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We studied 66 `Medjool' date palm (Phoenix dactylifera L.) accessions from Morocco, six varieties of dates from Egypt, and four `Medjool' accessions and one `Deglet Noor' accession from California to investigate the hypothesis that `Medjool' is a landrace variety in Morocco. We used four sets of fluorescent-labeled amplified fragment length polymorphism (AFLP) markers to examine these accessions. A total of 402 bands were generated, of which 217 were polymorphic (54.0%). The 66 `Medjool' accessions from Morocco shared a minimum of 79% genetic similarity. These results support the hypothesis that `Medjool' is a landrace variety in Morocco and it is not genetically uniform. `Medjool' is the first confirmed landrace variety of date palm in the world. This finding raises the possibility that other date palms may be landrace varieties in different growing areas. Confirmation of a landrace variety in date palm has significant implication for future date palm germplasm collection and preservation. The mechanism(s) generating the genetic variation within `Medjool' accessions remains unknown. One possibility is that spontaneous genetic changes could occur frequently within vegetative tissues like offshoots under high temperature and drought stress.
Ornamental Ficus L. is a group of lactiferous trees, shrubs, and woody root-climbing vines that are cultivated either as landscape plants in the tropics and subtropics or as foliage plants used worldwide for interiorscaping. With the recent rapid expansion of the ornamental plant industry, more new Ficus species and cultivars have been introduced. However, no study has thus far addressed the genetic relationships of cultivated ornamental Ficus. Using amplified fragment length polymorphism (AFLP) markers with near-infrared fluorescence-labeled primers, this study analyzed the genetic relatedness of 56 commercial cultivars across 12 species. Forty-eight EcoRI + 2/MseI + 3 primer set combinations were initially screened, from which six primer sets were selected and used in this investigation. Most cultivars were differentiated by their AFLP fingerprints, and their relationships were determined using the unweighted pair-group method of arithmetic average cluster analysis. The 56 cultivars were divided into 12 clusters that correspond to 12 species, indicating that no interspecific hybrids of ornamental Ficus are in commercial production. The 12 species are genetically diverse, with Jaccard's similarity coefficients ranging from 0.21 to 0.43. However, cultivars within three species—Ficus benjamina L., Ficus elastica Roxb. Ex Hornem., and Ficus pumila L.—are genetically close. Twenty-seven of the 29 cultivars of F. benjamina and five cultivars of F. pumila had Jaccard's similarity coefficients of 0.98 or higher respectively. Nine cultivars of F. elastica shared Jaccard's coefficients higher than 0.96. These results indicate potential genetic vulnerability of these cultivars within the three species. Because there are increasing reports of invasive pests in the ornamental plant industry, strategies for conserving genetic resources and broadening genetic diversity of cultivated Ficus are discussed.
Many reports indicate that an abundance of really interesting new gene (RING) play key roles in regulating defense responses against abiotic and biotic stresses in plants. In this study, the cloning and functional characterization of a RING gene, MaRING2, in banana (Musa acuminata) fruit are reported. MaRING2 belongs to the NEP1-interacting protein (NIP) RING-H2 finger protein family. Gene expression profiles revealed that MaRING2 was cold responsive and induced by abscisic acid (ABA) treatment during cold storage. In this study, the MaRING2 under control of the Cauliflower mosaic virus 35S (CaMV 35S) promoter was transformed to tobacco (Nicotiana benthamiana) using agrobacterium (Agrobacterium tumefaciens)-mediated transformation. The resultant MaRING2-overexpressing transgenic plants (35S:MaRING2) exhibited significantly increased tolerance to low temperatures and were hypersensitive to exogenous ABA in terms of germination and early seedling growth. In addition, overexpression of MaRING2 enhanced the expression of stress-responsive genes under normal (before cold stress) or cold conditions. These results demonstrate the biological role of MaRING2 in conferring cold tolerance. Taken together, these results suggest that MaRING2, a C3H2C3-type RING protein, is a positive regulator of the ABA-dependent stress response.
The genus Dendrobium is important in traditional Chinese herbal medicine, and the precise identification of Dendrobium species is critical for the treatment and for pharmacological research. In the present study, a ribosomal DNA (rDNA) internal transcribed spacer (ITS) region-based analysis was used to ascertain the phylogenetic relationship among 20 Dendrobium species. The lengths of the ITS regions among the 20 species ranged from 636 to 653 bp, and the identities of the rDNA regions among the different species ranged from 75.7% to 99.1%. The results also showed that the ITS1 and ITS2 regions exhibit more variation than the 5.8S rDNA. A phylogenetic tree derived from the ITS sequence indicated that six medicinal Dendrobium species, of which five are common medicinal plants in the Taiwan market, were closely related and shared a common clade. Multiplex polymerase chain reaction (PCR) amplification was successfully performed to identify the six medicinal Dendrobium species, and amplification refractory mutation system (ARMS) PCR was used to distinguish D. tosaense specifically from the 19 other Dendrobium species. The established PCR-based (multiplex and ARMS) analyses can be used for the authentication of the raw materials of medicinal Dendrobium from other species.
Ethylene response factor (ERF) genes have been characterized in numerous plants, where they are associated with responses to biotic and abiotic stress. Modified atmosphere packaging (MAP) is an effective treatment to prevent lotus root browning. However, the possible relationship between ERF transcription factors and lotus root browning under MAP remains unexplored. In this study, the effects of phenol, phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD) enzyme activities; and PPO, PAL, POD, and ERF gene expression on fresh-cut lotus root browning were studied with MAP. The expression pattern of ERF2/5 correlated highly with the degree of browning. It is suggested that NnERF2/5 can be used as an important candidate gene for the regulation of fresh-cut lotus root browning under MAP, and the correlation of each gene should be studied further.