Among Cucurbitaceae, Cucumis melo is one of the most important cultivated cucurbits. They are grown primarily for their fruit, which generally have a sweet aromatic flavor, with great diversity and size (50 g to 15 kg), flesh color (orange, green, white, and pink), rind color (green, yellow, white, orange, red, and gray), form (round, flat, and elongated), and dimension (4 to 200 cm). C. melo can be broken down into seven distinct types based on the previously discussed variations in the species. The melon fruits can be either climacteric or nonclimacteric, and as such, fruit can adhere to the stem or have an abscission layer where they will fall from the plant naturally at maturity. Traditional plant breeding of melons has been done for 100 years wherein plants were primarily developed as open-pollinated cultivars. More recently, in the past 30 years, melon improvement has been done by more traditional hybridization techniques. An improvement in germplasm is relatively slow and is limited by a restricted gene pool. Strong sexual incompatibility at the interspecific and intergeneric levels has restricted rapid development of new cultivars with high levels of disease resistance, insect resistance, flavor, and sweetness. In order to increase the rate and diversity of new traits in melon it would be advantageous to introduce new genes needed to enhance both melon productivity and melon fruit quality. This requires plant tissue and plant transformation techniques to introduce new or foreign genes into C. melo germplasm. In order to achieve a successful commercial application from biotechnology, a competent plant regeneration system of in vitro cultures for melon is required. More than 40 in vitro melon regeneration programs have been reported; however, regeneration of the various melon types has been highly variable and in some cases impossible. The reasons for this are still unknown, but this plays a heavy negative role on trying to use plant transformation technology to improve melon germplasm. In vitro manipulation of melon is difficult; genotypic responses to the culture method (i.e., organogenesis, somatic embryogenesis, etc.) as well as conditions for environmental and hormonal requirements for plant growth and regeneration continue to be poorly understood for developing simple in vitro procedures to culture and transform all C. melo genotypes. In many cases, this has to be done on an individual line basis. The present paper describes the various research findings related to successful approaches to plant regeneration and transgenic transformation of C. melo. It also describes potential improvement of melon to improve fruit quality characteristics and postharvest handling. Despite more than 140 transgenic melon field trials in the United States in 1996, there are still no commercial transgenic melon cultivars on the market. This may be a combination of technical or performance factors, intellectual property rights concerns, and, most likely, a lack of public acceptance. Regardless, the future for improvement of melon germplasm is bright when considering the knowledge base for both techniques and gene pools potentially useable for melon improvement.

http://www.ira.cinvestav.mx/LinkClick.aspx?fileticket=t04jgkRz2yg%3D&tabid=107&language=es-MX

Melon Fruits: Genetic Diversity, Physiology, and Biotechnology Features

An Agrobacterium-mediated gene transfer method for production of transgenic melon plants has been optimized The HAL1 gene, an halotolerance gene isolated from yeast, was inserted in a chimaeric construct and joined to two marker genes: a selectable-neomycin phosphotransferase-II (nptII)-, and a reporter-β-glucuronidase (gus)- The entire construct was introduced into commercial cultivars of melon Transformants were selected for their ability to grow on media containing kanamycin Transformation was confirmed by GUS assays, PCR analysis and Southern hybridization Transformation efficiency depended on the cultivar, selection scheme used and the induction of vir-genes by the addition of acetosyringone during the cocultivation period The highest transformation frequency, 3% of the total number of explants cocultivated, was obtained with cotyledonary explants of cv ‘Pharo’ Although at a lower frequency (13%), we have also succeeded in the transformation of leaf explants A loss of genetic material was detected in some plants, and results are in accordance with the directional model of T-DNA transfer In vitro cultured shoots from transgenic populations carrying the HAL1 gene were evaluated for salt tolerance on shoot growth medium containing 10 g l−1 NaCl Although root and vegetative growth were reduced, transgenic HAL1-positive plants consistently showed a higher level of tolerance than control HAL1-negative plants

Transfer of the yeast salt tolerance gene HAL1 to Cucumis melo L. cultivars and in vitro evaluation of salt tolerance.

The complete nucleotide sequence (6043 nt) of RNA 1 from Potato mop-top virus (PMTV-Sw), the type member of the genus Pomovirus, was determined. The first (5′-terminal) open reading frame (ORF 1) encodes a predicted protein of 148 kDa. ORF 2 extends through the opal stop codon of ORF 1 producing a predicted readthrough protein of 206 kDa which resembles the RNA-dependent RNA polymerases (RdRp) of other fungal-transmitted viruses. It includes a methyltransferase, a helicase and a GDD RdRp motif, respectively. Phylogenetic analyses of RdRps indicated that PMTV is most closely related to Beet soil-borne virus (genusPomovirus), Broad bean necrosis virus (genus Pomovirus) and Soil-borne wheat mosaic virus (genus Furovirus), and is more distantly related to the other viruses of the former furovirus group. The 5′ and 3′ termini of RNA 1 in PMTV contained untranslated regions (UTR) of 114 nt and 489 nt, respectively. The 3′-UTR of RNA 1 contained a tRNA-like structure, which has previously been reported in the 3′-UTR of RNA 2 but not RNA 3. However, in this study, the tRNA-like structure was also found in the 3′-UTR of RNA 3, which confirms its presence in the 3′-UTRs of all three RNAs of PMTV.

Complete sequence of RNA 1 and the presence of tRNA-like structures in all RNAs of potato mop-top virus, genus Pomovirus.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1076&context=ncrpis_pubs

Cucurbits (Cucurbitaceae; Cucumis spp., Cucurbita spp., Citrullus spp.)

Summary The nucleotide sequence of RNA 1 of the Fny strain (Subgroup I) of cucumber mosaic virus (CMV) was determined and compared at both the nucleic acid and protein levels with the corresponding sequence of RNA 1 of the Q strain (Subgroup II) of CMV. Fny-CMV RNA 1 consisted of 3357 nucleotides and contained a single long open reading frame (ORF) of 2979 nucleotides, whereas Q-CMV RNA 1 consists of 3389 nucleotides and contains a single ORF of 2973 nucleotides. The levels of sequence homology between the two RNAs were 76% at the nucleotide level and 85% at the protein level. These homologies were distributed widely over the molecules, with 45% of the non-conservative differences in amino acid sequence located between amino acids 503 and 705, and another 15% of the differences located between amino acids 224 and 298. While the C-terminal 141 amino acids contain more basic than acidic amino acids, the region of greatest amino acid sequence heterogeneity, amino acids 503 to 600, contained a preponderance of acidic amino acids in the putative translation products of RNAs 1 of both Q-CMV and Fny-CMV. The last 180 nucleotides of the 3′-terminal non-coding region of Fny-CMV RNAs 1 and 2 were 96% homologous, whereas the sequence homology between Fny-CMV RNA 1 and Q-CMV RNA 1 was 64% in this region. Furthermore, the tRNA-like secondary structures formed by the 3′-terminal non-coding regions of Fny-CMV RNAs 1 and 2 were virtually identical. By contrast, there was only 84% sequence homology between the 5′-terminal non-coding regions of these two RNAs and 81% sequence homology between the 5′-terminal non-coding regions of Q-CMV RNA 1 and Fny-CMV RNA 1. The non-equivalent divergence in the non-coding regions of these RNAs, as well as possible functions for the translation product of RNA 1, are discussed.

Nucleotide sequence and evolutionary relationships of cucumber mosaic virus (CMV) strains: CMV RNA 1.

/pdf/wagaguo-niokeru-potato-mop-top-virus-nofa-sheng-tosono2-71f6nkwchq.pdf

薫花田

Papers

わが国における Potato mop top virus の発生とその2, 3の性質

Successful Transfer of the Cucumber Mosaic Virus Coat Protein Gene to Cucumis melo L.

Virus Resistance in Transgenic Melon Plants That Express the Cucumber Mosaic Virus Coat Protein Gene and in Their Progeny.

Genetic analysis of cucumber mosaic,Peanut stunt and chrysanthemum mild mottle viruses.

The Presence of Three Pairs of Possibly Complementary RNA Species in Isolated Nucleocapsid Material of Tomato Spotted Wilt Virus.

薫 花田