K. Nagendran

Exploiting endophytic bacteria for the management of sheath blight disease in rice

Sheath blight of rice caused by Rhizoctonia solani Kuhn is an important soil-borne disease throughout the rice-producing areas of the world. Twenty-nine bacterial endophytes were isolated from different plant sources and tested for their efficacy against R. solani inciting sheath blight in rice. Bacillus subtilis var. amyloliquefaciens (FZB24) caused a maximum 36% inhibition of R. solani over the control in vitro. Rice plants (cv. ADT 39) treated with FZB24, in combination with seed treatment @ 4 g kg− 1, seedling dip @ 4 g l− 1, soil application @ 500 g ha− 1 and foliar application @ 500 g ha− 1, gave the lowest severity of sheath blight (33%) with around 55% reduction over the control under glasshouse conditions. In addition, the B. subtilis (FZB24) treated rice plants showed higher induction of defence-related enzymes, peroxidase, polyphenol oxidase and phenylalanine ammonia lyase, and resulted in higher accumulation of total phenols than in the untreated control plants. The endophyte-treated rice plots had a significantly lower intensity of sheath blight than untreated control plots and also recorded a higher grain and straw yield.

WITHDRAWN: A specific and sensitive method for the detection of Colletotrichum musae in banana fruit

BACKGROUND: Banana anthracnose incited by Colletotrichum musae (Berk & Curt.) Arx. is a serious disease both in field and in postharvest marketing stage. Molecular methods are most suitable for the early detection of infection. AIM: The latent infection of C. musae makes it very difficult to detect the infected fruit lot, hence aim is to detect the latent infection using molecular approach. METHODS: The molecular variability generated from fourteen isolates of C. musae by RAPD-PCR technique was utilized to determine the phylogentic relationship and develop SCAR markers. RESULTS: The genetic similarity coefficient within each group and variation between the groups were observed. Decamer OPA-01 generated a RAPD polymorphic profile that distinguished C. musae from the other organism. Cloning and sequencing of the specific band yielded 588bp sequences, to which forward CM-SCAR-FP and reverse CM-SCAR-RP were designed. The SCAR primer pair amplified a single SCAR of 490bp from each of the 14 isolates of C. musae, and was able to detect the pathogen in as low as 30ng of DNA from infected fruit peel tissue. CONCLUSION: The developed SCAR markers can aid the detection process every quickly and accurately which will help exporters.

Molecular characterization and in vitro evaluation of endophytic bacteria against major pathogens of rice

Lallemantia royleana (Benth.) is an important folk medicine in Pakistan. This natural herb is used as folk remedy for number of ailments. This study was conducted to assess the antibacterial activity of four different organic extracts of L. royleana seeds against four bacterial strains (Escherichia coli, Enterobacter cloaceae, Pseudomonas aeruginosa and Staphylococcus aureus) for the first time by disc diffusion method. Except aqueous extracts, all organic extracts of L. royleana seeds displayed significant anti-bacterial activity against all the tested bacteria. The chloroform extract exhibited highest anti-bacterial activity for all bacterial strains. Results shows that L. royleana seeds possess significant antibacterial potential against S. aureus, E. coli and E. cloaceae, therefore, it can be a good remedy for skin disease and gastro-intestinal problems caused by human pathogenic bacterial strains. Further screening for phytochemicals should be carried out in search of novel therapeutic compounds.

Characterization and management of watermelon bud necrosis virus infecting watermelon in India

Bud necrosis disease is an emerging threat for watermelon cultivation in India. It is characterized by necrotic spots and patches on leaves, bud and fruits with characteristic chlorotic ring spots as documented in Coimbatore and Villupuram districts of Tamil Nadu, India. The causative agent of this disease was identified as watermelon bud necrosis virus (WBNV) by reverse-transcription polymerase chain reaction (RT-PCR) followed by sequence analysis of amplified fragment using Orthotospovirus universal degenerate primer pair. Upon mechanical inoculation, the virus produced circular chlorotic local lesions on leaves of cowpea and Chenopodium amaranticolor, necrotic local lesions on Trianthema portulacastrum and bottle gourd, systemic vein clearing on Luffa aegyptiaca, whereas both local and systemic symptoms were observed on Nicotiana tabacum and watermelon. The complete nucleotide sequences of the coat protein (NP), movement protein (MP), replicase (RdRp) and NSs protein genes from WBNV genome of Coimbatore isolate (TN KTP WM1) had a maximum identity of 97% with the genome of the WBNV-JT strain from Southern India. WBNV infection causes significant reduction in nutritional parameters such as carbohydrate, protein, crude fibre, calorific value, total sugar, reducing sugar and vitamin A in infected fruits when compared to the healthy ones. For the management of WBNV in watermelon, an Integrated Pest Management (IPM) module has been devised which reduced the thrips population and WBNV incidence to a great extent besides increasing the fruit yield.

First report of lily mottle virus on lily (Lilium sp.) in southern India

Lily samples collected from commercial cut flower growing field at Nilgiris, Tamil Nadu, India were serologically tested through direct antigen coating—ELISA and dot immuno binding assay for the infection of potyvirus through potyvirus group specific polyclonal antibody. The RT-PCR using potyvirus universal degenerate primers (PNIbF1/PCPR1) showed the presence of a potyvirus and the sequencing results showed the association of lily mottle virus (LMoV). Further LMoV was confirmed by RT-PCR amplification using newly designed primer pair covering entire coat protein gene and sequence results showed 100% nucleotide identity with the LMoV reported from South Korean. To our knowledge, this is the first confirmed evidence for the occurrence of LMoV on lily in southern India.