Abstract
<i>Trichoderma</i> species are frequently used for the biological control of phytopathogenic fungi and they have also been reported as plant growth promoters. In the present study, the effect of two <i>Trichoderma</i> spp. <i>i.e. Trichoderma asperellum</i> and <i>Trichoderma virens</i> isolated from the soils of onion fields on the growth of <i>Allium cepa</i> L. plants and suppression of damping off and basal rot diseases was evaluated under field conditions. The two <i>Trichoderma</i> spp. were mass cultured in a low cost medium containing molasses and yeast and added to a low cost carrier medium consisting of talc. Two formulations, <i>i.e. T. asperellum</i> only and <i>T. asperellum</i> in combination with <i>T. virens</i> were prepared and the formulations were tested for their effect on onion seedlings at the nursery stage and also on transplanted plants in the field. At the nursery stage, the two formulations were applied using two methods <i>i.e.</i> soil application prior to planting of onion seeds or priming of onion seeds with the two formulations separately before planting. Both methods reduced the incidence and severity of damping off disease while increasing the growth of seedlings significantly (p ≤ 0.05) at the nursery stage. Additional treatment with the two formulations as seedling root dips or soil applications before transplanting the seedlings in the field were effective in controlling basal rot disease of <i>A. cepa</i> L. and enhancing the growth of <i>Allium cepa</i> L. plants significantly (p ≤ 0.05) in the field.
Highlights
Big onion (Allium cepa L.) is a condiment grown for its flavorful bulbs in Sri Lanka as well as a number of other countries in the world
The Fusarium isolate was identified as Fusarium solani (NCBI GeneBank accession numbers obtained after deposition of accessions Trichoderma asperellum, Trichoderma virens and Fusarium solani are MG198706, MG199587 and MF685335 respectively) [18]
Results revealed that the average of 30 days old A. cepa L. seedling height with Trichoderma spp. application were in the range of 23.8933±0.68 cm - 26.92±0.58 cm, n=15 compared to 15.9067±0.28 cm, n=15 in the control seedlings infected by Fusarium solani and to 21.5±0.48 cm in the uninfected control seedlings
Summary
Big onion (Allium cepa L.) is a condiment grown for its flavorful bulbs in Sri Lanka as well as a number of other countries in the world. In Sri Lanka about 627 Hactares is cultivated in the Matale and Anuradhapura districts. The local cultivation does not meet the annual requirement of big onion approximately 203,993 MT per year [1]. One major factor contributing towards yield reduction is infectious diseases that occur both during the nursery stage and in transplanted field conditions. Some of the more economically significant diseases that reduce yields are caused by fungal pathogens. Diseases caused by fungal pathogens can be broadly divided into seedling diseases, foliage diseases and bulb diseases. The most common fungal genera responsible for big onion diseases are Fusarium, Frontiers in Environmental Microbiology 2020; 6(3): 40-51
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