Prevalence, species composition, genetic variation and pathogenicity of clover rot (Sclerotinia trifoliorum) and Fusarium spp. in red clover in Finland

Abstract

Prevalence, species composition, genetic variation and pathogenicity of clover rot (Sclerotinia trifoliorum) and Fusarium spp. in red clover in Finland Abstract The species composition of a total of 173 red clover root fungal isolates from red clover roots from two established organic fields, a field in a transitional phase to organic and from two conventional fields was investigated based on morphology and molecular methods. Fusarium avenaceum was the most common Fusarium species overall but it occurrred less frequently in older organic fields. Gliocladium spp., Trichoderma spp. and Rhizoctonia spp. isolates were more common in the established organic clover fields, which had been under organic management for more than ten years and in one conventional field, than in a field still in the transitional phase. The taxonomical status of certain Fusarium, Alternaria and Sclerotinia isolates difficult to identify by morphological traits alone could be confirmed by species-specific primers and by comparing their ITS (internal transcribed spacer region) sequences to known sequences. The fingerprinting patterns of RAPD-PCR products could be used for the identification of fungal isolates and for studying the genetic variation among the isolates. Only one of the Fusarium isolates originating from apparently healthy red clover roots was clearly pathogenic to germinated red clover seedlings. In detached leaf experiments, the cvs Jokioinen and Ilte were more susceptible to one of the Sclerotinia trifoliorum isolates than cvs Betty and Bjursele, while all of them were equally susceptible to two other S. trifoliorum isolates. In further greenhouse experiments with intact plants it was possible to slow down the development of clover rot to some extent by means of one of the biological agents tested (Bacillus subtilis 10-VIZR, commercial name Alirin B), and almost completely by chemical control. IntroductionRed clover (Trifolium pratense) is the main perennial leguminous fodder crop with symbiotic Rhizobium bacteria for nitrogen fixation in Finland. Practically Eur J Plant Pathol (

Morphological and Pathogenic Characterization of Genetically Diverse Sclerotinia Isolates from European Red Clover Crops (Trifolium Pratense L.)

“…In S. trifoliorum , Yli‐Mattila et al. () inoculated three isolates from red clover on detached red clover leaves: the isolates also differed in aggressiveness and isolate x cultivar interaction was present. Our results are consistent with these previous studies.…”

“…; Yli‐Mattila et al. ), little is known about pathogenicity of different Sclerotinia isolates from red clover. To our knowledge, no publications have compared pathogenicity of S. trifoliorum and S. sclerotiorum isolates on red clover.…”

Differences in Yield of Diploid and Tetraploid Red Clover in Lithuania

“…Root rot, mainly caused by Fusarium spp. causes severe injuries in older red clover crops (Yli-Mattila et al, 2010). Svirskis and Juknevièius (2006) considered that new Lithuanian red clover cultivars have good disease resistance.…”

Pests and diseases in a changing climate a major challenge for Finnish crop production

“…In addition to the lengthening of the growing season, overwintering conditions for perennial grasses and legumes could become better with climate change, when the snow cover during the winter thins and stays for a shorter period (Jylhä et al 2008). Under the present climatic conditions, deep and long lasting snow cover often favours low temperature fungi that damage the canopy and reduce the yield of crops in the following growing season (Ylimäki 1969, Nissinen 1996, Yli-Mattila et al 2010). On the other hand, without snow cover, perennial grasses and legumes can face the same problems as autumn sown cereals; ice encasement, ice scorch and heaving injury (Hömmö 1994), often followed by disease attacks (Ylimäki 1967).…”

“…The pathogens that infect red clover, clover rot (Sclerotinia trifoliorum Erikss.) and root rot (several Fusariumspecies) thrive best under thick snow cover, and especially when snow cover stays for a long period (Ylimäki 1967, 1969, Willets and Wong 1980, Yli-Mattila et al 2010. With milder winters and thinning of the snow cover red clover, as well as other perennial grasses and legumes, might survive better in Finnish leys, which will prolong the profitable period of yield production and thus reduce the cultivation costs.…”