Contrasting infection frequencies of Neotyphodium endophyte in naturalized Italian ryegrass populations in Japanese farmlands

Abstract

Neotyphodium endophytes often confer benefits to their host grasses and may enhance invasiveness of some grasses. The knowledge of infection frequencies of endophytes among invading weed populations is necessary to understand the relationships between endophyte infection and invasiveness. Here we present data on infection frequencies of Italian ryegrass (Lolium multiflorum Lam.), an important weed in some farmlands in Japan, persisting in contrasting farmlands: a terraced paddy field and a wheat‐soybean double‐cropped field in the western region of Shizuoka prefecture, Japan. The terraced paddy site is a mosaic of several landscape elements such as paddy fields, levees, fallow and abandoned fields, with a high percentage of non‐crop area. Rice (Oryza sativa L.) has been cultivated for more than a decade with no application of chemical fertilizers, pesticides and fungicides. The wheat‐soybean field is characterized by the aggregation of large‐scaled fields that were originally reconstructed paddy fields, showing a low percentage of non‐crop area. Wheat and soybean have been grown as winter and summer crops, respectively, using chemical fertilizers and herbicides. We examined the presence or absence of endophytes in a total of 1200 seeds sampled from the two Italian ryegrass populations. The terraced paddy population exhibited a markedly high infection frequency (91.0%), due possibly to selective feeding of non‐infected seeds by insects. In contrast, the wheat‐soybean farmland population showed almost no infection (1.1%), whereas the putative source of the invasion in the proximity exhibited a relatively high infection rate (64.4%). Such a micro‐scale variation in infection frequencies may be attributable to a loss in endophyte viability within the wheat‐soybean field. The findings suggest that endophyte infection frequency may markedly differ among the Italian ryegrass populations even within the same region, presumably depending on the abundance of the seed‐eating insects, farmland management regimes and/or environmental conditions such as soil humidity.

Incidence of endophyte Neotyphodium occultans in Lolium rigidum from Australia

“…, 1988). A recent study (Yamashita et al. , 2010) found high infection frequencies within seed collected from terraced paddy farmland and, in contrast, low frequencies in wheat–soybean farmland.…”

Evaluating the fungal endophyte Neotyphodium occultans for resistance to the rice leaf bug, Trigonotylus caelestialium, in Italian ryegrass, Lolium multiflorum

“…Although artificial inoculation of grasses with N. occultans may be difficult as the fungus cannot be cultured on media (Moon et al, 2000), infected Italian ryegrass is prevalent in many parts of the world including Japan and is easy to utilize as a genetic resource (Yamashita et al, 2010). Our results indicate that N. occultans, the native endophyte of Italian ryegrass may make a new candidate for this application, although we may have to select plants with high resistance to T. caelestialium by reference to its N-formylloline concentration.…”

“…Our results indicate that N. occultans, the native endophyte of Italian ryegrass may make a new candidate for this application, although we may have to select plants with high resistance to T. caelestialium by reference to its N-formylloline concentration. Although artificial inoculation of grasses with N. occultans may be difficult as the fungus cannot be cultured on media (Moon et al, 2000), infected Italian ryegrass is prevalent in many parts of the world including Japan and is easy to utilize as a genetic resource (Yamashita et al, 2010). Breeding an Italian ryegrass cultivar with high resistance to T. caelestialium may be possible by the use of the endophyte, and such a cultivar will enhance the coexistence of rice farming and forage grass production within a community.…”

Interference of weeds in vegetable crop cultivation, in the changing climate of Southern Europe with emphasis on drought and elevated temperatures: a review

“…Lolium rigidum and L. multiflorum Lam. (Italian ryegrass) are two important and commonly found weeds in areas cultivated with cereal crops that infected by the endophytic fungus, Neotyphodium occultans (Yamashita et al, 2010;Kirkby et al, 2011), while L. perenne L. (perennial ryegrass) is also infected by the fungal endophyte species, N. lolii (Kane, 2011). Recently, Leuchtmann et al (2014) recommended the reassignment of Neotyphodium species to the Epichloë genus with the exception of two species, Acremonium chilense and N. starrii.…”