The study of mycorrhizas of fruit trees was carried out in the 1980s in China. More progress has been made in resources, taxonomy, anatomy and morphology, physiology, ecology, effects, and application of mycorrhizas in fruit trees. The present status and research trends in the study of fruit tree mycorrhizas in China were introduced, and the application prospects of mycorrhizas in fruit tree cultivation also were discussed.
Liu Runjin, Xu Kun, and Liu Pengqi
Cheol Hee Lee, Kee Yoeup Paek, J. Brian Power, and Edward C. Cocking
This study was designed to assess the general limitations of somatic hybridization as one of the key technologies for genetic manipulation in plants. The limits of somatic hybridization against different taxonomic backgrounds, intraspecific to interfamilial, were also assessed. Protoplast culture studies provided essential information relating to the species cultural and morphogenetic capacity. several #elect Ion strategies for the recovery of somatic hybrid colonies/plants were developed and assessed using various combinations of protoplast sources and species in the genera Petunia, Nicotiana, Salpiglossis and Chrysanthemum. Morphological, cytological and biochemical analyses were performed to confirm the hybridity of plants or cell lines recovered following protoplasm fusion (using 4-5 methods) and selection.
The somatic hybrid callus/plants were obtained at intraspecific to interfamilial levels by complementation to chlorophyll proficiency, together with media selection or complementation of nitrate reductase deficient mutants as follows; P. Hybrida var. Monsanto (+) P. hybrida cv. Blue Lace (intraspecific), P. hybrida var. Monsanto (+) P. inflata and P. parviflora (interspecific), P. parviflora (+) N. tabacum (intergeneric), S. sinuata (+) P. hybrida var. Monsanto, P. parodii and N. tabacum (intertribal), and C. morifolium (+) S. sinuata.
From this study, it appeared that there were no taxonomic limits to the production and proliferation of somatic hybrid cell lines. However, obtaining morphologically normal hybrid plants met with limited success as the taxonomic relationships became more distant. The regeneration capacity of somatic hybrids seemed to be controlled by both parental species. Somatic incompatibility mechanism was also shown to operate on chromosome elimination. Such chromosome elimination may well be advantageous in plant improvement.
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.
A.G. Gillaspie, O.L. Chambliss, R.L. Fery, A.E. Hall, J.C. Miller Jr., and T.E. Morelock
The Vigna Crop Germplasm Committee has established a core subset for the USDA cowpea germplasm collection. The subset consists of 9.3% (700 accessions) of the 7525 accessions currently contained in the collection. The subset was selected on the basis of country of origin, taxonomic characteristics, and known disease and pest resistance characteristics. Theoretically, the lines in the subset represent the genetic diversity present in the entire collection. A listing of the accessions in the subset is available from the Vigna germplasm curator (A.G. Gillaspie). The listing can also be accessed through the USDA's Germplasm Resources Information Network (GRIN).
Y. Wang, Y. Liu, P. He, O. Lamikanra, and J. Lu
Resistance to grape anthracnose [Elsinoë ampelina (de Bary) Shear] was evaluated in 13 known Vitis species and five taxonomically undescribed grapes native to China. One hundred and eight clones of Chinese Vitis species were tested under field conditions between 1990 and 1992. Berry infection did not occur in these species. Leaves displayed strong resistance to anthracnose, although intraspecific variations were observed. There was no relationship between anthracnose resistance and geographical origin of the species. Results from this study indicate that oriental grape species are useful for disease-resistance breeding.
Jing-Tian Ling, Nick Gawel, and Roger J. Sauve
The genus of Hosta (plantain lily) is a shade-loving herbaceous plant with attractive foliage. Confusion exists in the genus regarding nomenclature and taxonomy. In this study, the possibility of application of RAPD markers to characterize Hosta species and cultivars was investigated. DNA was extracted from 28 Hosta species and cultivars. Thirty-six of 37 primers generated RAPD markers. Phylogenic analysis and principal components analysis showed groupings among cultivars. Results indicated that H. plantaginea and H. ventricosa were the most distant from the other tested species and cultivars. These results suggest RAPDs may be useful in the identification and analysis of relationships among Hosta.
W.E. Jones, A.R. Kuehnle, and K. Arumuganathan
Flow cytometry (FC) has proven to be an efficient and reliable method to estimate nuclear DNA content (genome size) in quantifiable units useful for genetic and molecular biology studies. This method also makes possible determination of the variation in nuclear DNA content between related taxa, which gives insights into the process of speciation. In this study, DNA content was determined in nuclei isolated from leaves of 21 Dendrobium species representing each of the major taxonomic groups used in the Univ. of Hawaii breeding program. Nuclei were mechanically isolated, stained with the nucleic acid-specific fluorochrom propidium iodide, and DNA content determined using a Coulter Epics 753 laser flow cytometer. Chicken erythrocyte nuclei (2C = 2.33 pg DNA) were used as an internal standard for direct comparative measurement. The mean diploid genome (2C) values for Dendrobium species ranged from 3.36 to 5.06 pg. Genome sizes were evaluated for possible use as discrete characters for taxonomic group assignment and compared to previous data on breeding compatibility and evolutionary relationship between species.
The forma now known as Trillium ovatum L. forma hibbersonii Taylor & Szczawinski (Liliaceae) was first discovered on the west coast of Vancouver Island, B.C., in 1938 by Jack Arthur Hibberson (Holotype UBC 73131). The obvious morphological differences that characterize the forma hibbersonii from T. ovatum are the dwarfing of all its parts, pink not white flower color at anthesis, and narrow lanceolate leaves. Although it has gained popularity as a garden plant, it has received very little attention in the scientific community. A description and designation as a distinct species (T. hibbersonii) was published by L. Wiley in 1968 but was considered invalid. The 1975 valid publication by T.M.C. Taylor and A.F. Szczawinski designated this taxon at the intraspecific level of forma. The present study was initiated to provide a comprehensive reevaluation of the taxonomic status: forma, separate species, subspecies, or variety? A change in taxonomic status from forma to species would elevate the taxon from rare to endangered status. This study considers morphological differences and flavonoid analysis of samples from both natural populations and cultivated plants. Habitat, dormancy requirements, and breeding strategy also were considered. Initial investigation using random amplified polymorphic DNA (RAPD) indicates this method is another valuable tool for distinguishing between the taxa.
S. Jorge, M.C. Pedroso, D.B. Neale, and G. Brown
Random amplified polymorphic DNA (RAPD) analysis was used to estimate genetic similarities between Portuguese Camelliasinensis (L.) O. Kuntze (tea plant) accessions and those obtained from the germplasm collections from the Tea Research Foundation of Kenya and from the National Research Institute of Vegetables, Ornamental Plants, and Tea of Japan. The accessions studied are taxonomically classified as C. sinensis, var. sinensis, var. assamica, or ssp. lasiocalyx. A set of 118 ten-base arbitrary primers was tested, of which 25 produced informative, reproducible, and polymorphic banding patterns. These primers were used to amplify DNA from 71 tea plant accessions and produced a total of 282 bands, of which 195 were polymorphic. The phenotypic frequencies were calculated using Shannon's Index and employed in estimating genetic diversity within tea plant populations. Our study demonstrates that tea plant populations, including the Portuguese tea plants, show considerable genetic variability. From the UPGMA cluster analysis based on a matrix using the Jaccard coefficient, it was possible to distinguish the Portuguese tea plants from the remaining accessions. The RAPD markers discriminated the three C. sinensis varieties. Moreover, within each variety cluster, subclusters formed according to geographic distribution. The RAPD analysis also separated the commercially cultivated tea plants from the Taiwanese wild tea plants. The present results show that RAPD analysis constitutes a good method to estimate genetic diversity within C. sinensis, and to differentiate C. sinensis accessions according to taxonomic variety and geographical distribution.
Mukadder Kayum, N. Kemal Koç, and Veli-Matti Rokka
Laser flow cytometry was used to analyze nuclear DNA contents (2C values) of five genera (Severinia Ten., Atalantia Corrèa, Fortunella Swing., Poncirus Raf., and Citrus L.) taxonomically grouped in subtribe Citrinae (citrus fruit trees) of the Rutaceae. The genotypes analyzed had 2C values ranging from 0.67 pg for diploid Severinia buxifolia (Poir.) Ten. to 1.27 pg for tetraploid Hongkong Fortunella hindsii Swing. There was no significant difference in the 2C values within the sexually compatible diploid species of 11 “true citrus fruit trees” [Citrus aurantium L., C. grandis (L.) Osbeck, C. limon (L.) Burm. f., C. limonia Osbeck, C. paradisi Macf., C. reshni Hort. ex Tanaka, C. sinensis (L.) Osbeck, C. volkameriana Ten. & Pasq., Poncirus trifoliata (L.) Raf., and the intergeneric hybrid C. sinensis × P. trifoliata]. The species Atalantia ceylanica (Arn.) Oliv. (a “near-citrus fruit tree”), sexually incompatible with Citrus spp., had a 2C value significantly different from those of the true citrus fruit tree species. The 2C value of Severinia buxifolia (a “primitive citrus fruit tree”), another species sexually incompatible with the Citrus spp., also differed from those of some of the true citrus fruit tree species. The data largely corresponds with taxonomical differences between a) the genera Citrus and Poncirus and b) the genera Severinia and Atalantia, all assigned to subtribe Citrinae.