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- Author or Editor: Chao Fang x
- Journal of the American Society for Horticultural Science x
Production of seedless mandarins such as `Nules' clementine mandarin (Citrus clementina Hort. Ex Tan.) and `Afourer' mandarin [C. sinensis (L.) Osbeck × C. reticulata Blanco] is increasing in California as consumers' interest in seedless, easy peeling, and good tasting mandarins increases. The fruit would produce seeds if cross-pollination with compatible pollen source occurred. It is almost impossible to prevent cross-pollination between compatible mandarin cultivars by honeybees (Apis mellifera L.) within the multi-faceted agricultural environment in California. To produce seedless mandarin, growers either plant a single cultivar in a large solid block or try to use pollen-sterile navel oranges (C. sinensis) or satsuma mandarins (C. unshiu Marco.) as buffers to prevent cross-pollination. The question of how many rows of buffer trees or spacing can effectively prevent cross-pollination by honeybees between compatible mandarins is unclear. We initiated a study using fluorescent-labeled AFLP markers to determine the pollen parentages of `Nules' clementine seedlings and `Afourer' mandarin seedlings from two orchards in California. The longest distance of pollen flow at an orchard near Madera was 521 m. The pollen of `Minneola' tangelo (C. reticulata × C. paradisi Macf.) was able to disperse across a minimum of 92 rows of `Lane Late' navel oranges plus two rows of `Afourer' mandarins to pollinate `Afourer' mandarins. We also found that all the seedlings of `Nules' clementine mandarin at an orchard near Bakersfield had been pollinated by `Afourer' mandarin pollen. The pollen of `Afourer' mandarin was able to disperse up to distances between 837 and 960 m to pollinate `Nules' clementine. The pollen dispersal distance found in this study was at least 16 times longer than previously reported in a citrus orchard. Growers need to consider a much larger space or buffer rows to prevent cross-pollination and produce seedless mandarins in California.
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.
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.