BackgroundBranch canker caused by Macrophoma theicola is a major stem disease of tea plants (Camellia spp.). In tea plantations, this disease causes crop loss and it is one of the major limiting factor for yield stagnation. In very few instances it causes considerable damage in new clearings (about 3 or 4 years old) and large number of bushes have been killed. As there is no control measures for branch canker disease in south Indian tea plantation, this field study was conducted in naturally infected pruned tea field at UPASI Tea Research Institute (Good Agricultural Practice), Valparai, Tamil Nadu, India.MethodsThe chemical fungicides, biological agents and bio products were evaluated under naturally infected field of seedling plants for two consecutive disease seasons (2014–2015) and there was 11 treatments with three applications. All the treatments were carried out in the time of February–March and October–November (2014–2015). The two set of application was conducted per year. Each set contains eight rounds during the month of February–March as well as October–November (2014–2015). The chemical fungicides, biological agents and commercial bio products were measured as per UPASI- TRF, recommendation viz., COC (50 g/ha and 0.2 g/plot), Companion (20 g/ha and 0.08 g/plot), biological agent of Bacillus amyloliquefaciens, Tichoderma harzianum, Gliocladium virens and Beauveria bassiana (5 kg/ha and 20.8 g/plot) and bio product of Tari (1 L/ha and 4.2 ml/plot) and Tricure (1 L/ha and 4.2 ml/plot).ResultsThe present investigation revealed the integrated application of Companion/Bacillus amyloliquefaciens showed superior control of branch canker disease followed by the treatment with Companion alone under field condition. Copper oxychloride/Bacillus amyloliquefaciens was moderately effective followed by Copper oxychloride. The significantly reduced canker size was recorded with treatment of Bacillus amyloliquefaciens followed by commercial organic fungicides of Tari (Organic Tea Special) and Tricure (0.03% Azadirachtin). The least canker size was observed with Gliocladium virens followed by Beauveria bassiana. Branch canker disease incidence was increased in untreated control plants when compared to treated plants.ConclusionAmong these 11 treatments, the integrated treatment of companion at rate of 0.08 g and Bacillus amyloliquefaciens (20.8 g) showed the most significantly decreased canker size (DPL, 5.76) followed by another treatment with companion (0.08 g) (DPL, 4.11). The moderate reduction of canker size was observed by the treatment with Copper oxychloride (0.2 g)/Bacillus amyloliquefaciens (20.8 g) (DPL, 3.05) followed by the treatment of copper oxychloride alone (DPL, 1.74). Therefore, the integrated application of Companion/Bacillus amyloliquefaciens proved significantly effective in the management of branch canker disease under the field conditions.

Plants regulate their rhizosphere microbiome, which partly comprises the fungal community. We conducted a study in order to determine the effect that five medicinal plant species (Origanum syriacum, Salvia fruticosa, Teucrium capitatum, Myrtus communis and Pistacia lentiscus) have on the fungal community in their rhizosphere. We measured abiotic parameters and used sequencing to determine the structure of the rhizosphere fungal community, both taxonomically, as phyla and genera, and functionally, as trophic modes. Our data shows that the rhizosphere fungal communities were significantly different, both taxonomically and functionally. The rhizosphere of M. communis had a significant relative abundance of saprotrophs and a lower relative abundance of symbiotrophs than the control soil and the rhizosphere of T. capitatum. The relative abundance of the genus Aureobasidium was significantly higher in the rhizosphere of P. lentiscus than in the control and for all other rhizospheres, but that of S. fruiticosa. The relative abundance of genus Alternaria was lower in the rhizospheres of S. fruticosa and M. communis than in the control soil. Our results highlight the potential use of these plants in agroforestry, as a means to influence the soil fungi population.

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Branch canker disease caused by the fungus Macrophoma theicola is a major stem disease that reduces the yield of south Indian tea plantations. Hence the present study aimed to assess the efficacy of the biocontrol agent Trichoderma spp against various isolates of Macrophoma spp. For this matter, different tea-growing regions of south India were surveyed for the isolation and characterization of Macrophoma spp. Then, fungal biocontrol strains (Trichoderma viride, Trichoderma atroviride, Trichoderma harzianum, and Gliocladium virens) were procured from microbial type culture collection Centre (MTCC) to screen their antagonistic potential on different isolates Macrophoma spp. The spores of Macrophoma spp were examined through a light microscope and identified by their peculiar morphological features such as non-septum pycnidiospores present in the sac and oval shape spore with stalk and confirmed using 18S rRNA gene sequence. The results revealed that the biocontrol G. virens followed by T. harzianum showed a higher inhibitory effect on different isolates of Macrophoma spp in the dual plate and culture filtrate studies. In the well diffusion method, the fungal biocontrol agents were found to be exhibit non-significant differences on different isolates of branch canker pathogen. The hyphal interactions studies showed that the pathogenic hyphal wall shrunk and penetrated by the interaction of G. virens.

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