ABSTRACT
Aims@#This study aimed to screen the plant growth-promoting fluorescent bacteria (FLB) which isolated from the healthy rice rhizophere and to evaluate its biocontrol and growth promotion properties against Pyricularia oryzae on aerobic rice seedling of MARDI Aerob 1. @*Methodology and results@#King’s B agar with glycerol was used as the selective medium to isolate FLB from the healthy rice rhizosphere soil. All FLB obtained were in vitro screened for antagonistic activities against P. oryzae using dual culture, volatile substances and hydrogen cyanide productions. The potential FLB isolates were further evaluated on rice seedling early growth promotion before identified using 16S rRNA gene sequencing. A total of 24 FLB were isolated from the healthy rice rhizosphere soil in Setiu, Terengganu, Malaysia. Isolates: FLB4, FLB5, FLB7 and FLB10 scored the total of percentage inhibition radial growth (PIRG) values ranged 99.5-105.0%. Further seedling growth promotion screening revealed that FLB4, FLB7 and FLB10 were significantly improved seedling growth with vigor index of 378.32%, 461.53% and 335.60% over control (133.31%). 16S rRNA sequencing identified that FLB7 as Bacillus subtilis and the FLB4 and FLB10 as Pseudomonas putida.@*Conclusion, significance and impact of study@#The selected FLB isolates (FLB4, FLB7 and FLB10) are potential to be developed as biological control agents against P. oryzae with growth promoting property on aerobic rice seedling.
ABSTRACT
Aims: Capsicum annuum (pepper) is one of the most important crops in the world. It contains an impressive list of phytonutrients that were found to have disease-preventing and health-promoting properties. Today, they are grown widely in many parts of the world as an important commercial crop. However, fungal infection is the main problem that leads to the common pepper disruptive disease, known as the Anthracnose, which lowers the yields of this plant. Therefore, this study was conducted to determine the growth, enzymatic antioxidant specific activities of catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (g-POD) as well as non-enzymatic antioxidants including ascorbic acid, α-tocopherol and carotenoids content in C. annuum as a response to the fungal infections by Colletotrichum capsici. Methodology and results: The assays were conducted at 0, 1, 2, 3, 4 and 5 weeks of fungal treatment periods. The results showed that plant growth (plant height, leaves number, length and width, chlorophyll content) was significantly lower in treated plants compared to controls. The CAT specific activity increased drastically at the early stages of the experiment and decreased thereafter. In contrast, the APX and g-POD specific activity were initially lower, but increased significantly at the later stages of the experiment. For the non-enzymatic antioxidants, the amount of ascorbic acid, α- tocopherol and carotenoids content were significantly higher at the first week of treatment and slowly reduced afterwards. Conclusion, significance and impact of study: This study shows that fungal infection inhibited the growth of pepper plants and the enzymatic and non-enzymatic antioxidants worked in concert to fight against the stress caused by the fungal infection, with their different specific roles in removing and reducing the reactive oxygen species in stress condition.