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Niche theory predicts that when two species exhibit major niche overlap, one will eventually be eliminated through competitive exclusion. Thus, some degree of niche specialization is required to facilitate coexistence. We examined whether two important seed bank pathogens on the invasive winter annual grass Bromus tectorum (cheatgrass, downy brome) exhibit niche specialization. These pathogens utilize seed resources in complementary ways. Pyrenophora semeniperda is specialized to attack dormant seeds. It penetrates directly through the seed coverings. Hyphae ramify first through the endosperm and then throughout the seed. Seed death results as the embryo is consumed. In contrast, the Fusarium seed rot pathogen (Fusarium sp.) is specialized to attack non-dormant seeds in the early stages of germination. It cannot penetrate seed coverings directly. Instead, it responds to a cue emanating from the radicle end with directional hyphal growth and subsequent penetration at the point of radicle emergence, causing seed death. Non-dormant seeds usually escape P. semeniperda through germination even if infected because it develops more slowly than Fusarium. When water stress slows non-dormant seed germination, both P. semeniperda and Fusarium can attack and cause seed mortality more effectively. The Fusarium seed rot pathogen can sometimes reach epidemic levels and may result in B. tectorum stand failure (‘die-off’). Stands usually re-establish from the persistent seed bank, but if P. semeniperda has also reached high levels and eliminated the seed bank, a die-off can persist indefinitely.

Infections of maize with phytopathogenic and toxinogenic Fusarium spp. may occur throughout the cultivation period. This can cause different types of diseases in vegetative and generative organs of the plant. Along with these infections, mycotoxins are often produced and accumulated in affected tissues, which could pose a significant risk on human and animal health when entering the food and feed chain. Most important fungal species infecting European maize belong to the Fusarium sections Discolour and Liseola, the first being more prevalent in cooler and humid climate regions than the second predominating in warmer and dryer areas. Coexistence of several Fusarium spp. pathogens in growing maize under field conditions is the usual case and may lead to multi-contamination with mycotoxins like trichothecenes, zearalenone and fumonisins. The pathways how the fungi gain access to the target organs of the plant are extensively described in relation to specific symptoms of typical rot diseases regarding ears, kernels, rudimentary ears, roots, stem, leaves, seed and seedlings. Both Gibberella and Fusarium ear rots are of major importance in affecting the toxinogenic quality of grain or ear-based products as well as forage maize used for human or animal nutrition. Although rudimentary ears may contain high amounts of Fusarium toxins, the contribution to the contamination of forage maize is minor due to their small proportion on the whole plant dry matter yield. The impact of foliar diseases on forage maize contamination is regarded to be low, as Fusarium infections are restricted to some parts on the leaf sheaths and husks. Mycotoxins produced in rotted basal part of the stem may contribute to forage maize contamination, but usually remain in the stubbles after harvest. As the probability of a more severe disease progression is increasing with a prolonged cultivation period, maize should be harvested at the appropriate maturity stage to keep Fusarium toxin contamination as low as possible. Ongoing surveillance and research is needed to recognise changes in the spectrum of dominating Fusarium pathogens involved in mycotoxin contamination of maize to ensure safety in the food and feed chain.

Summary Fusarium verticillioides (F. verticillioides) is a widely distributed phytopathogen that incites multiple destructive diseases in maize, posing a grave threat to corn yields and quality worldwide. However, there are few reports of resistance genes to F. verticillioides. Here, we reveal that a combination of two single nucleotide polymorphisms (SNPs) corresponding to ZmWAX2 gene associates with quantitative resistance variations to F. verticillioides in maize through a genome‐wide association study. A lack of ZmWAX2 compromises maize resistance to F. verticillioides‐caused seed rot, seedling blight and stalk rot by reducing cuticular wax deposition, while the transgenic plants overexpressing ZmWAX2 show significantly increased immunity to F. verticillioides. A natural occurrence of two 7‐bp deletions within the promoter increases ZmWAX2 transcription, thus enhancing maize resistance to F. verticillioides. Upon Fusarium stalk rot, ZmWAX2 greatly promotes the yield and grain quality of maize. Our studies demonstrate that ZmWAX2 confers multiple disease resistances caused by F. verticillioides and can serve as an important gene target for the development of F. verticillioides‐resistant maize varieties.

The plant microbiome and plant-associated bacteria are known to support plant health, but there are limited studies on seed and seedling microbiome to reveal how seed-associated bacteria may confer disease resistance. In this study, the application of antibiotics on soybean seedlings indicated that seed-associated bacteria were involved in the seed rot resistance against a soil-borne pathogen Calonectria ilicicola, but this resistance cannot be carried to withstand root rot. Using PacBio 16S rRNA gene full-length sequencing and microbiome analyses, 14 amplicon sequence variants (ASVs) including 2 ASVs matching to Bacillus altitudinis were found to be more abundant in the four most resistant varieties versus the four most susceptible varieties. Culture-dependent isolation obtained two B. altitudinis isolates that both exhibit antagonistic capability against six fungal pathogens. Application of B. altitudinis on the most resistant and susceptible soybean varieties revealed different colonization compatibility, and the seed rot resistance was restored in the five varieties showing higher bacterial colonization. Moreover, quantitative PCR confirmed the persistence of B. altitudinis on apical shoots till 21 days post-inoculation (dpi), but 9 dpi on roots of the resistant variety TN5. As for the susceptible variety HC, the persistence of B. altitudinis was only detected before 6 dpi on both shoots and roots. The short-term colonization of B. altitudinis on roots may explain the absence of root rot resistance. Collectively, this study advances the insight of B. altitudinis conferring soybean seed rot resistance and highlights the importance of considering bacterial compatibility with plant varieties and colonization persistence on plant tissues. Graphical Abstract Graphical Abstract

Pathological aspects of metal sulfide nanoparticles are lacunae in nanometal bioapplications. The present study is one of its own kind involving sonochemical synthesis and the phytopathological effect of aqua dispersed nanoparticles of ferrous sulfide (FeS-NPs) against the economically important fungus Fusarium verticillioides. In vitro antifungal evaluation against F. verticillioides showed the significant biopotential at 18 μg/ml, with deca-fold higher efficiency than the standard fungicide, carbendazim. Visible symptoms of conidial inhibition as well as membrane disruption in SEM nanographs rationalized the fungal inhibition. In vivo seed treatment on rice (Oryzae sativa) at 30 μg/ml revealed a significant reduction in seedling blight (76.08%) which is deca-fold greater than carbendazim (32.60% at 2000 μg/ml) with a comparable reduction in seed rot (82.12% for FeS-NPs and 80.76% for carbendazim). There were no morphologically visible signs of phytotoxicity at concentrations as high as 30 μg/ml giving a favorable edge to this novel FeS-NPs sample as antifungal nanopriming agent.

The present study focuses on antifungal potential of 1,2,4-triazole derivatives of allyl sulfides. The antifungal potential of synthesized 2-(allylthio)-1-(1'H-1',2',4'-triazol-1'-yl)ethanone (ATT) was compared with its diallyl analogue (a natural occurring) against Fusarium fujikuroi to unveil its improved antifungal potential. The synthesized compound ATT had significantly better antifungal potential having minimum inhibitory concentration (MIC) value of 25 μg/ml as compared to Diallyl sulfide (DAS) and standard fungicide carbendazim with corresponding values of 69 μg/ml and 29 μg/ml, respectively. Visible symptoms of abrasions on cell wall and hyphal distortion were observed in SEM morphographs as the rationale behind the antifungal potential. Seed treatment with DAS and ATT enhanced seed germination as compared to control and standard fungicide treatment, However, maximum increase (30%) in seed germination was recorded with ATT when applied at concentration of 2000 μg/g. Similar trends were observed for other seed quality parameters also. Seed rot and seedling mortality was minimum (19% and 21%, respectively) when seeds were treated with ATT and DAS at 2000 μg/g.

Fungal diseases of macadamia fruit in South Africa have the potential to cause notable economic damage in this rapidly growing industry. To improve our understanding of the species involved in husk rot in macadamia orchards, a survey was conducted over two consecutive growing seasons to identify Colletotrichum, Diaporthe and Calonectria spp. that are associated with husk rot-infected macadamia fruits, and to investigate the occurrence of these fungi in asymptomatic and symptomatic fruits at the four stages of fruit development. Of the 425 fungal isolates obtained from the survey, Colletotrichum and Diaporthe were the most frequently isolated genera confirming the important role that these causal agents play in the husk rot epidemics. The detection of Calonectria species was low, only from symptomatic fruits and limited to a few locations in the main macadamia-producing provinces in South Africa. Colletotrichum and Diaporthe species were detected throughout the season at different stages of fruit development and in both symptomatic and asymptomatic fruits. The study confirmed that three fungal pathogens cause husk rot of macadamia in South Africa, with Colletotrichum and Diaporthe species that may have a latent phase in macadamia fruit. Studies of the growth characteristics of the husk rot pathogens revealed varied optimal growth temperatures, which may influence their prevalence in the different provinces in South Africa where macadamia is grown. The significance of the varied prevalence and biology of the causal agents in husk rot epidemics are discussed, which may be helpful management strategies.

Background Fusarium ear rot (FER) caused by Fusarium verticillioides is a major disease of maize that reduces grain yield and quality globally. However, there have been few reports of major loci for FER were verified and cloned. Result To gain a comprehensive understanding of the genetic basis of natural variation in FER resistance, a recombinant inbred lines (RIL) population and one panel of inbred lines were used to map quantitative trait loci (QTL) for resistance. As a result, a total of 10 QTL were identified by linkage mapping under four environments, which were located on six chromosomes and explained 1.0–7.1% of the phenotypic variation. Epistatic mapping detected four pairs of QTL that showed significant epistasis effects, explaining 2.1–3.0% of the phenotypic variation. Additionally, 18 single nucleotide polymorphisms (SNPs) were identified across the whole genome by genome-wide association study (GWAS) under five environments. Compared linkage and association mapping revealed five common intervals located on chromosomes 3, 4, and 5 associated with FER resistance, four of which were verified in different near-isogenic lines (NILs) populations. GWAS identified three candidate genes in these consistent intervals, which belonged to the Glutaredoxin protein family, actin-depolymerizing factors (ADFs), and AMP-binding proteins. In addition, two verified FER QTL regions were found consistent with Fusarium cob rot (FCR) and Fusarium seed rot (FSR). Conclusions These results revealed that multi pathways were involved in FER resistance, which was a complex trait that was controlled by multiple genes with minor effects, and provided important QTL and genes, which could be used in molecular breeding for resistance.

Charcoal rot caused by Macrophomina phaseolina results in substantial yield losses in cowpea. Host plant resistance is the most reliable and cost-effective method of controlling this disease. Newly developed varieties need to be screened for their reaction to M. phaseolina as new strains of the pathogen keep evolving due to pathogen reproduction. This study sought to identify cowpea genotypes with stable resistance to M. phaseolina . Twenty-three cowpea genotypes were screened on the field and in pots under screenhouse conditions using a virulent M. phaseolina isolate. The pathogen effect on the genotypes and their agronomic performance and yield were determined. Disease parameters such as percentage Disease Incidence (DI) at the seedling stage, Seedling Infection Score (SIS), Root and Stem Severity (RSS), and Colony Forming Unit Index (CFUI) measured on the field were highly correlated with screen house experiments. These parameters were also significantly and positively correlated with each other suggesting that any of these parameters could be used in ranking the resistance or susceptibility of the genotypes. The disease parameters also had a significant negative correlation with percent germination/plant stand and pod yield and grain yield. It was observed that the charcoal rot disease was more severe at the seedling stage than at the reproductive stage. This is evidenced by the significant strong positive correlation between percent germination/plant stand and, pod yield and grain yield as the disease at the seedling stage causes seed rot and damping off. Based on the most Frequent Genotype Rank (FGR) generated by recording the highest occurring genotype rank of SIS, RSS, and CFUI of each genotype and comparison with grain yield data, IT11K-61-82, IT10K-837-1, SARI-3-11-100 and IT84S-2049 were ranked to be resistant to moderately resistant while IT07K-303-1, IT14K-1682-3 and IT13K-1070-2 were moderately susceptible. Additionally, IT14K-2030-2 and IT14K-2113-4 were susceptible to Charcoal rot disease while the remaining were moderately susceptible. Genotypes that combine resistance with farmer-preferred agronomic traits should be released as varieties while those that lack the farmer-preferred traits could be improved through hybridizations.

Judicial restraints on the use of commercial fungicides for seed treatment have made seed borne cultivations more prone to fungal infestations. Novel and safer alternatives in terms of engineered nanoparticles of essential and ecofriendly nature provide a potential way to combat this problem. In this study, ZnS nanospheres (nZnS) were synthesized in situ as water dispersible formulations (nZnS-WDF), and in vitro studies on rice seed mycopathogens revealed antifungal activity eight fold better than standard fungicide treatment (carbendazim). The antifungal activity is results from topological cellular deformations of treated hyphae,causing cell wall disruption and membrane depolarization, resulting in protein leakage and finally hyphal death. SEM-EDS of treated and disrupted hyphae revealed surface-associated nZnS as the reason for membrane disorganization. In silico binding analysis of nZnS on the active sites of the target enzymes14α-demethylase and 1,3-β-glucan synthase, revealed non hydrogen bonding interactions with enzymes causing enzyme inhibition. Nanopriming of infested rice seeds under controlled conditions with nZnS-WDF at 150 μg/ml significantly reduced the diseased parameters and a noticeable reduction in seed rot (62.59%) and seedling blight (64.02%) were observed in comparison to carbendazim. More importantly, nZnS had an invigorating effect on seeds, boosting the growth of seedlings over a short period. The work presented advocates the use of degradable and eco-safe nZnS for the effective control of seed-borne fungal pathogens necessary for sustainable agriculture. Schematic illustration of synthesis of nZnS-WDF, its in silico, in vitro effects on fungal pathogens and seed treatment studies.