Background: The endophytic fungus,Neotyphodium coenophialum, can enhance drought tolerance of its host grass, tall fescue. To investigate endophyte effects on plant responses to acute water deficit stress, we did comprehensive profiling of plant metabolite levels in both shoot and root tissues of genetically identical clone pairs of tall fescue with endophyte (E+) and without endophyte (E-) in response to direct water deficit stress. The E- clones were generated by treating E+ plants with fungicide and selectively propagating single tillers. In time course studies on the E+ and E- clones, water was withheld from 0 to 5 days, during which levels of free sugars, sugar alcohols, and amino acids were determined, as were levels of some major fungal metabolites.Results: After 2–3 days of withholding water, survival and tillering of re-watered plants was significantly greater for E+ than E- clones. Within two to three days of withholding water, significant endophyte effects on metabolites manifested as higher levels of free glucose, fructose, trehalose, sugar alcohols, proline and glutamic acid in shoots and roots. The fungal metabolites, mannitol and loline alkaloids, also significantly increased with water deficit.Conclusions: Our results suggest that symbioticN. coenophialumaids in survival and recovery of tall fescue plants from water deficit, and acts in part by inducing rapid accumulation of these compatible solutes soon after imposition of stress.

The black spored fungi of the subgenera Circumdata,the section Nigri (=Aspergillus niger group) is reviewed relative to their production of mycotoxins and their effects on plants as pathogens. Molecular methods have revealed more than 18 cryptic species, of which several have been characterized as potential mycotoxin producers. Others are defined as benign relative to their ability to produce mycotoxins. However, these characterizations are based on in vitro culture and toxins production. Several can produce the ochratoxins that are toxic to livestock, poultry, and humans. The black aspergilli produce rots of grapes, maize, and numerous other fruits and grain and they are generally viewed as post-harvest pathogens. Data are review to suggest that black aspergilli, as so many others, are symptomless endophytes. These fungi and their mycotoxins contaminate several major grains, foodstuffs, and products made from them such as wine, and coffee. Evidence is presented that the black aspergilli are producers of other classes of mycotoxins such as the fumonisins, which are known carcinogenic and known prior investigations as being produced by the Fusarium species. Three species are identified in U.S. maize and peanuts as symptomless endophytes, which suggests the potential for concern as pathogens and as food safety hazards.

Maize ( Zea mays L.) is susceptible to infection by Fusarium verticillioides through autoinfection and alloinfection, resulting in diseases and contamination of maize kernels with the fumonisin mycotoxins. Attempts at controlling this fungus are currently being done with biocontrol agents such as bacteria, and this includes bacterial endophytes, such as Bacillus mojavensis . In addition to producing fumonisins, which are phytotoxic and mycotoxic, F. verticillioides also produces fusaric acid, which acts both as a phytotoxin and as an antibiotic. The question now is Can B. mojavensis reduce lesion development in maize during the alloinfection process, simulated by internode injection of the fungus? Mutant strains of B. mojavensis that tolerate fusaric acid were used in a growth room study to determine the development of stalk lesions, indicative of maize seedling blight, by co-inoculations with a wild-type strain of F. verticillioides and with non-fusaric acid producing mutants of F. verticillioides. Lesions were measured on 14-day-old maize stalks consisting of treatment groups inoculated with and without mutants and wild-type strains of bacteria and fungi. The results indicate that the fusaric-acid-tolerant B. mojavensis mutant reduced stalk lesions, suggesting an in planta role for this substance as an antibiotic. Further, lesion development occurred in maize infected with F. verticillioides mutants that do not produce fusaric acid, indicating a role for other phytotoxins, such as the fumonisins. Thus, additional pathological components should be examined before strains of B. mojavensis can be identified as being effective as a biocontrol agent, particularly for the control of seedling disease of maize.

The benzoxazolinones, specifically benzoxazolin-2(3H)-one (BOA), are important transformation products of the benzoxazinones that can serve as allelochemicals providing resistance to maize from pathogenic bacteria, fungi, and insects. However, maize pathogens such as Fusarium verticillioides are capable of detoxifying the benzoxazolinones to 2-aminophenol (AP), which is converted to the less toxic N-(2-hydroxyphenyl) malonamic acid (HPMA) and 2-acetamidophenol (HPAA). As biocontrol strategies that utilize a species of endophytic bacterium, Bacillus mojavensis, are considered efficacious as a control of this Fusarium species, the in vitro transformation and effects of BOA on growth of this bacterium was examined relative to its interaction with strains of F. verticillioides. The results showed that a red pigment was produced and accumulated only on BOA-amended media when wild type and the progeny of genetic crosses of F. verticillioides are cultured in the presence of the bacterium. The pigment was identified as 2-amino-3H-phenoxazin-3-one (APO), which is a stable product. The results indicate that the bacterium interacts with the fungus preventing the usual transformation of AP to the nontoxic HPMA, resulting in the accumulation of higher amounts of APO than when the fungus is cultured alone. APO is highly toxic to F. verticillioides and other organisms. Thus, an enhanced biocontrol is suggested by this in vitro study.