Hydrangea popularity and use in the landscape has expanded rapidly in recent years with the addition of remontant varieties. Relatively little is known about the genetic background or combinability of these plants. We recently established microsatellite markers for hydrangea and evaluated their utility for estimating species diversity and identifying cultivars. We also verified an interspecific cross using these markers. Future research includes marker assisted breeding, particularly with respect to remontant flowering traits.
Timothy Rinehart, Sandra Reed, and Brian Scheffler
Aurora Díaz, Antonio Martín, Pilar Rallo, Diego Barranco, and Raúl De la Rosa
We studied the self-incompatibility of two main Spanish olive (Olea europaea L.) cultivars, `Picual' and `Arbequina', by testing the selfing of the seeds with microsatellites. For this purpose, we used a rapid single-seed DNA extraction method and four highly polymorphic microsatellites. We analyzed seeds produced in branches bagged for selfing from mono- and multi-cultivar orchards in 2002 and 2003. We did not find any seed coming from selfing in the bagged branches, for either cultivar, in the two types of orchards. Additionally, we tested seeds coming from free pollination in mono-cultivar orchards from different locations. In the case of `Picual' olive, only three seeds out of the 70 collected were the product of selfing, although they came from mono-cultivar orchards located in areas where the cultivar used as the female parent was predominant. From the 20 seeds of `Arbequina' olive harvested in the middle of two high-density plantations, not one was a product of selfing. According to this, olive would behave as an allogamous species in mono-cultivar growing conditions and the pollen coming from long distances would be able to produce a normal bearing. Therefore, there is strong evidence to support the idea that the cultivars studied could be self-incompatible. Future experiments in self-compatibility should include a paternity check of the possible self seeds obtained.
Kentaro Kitahara, Shogo Matsumoto, Toshiya Yamamoto, Junichi Soejima, Tetsuya Kimura, Hiromitsu Komatsu, and Kazuyuki Abe
We examined the genetic diversity and relatedness among apple (Malus ×domestica Borkh.) cultivars in Japan. The 42 apple cultivars, including major cultivars in Japan, were divided into five groups based on SSR genotypes. Most economically important cultivars belong in three groups: Fuji-Delicious, Golden Delicious, and Jonathan groups, and their genetic backgrounds seemed to be narrow. We also investigated the parent-offspring relationships of nine apple cultivars. `Jonathan', `Fuji', and `Rero 11' were identified as the respective paternal parents of three cultivars described as having unknown paternal parents (i.e., `Akagi', `Ambitious', and `Hokuto'). `Starking Delicious', `Senshu', and `Golden Delicious', rather than `Ralls Janet', `Hatsuaki', and `Indo', seemed to be the paternal parents of `Kinsei', `Kiou', and `Mellow', respectively. `Carolina Red June' was excluded as a paternal parent of `Ranzan'. Both attributed parents of `Scarlet' (`Akane' and `Starking Delicious') were excluded, and it was suggested that `Fuji' was used as either a maternal or a paternal parent of `Scarlet'. `Jonathan' rather than `McIntosh' seems to be a maternal parent of `Yukari'.
Warren F. Lamboy and Christopher G. Alpha
Curators of plant genetic resources collections must preserve germplasm possessing known useful characteristics as well as material displaying general genetic diversity. In order to ensure that both types of germplasm are included in a collection, germplasm curators require three fundamental types of information about each accession: taxonomic identity, genetic identity, and genetic relationship. Because simple sequence repeat DNA fragments (SSRs) have been successfully used to determine the genetic identity of grape clones, we conducted a study to determine if SSRs would supply all three types of information for the accessions in the cold-hardy Vitis (grape) germplasm collection. SSR fragments were amplified at six different loci for 23 accessions of cold-hardy grape spanning the range of species diversity in the collection. The minimum number of different alleles found at a locus was 9; the maximum was 26. Heterozygosity values ranged between 0.565 and 0.783, while gene diversity values were in the range 0.785 to 0.944. Two hundred fifty-two pairs of plants out of a possible 253 could be distinguished by their SSR profiles. Nei's genetic identities were computed between all pairs of plants and used in a UPGMA cluster analysis. The relationships obtained did not correspond well to expected relationships based on geography and taxonomy. Four species of grapes were represented by two or more accessions in this study. No DNA fragments found at these six loci served to unambiguously distinguish one species from another. Thus, SSR fragments from the six loci studied were useful in determining genetic identity of accessions, but were not helpful in determining genetic relationships or taxonomic identities. We are searching for additional loci that are informative for these types of information. Meanwhile we highly recommend SSRs for determining genetic identity in germplasm resources collections.
Shengping Zhang, Han Miao, Xing-fang Gu, Yuhong Yang, Bingyan Xie, Xiaowu Wang, Sanwen Huang, Yongchen Du, Rifei Sun, and Todd C. Wehner
(RFLP) marker, CMTC51 (0.5 cM), and one AFLP marker, E14M49-F-158-P2 (1.9 cM), linked to the Ccu gene using wide-based, merged maps. Thus far, no linkage of SSR markers to the Ccu gene has been reported, and no SSR marker with genetic distance less
Michael Dossett, Jill M. Bushakra, Barbara Gilmore, Carol A. Koch, Chaim Kempler, Chad E. Finn, and Nahla V. Bassil
polymorphic SSRs in a panel of diverse wild black raspberry accessions. Additional screening efforts of more than 250 SSR markers from a black raspberry expressed sequence tag (EST) library in a mapping population yielded only an additional five polymorphic
Xiaobai Li, Weirui Li, Chenlu Di, Ming Xie, Liang Jin, Cheng Huang, and Dianxing Wu
); amplified fragment length polymorphism markers ( Wang et al., 2004 ); polymorphisms of internal transcribed spacers of nuclear ribosomal DNA and plastids, as well as inter-SSR ( Lu et al., 2011 ); and SSR ( Capesius, 1976 ; Moe et al., 2010 ; Moea and
Shuang Jiang, Haishan An, Xiaoqing Wang, Chunhui Shi, Jun Luo, and Yuanwen Teng
breeding technology, the breeding process can be accelerated by molecular maker-assisted selection ( Collard et al., 2005 ). SSRs, also known as microsatellites, are one of the most efficient genetic markers. An SSR refers to a DNA sequence 1 to 6 bp in
Xiaoying Li, Hongxia Xu, Jianjun Feng, and Junwei Chen
). As a result, SSRs are simple and efficient markers useful in the analysis of codominance and highly polymorphic lines. SSRs have been used extensively in genetic diversity assessments ( Li et al., 2010a ), cultivar fingerprinting ( Wang et al., 2011
Colton Ives, Vidyasagar R. Sathuvalli, Brooke C. Colburn, and Shawn A. Mehlenbacher
linear with eight levels ( Mehlenbacher, 1997a ). Fluorescence microscopy is used routinely to identify S-alleles in cultivars and selections ( Mehlenbacher, 1997b ). The linkage map of Mehlenbacher et al. (2006) , constructed using RAPD and SSR markers