www.IndianJournals.com Members Copy, Not for Commercial Sale Downloaded From IP - 210.212.141.194 on dated 17-Jul-2014 Electronic Journal of Plant Breeding, 5(1): 22-29 (Mar 2014) ISSN 0975-928X http://sites.google.com/site/ejplantbreeding 22 Research Article Variable response of interspecific breeding lines of groundnut to Sclerotium rolfsii infection under field and laboratory conditions S. K. Bera*, S. V. Kasundra, J. H. Kamdar, Ajay B. C., Chuni Lal, P. P. Thirumalasmy, P. Dash and A. K. Maurya Directorate of Groundnut Research, Pb#05, Ivnagar Road, Junagadh-362001, Gujarat, India Emai: berask67@yahoo.co.in (Received: 03 Mar 2014; Accepted: 20 Mar 2014) Abstract Evaluation of interspecific derivatives of groundnut was carried out under field and laboratory conditions for stem rot caused by Sclerotium rolfsii during rainy and post-rainy seasons from 2005-2008. Disease incidence was higher during rainy compared to post-rainy season. During initial screening of interspecific derivatives for stem rot under sick plot, 42 lines were found to be promising with no disease incidence. Advanced screening of these promising lines was carried out in concrete block with sick soil under field conditions and earthen pot with sick soil under lab conditions. Interspecific lines NRCGCS-47, NRCGCS-99, NRCGCS-131 and NRCGCS-319 were found promising against stem rot during early stages and later stages of crop growth. Out of which interspecific line NRCGCS-319 was found to be most stable one with comparatively lower pooled disease incidence over concrete block and laboratory conditions. Key words: Groundnut, S. rolfsii, interspecific derivatives, rainy, post-rainy Introduction: Groundnut (Arachis hypogaea L.) is an important oilseed crop grown in approximately 25 m ha in Semi Arid Tropics region of the world (FAO, 2012). Stem rot of groundnut caused by S. rolfsii Sacc. is one of the major constraint to groundnut production in many countries in warm and humid areas, especially where groundnut cultivation under irrigated condition is expanding and/ or where cultural practices are changing. Stem rot is also known as southern-blight, southern-stem rot, Sclerotium rot, or white mold. They are widely distributed in India and USA. Besides, it causes serious losses in Bolivia, China, Egypt, Taiwan, and Thailand. Stem and pod rots caused by S. rolfsii cause economic losses on many crops but soybean, groundnut, sugar beet, pepper, tomato and potato suffer maximum losses. Yield loss in groundnut due to stem rot commonly ranges from 10-40%, but can reach over 80% in heavily infested fields (Poter et al.,1982, Mehan and Macdonald, 1990). S. rolfsii also causes indirect losses such as reduction in both dry weight and oil content of groundnut kernels besides downgrading the quality of pod and fodder. In the USA, annual yield losses caused by stem rot are valued at US$43 million (Branch and Brenneman, 1993). Stem rot is a persistent soil borne disease throughout India and its incidence is increasing even at maturity stage of the groundnut crop. Though S. rolfsii resides both on seed and soil, soil- borne nature of the disease is more prevalent than seed borne (Kumar et al., 2013). The occurrence of the disease is more visible at 30 to 45 days after germination and at the time of harvest under rainfed situations due to low and erratic distribution of rainfall. The fungus is ubiquitous, soil inhabitant, non-target and one of the most destructive plant pathogen. S. rolfsii preferentially attacks stem, but it can infect any part of the plant including root, leaf, flower and fruit. On erect plant, yellowing and wilting are usually preceded by light to dark brown lesions at collar region of the stem adjacent to the ground. Drying or shriveling of the foliage and ultimately death of the plants occur after wilting. Characteristic sclerotia, at first white and later brown to black, are produced on mats of mycelium on stem surface of the plant adjacent to soil or on soil surface. S. rolfsii penetrates non-wounded host seedlings directly by the formation of aspersoria. Penetration may also be affected through natural openings such as lenticels and stomata. The fungus is both inter and intra cellular. Batmen and Beer (1965) have claimed that both oxalic acid and pectic enzymes are involved in the destruction of host tissues by the fungus and that two fungal products acting together are more effective than either alone. Chemical and cultural practices have been the predominant means for the management of this disease (Porter et al., 1982). Persistence of the pathogen in soil and wide host range (about 500 species) often limits the effectiveness of chemical and cultural control of stem rot disease (Shew et al.,1987). However, such cultural practices coupled with resistant cultivars can increase the efficiency of the disease management (Shew et al.,1984). Host plant resistance is an important component of such an approach which is currently not available in groundnut. Because screening for resistance in the field is complicated by the non-uniform spatial distribution of the pathogen (Shew et al., 1984). As a result, consistent and reliable data is difficult to obtain in fields under natural infestation. While