Assessing the effects of Lecanicillium lecanii in the biological control of early and late leaf spot of peanut in vitro (Burkina Faso, West Africa)

Abstract

Early and late leaf spots caused by Cercospora arachidicola and Phaeoisariopsis personata respectively, are the most widespread peanut fungal diseases in West Africa. These diseases lead to notable crop losses in the rural area. In the recent decades, chemical fungicides are used to fight against crop losses, but these chemical substances cause big damages to the environment including the animals and human beings. Thus, the biological control is encouraged by scientific community and all government because it is well known to be safety and cost effective. For this reason, we investigated on the effectiveness of Lecanicillium lecanii on leaf spots of peanut in Burkina Faso. To do so, spore suspensions (10 6 spores / ml) from four strains of L. lecanii was used in vitro. The results revealed that L. lecanii 4181 inhibited the pathogen conidia germination up to 87%, as well as elongation germ tube with highest rate of 56%. Compared to the distilled water control, the severity scores vary between 5.7 and 8, but our results showed a notable decrease of score from 2.3 and 4.7. From our findings, the treatments with L. lecanii spore suspensions on peanut leaves significantly reduced the severity of leaf spots and may be potentially used to promote organic farming in West Africa.

Impact of Three Isolates of <i>Cercosporidium personatum</i> (Berk. Et M.A Curt.), a Pathogen of Late Leaf Spot, on Defoliation and Yield in Groundnut (<i>Arachis hypogaea</i> L.) under Controlled Conditions

“…According to [20], late leaf cause damage to plants by reducing the photosynthetic surface through the formation of lesions, increasing the number and surface area of lesions and causing affected leaflets to fall off [15]. The separation of the means of the percentage of defoliation at the 5% threshold revealed differences between the isolates and the control.…”

“…The collected leaves were incubated in Petri dishes on moist blotting paper at 25˚C -30˚C under a 12-hour light/12-hour dark photoperiod for 120 hours to ensure good sporulation of the conidia. For each of the three collection sites, a suspension of Cercosporidium personatum conidia was prepared by scraping leaf spots showing good sporulation with a scalpel after immersing the leaves in distilled water [14] [15]. Three isolates were prepared: Kouaré isolate with code I1TK, Gampela isolate with code I2TG and Farakoba isolate with code I3TF.…”

Evaluation under Semi-Controlled Conditions of the Pathogenicity of Three Isolates of <i>Phaeoisariopsis personata</i> (Berk. & M.A Curt.)

“…A suspension of P. personata conidia was prepared by scraping leaf spots showing good sporulation with a scalpel after immersing the leaves in distilled water [25]. The characteristics of these preparations are given in Table 2.…”

Prevalence, Pathogenicity and Physiological Studies of Cercospora tageticola Ellis and Everhart Causing Leaf Spot in Marigold

“…This disease causes a 70% yield loss in cultivars that are sensitive to it because it drastically reduces the amount of photosynthetic tissues in plant foliar regions (Thakur et al, 2013;Islam et al, 2015;Stewart, 2016;Mohammed et al, 2018;Tedford et al, 2019). Most scientists now have an inexhaustible desire to explore methods to mitigate the severity of the disease due to its economic significance (Zongo et al, 2019;Denwar et al, 2021;Nana et al, 2022). Cercospora leaf spot in marigold for the first time in Himachal Pradesh during the rainy season, when the intensity is quite high and an estimated loss to the crop of up to 62% was documented due to the favourable climatic conditions.…”