysis of molecular variance was performed partitioning the total variance into three components. The source of variation resulting from groups was defined considering the main use of the crop and accounted for a smaller percentage of variation than other sources of variation, proving that this division is not real. Populations clustered into seven different clusters using a similarity coefficient of 0.82. No clear association was evident between clusters and the main use of populations, suggesting genetic differences among populations could reflect differences in their origin/breeding or domestication. Spanish nabicol could have originated from a sample of couve-nabiças, and couve-nabiças could be used to improve nabicol landraces, because they have a narrow genetic basis that limits their potential for breeding.
Pilar Soengas, Pablo Velasco, Guillermo Padilla, Amando Ordás and Maria Elena Cartea
Tim Rinehart, Cecil Pounders and Brian Scheffler
Crapemyrtles (Lagerstroemia) are deciduous shrubs or trees with prolific summer flowers. Their popularity is due in large part to low maintenance requirements in sunny climates, wide range of growth habits, disease resistance, and bark characteristics, as well as having a long flowering period (up to 120 days). Once well-established, they are extremely tolerant to heat and drought. Lagerstroemia was first introduced to the southern U.S. from southeast Asia more than 150 years ago, and is comprised of at least 80 known species. Most modern cultivars are L. indica and L. fauriei hybrids. L. speciosa is a tropical crapemyrtle with very large flowers, but lacks cold hardiness. It is a vigorous plant, but only when grown in Hardiness zones 9 or 10. We recently established microsatellite markers for Lagerstroemia and evaluated their utility for verifying interspecific hybrids. Here we verify F1 hybrids between L. indica `Tonto', `Red River', and L. speciosa. We also genotyped two commercially available L. speciosa hybrids. Currently, we are using crapemyrtle SSRs for cultivar identification and germplasm conservation. Future research includes marker-assisted breeding to produce powdery mildew and flea beetle resistant cultivars, as well as improved growth habit and fall foliage color.
Tim Rinehart and Sandy Reed
Hydrangea popularity and use in the landscape has expanded rapidly in recent years with the addition of remontant varieties. Most cultivars in production belong to the species Hydrangea macrophylla but H. paniculata, H. arborescens, H. serrata, H. aspera, H. heteromalla, H. integrifolia, H. anomala, H. seemanii, and H. quercifolia are also commercially available. In addition to species diversity there is high intra-species variation, particularly in H. macrophylla, which includes mopheads, lacecaps, French, Japanese, dwarf, and variegated varieties. Relatively little is known about the genetic background or combinability of these plants. DNA sequence data, genome size, RAPD, AFLP, and ISSR markers have been used for taxonomic identification and to estimate diversity within the genus. All of these methods have limited usefulness in a large scale breeding program. We recently established microsatellite markers for Hydrangea and evaluated their utility for estimating species diversity and identifying cultivars within H. macrophylla and H. paniculata. We also verified an inter-specific cross between H. macrophylla and H. paniculata using these markers. Future research includes marker assisted breeding, particularly with respect to remontant flowering traits.
Jeremiah D. Lowe and Kirk W. Pomper
Pawpaw [Asiminatriloba (L.) Dunal] is a tree fruit native to areas in the Midwest and Southeast United States. Since 1994, Kentucky State University (KSU) has served as the USDA National Clonal Germplasm Repository, or gene bank, for pawpaw; therefore, the assessment of genetic diversity in pawpaw is an important research priority for the KSU program. There are over 1800 pawpaw accessions (trees) from 16 different states and over 40 cultivars that are planted on 8 acres at the KSU farm. The objectives of this study were to develop microsatellite markers for pawpaw, and to then use those markers to evaluate 19 cultivars in the repository collection. Leaves of the pawpaw cultivar Sunflower were sent to Genetic Information Systems (Chatsworth, Calif.) for simple sequence repeat (SSR) primer and marker development. A total of 34 microsatellite primers were developed for pawpaw. These primers were then used in a preliminary screening with five pawpaw cultivars (`Sunflower', `Mitchell', `Sweet Alice', `Overleese', and `Prolific'). Results from this preliminary screening indicate that four of the primers failed to amplify any product, 12 primers were monomorphic, and 18 primers were polymorphic. Eleven additional cultivars were then screened, which produced numerous polymorphic products. For example, Primers B3 and B118 produced products ranging in size from 490 to 350 bp. Polymorphic products will be used to examine genetic variation among the pawpaw cultivars screened.
Summaira Riaz, Keith E. Garrison, Gerald S. Dangl, Jean-Michel Boursiquot and Carole P. Meredith
In total, 25 clones of Vitis vinifera `Pinot noir' and 22 clones of `Chardonnay' were analyzed with 100 microsatellite markers, selected from an initial screening of 228 markers. Of the 100 markers, 17 detected polymorphism within one or both of the cultivars. In `Pinot noir', 15 polymorphic markers detected 15 different genotypes, uniquely distinguished 12 clones out of the 25 and separated the remaining 13 clones into 3 groups. In `Chardonnay', 9 polymorphic markers detected 9 genotypes and uniquely distinguished 6 clones out of the 22. The remaining 16 clones were separated into 3 groups. For markers that were polymorphic in `Pinot noir' and `Chardonnay', none of the variant alleles were common to both cultivars. It is inferred from this result that the natural cross that produced `Chardonnay' probably occurred when `Pinot' was still relatively young. Many of the variant genotypes were expressed as three alleles. Further analysis revealed the presence of chimeras in which the third allele was present in leaf but not root or wood tissues, confirming that the grape apical meristem is functionally two-layered. Some clones that share the same microsatellite genotype are documented to have originated in the same locality, suggesting that the origins of undocumented clones may be traced by comparing their microsatellite genotypes with those of well-documented clones. Because clones of `Pinot noir' and `Chardonnay' are often visually indistinguishable, microsatellite genotyping may also be useful to detect identification errors in collections and nurseries.
Richard E. Veilleux
Anther culture has been one of the most successful techniques for generating haploid plants over a wide range of species. It is a reasonably simple procedure that can be accomplished successfully without sophisticated laboratory facilities; yet, the plants generated through anther culture can be used to demonstrate the application of many modern methods that have direct applicability to plant breeding. Anthers of diploid potato clones that have been selected for competence in anther culture can be cultured in a simple medium to yield androgenic embryos after 5 weeks. Plant regeneration requires an additional 3 to 4 weeks. Regenerated plants should be large enough 2 weeks after transfer to basal medium for ploidy determination by any of three methods depending on available facilities: chromosome counts in root tips; chloroplast counts in stomatal guard cells; or flow cytometry of nuclei released from in vitro plantlets. DNA can be extracted from anther-derived plantlets using a rapid extraction procedure to demonstrate segregation of PCR (polymerase chain reaction)-based markers such as RAPD (randomly amplified polymorphic DNA), RAMPs (randomly amplified microsatellite polymorphisms), or microsatellites. Microsatellite markers that were heterozygous in the anther donor can be used to verify haploidy in anther-derived plants. If an anther culture laboratory is scheduled early in a semester, such molecular analysis can be planned for late in the same semester.
Gayle Volk, Christopher Richards, Adam Henk, Ann Reilley, Nahla Bassil and Joseph Postman
Edible European pears (Pyrus communis sp. communis L.) are thought to be derived from wild relatives native to the Caucasus Mountain region and eastern Europe. We collected genotype, phenotype, and geographic origin data for 145 P. communis individuals derived from seeds collected from wild relatives. These individuals are currently maintained in the USDA–ARS National Plant Germplasm System (NPGS) in Corvallis, Ore. Pear genotypes were obtained using 13 microsatellite markers. A Bayesian clustering method grouped the individual pear genotypes into 12 clusters. The subspecies of pears native to the Caucasus Mountains of Russia, Crimea, and Armenia could be genetically differentiated from the subspecies native to eastern European countries. Pears with large fruit clustered closely together and are most closely related to a group of genotypes that are intermediate to the other groups. Based on the high number of unique alleles and heterozygosity in each of the 12 clusters, we conclude that the genetic diversity of wild P. communis is not fully represented in the NPGS
Ying Li, Xiao-Li Hu, Robert N. Trigiano, Herbert Aldwinckle and Zong-Ming (Max) Cheng
Apple blotch caused by Alternaria alternata apple pathotype is a severe disease of apple (Malus ×domestica Borkh) occurring throughout the world, especially in eastern Asia. Phenotypic and genetic information about resistance/susceptibility of apple germplasm to this disease will be extremely valuable for selecting and developing new disease resistant cultivars. In this study, 110 apple cultivars obtained from the USDA apple germplasm in Geneva, NY, were evaluated for their resistance/susceptibility to apple blotch by field surveys, and inoculation of detached leaves with a suspension of germinated conidia of A. alternata apple pathotype. Disease incidence were different among the cultivars and categorized into resistant (R), moderately resistant (MR), or susceptible (S). Two molecular markers, S428, a random amplified polymorphic DNA (RAPD) marker associated with disease resistance, and a simple sequence repeat (SSR or microsatellite) marker CH05g07, linked to susceptibility were used to correlate the phenotypes expressed in field surveys and laboratory inoculations. The detection using either the S428 marker or the CH05g07 marker in 50 common breeding cultivars was consistent with R or S traits except for ‘Bisbee’ and ‘Priscilla’. These two cultivars were MR to apple blotch through phenotyping. However, SSR markers were detected, but RAPD markers were not and therefore were considered susceptible. Combined with the record of resistance to fire blight from Germplasm Resources Information Network (GRIN), ‘Dayton’, ‘Mildew Immune Seedling’, ‘Puregold’, and ‘Pumpkin Sweet’ were highly resistant to both diseases and considered as the best choices of parents for stacking resistance to multiple diseases in breeding program.
Eiichi Inoue, Lin Ning, Hiromichi Hara, Shuan Ruan and Hiroyuki Anzai
(PCR) and electrophoresis. Microsatellite markers for japanese chestnuts and european chestnuts have been developed and used ( Buck et al., 2003 ; Yamamoto et al., 2003 ); however, there have been no studies on the development of microsatellite markers
Ying Wang, Ming Kang and Hongwen Huang
been reported on Chinese Castanea species using microsatellite markers due to the lack of efforts in development of microsatellite markers for Chinese chestnuts. Nevertheless, the lack of microsatellite markers directly developed from Chinese