Ecological applications of Pseudomonas as a biopesticide to control two-spotted mite Tetranychus urticae: chitinase and HCN production

Abstract

The two-spotted spider mite (Tetranychus urticae Koch) is an important pest of many horticultural crops. A study was conducted to evaluate the effect of three fluorescent Pseudomonas isolates obtained from rhizospheric soil of tomato (Solanum lycopersicon) in Agadir, Morocco: Q110B, Q036B and Q172B, as potential biological control agents for T. urticae. Both acaricide and repellent activities were assessed on homogenous adult mites. The acaricidal activity test evaluated five concentrations of bacterial suspensions: 0 (control), 10 2 , 10 4 , 10 6 , 10 8 , and 10 10 cfu ⋅ ml -1 , while only the 10 10 cfu • ml −1 concentration of each bacterium was used for the repellent bioassay. The mortality rate and repellentindex were recorded 24, 48 and 72 h after application. Results indicated that the survival rate of T. urticae was reduced (p ≤ 0.01) by all three bacterial isolates compared to control. Within the 24-72 h time period the mortality rates ranged from 8 to 87%, 16 to 99%, and 13 to 89%, for Q110B, Q036B and Q172B isolates, respectively. The isolate Q036B (LC 50 = 0.598 cfu ⋅ ml -1 ) provided higher mortality rates than Q172B and Q110B with LC 50 values of 90,846 and 169,585 cfu ⋅ ml -1 , respectively. Repellent activity was also the highest with Pseudomonas Q036B having a 71% repellence index at 48 h after application. Regarding the mechanism of action, all three isolates produced hydrogen cyanide, and exhibited protease and cellulose activities, although only Q036B and Q172B had potential chitinase action. Identification analysis showed that the isolates were either Pseudomonas putida (Q172B) or P. fluorescens (Q110B and Q036B). Our results indicate that the P. fluorescens isolate Q036B is a promising candidate for biological control of T. urticae, and has potential to contribute to an integrated pest management program to control this important pest. Then the fruits produced will be qualified as safe for consumers and the environment. The present work was customized to give support for policy decision makers as an agroecological potential meeting needs of industries and ecological balance.

Beneficial Soil Microbes Negatively Affect Spider Mites and Aphids in Pepper

“…and Bacillus spp. isolates have mainly been assessed for their acaricidal effects in mortality tests or after being sprayed on the plants [27,28]. Remarkably, all of the above studies have identified several strains of entomopathogens with plant protection capabilities when applied in the soil.…”

The Microbiota of a Mite Prey-predator System on Different Host Plants Are Characterized by Functional Redundancy and Dysbiosis

“…Several species of Pseudomonas have been shown to bene t plants by alleviating certain stress conditions, and to provide, for example, plant protection [70][71][72]. Members of Pseudomonas have been investigated as biopesticides for control of mites [73,74] and insects [75,76]. Pseudomonas associated with plants that orally infect and kill herbivorous arthropods carry surface glycan decorations to escape the host humoral immune defense [77], killing the hosts by producing molecules with potent insecticidal activity and lytic enzymes (chitinases, phospholipases) (Flury et al 2017;Vacheron et al 2019).…”

Inoculation of tomato plants with rhizobacteria suppresses development of whitefly Bemisia tabaci (GENNADIUS) (HEMIPTERA: ALEYRODIDAE): Agro-ecological application

“…These bacteria can act by several mechanisms in the biocontrol of diseases and pests. The ability to degrade chitin is considered the main mechanism involved in the control of pests [17,18]. Chitinolytic organisms such as Pseudomonas sp.…”

“…and Streptomyces sp. isolated from the rhizosphere have been shown to be potential biocontrol agents [16,17,33]. Vodovar et al [15] reported that Pseudomonas entomophila exhibits virulence against D. melanogaster due to strong hemolytic activity involving proteins such as lipases, chitinases and/or hydrolases.…”

“…The total bacterial flora in soil was shown to be higher in samples containing roots [16]. Previous research shows a significant effect of rhizobacteria against the tomato leafminer Tuta absoluta and the mite Tetranychus urticea [17,18]. Therefore, this study investigated the efficacy of three Pseudomonas isolates as biological control agent, isolated from rhizospheric soil of tomatoes in Morocco, on the second instar and adults of B. tabaci under laboratory and glasshouse conditions.…”