~ 1641 ~ International Journal of Chemical Studies 2019; 7(3): 1641-1644 P-ISSN: 2349–8528 E-ISSN: 2321–4902 IJCS 2019; 7(3): 1641-1644 © 2019 IJCS Received: 25-03-2019 Accepted: 27-04-2019 Tokmem Siram Department of Plant Pathology, College of Agriculture, Central Agricultural University, Imphal, Manipur, India Sobita Devi Department of Plant Pathology, College of Agriculture, Central Agricultural University, Imphal, Manipur, India Bireswar Sinha Department of Plant Pathology, College of Agriculture, Central Agricultural University, Imphal, Manipur, India Tusi Chakma Department of Plant Pathology, College of Agriculture, Central Agricultural University, Imphal, Manipur, India Linda Lalduhzuali Department of Plant Pathology, College of Agriculture, Central Agricultural University, Imphal, Manipur, India Kota Chakrapani Department of Plant Pathology, College of Agriculture, Central Agricultural University, Imphal, Manipur, India Correspondence Tokmem Siram Department of Plant Pathology, College of Agriculture, Central Agricultural University, Imphal, Manipur, India In vitro evaluation of bio control agents against Alternaria spp. causing Alternaria blight of marigold Tokmem Siram, Sobita Devi, Bireswar Sinha, Tusi Chakma, Linda Lalduhzuali and Kota Chakrapani Abstract Blight disease of marigold is one of the important disease caused by many species of Alternaria. The antagonistic potential of six Trichoderma spp., viz., T. asperellum (KU933475), T. koningiopsis (KU904460), Hypocrea lixii (KX0113223), T. hargianum (KU904458), T. ovalisporum (KU904456) and T. atroviridae (KU933472) were evaluated in vitro against Alternaria pathogen causing Alternaria blight of marigold following dual culture technique. Among bio-agents used, T. harzianum showed the highest growth inhibition per cent (68.24%) followed by T. atroviridae (67.05%), T. asperellum (60.35%), T. ovalisporum (60%), Hypocrea lixii (58.82%) and T. koningiopsis (57.64%) respectively. All species of Trichoderma considerably inhibited the growth of pathogen. The findings indicates the ability of Trichoderma spp. as potential antagonists against the growth of Alternaria spp. causing Alternaria blight of marigold. Keywords: Alternaria spp., antagonist, bio-agents, dual culture, growth inhibition, Trichoderma spp. Introduction Marigold (Tagetes spp.) belongs to family Asteraceae and is one of the most important flower preferred traditionally for decoration and religious purposes in India. It is native to North and South America. Marigold is commercially cultivated all over India in around 63.13 thousand ha (2015-16) with total production of 603.18 thousand MT (2015-16) (Horticultural Statististics at a Glance 2017) [5] . The essential oil of the flower contain antioxidants and is most effective against the nematode species Pratylenchus penetrans (Olabiyiand and Oyedunmade 2000) [6] . Plant has also mosquitocidal potentiality (Rajasekaran et al. 2004) [7] . The leaves and flowers possess medicinal values having phenolics. The crops suffers badly with Alternaria blight caused by Alternaria spp. Symptoms first appeared on older leaves as circular, brown lesions that later enlarged, coalesced, and turned dark brown to black. Severely infected plants become black, appeared scorched and eventually died. The pathogen was identified as A. tagetica (Shome and Mustafee 1966) [9] . Symptoms caused by A. alternata appear as circular spots with brown margins in early stages, in the latter stages the lesions turn brown (Bhat et al. 2013) [2] . Cotty et al. (1983) [4] reported 50-60% loss of flower yield due to marigold blight disease caused by A. tagetica. There are various method of disease control but the use of bio control agents for disease management is one of the best management method as it does not have negative impact on environment unlike chemical control. Trichoderma spp. are most commonly used biocontrol agents because of the ability to protect plants and inhibit pathogen populations under different soil conditions. Trichoderma spp. also produce various biologically active compounds, including cell wall degrading enzymes, and secondary metabolites (Vinale et al. 2008) [10] . Therefore, antagonistic effects of six native Trichoderma spp. were evaluated against Alternaria spp. causing Alternaria blight of marigold in vitro by dual culture method. Materials and Methods Collection of the diseased samples and isolation of the fungus Diseased samples were collected from infected marigold plants and observed under microscope. The infected tissues were cut into small pieces of 2-3 mm size containing 50% diseased and 50% healthy portion with the help of sterilized blade.