Molecular Insights into Defense Responses of Vietnamese Maize Varieties to Fusarium verticillioides Isolates

Abstract

Fusarium ear rot (FER) caused by Fusarium verticillioides is one of the main fungal diseases in maize worldwide. To develop a pathogen-tailored FER resistant maize line for local implementation, insights into the virulence variability of a residing F. verticillioides population are crucial for developing customized maize varieties, but remain unexplored. Moreover, little information is currently available on the involvement of the archetypal defense pathways in the F. verticillioides–maize interaction using local isolates and germplasm, respectively. Therefore, this study aims to fill these knowledge gaps. We used a collection of 12 F. verticillioides isolates randomly gathered from diseased maize fields in the Vietnamese central highlands. To assess the plant’s defense responses against the pathogens, two of the most important maize hybrid genotypes grown in this agro-ecological zone, lines CP888 and Bt/GT NK7328, were used. Based on two assays, a germination and an in-planta assay, we found that line CP888 was more susceptible to the F. verticillioides isolates when compared to line Bt/GT NK7328. Using the most aggressive isolate, we monitored disease severity and gene expression profiles related to biosynthesis pathways of salicylic acid (SA), jasmonic acid (JA), abscisic acid (ABA), benzoxazinoids (BXs), and pathogenesis-related proteins (PRs). As a result, a stronger induction of SA, JA, ABA, BXs, and PRs synthesizing genes might be linked to the higher resistance of line Bt/GT NK7328 compared to the susceptible line CP888. All these findings could supply valuable knowledge in the selection of suitable FER resistant lines against the local F. verticllioides population and in the development of new FER resistant germplasms.

Streptomyces Strains Promote Plant Growth and Induce Resistance Against Fusarium verticillioides via Transient Regulation of Auxin Signaling and Archetypal Defense Pathways in Maize Plants

“…Also, BXs-dependent resistance of maize toward Spodoptera littoralis , a leaf feeder, has been reported ( Maag et al, 2016 ). In agreement with Tran et al (2021c) , F. verticillioides induced the upregulation of the BXs genes in leaves of line Bt/GT NK7328. This finding might be helpful for one who wants to develop FER-resistant maize lines associated with these genes.…”

“…After uncovering the direct antagonism of the biocontrol strain on maize seedlings by the reduction of the DNA level of F. verticillioides in soil ( Figure 4 ), we explored whether the growth of plants was impacted. To examine this, we used two hybrid maize lines CP888 and Bt/GT NK7328 predominantly planted in the central highlands of Vietnam ( Tran et al, 2021c ). For line CP888, the growth of plants infected with the fungus (FV + W) was negatively affected with significantly lower fresh leaf and root biomass weight when compared to the control non-infected plants ( Figure 6A ).…”

“…In this assay, we used two hybrid maize lines Bt/GT NK7328 (supplied by Syngenta company, Vietnam) and CP888 (supplied by C. P. company, Vietnam) as they are predominantly planted in the central highlands of Vietnam ( Tran et al, 2021c ). Maize seeds were disinfected with 1% NaOCl solution and germinated in a rectangular plastic pot (20 × 16 × 6 cm) with vermiculite substrate (Vermex, Soprema, Belgium) for 5 days.…”

A Case Study in Saudi Arabia: Biodiversity of Maize Seed-Borne Pathogenic Fungi in Relation to Biochemical, Physiological, and Molecular Characteristics

“…Forty-one fungal species comprising saprophytic and pathogenic ones were detected, in which their percent infestation was variable according to the locations. Our results revealed that maize seeds were infected by varying degrees with several pathogenic fungi, like F. verticillioides , F. proliferatum , Alternaria alternata , Drechslera maydis, and S. strictum, which are the primary causal agents of pink ear rot, Alternaria leaf blight, Southern corn leaf blight, and wilt diseases in most world maize-growing areas [ 39 , 40 , 41 , 42 ].…”

“…Sarocladium zeae was previously described as producing extracellular hydrolases, e.g., cellulases, amylases, and proteases [ 47 ], which are reported to play a role in the host-pathogen interaction; these enzymes were also reported in our isolates. On the other hand, a recent study identified S. zeae as the beneficial endophyte in maize seeds [ 42 ]. This contradiction may be due to the presence of different strains having, or not, various pathogenic activities on plants.…”