Abstract
Lettuce drop, caused by the soil borne pathogen Sclerotinia sclerotiorum, is one of the most common and serious diseases of lettuce worldwide. Increased concerns about the side effects of chemical pesticides have resulted in greater interest in developing biocontrol strategies against S. sclerotiorum. However, relatively little is known about the mechanisms of Streptomyces spp. as biological control agents against S. sclerotiorum on lettuce. Two Streptomyces isolates, S. exfoliatus FT05W and S. cyaneus ZEA17I, inhibit mycelial growth of Sclerotinia sclerotiorum by more than 75% in vitro. We evaluated their biocontrol activity against S. sclerotiorum in vivo, and compared them to Streptomyces lydicus WYEC 108, isolated from Actinovate®. When Streptomyces spp. (106 CFU/mL) were applied to S. sclerotiorum inoculated substrate in a growth chamber 1 week prior lettuce sowing, they significantly reduced the risk of lettuce drop disease, compared to the inoculated control. Interestingly, under field conditions, S. exfoliatus FT05W and S. cyaneus ZEA17I protected lettuce from drop by 40 and 10% respectively, whereas S. lydicus WYEC 108 did not show any protection. We further labeled S. exfoliatus FT05W and S. cyaneus ZEA17I with the enhanced GFP (EGFP) marker to investigate their rhizosphere competence and ability to colonize lettuce roots using confocal laser scanning microscopy (CLSM). The abundant colonization of young lettuce seedlings by both strains demonstrated Streptomyces' capability to interact with the host from early stages of seed germination and root development. Moreover, the two strains were detected also on 2-week-old roots, indicating their potential of long-term interactions with lettuce. Additionally, scanning electron microscopy (SEM) observations showed EGFP-S. exfoliatus FT05W endophytic colonization of lettuce root cortex tissues. Finally, we determined its viability and persistence in the rhizosphere and endorhiza up to 3 weeks by quantifying its concentration in these compartments. Based on these results we conclude that S. exfoliatus FT05W has high potential to be exploited in agriculture for managing soil borne diseases barely controlled by available plant protection products.
Highlights
The world population will continue to grow until at least 2050, and possibly increase from 7 to 11 billion people (Van Den Bergh and Rietveld, 2004)
When lettuce was sown the same day of the pathogen and Streptomyces inoculation, the number of dead plants was recorded from the 4th day after sowing to the 18th day after sowing (Supplementary Table 1)
The disease incidence of S. sclerotiorum inoculated control at the end of the experiment was 85% and none of the Streptomyces strains showed significant protection against lettuce drop according to both log-rank test and Cox model analysis (Table 1)
Summary
The world population will continue to grow until at least 2050, and possibly increase from 7 to 11 billion people (Van Den Bergh and Rietveld, 2004). For this reason, food security has become one of the main challenges to human development, and any plant pathogen causing substantial crop yield losses needs to be minimized. Coniothyrium, Trichodema, Bacillus, and Pseudomonas spp. have been used for the management of numerous diseases (Walsh et al, 2001; Howell, 2003; Jacobsen et al, 2004) In comparison to these wellknown BCAs, there is only limited application of Streptomyces in agriculture, contrary to its exploitation in pharmaceutical industry
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
