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Variation in Five Isolates of Colletotrichum Falcatum the Causal Fungus of Red Rot of Sugarcane

I.H.Mian
Department of Plant Pathology, Institute of Postgraduate Studies in Agriculture, Salna, Gazipur, Bangladesh.

D.K.Pyne
Assistant Cane Development Officer, Natore Sugar Mills Ltd., Natore.

S.Rahman
Pathology Division, Sugarcane Research & Training Institute, Ishurdi, Pabna

M.I.Talukder
Pathology Division, Sugarcane Research & Training Institute, Ishurdi, Pabna

Abstract/ Executive Summary:

Variation among five isolates of red rot pathogen, Colletotrichum fa/catum Went (Physa/ospora tucumanensis Speg), namely SRTI, NRS, RJSM, KCSM and RSM were determined studying the influence of temperature, pH and fungicide sensitivity on radial growth of colony, and pathogenicity on five host varieties. The isolates were grown on PDA at 20, 25, 30 and 35 ± 0.5°C maintaining pH levels of 5,6,7 and 8. To find out the fungicide sensitivity on colony growth, the isolates were grown on PDA amended with Vitavax-200 at 0,10,50 and 100 ppm and Nystatin at 0, 50, 100 and 1000 ppm. Pathogenicity test was made by inoculating the cane varieties, Isd 1/53, Isd 2/54. Isd 17, Isd 18 and Isd 22. Variation in colony diameter of each isolate at each level temperature and pH were remarkable. The optimum temperature for the isolate RJSM, NRS, KCSM and RSM was 30± 0.5°C but for isolate SRTI was 35±0.5°C. Above 30°C reduction in growth of RJSM, NRS, KCSM and RSM was observed. Similarly, range of pH for growth was notably wide, 5 to 8. All the isolates showed maximum growth at pH 7, above which growth was reduced except KCSM which had maximum growth at pH 8. Variations in colony diameter of the isolate on PDA amended with different concentrations of Vitavax- 200 or Nystatin were considered. Even at the same concentration of each fungicide, reduction in radial growth varied greatly. Prominent variation in pathogenicity and virulence among the isolates and reaction of cane varieties of the pathogen differed significantly.

Keywords: Isolates,Causal fungus, Red rot, Sugarcane

Location: BSRI

Start Date:

End Date:

Program Area: Pest Management

Commodity: Sugarcane

Objectives:

To determine the variation in five isolates of C. falcatum due to influence of temperature and pH on radial growth of colony and their sensitivity to fungicide and pathogenicity on some sugarcane varieties.

Methodology:

Collection of Isolates of red rot fungus: Pure culture of five isolates of C. falcatum were obtained from the Sugarcane Research & Training Institute (SRTI) Ishurdi, Pabna. They were isolated from red rot infected cane pieces collected from sugarcane growing areas of SRTI, -Rajshahi Sugar Mills (RJSM), SRTI-Northern Regional Station (NRS), Kaliachapra Sugar Mills (KCSM) and Rangpur Sugar Mills (RSM). The isolates were named after abbreviated names of the places from where diseased specimens were collected. Pure cultures were prepared following single spore culture technique. The stock cultures of isolates were maintained on oat meal agar in test tubes at 4± 1 cC. Culture medium and preparation of inocula: The medium used to grow the fungus and to study its growth in the laboratory was extra pure potato dextrose agar (PDA) manufactured by DIFCO. The dehydrated PDA was rehydrated in distilled water at 39 g/liter. Twenty millilitre of the medium per petridish was used. The pH of the cooked medium was adjusted to 6.5 for all experiments except the experiment on the effect of pH on radial growth of C. fa/catum where the pH of the medium was adjusted to four different levels. To inoculate test plates under in vitro experiments and sugarcane varieties under pathogenicity test, inocula were prepared by cutting circular blocks of 20 d old culture on 3.9% PDA (DIFCO) containing mycelium and conidia with sterilized 6 mm diameter cork borer.

Source of Information: Bangladesh J. Sugarcane, 16 : 49-59 July, 1994

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The findings of this investigation reveal that each test isolate of C. falcatum differs from others as regard to radial growth of colony on PDA at different levels of temperature as well as pH. The sensitivity to Vitavax-200 or Nystatin on growth on PDA amended with different rates varies remarkably. from pathogenicity test it is clear that each isolate has distinct variations in parasitic relationship with individual variety. The results prove that isolates have different host specificity as regards parasitism.

Knowledge Management: Journal