Rice-infecting viruses have caused serious damage to rice production in Asian, American, and African countries, where about 30 rice viruses and diseases have been reported. To control these diseases, developing accurate, quick methods to detect and diagnose the viruses in the host plants and any insect vectors of the viruses is very important. Based on an antigen–antibody reaction, serological methods such as latex agglutination reaction and enzyme-linked immunosorbent assay have advanced to detect viral particles or major proteins derived from viruses. They aid in forecasting disease and surveying disease spread and are widely used for virus detection at plant protection stations and research laboratories. From the early 2000s, based on sequence information for the target virus, several other methods such as reverse transcription-polymerase chain reaction (RT-PCR) and reverse transcription-loop-mediated isothermal amplification have been developed that are sensitive, rapid, and able to differentiate closely related viruses. Recent techniques such as real-time RT-PCR can be used to quantify the pathogen in target samples and monitor population dynamics of a virus, and metagenomic analyses using next-generation sequencing and microarrays show potential for use in the diagnosis of rice diseases.

Neotyphodium fungal 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 caelestialium Kirkaldy (Heteroptera: Miridae), which reproduces on Lolium species grown as forage. To determine the potential of Neotyphodium endophytes to reduce the invasion of rice crops by T. caelestialium from adjacent Lolium crops, we carried out choice and no-choice feeding tests using endophyte-infected and endophyte-free clonal perennial ryegrass ( Lolium perenne L.) (Poaceae). Our experiments revealed that the presence of the Neotyphodium endophyte strongly deterred the feeding of both first-instar larvae and adults of T. caelestialium . These results show the potential of Neotyphodium endophytes to reduce the number of T. caelestialium in forage fields and grasslands, and thus to reduce the damage to rice grains caused by this insect pest.

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 μ g/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.

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