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A toothpick inoculation method was applied for evaluating the disease severity and infection frequency of Pythium root rot, which seriously restricts forage corn production in Japan. Seven corn hybrids were inoculated with toothpicks infested with Pythium arrhenomanes, the causal pathogen of the disease. Between 2011 and 2013, toothpicks were inserted into holes of the bottom stalks of corn plants just above the ground at the silking stage. At the inoculation plots throughout the experimental years, the infection frequencies of highly susceptible hybrids were stable even under suboptimal climate conditions. Therefore, we have concluded that the toothpick method is useful especially for discarding highly susceptible hybrids based on the data obtained from a single year. Further experiments will be required to overcome such problems as the low correlation between hybrids and their parental inbreds, and the development of more accurate screening systems for selecting resistant genotypes. [ABSTRACT FROM AUTHOR]

Epichloë ( Neotyphodium) endophytes are symbiotic fungi in association with gramineous plants and produce a range of alkaloids that enhance the resistance of host plants to insect pests. N-formylloline, one of the Epichloë-produced alkaloids, is known to be toxic to some insects but not to mammals. Therefore, Epichloë-infected grasses with high N-formylloline concentrations are expected to reduce the population of some insect pests in meadows. To assess the adverse effects of N-formylloline on the survival of the sorghum plant bug ( Stenotus rubrovittatus) known as a major pest, artificial feeding of N-formylloline through feeding sachets was carried out. N-formylloline reduced the survival of S. rubrovittatus, even at 50 ppm, which was considerably lower than the concentrations in most Epichloë-infected grasses. The results suggest that N-formylloline in Epichloë-infected grasses can reduce the population of S. rubrovittatus in meadows. [ABSTRACT FROM AUTHOR]

Plant symbiotic fungi (endophytes) of the genus Neotyphodium [anamorphs, asexual derivatives of Epichloë (Ascomycota: Clavicipitaceae)] often associate with grass species of the subfamily Pooideae, which includes important forage and turf species. These endophytes are known to produce a range of alkaloids that enhance their host's resistance to insects or are toxic to grazing animals. Among the alkaloids, loline alkaloids (saturated 1-aminopyrrolizidines) are generally observed in the highest concentrations in many Neotyphodium–grass symbiotic associations, and are known to be toxic to insects but not to mammals. Some Neotyphodium-infected grasses have enhanced resistance to rice leaf bug, Trigonotylus caelestialium (Kirkaldy) (Heteroptera: Miridae), one of the major pests for rice production in Japan. Our laboratory experiments quantified the effects of purified loline ( N-formylloline) and in planta synthesis of loline alkaloids by meadow fescue [ Lolium pratense (Huds.) S.J. Darbyshire (syn. Festuca pratensis Huds.)]– Neotyphodium uncinatum (Gams, Petrini & Schmidt) Glenn, Bacon & Hanlin and Italian ryegrass ( Lolium multiflorum Lam.)– Neotyphodium occultans Moon, Scott & Christensen associations on the development and survival of T. caelestialium. No-choice feeding assays with laboratory populations of the insect revealed that their growth was significantly decreased by the infected grasses, and the effect was greater for N. uncinatum than for N. occultans, in keeping with differences in N-formylloline concentrations in the plants. Artificial feeding of N-formylloline through feeding sachets indicated that the chemical has an adverse effect on survival of larvae, even at the lowest concentration tested (50 µg/g), which was considerably lower than the typical concentrations in many Neotyphodium–grass association s. The results confirmed the ability of Neotyphodium-infected forage grasses to control T. caelestialium propagation in meadows, which may cause damages to nearby rice paddies. [ABSTRACT FROM AUTHOR]

Neotyphodiumfungal endophytes form mutualistic symbiotic associations with many grasses of the subfamily Pooideae, including important forage and turfgrass species. This relationship provides a competitive advantage to the host plant by increasing abiotic/biotic stress tolerance, such as its resistance to drought, diseases, and insect pests. The insect deterrent effects of endophytes are now receiving attention in Japan, as insect pests growing in meadows are causing problems in adjacent rice paddies. One of the most serious problems is the kernel spotting of rice grains caused by the rice leaf bug,Trigonotylus caelestialiumKirkaldy (Heteroptera: Miridae), which reproduces onLoliumspecies grown as forage. To determine the potential ofNeotyphodiumendophytes to reduce the invasion of rice crops byT. caelestialiumfrom adjacentLoliumcrops, we carried out choice and no-choice feeding tests using endophyte-infected and endophyte-free clonal perennial ryegrass (Lolium perenneL.) (Poaceae). Our experiments revealed that the presence of theNeotyphodiumendophyte strongly deterred the feeding of both first-instar larvae and adults ofT. caelestialium. These results show the potential ofNeotyphodiumendophytes to reduce the number ofT. caelestialiumin forage fields and grasslands, and thus to reduce the damage to rice grains caused by this insect pest. [ABSTRACT FROM AUTHOR]

Black oat ( Avena strigosa Schreb.) is used as a cereal crop, forage crop or green manure in temperate regions. In Japan, it is mainly cultivated in Hokkaido island and, because of the vigorous initial growth and ability to suppress the proliferation of plant pathogenic nematodes (Uesugi et al. 2018), its use is recently increasing. In November 2021, a leaf spot and blight disease was observed in the grass cultivated in Kitahiroshima city (N43°0, E141°31). At first, blackish brown spindle-shaped or elliptical lesions, about 3 to 5 × 1 to 2 mm were formed on leaves, and they expanded by forming yellowish-brown halos around them, eventually resulting in leaf blight later on (Fig.1), damaging 5-10 % of leaf area, varied by cultivar. The lesions were excised, surface-sterilized, and incubated on water agar under near-UV light. Three single-spore isolates of Pyrenophora -like fungus were obtained from the lesions and deposited at the NIAS Genebank, Japan (https://www.gene.affrc.go.jp/index_en.php) as MAFF511692, 511693 and 511694. The sequences of ribosomal RNA gene (rDNA) and its internal transcribed spacer (ITS), and the gpd sequences of the isolates were analyzed as described by Marin-Felix et al. 2019. The rDNA-ITS sequences (GenBank accession no. LC769170, LC769171 and LC769172) of the isolates matched with that of the ex-type strain of Pyrenophora avenicola (MK539972) isolated from Avena seed. The sequences of the gpd (accession no. LC795722, LC795723 and LC795724) matched well with that of the ex-type strain (MK540180). Conidiophores of the isolates were septate, straight or flexuous, pale brown to olivaceous brown, 81.4 to 125.7 × 4.2 to 6.5 (ave. 106.4×5.7µm, n=50) µm, with hyaline vegetative hyphae (Fig.2). Conidia were slightly verrucose, cylindrical to obclavate, pale brown to olivaceous brown, 42.2 to 78.5 × 9.0 to 13.3 µm (ave. 56.9 ×10.4µm, n =50) and 2 to 7 distoseptate. This description overlap with the original description of P. avenicolai (Marin-Felix et al. 2019) and the leaf spot pathogen of Avena sativa reported in China (Chen et al. 2022). The fungus was identified as P. avenicola on the basis of morphology and molecular phylogenetic analysis. To produce inoculum, the isolate MAFF511692 was grown on V8 juice agar at 25°C under near-UV light for 7 days. Five plants each of cv. 'Soil saver', 'New oats' of A. strigosa (Kaneko seeds co.) and 'New almighty' of A. sativa (Snow brand seed co.) were grown in a greenhouse for approximately 14 days and then inoculated by atomizing them with the conidial suspension (10 4 conidia/ml) at the five-leaf stage. Five plants of each cultivar sprayed with sterilized distilled water served as the control. Inoculated plants were covered with plastic bags for 24 h at 25°C. After 5 days, blackish brown elliptical lesions developed on the leaves of all inoculated plants of both cultivars of A. strigosa (Fig. 3) and A. sativa , implying broad pathogenicity of the fungus to species and cultivars of Avena plants. Halo was not observed, maybe due to fewer stress in the greenhouse environment. Controls remained asymptomatic. The produced lesions were incubated as described above and the reisolated fungus was identified as P. avenicola based on the morphology, confirming Koch's postulates. To our knowledge, this is the first report of leaf blight caused by P. avenicola on black oat in Japan.