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Disease Reaction of Different Crops Against Virulent Potato Isolates of Rhizoctonia Solani Kuhn

Md. Maniruzzaman Khandaker
Department of Botany, Govt. Saadat College, Tangail, Bangladesh

Abul Khair
Department of Botany, Jahangirnagar University, Savar, Dhaka, Bangladesh.

Md. Khurshed Alam Bhuiyan
Department of Plant Pathology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh.

Abstract/ Executive Summary:

A total of 33 hosts from different crop types viz. cereal, pulse, oil, vegetable and fiber plants were tested for pathogenicity in artificially inoculated condition against two isolates (BTB115 and DK64) of Rhizoctonia solani, virulent to potato. In respect of symptoms developed on the stems, the most susceptible hosts against both the isolates were string bean, bottle gourd, groundnut, pea and pumpkin. Soybean stems were highly susceptible to DK64 and less susceptible to BTB115. Disease symptoms did not develop on stems of five crops namely brinjal, proso millet (Panicum miliaceum L.), stem-amaranth, kangkong (Ipomoea reptans L.) and tomato. Symptoms appeared on leaves of all the crops tested. Leaves of groundnut, bush bean, bottle gourd and okra were highly susceptible while those of barley and millet were less susceptible.

Keywords: Rhizoctonia solani, Virulent, Pathogenecity, Crop hosts

Location: Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh.

Start Date:

End Date:

Program Area: Pest Management

Commodity: Diseases

Objectives:

To find out the pathogenic reaction of two virulent potato isolates of R. solani to other crops, especially the crops which are grown in Bangladesh following harvest of potato.

Methodology:

Two isolates of R. solani viz. DK64 and BTB115 which were found to be most virulent to potato were selected during this study for the assessment of disease reaction against 33 hosts from different crop types viz. cereals, pulses, oil, vegetable and fiber plants, which are grown mostly in the potato fields of Bangladesh. Seeds of the crops were collected from Bangladesh Agricultural Research Institute, Gazipur. The experiment was conducted at Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh. Inoculum of R. solani isolates were grown in water soaked wheat grains in flasks and sterilized in autoclave for one hour at 121ºC and 15 lb pressure on three consecutive days. Each flask was inoculated with fifteen mycelial plugs, each of 5 mm diameters, taken from three-day-old culture of each of the isolates grown on PDA medium. The flasks were then incubated at 25ºC for three weeks. After incubation the colonized wheat grains were air dried on sterilized paper and stored at 4 ºC until use. Pathogenicity of the isolates to hypocotyls of seedlings was tested by growing the plants in soil amended with the test inocula of R. solani. The soil used was shifted through a 2 mm mesh sieve and steam sterilized. For inoculation of the sterilized soil with fungal isolate, 10 g of inocula was mixed with one kg of soil and was kept moist for three days. The inoculated soil was filled in polybags (10 cm × 16 cm) before planting. Inoculation with the two isolates of R. solani, DK64 and BTB115, was done separately. Soil in polybags mixed with only autoclaved and air dried wheat grains served as control. Three polybags were used for each treatment and five to ten seeds, based on size, were planted in each polybag. Crop seeds with 90–100% germination rate were selected for sowing. Thirty days after planting seedlings in each polybag were uprooted and washed under running tap water and rated for disease severity following 0 (no apparent symptoms) to 4 (more than 75% hypocotyl tissue necrotic or seedling killed) scale. Pathogenicity of the isolates to the leaves of crop hosts was determined by inoculating detached leaves of 30-day-old crops kept in plastic Petri plates. Inoculation was made aseptically at the centre of a leaf by placing a 5 mm mycelial agar disc from a threeday-old culture of each of the two isolates of R. solani grown on PDA plates. After inoculation proper moist condition was maintained inside the plastic Petri plates using three-fold filter paper saturated with sterile water. Leaves that received only PDA discs without the test inocula served as control. There were three leaves per petri dish, replicated three times for each of the crop. Five days after inoculation, the severity of leaf infection was rated following 0 to 4 scales. Both disease incidence and per cent disease index (PDI) of stems and only PDI of leaves of all the crop hosts were calculated on the basis of arc sine transformed values. PDI of hypocotyls parts (stems) and leaves were measured with the following formula: PDI = Summation of all ratings/Number of plants observed maximum rating (4) X 100.

Source of Information: Bangladesh J. Bot. 37(1): 75-80, 2008 (June)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The disease reaction of the isolates varied considerably among the crops. Only five crops namely brinjal, proso millet, stem amaranth, kangkong and tomato did not respond to R. solani isolates in producing disease symptom on stem. Leaves of all the crops were found to be susceptible and produced symptoms when mycelial blocks were inoculated on leaves. Earlier reports indicated that virulent isolate of R. solani of a crop host might be virulent or less virulent or avirulent for other crop (Kang and King 1986, Ogoshi et al. 1990, Nelson et al. 1996, Yang et al. (1996). The above mentioned findings are in close agreement with the present investigation as the pathogenicity of the test isolates varied in different crops, and on stems and leaves of a same crop. In conclusion it may be stated that isolates of R. solani which were virulent to potato may survive in the soils and perpetuate with other crop plants grown in the same fields after harvest of potato.

Knowledge Management: Journal