Late wilt, a disease severely affecting maize fields throughout Israel, is characterized by the relatively rapid wilting of maize plants from the tasseling stage to maturity. The disease is caused by the fungus Magnaporthiopsis maydis, a soil and seed-borne pathogen. The pathogen is controlled traditionally through the use of maize cultivars having reduced sensitivity to the disease. Nevertheless, such cultivars may lose their immunity after several years of intensive growth due to the presence of high virulent isolates of M. maydis. Alternative effective and economical chemical treatment to the disease was recently established but is dependent on the use of a dripline assigned for two adjacent rows and exposes the risk of fungicide resistance. In the current work, eight marine and soil isolates of Trichoderma spp., known for high mycoparasitic potential, were tested as biocontrol agents against M. maydis. An in vitro confront plate assay revealed strong antagonistic activity against the pathogen of two T. longibrachiatum isolates and of T. asperelloides. These species produce soluble metabolites that can inhibit or kill the maize pathogen in submerged and solid media culture growth assays. In greenhouse experiments accompanied by real-time PCR tracking of the pathogen, the Trichoderma species or their metabolites managed to improve the seedlings’ wet biomass and reduced the pathogen DNA in the maize roots. A follow-up experiment carried out through a whole growth session, under field conditions, provided important support to the Trichoderma species’ beneficial impact. The direct addition of T. longibrachiatum and even more T. asperelloides to the seeds, with the sowing, resulted in a yield improvement, a significant increase in the growth parameters and crops, to the degree of noninfected plants. These bioprotective treatments also restricted the pathogen DNA in the host tissues (up to 98%) and prevented the disease symptoms. The results encourage more in-depth research to uncover such biological agents’ potential and the methods to implement them in commercial fields. If adequately developed into final products and combined with other control methods, the biological control could play an important role in maize crop protection against Late wilt.

Pathogenicity mitogen-activated protein kinases (MAPKs), related to yeast FUS3/KSS1, are essential for virulence in fungi, including Cochliobolus heterostrophus, a necrotrophic pathogen causing Sou...

Over the past decade, there have been accumulating reports from farmers and field extension personnel on the increasing incidence and spread of onion (Allium cepa) bulb basal rot in northern Israel. The disease is caused mainly by Fusarium species. Rotting onion bulbs were sampled from fields in the Golan Heights in northeastern Israel during the summers of 2017 and 2018. Tissue from the sampled onion bulbs was used for the isolation and identification of the infecting fungal species using colony and microscopic morphology characterization. Final confirmation of the pathogens was performed with PCR amplification and sequencing using fungi-specific and Fusarium species-specific primers. Four Fusarium spp. isolates were identified in onion bulbs samples collected from the contaminated field: F. proliferatum, F. oxysporum f. sp. cepae, and two species less familiar as causative agents of this disease, F. acutatum and F. anthophilium. Phylogenetic analysis revealed that these species subdivided into two populations, a northern group isolated from white (Riverside cv.) onion bulbs, and a southern group isolated from red (565/505 cv.) bulbs. Pathogenicity tests conducted with seedlings and bulbs under moist conditions proved that all species could cause the disease symptoms, but with different degrees of virulence. Inoculating seeds with spore suspensions of the four species, in vitro, significantly reduced seedlings’ germination rate, hypocotyl elongation, and fresh biomass. Mature onion bulbs infected with the fungal isolates produced typical rot symptoms 14 days post-inoculation, and the fungus from each infected bulb was re-isolated and identified to satisfy Koch’s postulates. The onion bulb assay also reflected the degree of sensitivity of different onion cultivars to the disease. This work is the first confirmed report of the direct and primary cause of Fusarium onion basal rot disease in northeastern Israel. These findings are a necessary step towards uncovering the mycoflora of the diseased onion plants and developing a preventive program that would reduce the disease damage.

Late wilt disease (LWD) of maize, caused by Magnaporthiopsis maydis, is considered a major threat to commercial fields in Israel, Egypt, Spain, and India. Today’s control methods include chemical and agronomical intervention but rely almost solely on resistant maize cultivars. In recent years, LWD research focused on eco-friendly biological approaches to restrain the pathogen. The current study conducted during two growing seasons explores the potential of three Trichoderma species as bioprotective treatments against LWD. These species excelled in preliminary assays performed previously under controlled conditions and were applied here in the field by directly adding them to each seed with the sowing. In the first field experiment, Trichoderma longibrachiatum successfully rescued the plants’ growth indices (weight and height) compared to T. asperelloides and the non-treated control. However, it had no positive effect on yield and disease progression. In the subsequent season, this Trichoderma species was tested against T. asperellum, an endophyte isolated from susceptible maize cultivar. This experiment was conducted during a rainy autumn season, which probably led to a weak disease burst. Under these conditions, the plants in all treatment groups were vivid and had similar growth progression and yields. Nevertheless, a close symptoms inspection revealed that the T. longibrachiatum treatment resulted in a two-fold reduction in the lower stem symptoms and a 1.4-fold reduction in the cob symptoms at the end of the seasons. T. asperellum achieved 1.6- and 1.3-fold improvement in these parameters, respectively. Quantitative Real-time PCR tracking of the pathogen in the host plants’ first internode supported the symptoms’ evaluation, with 3.1- and 4.9-fold lower M. maydis DNA levels in the two Trichoderma treatments. In order to induce LWD under the autumn’s less favorable conditions, some of the plots in each treatment were inoculated additionally, 20 days after sowing, by stabbing the lower stem section near the ground with a wooden toothpick dipped in M. maydis mycelia. This infection method overrides the Trichoderma roots protection and almost abolishes the biocontrol treatments’ protective achievements. This study suggests a biological Trichoderma-based protective layer that may have significant value in mild cases of LWD.

Late wilt disease (LWD) is a destructive vascular disease of maize (Zea mays L.) caused by the fungus Magnaporthiopsis maydis. Restricting the disease, which is a significant threat to commercial production in Israel, Egypt, Spain, India, and other countries, is an urgent need. In the past three years, we scanned nine Trichoderma spp. isolates as biological control candidates against M. maydis. Three of these isolates showed promising results. In vitro assays, seedlings pathogenicity trials, and field experiments all support the bio-control potential of these isolates (or their secretions). Here, a dedicated effort led to the isolation and identification of an active ingredient in the growth medium of Trichoderma asperellum (P1) with antifungal activity against M. maydis. This Trichoderma species is an endophyte isolated from LWD-susceptible maize seeds. From the chloroform extract of this fungal medium, we isolated a powerful (approx. 400 mg/L) active ingredient capable of fully inhibiting M. maydis growth. Additional purification using liquid chromatography–mass spectrometry (LC–MS) and gas chromatography–mass spectrometry (GC–MS) separation steps enabled identifying the active ingredient as 6-Pentyl-α-pyrone. This compound is a potential fungicide with high efficiency against the LWD causal agent.