<Emphasis Type="Italic">Mutator</Emphasis>-like elements identified in melon,Arabidopsis and rice contain ULP1 protease domains

The transposon Mutator was first identified in maize, and is one of the most active mobile elements in plants. The Arabidopsis thaliana genome contains at least 200 Mutator-like elements (MULEs), which contain the Mutator-like transposase gene, and often additional genes. We have detected a novel type of MULEs in melon (CUMULE), which, besides the transposase, contains two ubiquitin-like specific protease-like sequences (ULP1). This element is not present in the observed location in some melon cultivars. Multiple copies of this element exist in the Cucumis melo genome, and it has been detected in other Cucurbitaceae species. Analysis of the A. thaliana genome revealed more than 90 CUMULE-like elements, containing one or two Ulp1-like sequences, although no evidence of mobility exists for these elements. We detected various putative transposable elements containing ULP1-like sequences in rice. The discovery of these MULEs in melon and Arabidopsis, and the existence of similar elements in rice and maize, suggest that a proteolytic function may be important for this subset of the MULE transposable elements. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. Nucleotide sequence data reported are available in the GenBank database under the accession number AY524004.     

Use of targeted SNP selection for an improved anchoring of the melon (Cucumis melo L.) scaffold genome assembly

Background

The genome of the melon (Cucumis melo L.) double-haploid line DHL92 was recently sequenced, with 87.5 and 80.8% of the scaffold assembly anchored and oriented to the 12 linkage groups, respectively. However, insufficient marker coverage and a lack of recombination left several large, gene rich scaffolds unanchored, and some anchored scaffolds unoriented. To improve the anchoring and orientation of the melon genome assembly, we used resequencing data between the parental lines of DHL92 to develop a new set of SNP markers from unanchored scaffolds.

Results

A high-resolution genetic map composed of 580 SNPs was used to anchor 354.8 Mb of sequence, contained in 141 scaffolds (average size 2.5 Mb) and corresponding to 98.2% of the scaffold assembly, to the 12 melon chromosomes. Over 325.4 Mb (90%) of the assembly was oriented. The genetic map revealed regions of segregation distortion favoring SC alleles as well as recombination suppression regions coinciding with putative centromere, 45S, and 5S rDNA sites. New chromosome-scale pseudomolecules were created by incorporating to the previous v3.5 version an additional 38.3 Mb of anchored sequence representing 1,837 predicted genes contained in 55 scaffolds. Using fluorescent in situ hybridization (FISH) with BACs that produced chromosome-specific signals, melon chromosomes that correspond to the twelve linkage groups were identified, and a standardized karyotype of melon inbred line T111 was developed.

Conclusions

By utilizing resequencing data and targeted SNP selection combined with a large F2 mapping population, we significantly improved the quantity of anchored and oriented melon scaffold genome assembly. Using genome information combined with FISH mapping provided the first cytogenetic map of an inodorus melon type. With these results it was possible to make inferences on melon chromosome structure by relating zones of recombination suppression to centromeres and 45S and 5S heterochromatic regions. This study represents the first steps towards the integration of the high-resolution genetic and cytogenetic maps with the genomic sequence in melon that will provide more information on genome organization and allow for the improvement of the melon genome draft sequence.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-014-1196-3) contains supplementary material, which is available to authorized users.     

A histological and NMR study of the melon of the striped dolphin (Stenella coeruleoalba)

The melon, the echolocation organ of the striped dolphin (Stenella coeruleoalba), was investigated by morphological and high-resolution (13)C nuclear magnetic resonance (NMR) methods, in order to characterize structure and composition gradient at the histological and molecular level. Morphological analysis showed that the lipidic components are organized in an adipose tissue; moreover, a clear muscular component was observed. Age-related structural differences also were noted. Furthermore, NMR yielded detailed information at a qualitative-quantitative level on the lipid components.     

Development and characterization of microsatellite markers in Cucumis

This study provides a set of useful SSR markers and describes their development, characterization and application for diversity studies.Sixty one Cucumis SSR markers were developed, most of them (46) from melon (Cucumis melo L.) genomic libraries. Forty of the markers (30 melon and 10 cucumber SSRs) were evaluated for length polymorphism in a sample of 13 melon genotypes and 11 cucumber (Cucumis sativus L.) genotypes. PCR-amplification revealed up to six size alleles among the melon genotypes and up to five alleles among the cucumber genotypes, with mean gene-diversity values of 0.52 and 0.28 for melon and cucumber, respectively. These differences are in accordance with the known narrower genetic background of the cucumber. SSR data were applied to phylogenetic analysis among the melon and cucumber genotypes. A clear distinction between the ’exotic’ groups and the sweet cultivated groups was demonstrated in melon. In cucumber, separation between the two sub-species, C.sativus var. sativus and C.sativus var. hardwickii,was obtained. Conservation of SSR loci between melon and cucumber was proven by sequence comparisons. Received: 17 April 2000 / Accepted: 16 May 2000     

甜瓜(Cucumis melo L.)AFLP标记的多态性及聚类分析研究

利用 AFLP 技术对30个甜瓜材料进行多态性和聚类分析研究。从120对 MseI 和 PstI 引物中筛选出25对扩增效果好的引物,共扩增出262条多态性带。聚类分析结果新疆甜瓜中的夏甜瓜类型,新疆甜瓜中的冬甜瓜类型、美国粗皮甜瓜类型、日本甜瓜类型、梨瓜类型各聚为一组。上述材料的聚类分析结果与依据生态类型和地理起源的分类结果基本吻合,表明 AFLP 用于甜瓜种内不同材料间的遗传变异性分析是可行的。     

Effect of salinity on quality of various agricultural crops

Summary The effect of salinity on the quality of various agricultural crops has not yet been explored much. This information is very important to Israel due to the increasing use of saline water for irrigation. This paper reports the effect of saline irrigation water on the quality, especially the taste, of several crops. Fruits from a processing tomato cultivar exposed to various degrees of salinity had higher values for total soluble solids (TSS) and acidity than their controls. The yield of fruit after saline water irrigation is lower, but this is offset by the nigher fruit quality and its consequent higher value. Melon fruits from plants subjected to saline water scored higher in taste than their controls when the fruits were analyzed fresh. After 3–4 weeks of storage at room temperature, there was no longer any difference in taste. Even though salinity slightly increased the TSS content, this did not correlate with the taste scores. Iceberg lettuce grown with saline water did not significantly differ in taste from its control, even when the sensitive triangle taste test was used. The same was true for peanuts. Thus, for these two crops no advantage of better quality would compensate for possible lower yields. Salinity had little effect on the yield of two varieties of Chinese cabbage, but increased the frequency of tipburn.     

A genetic map of melon (Cucumis melo L.) based on amplified fragment length polymorphism (AFLP) markers

 Genetic maps facilitate the study of genome structure and evolution, and the identification of monogenic traits or Mendelian components of quantitative traits. We evaluated 228 RAPD, microsatellite and AFLP markers for linkage analysis in melon (Cucumis melo L.) varieties MR-1 (resistant to Fusarium wilt, powdery and downy mildews) and Ananas Yokneum (AY; susceptible to these diseases) and constructed a detailed genetic map. The mapping population consisted of 66 backcross progenies derived from AY×(MR-1×AY). Despite a relatively low level of polymorphism in the species, AFLP markers were found to be more efficient in mapping the melon genome than RAPD or microsatellite markers. The map contains 197 AFLPs, six RAPDs and one microsatellite marker assigned to 14 major and six minor linkage groups, and covers 1942 cM with the average distance between adjacent markers of approximately 10 cM. The maximum distance allowed between markers is 27.5 cM. About 11% of the intervals (20 out of 173) are over 20 cM (but less than 27.5 cM). The map has immediate utility for identifying markers linked to disease resistance genes that are suitable for marker-assisted breeding. The use of microsatellite markers for integration with other maps is also discussed. Received: 12 March 1997 / Accepted: 20 May 1997     

甜瓜诱变材料的同工酶电泳聚类分析

本文应用PAGE技术,分析了经秋水仙碱诱变的甜瓜的四个品种、一个新品系的13份材料和3个对照的POD、EST、MDH、ADH、GDH、SOD的同工酶．根据16份材料的谱带特征二态数字矩阵,用MEGA程序计算了它们间的Numberofdifference,Proportionofdifference和Kimura-2-parameterdistance遗传距离,分别用UPGMA和Neighbor-joining进行聚类分析．结果表明,甜瓜材料经秋水仙碱诱变均产生了一定的变异,品种内的遗传分化程度与形态性状和细胞学检测相符合．同工酶遗传变异的大小可以反映诱变材料变异大小,在一定程度上可为有效选择育种材料提供依据．     

Management Fusarium wilt on melon and watermelon by Penicillium oxalicum

The potential of the biological control fungus Penicillium oxalicum to suppress wilt caused by Fusarium oxysporum f. sp. melonis and F. oxysporum f. sp. niveum on melon and watermelon, respectively, was tested under different growth conditions. The area under disease progress curve of F. oxysporum f. sp. melonis infected melon plants was significantly reduced in growth chamber and field experiments. In glasshouse experiments, it was necessary to apply P. oxalicum and dazomet in order to reduce Fusarium wilt severity in melons caused by F. oxysporum f. sp. melonis. For watermelons, we found that P. oxalicum alone reduced the area under the disease progress curve by 58% in the growth chamber experiments and 54% in the glasshouse experiments. From these results, we suggested that P. oxalicum may be effective for the management of Fusarium wilt in melon and watermelon plants.