U.S. SHARATH CHANDRAN1, *K. VEMANA1, R. SARADAJAYALAKSHMI DEVI1, MAMTA SHARMA2

1 Department of plant pathology, S.V. Agricultural College, ANGRAU, Tirupati – 517 502, Chittoor (Dist.)

Andhra Pradesh

2 International Crop Research institute for Semi-Arid Tropics, Patancheru, Hyderabad, Telangana

ABSTRACT

Pigeonpea cultivation is subjected to high yield losses every year. Dry root rot or Macrophomina stem canker caused by Rhizoctonia bataticola (Taub.) of pigeonpea is an emerging and serious problem in late sown or summer crops and in perennial or ratooned pigeonpea. Keeping in mind the minimal work done with respect to this pathogen, the present study was conducted to explore the cultural variability of the different R. bataticola isolates of pigeonpea. Ten isolates were characterized in vitro to study their cultural characteristics.The presence of cultural variability among the different isolates were evident from the study.

KEYWORDS:

Organic, inorganic, sheep penning, rainfed, protective irrigation, groundnut yield.

INTRODUCTION

Pigeonpea (Cajanus cajan (L) Mill sp.) is an grain legume crop of rain fed agriculture in semi-arid trop-ics and is the second most important pulse crop grown in India. Being a hardy crop, it is a natural choice for small and marginal farmers particularly, in semi-arid dryland areas because it can be grown successfully under rainfed or low input condition and provides nutritive food, feed, fodder and fuel wood. Pigeonpea cultivation is subjected to high yield losses every year. Of the many factors re-sulting in the economic loss, diseases appear to be the major biological constraints to pigeonpea production. Dry root rot or Macrophomina stem canker caused by Rhizoctonia bataticola (Taub.) Butler [syn-Macrophomina phaseolina (Tassi) Goidanich] of pigeonpea is an emerging and serious problem in late sown or summer crops and in perennial or ratooned pigeonpea. Rhizoctonia bataticola is a soil and seed borne necrotrophic fungal pathogen that has a global distribu-and causes disease in more than 500 cultivated and wild species plant species including several economically im-portant crops (Kaur et al., 2012).

tion (Farr et al., 1995) In contrast to many pathogens favored by changes to moisture conditions (Garrett et al., 2006), R. bataticola is problematic in agricultural areas where climate change results in longer drought periods

and higher temperatures. A very little work has been done

on dry root rot pathogen in pigeonpea crop with respect

to its variability. Keeping in mind the importance of the

disease with respect to changing climate, the present study

explores the cultural variability of the different R.

bataticola isolates of pigeonpea.

MATERIALS AND METHODS

Fungal cultures

Ten isolates of the pathogen Rhizoctonia bataticola (syn. Macrophomina phaseolina) was procured from the Legumes Pathology Division, ICRISAT, Patancheru, Hyderabad. The isolates were sub cultured and transferred on PDA and was serially designated from Rb1 to Rb10.

Cultural Characterization

All ten isolates were characterized in vitro for their cultural characteristics. The mycelial discs of 5 mm diameter were cut from the periphery of three days old culture and transferred to 90mm Petri dish containing 20ml PDA. These plates were incubated at 30°C with 12h photoperiod. Each treatment was replicated thrice. Radial growth of the cultures was measured at 48h after inoculation. Seven days old cultures were used to record texture, colour and presence or absence of aerial mycelium

RESULT AND DISCUSSION

Cultural variability existed among the isolates tested (Table 1). The radial growth at 48 HAI ranged from 71.17 mm (Rb 6) to 50.67 mm (Rb 2) (Fig.1). The colony colour varied from black to grey except for Rb 1 producing off white colonies. The colony texture was fluffy to partially fluffy (Fig.2). The presence of aerial mycelia was observed in all isolates. Similar results were observed by Charul and Biswas (2009) while evaluating morphological variability of R. bataticola which is the causal agent of leaf spot and blight disease of pigeon pea. Their results revealed that the nature of mycelium varied from fluffy dark brown to partially fluffy mycelium colony with smooth margin. Also, Hildebrand et al. (1945) observed the sclerotial colour to be black and smooth varying from spherical to oblong to irregular shaped and also reported that the sclerotial shape of any isolate varied with substrate on which fungus was grown.

CONCLUSION

In this study we have demonstrated the presence of cultural variability among the different R.bataticola isolates of pigeonpea tested. For a better understanding of the changes in the pathogenic nature of R. bataticola of pigeonpea depending on spatial or temporal distribution, frequent cultural and morphological characterization studies of the pathogen is essential.

LITERATURE CITED

Charul, K and Biswas, S.K. 2009. Enzymatic activity of Rhizoctonia bataticola causal agents of leaf spot and blight disease of arhar. Annals of Plant Protection Sciences. 17(2). 518-520.
Farr, D.F., Bills, G.F., Chamuris, G.P and Rossman, A.Y. 1995. Fungi on plants and plant products in the United States, 2nd edition St Paul, MN: American Phytopathological Society Press.
Garrett, K.A., Dendy, S.P., Frank, E.E., Rouse, M.N.and Travers, S.E. 2006. Climate change effects on plant disease: genomes to ecosystems. Annual Review of Phytopathology. 44:489–509.
Hildebrand, A.A., Miller, J.J and Koch, L.W. 1945. Some studies on Macrophomina phaseoli (Maubl.) Ashby. Ontario. Science Agriculture. 25: 690696.
Kaur, S., Dhillon, G.S., Brar, S.K., Vallad, G.E., Chand, R and Chauhan, V.B. 2012. Emerging phytopathogen Macrophomina phaseolina: biology, economic importance and current diagnostic trends. Critical Reviews in Microbiology.38(2):136-151.