Trichoderma Biological Control to Protect Sensitive Maize Hybrids against Late Wilt Disease in the Field.

Ofir Degani,Shlomit Dor

doi:10.3390/jof7040315

Ofir Degani, Shlomit Dor

Open Access

https://doi.org/10.3390/jof7040315

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Abstract

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.

Highlights

In Israel, corn is a major crop in open areas, with a 3350 ha area harvested in 2019 and a volume production of 77,801 tons (FAOSTAT, 2019 Food and Agriculture Commodity Production data)
The isolate was grown on potato dextrose agar (PDA; Difco Laboratories, Detroit, MI, USA) at a temperature of 28 ± 1 ◦ C in the dark
The use of pesticides to deal with the late wilt of maize in corn, which has been extensively researched in former studies, has the potential risk for environmental damage and health harm and is likely to induce pathogen resistance

Summary

Introduction

Corn (Zea mays, maize) is considered one of the most important grain crops globally, with the United States and China being the top maize-producing countries [1]. In Israel, corn is a major crop in open areas, with a 3350 ha area harvested in 2019 and a volume production of 77,801 tons (FAOSTAT, 2019 Food and Agriculture Commodity Production data). Israel’s development of corn is under threat from severe disease—late wilt (LWD)—. LWD is characterized by the rapid wilt of sweet and fodder maize, mainly from the tasseling stage until shortly before maturity [4]. The pathogen is a hemibiotrophic, soil-borne [5], and seed-borne [6] fungus transmitted as spores, sclerotia, or hyphae on plant remains. M. maydis can survive for long periods in the soil or inside an alternative host plant, such as Lupinus termis L. M. maydis can survive for long periods in the soil or inside an alternative host plant, such as Lupinus termis L. (lupine) [7], Gossypium hirsutum L. (cotton), Citrullus lanatus (watermelon), and Setaria viridis (green foxtail) [8,9]

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