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 ...
Read More
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.
