Biological Control of Chili Damping-Off Disease, Caused by Pythium myriotylum

Abstract

Pythium myriotylum is a notorious soil-borne oomycete that causes post-emergence damping-off in chili pepper. Of various disease management strategies, utilization of plant growth promoting rhizobacteria (PGPR) in disease suppression and plant growth promotion is an interesting strategy. The present study was performed to isolate and characterize PGPR indigenous to the chili rhizosphere in Pakistan, and to test the potential to suppress the damping-off and plant growth promotion in chili. Out of a total of 28 antagonists, eight bacterial isolates (4a2, JHL-8, JHL-12, 1C2, RH-24, 1D, 5C, and RH-87) significantly suppressed the colony growth of P. myriotylum in a dual culture experiment. All the tested bacterial isolates were characterized for biochemical attributes, and 16S rRNA sequence based phylogenetic analysis identified these isolates as Flavobacterium spp., Bacillus megaterium, Pseudomonas putida, Bacillus cereus, and Pseudomonas libanensis. All the tested bacterial isolates showed positive test results for ammonia production, starch hydrolase (except 4a2), and hydrogen cyanide production (except 4a2 and 1D). All the tested antagonists produced indole-3-acetic acid (13.4–39.0 μg mL–1), solubilized inorganic phosphate (75–103 μg mL–1), and produced siderophores (17.1–23.7%) in vitro. All the tested bacterial isolates showed varying levels of susceptibility and resistance response against different antibiotics and all these bacterial isolates were found to be non-pathogenic to chili seeds and notably enhanced percentage seed germination, plumule, redical length, and vigor index over un-inoculated control. Additionally, under pathogen pressure, bacterization increased the defense related enzymes such as Peroxidase (PO), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) activates. Moreover, the treatment of chili seeds with these bacterial isolates significantly suppressed the damping-off caused by P. myriotylum and improved PGP traits compared to the control. In addition, a positive correlation was noticed between shoot, root length, and dry shoot and root weight, and there was a negative correlation between dry shoot, root weight, and seedling percentage mortality. These results showed that native PGPR possesses multiple traits beneficial to the chili plants and can be used to develop eco-friendly and effective seed treatment formulation as an alternative to synthetic chemical fungicides.

Bacillus velezensis TSA32-1 as a Promising Agent for Biocontrol of Plant Pathogenic Fungi

“…In addition, Hyder et al (2021) showed that the effects of Bacillus sp. on the germination rate of chili pepper seeds and its potential function as a biocontrol agent were evaluated by measuring the antagonistic effect and germination rate against the Pythium pathogen [ 37 ]. Analysis of the germination rate of corn and pepper seeds treated with TSA32-1 showed a higher germination rate than when each pathogen was treated alone ( Figure 4 ).…”

“…Corn and pepper seeds treated with TSA32-1 were infected with soil-borne pathogens, and the sprout germination rate showed a tendency to increase when compared to the values of those infected with pathogens alone. Soil-borne pathogens like F. graminaearum and Pythium infection mainly occur in seeds, seedlings, and young roots, and it is known that it has a significant impact on the growth of seedlings, causing great economic loss and a ripple effect [ 37 ]. Against these soil-borne pathogens, TSA32-1 may contribute to the control effect that helps prevent disease in seeds.…”

First Report of Acrophialophora jodhpurensis Causing Root Rot and Seedling Damping-Off of Pepper (Capsicum annum L.) in Karbala Province, Iraq

“…This may be attributed to several reasons, including infection with many pathogens, especially those affect the roots, bases of stems and seedlings. Phytophthora spp., Pythium spp., Rhizoctonia spp., Fusarium spp., Macrophomina phaseolina are the most important pathogenic fungi [6][7][8][9][10]. They are the main causes of rotting of the roots of pepper IOP Publishing doi:10.1088/1755-1315/1262/3/032009 2 leading to significant economic losses and reduction in the amount of production in protected and open cultivation [11][12][13].…”

Efecto de rizobacterias promotoras del crecimiento vegetal en el desarrollo y rendimiento del chile jalapeño

“…Los hongos que afectan el cultivo de chile son Phytophthora capsici, Fusarium sp., Sclerotiorum sp., Rhizoctonia solani y Pythium causando el Damping off o la marchitez (Morra y Bilotto, 2015;Hyder et al, 2021). Para contrarrestar los problemas de fertilidad en los suelos y presencia de enfermedades, los productores se apoyan con el uso de productos químicos, los cuales, al hacer uso excesivo de estos, provocan contaminación en los ecosistemas y el medio ambiente, resultando la salinidad del suelo, la eutrofización del agua y la acumulación de nitritos y nitratos, mismos que pueden ser una fuente de contaminación ambiental y una amenaza para la salud humana (Castellanos et al, 2017).…”