Breeding and Biotechnology of Plant and Flower
Farhad Shokouhifar; Mojtaba Mamarabadi; Sahba Toosi
Abstract
Introduction
Melon (Cucumis melo L.) is a diploid plant with (2n = 2x = 24) chromosomes, dicotyledonous and annual, which has been receiving lots of attention for its biological characteristics and economic value for a long time. Iran with production of about 1.6 million tons per year ranks third in ...
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Introduction
Melon (Cucumis melo L.) is a diploid plant with (2n = 2x = 24) chromosomes, dicotyledonous and annual, which has been receiving lots of attention for its biological characteristics and economic value for a long time. Iran with production of about 1.6 million tons per year ranks third in melon production in the world after China and Turkey. Vascular wilt caused by the soil borne fungus Fusarium oxysporum f. sp. melonis is one of the most important diseases causing damage to the melon plant. Due to the survival of this fungus in the form of chlamydospores in the soil and plant debris its control has been a difficult challenge so that, the only way to deal with this disease is to use resistant cultivars. The present study was conducted to characterize morphologically different melon cultivars with varying levels of resistance against Fusarium vascular wilt. Furthermore, the presence pattern of two MRGH genes belonging to the MRGH21 linkage group was tracked in the genome of the melon line, and their variations were defined. Moreover, the potential for using these genes in gene-assisted selection was investigated.
Materials and Methods
Five different varieties of melon named Charentais T, Charentais Fom1, Charentais Fom2, BG-5384 and the local cultivar Khatouni were grown under greenhouse conditions. Different characteristics of the plant, including leaf shape, male flowers, female flowers and normal flowers, and after harvesting the fruits, fruit weight, fruit diameter and length, diameter of flesh and middle cavity. The differentiation of resistant and sensitive cultivars was investigated based on the evaluated morphological traits. Additionally, the presence patterns of resistance genes were examined in the genomic data of the aforementioned melon cultivars. The genomic analysis of melons aimed to locate the MRGH21 linkage group, which carries several resistance genes. The sequence of this linkage group was tracked from two gene bank databases in NCBI and MELONOMICS database.
Results
Based on the obtained results, although it was possible to differentiate melon cultivars based on morphological traits, but since the study of these traits in the evaluation of a large number of samples in selective studies is a very time-consuming and costly task. Therefore, the presence pattern of resistance genes were analyzed in the genomic data of different melon cultivars. The sequence between two genes MRGH12 and MRGH13 including MRGH21 linkage group as one of the linkage groups carrying a number of resistance genes on Ch09 chromosome was retrieved form two gene bank databases in NCBI and MELONOMICS. Due to the presence of multiple point mutations in the genomic data, the MRGH13 gene sequence was selected for investigation in melon cultivars. Specific primers, PSh21-F/R, were designed to track part of this gene's sequence. The tracking results showed that a single specific band, corresponding to the expected size, could be detected in the cultivars Charentais Fom1 and BG-5384. Sequence analysis using the InterPro network tool confirmed the possible role of the protein coded by the MRGH13 gene. It was identified as a member of the protein family carrying leucine-rich repeat sequences, including the TIR, NB-ARC, and LRR domains.
Discussion
Attaining suitable markers to distinguish melon cultivars resistant to Fusarium wilt disease can support the development of breeding programs with higher accuracy and speed. The results of the present study showed that based on the morphological traits such as leaf shape, the presence of full flowers, and the number of petals, some differences can be observed between different melon cultivars, but the noteworthy point is that in selection programs searching for these morphological traits will be a very time-consuming and expensive task due to the large number of investigated samples. Therefore, if molecular markers related to the resistance trait are available, the efficiency of breeding programs is expected to increase significantly. In the present study MRGH13 gene was selected to be investigated for tracking in melon cultivars and specific primers were designed to track part of the sequence of this gene. The tracking results showed that a single specific band could be detected in the cultivars Charentais Fom1 and BG-5384. Biological processes related to MRGH13 protein in the QuickGO network tool showed its relevance in the signaling pathway that regulates immune responses. In future studies, it is suggested to evaluate the ability to distinguish resistant cultivars based on resistance genes, including the MRGH13 gene, in a larger number of samples. Moreover, considering to the predicted functions of MRGH13 protein, more investigation on its interaction with other resistance proteins as well as proteins of pathogenic agents can be useful for identification of its functional role in resistance.
Zohreh Chenarani; Farhad Shokouhifar; Mojtaba Mamarabadi
Abstract
Introduction: Iran is the third producer of Melon (Cucumismelo L.) after China and Turkey in the World.Melon is one of the main crops in Khorasan province in the term of cultivation area. The cultivar of Khatooni, among many varieties of melon, can be considered as a breeding cultivar because of its ...
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Introduction: Iran is the third producer of Melon (Cucumismelo L.) after China and Turkey in the World.Melon is one of the main crops in Khorasan province in the term of cultivation area. The cultivar of Khatooni, among many varieties of melon, can be considered as a breeding cultivar because of its great qualitative traits including sweetness and flavor. This cultivar is also economically important and has many attractions for export. However, this cultivar is susceptible to some of plant diseases caused by different bacterial, viral and fungal pathogens which among them vascular wilt caused by Fusariumoxysporum f. sp. melonis (Leach &Currenu) Snyder & Hansen (FOM) is one of the most destructive soil-borne diseases in melon in Iran particularly in temperate and cold regions. The control of melon diseases has depended increasingly on the extensive use of toxic chemicals (pesticides). Many of these chemicals have been shown to be toxic to non-target microorganisms and animals and may be toxic to humans. Another problem with using chemicals to control plant pathogens is that a pathogen may become resistant to the chemicals.
The most promising control approaches are included conventional breeding and genetic engineering of disease-resistant plants. However, the conventional breeding method of melon is very complicated therefore; genetic engineering could be an effective and quick tool for producing new cultivars. In vitro direct regeneration is one of the most crucial step in gene transferring programs (20). In the present study, the effects of explant type and medium were considered in order to optimize the regeneration condition for melon (cv. Khatooni).
Material and Methods: The Khatoonicv.was provided by the Seed Bank of Plant Sciences Research Center from Ferdowsi University of Mashhad. The seeds were disinfected by NaClO in 1 % concentration, washed three times by distilled water and cultivated on MS medium (Murashigo and Skoog) for germination. The explant types were; lateral buds of cotyledon and the true leaves and hypocotyls. The selected media were: M1(0.1 mg.l-1 BAP (6-Benzyl amino purine)), M2 (0.25 mg.l-1 BAP), M3 (0.5 mg.l-1 BAP), M4 (0.75 mg.l-1 BAP),M5 (1 mg.l-1 BAP)and M6(including 0.5 mg.l-1 BAP and 0.01 mg.l-1 NAA (1-Naphthalene acetic acid))The experiment was repeated three times. The experimental –was conducted factorial based on completely randomized design and statistical analysis was performed using the SAS and JMP software. The corresponded graphs were drawn by Microsoft excel 2007.
Results and Discussion: The greatest amount of shoot regeneration in cotyledons was observed in M5 with 1 mg.l-1 BAP while minimum shoot regeneration was observed in M1with 0.1 mg.l-1 BAP. Cotyledon leaves showed the best regeneration efficiency among the other evaluated explants as it has also been reported by many other researchers (12, 8, 20, 21, and 2). The observations showed that in all BAP concentration, hypocotyls only formed callus tissue and did not produce any stem. In all three explants (true leaves, cotyledon and hypocotyls) rooting was observed in a treatment combination including 0.5 mg.l-1BAP and 0.01 mg.l-1 NAA 20 days after cultivation while no stem was formed at the same time. In three weeks after exposure , a weak root system was formed on the rooting mediumin without hormonetreatment . In MS medium enriched with 0.01 and 0.05 mg.l-1 NAA an appropriate root system was formed after 8 to 10 days. The medium containing 0.01mg.l-1 NAA was more appropriate for root regeneration (rooting).
Conclusion: Many studies have been shown that, the manipulation of different phytohormones ratio such as auxin and cytokinin in cultural medium is a suitable strategy to manage differentiation and organogenesis programs in plant (9). In the present study, the effects of explant type and medium were investigated in order to optimize the regeneration condition for melon (cv. Khatooni). As a result, in all BAP concentration, hypocotyls only formed callus tissue and did not produce any stem. However, by increasing of BAP hormone concentration in the cultivated media, shoot regeneration will also increase. The result of our study showed that, cotyledon leaves were more effective on shoot regeneration compared to the true leaves and hypocotyls as it has also been reported by other researchers.
