Biochemical basis of disease resistance was studied by analysis of total phenols, peroxidase and ß-1,3-glucanase activities in calli of Fusarium wilt resistant and susceptible genotypes and one in vitro selected resistant cell line of chickpea (Cicer arietinum L.). The callus growth of cvs. JG62, C235 and WR315 was completely inhibited at 2% (v/v) concentration of culture filtrate of the fungus, whereas, the callus growth of in vitro selected resistant cell line FWR was not inhibited even at 4% (v/v) concentration of culture filtrate, indicating that a cultivar resistant under field conditions could show susceptibility under in vitro conditions. Total phenols were more in the resistant cell line than in the susceptible cultivars. However, increase in phenolics was higher in resistant cell line than in susceptible cultivars after treatment with the cultural filtrate, indicating that phenols reach an inhibitory level to the fungus in the resistant cell line. Peroxidase followed a similar pattern. Increase in ß-1,3-glucanase activity, after treatment, was higher in resistant cell line than in susceptible cultivars. Role of total phenols, peroxidase and ß-1,3-glucanase in defense against Fusarium wilt disease of chickpea is discussed.
Authors:A. Kamalakannan, L. Mohan, K. Kavitha, S. Harish, R. Radjacommare, S. Nakkeeran, V. K. Parthiban, R. Karuppiah and T. Angayarkanni
Five isolates of Trichoderma viride, Pseudomonas fluorescens and four isolates of Bacillus subtilis were evaluated for their ability to control Rhizoctonia solani, the causal agent of stem and stolon rot of peppermint (Mentha piperita Lin.). Of the various isolates of T. viride, P. fluorescens and B. subtilis tested, TVUV10, PFMMP and BSG3 showed the maximum inhibition of mycelial growth of R. solani. Among these isolates, P. fluorescens, PFMMP recorded the highest inhibition zone against R. solani in vitro and was very effective in reducing disease incidence in greenhouse condition. The effective isolates were evaluated for their ability to induce defense related enzymes and chemicals in plants. Increased activity of phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenoloxidase (PPO) and total phenolics were recorded in the biocontrol agents pretreated peppermint plants challenged with R. solani. P. fluorescens isolate PFMMP recorded early and increased synthesis of all defense related enzymes and total phenol. Thus, the present study shows that application of biocontrol agents; induce defense related enzymes involved in phenyl propanoid pathway in addition to direct antagonism which collectively contribute for enhanced resistance against invasion of R. solani in M. piperita.
Authors:A.M. Tran, T.B. Nguyen, V.D. Nguyen, E. Bujna, M.S. Dam and Q.D. Nguyen
Four strains of Lactobacillus and Bifidobacterium including L. plantarum 01, L. fermentum D13, L. rhamnosus B01725, and B. bifidum B7.5 exhibiting naringinase production were applied in grapefruit juice fermentation. All investigated strains grew well in grapefruit juice without nutrition supplementation. In all cases, cell counts were 108–109 CFU ml−1 after 24 hours of fermentation. The highest lactic acid and acetic acid productions were observed in the case of strain L. plantarum 01. The L. plantarum 01 and L. fermentum D13 strains prefer glucose over fructose and sucrose, whereas fructose was the most favoured sugar for L. rhamnosus B01725 and B. bifidum B7.5. At the end of the fermentation process, antioxidant activity and total polyphenol content of grapefruit juice decreased in all cases, but the changes were not significant. Significant decrease of naringin was observed in the case of L. plantarum 01, 28% naringin in grapefruit juice was removed after fermentation. This result is promising for development of technology for production of probiotic grapefruit juice.