Document Type : Research Article
Abstract
Introduction: Gladiolus belongs to the family Iridiaceae. It is commercially cultivated in all parts of the world. This plant is mainly affected by wilt disease caused by Fusarium oxysporum Schlecht Fr f .sp. gladioli (Massey) Snyd. and Hans. It results in death of plant and rotting of corms. Fusarium disease of gladiolus is commonly known as yellows, wilt or corm rot. The wilt disease of gladiolus is known to occur in almost all gladiolus growing areas. Wilt disease is one of limiting factors of cultivation and development of gladiolus in Jiroft, Kerman, Iran. Different fungi such as Fusarium oxysporum f.sp. gladioli, F. moniliforme, F. sporotrichiella, F. hetrosporium and Penicillium gladioli, P. rubrum have been reported as causal agents of gladiolus wilt, root and corm rot disease in many countries. The disease symptoms, including yellowing of leaves, weakness of plant, flower imperfect, root and corm rot, browning of infected root and corm, wilting and finally death of infected plants which observed in infected samples. No research has been carried out in Jiroft, therefore, this research aims to study and identify the causal agent of wilt disease on gladiolus.
Materials and Methods: During survey, characteristic symptoms of wilt disease were recorded and also samples were collected for isolation of pathogens that infect on Gladiolus. The infected corms showing typical symptoms of wilt disease were used for the isolation of pathogen. The standard tissue isolation procedure was followed to isolate the pathogen. To identify the causal agent of gladiolus wilt, infected tissues from symptomatic plants were first surface disinfestations, dehydrated and cultured on Potato Dextrose Agar Medium and incubated at 25± 2oc. Isolated fungi identified using morphological and microscopic characters. To pathogenicity test, corms were inoculated using the dip method in conidial suspension and then planted in pots containing sterilized soil. Inoculated plants were checked for disease symptoms. Distilled water used for inoculation of plants as a control. Observations were made regularly for the appearance and development of symptoms. After symptom development, re-isolation was done from the artificially infected corms.
Results and Discussion: The disease symptoms, including yellowing of leaves, weakness of plant, flower imperfect, root and corm rot, browning of infected root and corm, wilting and finally death of infected plants observed in infected samples. The type of disease symptoms was similar to others which have been reported before. A fungus with white aerial mycelium and little dense colony recovered from infected cultured samples. The produced micro conidia were single, sometimes two cells, oval to ellipsoid in shape, in diameter 3.75-5 * 8-10 micrometer which formed on single and short phialides. Macroconodia were mostly 3-4 celled, in diameter 3-5 * 18-35 micrometer and formed on spordochia. Chlamidospores were spherical to round shape, mostly single, sometimes in the short chain and formed intercalary and terminal. 10 to 14 days after inoculation the symptoms of the disease were seen as yellowing, plant weakness, and wilt. Based on morphological and pathogenicity test, the isolated fungus identified as Fusarium oxysporum f. sp. gladioli and confirmed by the Iranian Research Institute of Plant Protection. Infantino and Rumine (1993) reported that the F. oxysporum f .sp. gladioli infected other members of the Iridiaceae family. Other Fusarium species associated with the corms of gladiolus are Fusarium solani (Mart) Sacc., Fusarium subglutinans (Woolenweb and Reinking) Fusarium heterosporum. Nees ex Fr and Fusarium sporotichoides Sherb. ( Georgieva and Peikova, 1976). This is the first report of Fusarium wilt of Gladiolus on three different cultivar (White, pink and red) in Jiroft, located in the south part of Kerman, Iran. Few resistant cultivars are available in the world. It found that Australian fair and Monsoer were tolerant to F. oxysporum. f .sp. gladioli.
Conclusion: based on this research project, the causal agents of gladiolus wilt disease in Jiroft is Fusarium oxysporum f. sp. gladioli. Disease incidence was different on three gladiolus cultivars which cultivated in this area. Field observation showed, the white cultivar was more tolerant in comparing to red and pink gladiolus cultivars. In gladiolus wilt disease control managements, more emphasis should be focused on disease resistance. The more resistant cultivars should be tested for resistance to several Fos isolates.
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