Wild Melons Research Articles

Bulked Segregant Analysis by Sequencing-Based Genetic Mapping of the Green Spotted Fruit Rind Regulating Locus in Wild Melon XNM020 Reveals Four Possible Candidate Genes

Fruit rind patterns are vital commercial quality traits in melon, in which the spotted or striped fruit rinds contribute to the commercial value of melon and can directly affect the choice of consumers. Although the spotted or non-spotted fruit rind pattern was studied in several cultivated melon accessions, the inheritance and regulating locus of this trait in wild melons are still unknown. Therefore, in this study, the inheritance and regulating loci of the green spotted fruit rind in a wild melon accession XNM020 were explored with F2 segregating populations derived from crossing between XNM020 and a cultivated melon XNM125. Segregating ratios of phenotypic data indicated that the green spotted fruit rind in XNM020 has a monogenic dominant inheritance. BSA-Seq showed that two potential genomic regions on chromosomes 4 (from 0.00 to 2.97 Mb) and 5 (from 0.00 to 2.34 Mb) regulate the formation of the green spotted fruit rind in wild melon XNM020. According to the annotations of polymorphic SNPs (single-nucleotide polymorphisms) and small InDels (insertions and deletions) in target genomic regions and the predicted gene functions, four genes MELO3C003316, MELO3C003375, MELO3C003388, and MELO3C014660 regulating chloroplast development or chlorophyll biosynthesis may be the best candidate genes. The results of this study enriched the inheritances of spotted fruit rinds in melon and also provided target genomic regions for marker-assisted selection breeding of melon focusing on fruit rinds.

Floral biology studies in wild melon [Cucumis melo L. ssp. agrestis (Naudin) Pangalo var. agrestis Naudin

Studies on floral morphology, phenology and biology of wild melon revealed that the ratio of staminate and pistillate flowers was 3.40:1. The longevity of the male flowers were between 5 and 6 days, whereas, female flowers between 6 and 7 days. Anthesis was observed from 4.00 am to 10.00 am, while, the anther dehiscence started from 5.00 am which was continued to 7.00 am. The peak anthesis was observed from 8.00 am to 9.00 am and anther dehiscence from 6.00 am to 6.30 am. Freshly opened flowers showed pollen viability up to 98.35%, decreased upon closure and crashed to 17.48% in 3 days. Pollen germination was occurred after 15 minutes of incubation and continued up to 24 h of incubation. The stigma receptivity lasts from one to two days of anthesis. Major pollinator of wild melons observed was honey bee, mostly visited between 9:00 am to 6:00 pm.

Evidence of the Role of QTL Epistatic Interactions in the Increase of Melon Fruit Flesh Content during Domestication

Cultivated melon was domesticated from wild melons, which produce small fruits with non-edible fruit flesh. The increase in fruit flesh is one of the major domestication achievements in this species. In previous work, a quantitative trait locus (QTL) on chromosome 6 (paqt6.1) linked to fruit flesh content was detected in a cross between cultivated (“Piel de Sapo”, PS) and wild (Ames 24294, TRI) accessions. The QTL was introgressed into the PS background, generating the TRI_6-3 introgression line (IL) that confirmed the effects of paqt6.1. The primary objective of this work was to fine-map paqt6.1 as the first step for the map-based cloning. Two different approaches were carried out; however, the results were not consistent, precluding the fine mapping of paqt6.1. TRI_6-3 and other related ILs were genotyped by genotyping-by-sequencing, finding additional introgressions in other chromosomes. In an F2 population from TRI_6-3-x-PS, we found an epistatic interaction between paqt6.1 and another locus on chromosome 11. The interaction was verified in advanced populations, suggesting that the effects of paqt6.1 are conditioned by the allelic composition at another locus in chromosome 11. Both loci should have TRI alleles to reduce the flesh content in the PS background. The implications on the history of melon domestication are discussed.

Re-evaluation of the role of Indian germplasm as center of melon diversification based on genotyping-by-sequencing analysis

BackgroundThe importance of Indian germplasm as origin and primary center of diversity of cultivated melon is widely accepted. Genetic diversity of several collections from Indian has been studied previously, although an integrated analysis of these collections in a global diversity perspective has not been possible. In this study, a sample of Indian collections together with a selection of world-wide cultivars to analyze the genetic diversity structure based on Genotype by Sequence data.ResultsA set of 6158 informative Single Nucleotide Polymorphism (SNP) in 175 melon accessions was generated. Melon germplasm could be classified into six major groups, in concordance with horticultural groups. Indian group was in the center of the diversity plot, with the highest genetic diversity. No strict genetic differentiation between wild and cultivated accessions was appreciated in this group. Genomic regions likely involved in the process of diversification were also found. Interestingly, some SNPs differentiating inodorus and cantalupensis groups are linked to Quantitiative Trait Loci involved in ripening behavior (a major characteristic that differentiate those groups). Linkage disequilibrium was found to be low (17 kb), with more rapid decay in euchromatic (8 kb) than heterochromatic (30 kb) regions, demonstrating that recombination events do occur within heterochromatn, although at lower frequency than in euchromatin. Concomitantly, haplotype blocks were relatively small (59 kb). Some of those haplotype blocks were found fixed in different melon groups, being therefore candidate regions that are involved in the diversification of melon cultivars.ConclusionsThe results support the hypothesis that India is the primary center of diversity of melon, Occidental and Far-East cultivars have been developed by divergent selection. Indian germplasm is genetically distinct from African germplasm, supporting independent domestication events. The current set of traditional Indian accessions may be considered as a population rather than a standard collection of fixed landraces with high intercrossing between cultivated and wild melons.

Microsatellite Markers Reveal Genetic Diversity and Relationships within a Melon Collection Mainly Comprising Asian Cultivated and Wild Germplasms.

Melon, Cucumis melo L., is an important horticultural crop with abundant morphological variability, but the genetic diversity and relationships within wild and cultivated melons remain unclear to date. In this study, thick-skinned (TC) (cultivated subspecies melo), thin-skinned (TN) (cultivated subspecies agrestis), and wild accessions were analyzed for genetic diversity and relationships using 36 microsatellite markers. A total of 314 alleles were detected with a mean allelic number of 8.72 and polymorphism information content of 0.67. Cluster analysis of the accessions resulted in four distinct clusters (I, II, III, and IV) broadly matching with the TC, TN, and wild groups. Cluster I contained only two Indian wild accessions. Cluster II was consisted of 49 South Asian accessions, 34 wild accessions, and 15 TN accessions. Cluster III was a typical TC group including 51 multiorigin TC accessions and one wild accession. The remaining 88 accessions, including 75 TN accessions, 6 wild accessions, and 7 TC accessions, formed the cluster IV, and all the TN and wild accessions in this cluster were from China. These findings were also confirmed by Principal component analysis and STRUCTURE analysis. The South Asian subspecies agrestis accessions, wild and cultivated, had close genetic relationships with a distinctive genetic background. Chinese wild melons showed closeness to cultivated subspecies agrestis landraces and could be a return from the indigenous cultivated melons. The AMOVA and pairwise F statistics (FST) presented genetic differentiation among the three groups, with the strongest differentiation (FST = 0.380) between TC and TN melons. These results offer overall information on genetic diversity and affiliations within a variety of melon germplasms and favor efficient organization and utilization of these resources for the current breeding purpose.

Molecular and morphological characterisation of the oldest Cucumis melo L. seeds found in the Western Mediterranean Basin

In 2008–2009, a rescue excavation uncovered an intact Late Bronze Age well in Sa Osa, Sardinia (Italy). The structure yielded a large number of waterlogged plant remains, of which a group of melon seeds (Cucumis melo L.) were some of the most remarkable. These seeds represent the earliest recorded remains of this taxon in the Western Mediterranean and are some of the oldest ever recorded. The plant remains were preserved in anoxic conditions and were found in a perfect state of conservation, making them ideal candidates for morphometric and molecular characterisation. A total of 96 parameters, measured using an automatic image analysis system, were specifically designed to evaluate the morphological features of 15 preserved whole seeds. DNA extraction from archaeological samples followed a procedure specifically set up to avoid any kind of contamination. A 123-SNP genotyping platform that had been validated previously was used. The morphological and molecular data of the archaeological seeds were successfully compared with those of a set of 179 accessions, including landraces, of feral and wild melons from Europe, Africa, and Asia. Both analyses confirmed that these ancient seeds did not belong to a wild melon, but instead to a cultivated one. This primitive melon could have belonged to a group of ancestral non-sweet or semi-sweet forms of chate, flexuosus, or ameri varieties, showing similarities to North African and Central Asian accessions. This finding is coherent with the reportedly important role of cucumber-like melons in the species’ diversification process and with the accepted role of the ameri group as the ancestors of the modern sweet varieties.

Substrates across horticultural and livestock industries that support the development of stable fly, Stomoxys calcitrans (Diptera: Muscidae)

AbstractThis study examined a multitude of potential substrates across horticultural and livestock industries that supported the development of the stable fly, Stomoxys calcitrans (Linneaus) (1081 samples from over 100 properties (2010–2016)). Stable fly developed in high numbers from vegetable crop residues left after harvest, notably celery and leeks as well as several brassica crops, lettuce and silverbeet. Unmarketable vegetables (reject produce) and processing waste provided another source of stable fly development, in particular from carrot production (green tops and processing washings) as well as beetroot and daikon leaves, reject zucchinis, rockmelons, eggplants, turnips and squashes. Reject produce from mostly solanaceous plants either did not support any or rarely supported the development of adult stable fly. Reject vegetable produce fed to livestock presented a source for stable fly to develop in the vegetable/manure mix, especially from carrots and corn cobs. Large accumulations of cattle dung in feedlot situations, hay feeding out sites, wet grain feed and exposed silage produced the highest numbers of stable fly from livestock industries. Cattle dung from rangeland pastures, pig manure and horse manure rarely if ever supported the development of stable fly. Only cattle dung that had aged or pig manure that had been mixed with straw and left to age allowed for any stable fly development. Miscellaneous sources of stable fly development include rotting lawn clippings, rotting weeds, ageing olive pressing residue, and to a lesser extent, rotting wild melons and seaweed.

Quantitative trait loci analysis of melon (Cucumis melo L.) domestication-related traits.

Loci on LGIV, VI, and VIII of melon genome are involved in the control of fruit domestication-related traits and they are candidate to have played a role in the domestication of the crop. The fruit of wild melons is very small (20-50g) without edible pulp, contrasting with the large size and high pulp content of cultivated melon fruits. An analysis of quantitative trait loci (QTL) controlling fruit morphology domestication-related traits was carried out using an in vitro maintained F2 population from the cross between the Indian wild melon "Trigonus" and the western elite cultivar 'Piel de Sapo'. Twenty-seven QTL were identified in at least two out of the three field trials. Six of them were also being detected in BC1 and BC3 populations derived from the same cross. Ten of them were related to fruit morphological traits, 12 to fruit size characters, and 5 to pulp content. The Trigonus alleles decreased the value of the characters, except for the QTL at andromonoecious gene at linkage group (LG) II, and the QTL for pulp content at LGV. QTL genotypes accounted for a considerable degree of the total phenotypic variation, reaching up to 46%. Around 66% of the QTL showed additive gene action, 19% exhibited dominance, and 25% consisted of overdominance. The regions on LGIV, VI, and VIII included the QTL with more consistent and strong effects on domestication-related traits. QTLs on those regions were validated in BC2S1, BC2S2, and BC3 families, with "Trigonus" allele decreasing the fruit morphological traits in all cases. The validated QTL could represent loci involved in melon domestication, although further experiments as genomic variation studies across wild and cultivated genotypes would be necessary to confirm this hypothesis.

The phenology and seed production of Cucumis melo as an invasive weed in northern Iran

Accurately representing plant development is essential for applying phenology knowledgement to investigate the effects of climate on weed management. Development in wild melon (Cucumis melo L.) is driven by temperature; thus, it could be simulated by thermal-time (TT) accumulation using limited accumulation when a lower optimum temperature (Topt) is exceeded. Experiments were conducted to investigate wild melon phenology (development rate) and seed production in soybean (Glycine max L.) at seven different sowing dates (April to August) in a completely randomised design (CRD) at Research Farm of Gorgan University of Agricultural Sciences and Natural Resources, Iran, during 2012. Results indicated that a slight shift in developmental rates occurs among plantings dates, except for those plants sown in August. The estimated TT for April–August planting dates were ~411 Celcius degree days, 448 Celcius degree days, 733 Celcius degree days, 672 Celcius degree days, 604 Celcius degree days, 558 Celcius degree days and 251 Celcius degree days respectively. Depending on planting date, weed emergence occurred at 5–20 days after planting. During the 79, 75, 92, 81, 71, 67 and 61 days of wild-melon growth, the mean number of fruits per plant and seeds per fruit were significantly different at each sowing date. Wild melon could produce a lot of fruits and seeds (up to 5000) within a growth cycle (average in 75 days) and also weed management is needed during the May and June because of the highest seed production of wild melons that emerged during May. The results attained here suggest that temperature alone could not reflect the effect of environment on C. melo development at each given growth stage. Thus, other environmental factors, such as daylength, maybe needed to better estimate weed development. Future research may use multiplicative models to clarify this claim. These results highlighted the value of testing a model over a wide range of environments.

Microsatellite analysis of genetic relationships between wild and cultivated melons in Northwest and Central China.

The genetic relationships between the wild and cultivated melon accessions from Northwest and Central China were dissected using 22 microsatellite markers. A total of 153 alleles, a high level of expected heterozygosity (0.669), and a low observed heterozygosity (0.156) were detected in the total panel. Differences on the allelic composition and heterozygosity levels were found between the two accession types and the wild accessions revealed a higher level of genetic diversity. The UPGMA analysis of the total panel showed that (a) most wild accessions from Northwest China were clustered independently from the cultivated accessions, and (b) the wild and cultivated accessions from Central China presented a high genetic closeness and showed a divergence from those of Northwest China. Similar positioning of the most accessions was observed with the principal coordinate analysis and STRUCTURE analysis. Pairwise FST and Nei's genetic distance quantified the genetic differentiation among the different accession types and further verified our findings. We concluded that the wild melons from Northwest China have a distinctive genetic background and could be the true wild forms, while the wild melons from Central China showed a close relationship to the local cultivars and could be a return from the cultivated melons in the same region. Our results offer an insight into the genetic resources of the main melon producing regions in China, which is essential for maximizing utilization of the traits of interest in wild melons.

English

Melons are good models used for explaining the physiological and biochemical changes in postharvest ripening. In this study, transgenic melons expressing apple ACC oxidase gene when treated with ethylene (AS3) were evaluated. Cell wall expression (MPG1; MPG2), ethylene synthesis ACC oxidase (ACCO1), flavour synthesis AAT (alcohol acyltransferase) and physiochemical parameters such as pulp firmness, titratable acidity (TA), soluble solid content (SSC), volatile esters, ethylene productions, antioxidant assay capacity and ascorbic acid content were evaluated. In cell wall expression analysis, MPG1 increased when fruits of transgenic melons were exposed to ethylene; showing they are ethylene- dependent. MPG2 decreased gradually when fruits were subjected to ethylene application. Fruit firmness was modified in transgenic fruits when ethylene was applied. There was a great reduction similar to that of non- transgenic fruits. However, TA in transgenic fruits remained lower than in non- transgenic fruit. The ethylene applied in transgenic fruit made the titratable acid to increase during 48 h and after it, a reduction was observed. In relation to soluble solid contents, transgenic fruits treated with or without ethylene did not reduce gradually compared to the wild type melons in all the periods. Ethylene productions in transgenic fruits were reestablished when ethylene was applied, exhibiting the same behavior as transgenic fruits. Antioxidant assay levels were more active in transgenic fruits when ethylene was applied than in control fruits, and it was only in transgenic fruits without ethylene. Ascorbic acid was kept in transgenic fruits with or without the application of ethylene. Results obtained show that the application of ethylene in transgenic ACC oxidase melons is able to change the metabolism of the cell wall, flavors and antioxidant capacity levels in fruit during the ripening process. Keywords: Esters, antioxidant, solid soluble content, ascorbic acid African Journal of Biotechnology , Vol 13(31) 3252-3261

GENETIC ANALYSIS OF RESISTANCE TO RACE 2F. OF PODOSPHAERA XANTHII IN WILD MELON MATERIAL 'YUNTIAN-930'

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): III International Symposium on Plant Genetic Resources GENETIC ANALYSIS OF RESISTANCE TO RACE 2F. OF PODOSPHAERA XANTHII IN WILD MELON MATERIAL 'YUNTIAN-930'

Genetic analysis of resistance of wild melon to Podosphaera xanthii race 2F

Yuntian-930 is a wild melon that is highly resistant to powdery mildew (PM). To determine the inheritance of resistance to PM, Yuntian-930 was crossed with another cultivated melon, Hualaishi, which is susceptible to PM. Inheritance of resistance to Podosphaera xanthii race 2F. in six plant generations (P1, P2, F1, B1, B2, and F2) was studied using the mixed major-gene plus polygene inheritance mode with joint analysis method. Inheritance of resistance in wild melons fitted the model of two pairs of additive-dominance-epistasis major genes plus additive-dominant-epistasis polygene. The additive, dominant and epistatic effects between the two major genes played an important role in inheritance. The estimated values of heritability of major genes in B1, B2 and F2 were 62.98, 58.58 and 90.89% and those of polygene heritability were 28.93, 31.47 and 3.22%, respectively. The ratios of the environmental variance to phenotype variance were 5.89 to 9.94%. Thus, resistance of Yuntian-930 to PM was controlled not just by two major genes, but was also affected by polygene and the environment. The selection efficiency for a major gene of F2 was highest in the resistance breeding program. Key words: Wild melon, powdery mildew, resistance, P. xanthii race 2F, inheritance.

Wild melon diversity in India (Punjab State)

We present here the first comprehensive genetic characterization of wild melon accessions from northern India. The genetic diversity among 43 wild melon accessions collected from the six agro-ecological regions of the Punjab State of India was assessed by measuring variation at 16 Simple Sequence Repeat (SSR) loci, morphological traits of plant habit and fruit morphological traits, two yield-associated traits, root nematode resistance and biochemical composition (ascorbic acid, carotenoids, titrable acidity). Variation among accessions was observed in plant habit and fruit traits and wild melon germplasm with high acidity and elevated carotenoid content and possessing resistance to Meloidogyne incognita was identified in the collection. A high level of genetic variability in wild melon germplasm was suggested by SSR analysis. Comparative analysis using SSRs of the genetic variability between wild melons from the north and other melons from the south and east regions of India and also reference accessions of cultivated melon from Spain, Japan, Korea, Maldives, Iraq and Israel, showed regional differentiation among Indian melon accessions and that Indian germplasm was not closely related to melon accessions from other parts of the world. A highly drought tolerant accession belonging to var. agrestis Naud. was also identified.

GENETIC DIVERSITY OF CHINESE THIN-SKINNED MELON CULTIVARS (CUCUMIS MELO L.) BASED ON SIMPLE SEQUENCE REPEAT MARKERS**

ISHS XXVII International Horticultural Congress - IHC2006: International Symposium on Structural and Functional Genomics of Horticultural Plants GENETIC DIVERSITY OF CHINESE THIN-SKINNED MELON CULTIVARS (CUCUMIS MELO L.) BASED ON SIMPLE SEQUENCE REPEAT MARKERS**