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Boll Rot of Cotton (gossypium Hirsutum L.) Caused by Rhizopus 0ryzae Went & Prins. Geerl.-a New Record in Bangladesh

SHAMIM SHAMSI
Professor
Department of Botany, University of Dhaka, Dhaka-1000

NAJMUN NAHER
Lecturer
Department of Botany, Life and Earth Science Group, National University, Gazipur-1704, Bangladesh.

Abstract/ Executive Summary:

Boll rot disease of cotton is one of the notorious disease of cotton. In the present investigation, Rhizopus oryzae Went & Prins. Geerl. (=R. arrhizus Fisher) was first time isolated from boll rot infected cotton variety CB6 and CB11. Disease severity of boll rot was recorded at (0-6) DS scale during the months of December 2012 to March 2013. Highest severity of the boll rot disease was recorded as DS-6 in the second week of February followed by DS-5 in 30th January. Lowest DS-2 was recorded in 15th February and 15th March . Boll rot exhibit a high level of complexity in its sympotomology and pathogenicity. Present investigation estimated that 75% of total fruit loss due to boll rot symptom caused by R. oryzae. Cotton boll is an excellent substrate for the growth of fungi. So far Ascochyta gossypii, Colletotrichum gossypii , Fusarium spp., Lasiodiplodia theobrome (Pat.) Griffon & Maubl, Botryosphaeria rhodina (Cooke) Arx, Phytophthora spp. and Rhizoctonia solani have been reported from boll rot symptom. Sclerotium rolfsii was reported on stem and root of infected cotton. From Bangladesh, Sclerotium rolfsii was isolated from infected cotton boll of CB3 for the first time (Shamsi et al., 2008). In the present study, R. oryzae was the exclusive fungal species isolated from infected inocula and it was found to be pathogenic on inoculated fruits.

Keywords: Boll rot, Cotton, Rhizopus oryzae, New record, Bangladesh

Location: Botanic Garden, University of Dhaka,

Start Date: 00-01-2013

End Date: 00-02-2013

Program Area: Crop-Soil-Water Management

Commodity: Cotton

Objectives:

Considering importance of the disease, the present investigation was conducted to identify fungal pathogens associated with the disease under Bangladesh conditions.

Methodology:

During the period of January and February 2013, cotton varieties CB-1 to CB-11 those were grown in the Botanic Garden, University of Dhaka, exhibit a high level of boll rot infection. For visual estimation of severity of infected fruit, 0-6 point scale has been designed following 0 – 9 point scale used for rating of all foliar diseases studied (PDI=McKinney’s Index, Ghosh et al., 2009). No infection – 0, 1 = upto 10% fruit area infected, 2 = 10 – 20% fruit area infected, 3 = 20 – 30% fruit area infected, 4 = 30 – 40% fruit area infected, 5 = 40 – 50% fruit area infected, 6 = more than 50% fruit area infected. Cotton plants of varieties CB1 to CB11 having boll rot infected fruits were selected. Disease symptoms and DS observed on naturally infected boll were recorded . Boll rot infected fruit samples of cotton were collected for further studies. The fungus associated with the diseased samples was isolated following tissue planting method (CAB, 1968). The samples were washed with fresh water, cut into small pieces ( 2 mm × 2 mm) having 50% healthy tissues, surface sterilizes with 10% chlorox for 3-5 minutes and rinsed with sterilized distilled water for three times. Surface sterilized inocula were placed in Petri dishes containing potato dextrose agar (PDA) at 3 inocula per plate. The inoculated plates were incubated at 25±1^oC for 3 – 5 days. Fungus grew from the specimens was transferred to petridishes containing fresh PDA. After sporulation, temporary mount was prepared and observed under a compound microscope. Morphological characters of hyphae, sporagiophores, sporangia and sporangiospores of the fungus grew from the specimens were recorded. Pathogenecity of the fungus was also performed following detached fruit inoculation method (Shamsi et al., 2010).

Source of Information: Bangladesh J. Agril. Res. 39(3): 547-551, September 2014 ISSN 0258-7122

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The boll rot of cotton caused by R. oryzae is new record in Bangladesh and literature search does not show reports of its presence in other parts of the world where cotton is cultivated.

Knowledge Management: Journal