Parasitic weeds are a major threat to food security in Africa and control measures mostly done by smallholder farmers are not effective in eradicating the parasites.This results in a yield loss up to 100%.Parasitic we...Parasitic weeds are a major threat to food security in Africa and control measures mostly done by smallholder farmers are not effective in eradicating the parasites.This results in a yield loss up to 100%.Parasitic weeds comprise Alectra vogelii,Striga spp.,Orobanche spp.,Rafflesia spp.,and Phoradendron spp.Parasitic attachment is successful when three necessary conditions have been fulfilled namely the compatible host,suitable environment,and parasitic weed.These species parasite plant species through special attachment features such as modified leaves,suckers,haustoria,or modified roots.In Africa,the variability of parasitic weeds is largely driven by environmental factors such as temperature,rainfall,soil type,and crop husbandry practices.Warmer temperatures create more hospitable conditions for certain parasitic weeds,and allowing them to spread to new areas.Parasitic weed control is vital for effective crop production and the control strategies can be achieved through integrated weed control method that embraces mechanical,cultural,chemical,and biological methods.However,the most effective and crucial method is the cultivation of resistant varieties that provide long-term protection against parasitic weeds.Studies have been done on host-parasite attachment where dodder can send out new roots to infected neighbouring plants and spread their parasitic behaviour.More insight and knowledge should offer new goals for control within the life cycle of the parasitic weeds and their metabolic activities.Lastly,disciplines such as agronomy,plant breeding,nutrition,economics,and IT should play their roles effectively in combating parasitic weeds.展开更多
Malania oleifera(Olacaceae)is a valued tree species,mostly because its seeds have high precious fatty acid content(particularly nervonic acid).However,seedling mortality rates are often high and regeneration of this t...Malania oleifera(Olacaceae)is a valued tree species,mostly because its seeds have high precious fatty acid content(particularly nervonic acid).However,seedling mortality rates are often high and regeneration of this tree has been problematic,which greatly hinders its utilization at a large scale.Cultivation difficulties of some tree species in the family Olacaceae have been attributed to their root hemiparasitic habit.Prompted by field observations and the taxonomic proximity of M.oleifera to root hemiparasites in Olacaceae,we hypothesized that tuberous structures observed on the roots of M.oleifera are parasitic organs known as haustoria.To test this hypothesis,we collected root samples from M.oleifera plants of various ages and growth conditions,investigated the morphological and anatomical features of tuberous structures and their connections to neighboring roots.Our analyses confirmed that M.oleifera are root hemiparasites.To the best of our knowledge,this is the first empirical report on root hemiparasitism in M.oleifera.Because life strategies of root hemiparasitic plants differ greatly from autotrophic plants,the root hemiparasitic habit needs to be taken into account for successful seedling regeneration of M.oleifera.This study establishes the foundation for investigations into a long-neglected but essential aspect in research of these highly valued tree species.展开更多
Haustorium formation is the characteristic feature of all parasitic plants and a vital process for successful parasitism.Previous investigations on haustorium initiation and development are constricted to induced proc...Haustorium formation is the characteristic feature of all parasitic plants and a vital process for successful parasitism.Previous investigations on haustorium initiation and development are constricted to induced processes by host-derived signals or synthetic analogs.Spontaneous haustorium formation in the absence of host signals,a process representing an early stage in the evolution of parasitic plants,remains largely unexplored.Lack of fast and frequent formation of spontaneous haustoria greatly hinders full understanding of haustorium formation in root hemiparasites.In this study,seedlings of Pedicularis kansuensis Maxim.,a facultative root hemiparasitic species in Orobanchaceae observed to produce many spontaneous haustoria,were grown in autoclaved water agar in the absence of any known haustoriuminducing stimulants.We aimed to test the temporal and developmental pattern of spontaneous haustorium formation.Also,effects of sucrose supply and root contact on spontaneous haustorium formation were tested.Spontaneous haustoria were observed starting from six days after germination,much earlier than previously reported root hemiparasites.A majority of the spontaneous haustoria formed on lateral roots.Percentage of seedlings with spontaneous haustoria was 28.8% when grown on water agar plates,with a mean of four haustoria per seedling two weeks after germination.Haustorium formation by seedlings grown in water agar amended with 2% sucrose was more than twice of those without sucrose amendment.Singly grown seedlings were able to develop spontaneous haustoria at similar levels as those grown with another conspecific seedling.In view of the fast and abundant formation of spontaneous haustoria,P.kansuensis may be developed as an excellent experimental system in future investigations for unraveling endogenous regulation of haustorium initiation and development in root hemiparasitic plants.展开更多
Here,we show that Lichinodium(Lichinaceae,Lichinomycetes,Ascomycota)constitutes a formerly unrecognized lineage within the Leotiomycetes,thus being the first lichenized lineage recognized in the superclass Sordariomyc...Here,we show that Lichinodium(Lichinaceae,Lichinomycetes,Ascomycota)constitutes a formerly unrecognized lineage within the Leotiomycetes,thus being the first lichenized lineage recognized in the superclass Sordariomyceta(Leotiomycetes,Laboulbeniomycetes and Sordariomycetes).To infer the position of Lichinodium,we constructed two multilocus phylogenies based on six and five gene regions(nuLSU rDNA,nuSSU rDNA,mtSSU rDNA,RPB1,RPB2 and MCM7)including main Pezizomycotina groups in the first analysis and focusing secondly on a comprehensive selection of Sordariomyceta.The results show that Lichinodium is sister to Leotiaceae.We discuss the morphological and ecological similarities between Lichinodium and other Leotiomycetes,and describe the new order Lichinodiales and family Lichinodiaceae.The sister relationship between Sordariomycetes and Laboulbeniomycetes is here supported as it is the relationship between this clade and the Leotiomycetes.The results also support the polyphyly of Helotiales,the recognition of the Leotiales in a strict sense or the inclusion of the Triblidiales in Leotiomycetes.The photobionts of Lichinodium were sequenced for two genetic markers(rbcLX and 16S rDNA)and identified as Rhizonema,a recently described genus of filamentous cyanobacteria belonging to Nostocaceae.TEM studies revealed that the mycobiont-cyanobiont interface in Lichinodium does not produce haustoria,thus differing from a typical Lichinomycete(e.g.Ephebe).展开更多
文摘Parasitic weeds are a major threat to food security in Africa and control measures mostly done by smallholder farmers are not effective in eradicating the parasites.This results in a yield loss up to 100%.Parasitic weeds comprise Alectra vogelii,Striga spp.,Orobanche spp.,Rafflesia spp.,and Phoradendron spp.Parasitic attachment is successful when three necessary conditions have been fulfilled namely the compatible host,suitable environment,and parasitic weed.These species parasite plant species through special attachment features such as modified leaves,suckers,haustoria,or modified roots.In Africa,the variability of parasitic weeds is largely driven by environmental factors such as temperature,rainfall,soil type,and crop husbandry practices.Warmer temperatures create more hospitable conditions for certain parasitic weeds,and allowing them to spread to new areas.Parasitic weed control is vital for effective crop production and the control strategies can be achieved through integrated weed control method that embraces mechanical,cultural,chemical,and biological methods.However,the most effective and crucial method is the cultivation of resistant varieties that provide long-term protection against parasitic weeds.Studies have been done on host-parasite attachment where dodder can send out new roots to infected neighbouring plants and spread their parasitic behaviour.More insight and knowledge should offer new goals for control within the life cycle of the parasitic weeds and their metabolic activities.Lastly,disciplines such as agronomy,plant breeding,nutrition,economics,and IT should play their roles effectively in combating parasitic weeds.
基金financially supported by funding for Airong Li from Yunnan Ten Thousand Talents Plan Young and Elite Talents Project (YNWR-QNBJ-2018-092)Youth Innovation Promotion Association of Chinese Academy of Sciences (2011276)+2 种基金Young Academic and Technical Leader Raising Foundation of Yunnan Province (2014HB047)funding for Yunju Li from Young Academic and Technical Leader Raising Foundation of Yunnan Province (2019HB060)Yunnan Science and Technology Innovation Team Program (Grant No. 2019HC015)
文摘Malania oleifera(Olacaceae)is a valued tree species,mostly because its seeds have high precious fatty acid content(particularly nervonic acid).However,seedling mortality rates are often high and regeneration of this tree has been problematic,which greatly hinders its utilization at a large scale.Cultivation difficulties of some tree species in the family Olacaceae have been attributed to their root hemiparasitic habit.Prompted by field observations and the taxonomic proximity of M.oleifera to root hemiparasites in Olacaceae,we hypothesized that tuberous structures observed on the roots of M.oleifera are parasitic organs known as haustoria.To test this hypothesis,we collected root samples from M.oleifera plants of various ages and growth conditions,investigated the morphological and anatomical features of tuberous structures and their connections to neighboring roots.Our analyses confirmed that M.oleifera are root hemiparasites.To the best of our knowledge,this is the first empirical report on root hemiparasitism in M.oleifera.Because life strategies of root hemiparasitic plants differ greatly from autotrophic plants,the root hemiparasitic habit needs to be taken into account for successful seedling regeneration of M.oleifera.This study establishes the foundation for investigations into a long-neglected but essential aspect in research of these highly valued tree species.
基金financially supported by the Natural Science Foundation of China(31370512,U1303201,and 31400440)Natural Science Foundation of Yunnan Province(2016FB059)+1 种基金funding for Airong Li from The Youth Innovation Promotion Association of Chinese Academy of Sciencesthe Young Academic and Technical Leader Raising Foundation of Yunnan Province(2014HB047)
文摘Haustorium formation is the characteristic feature of all parasitic plants and a vital process for successful parasitism.Previous investigations on haustorium initiation and development are constricted to induced processes by host-derived signals or synthetic analogs.Spontaneous haustorium formation in the absence of host signals,a process representing an early stage in the evolution of parasitic plants,remains largely unexplored.Lack of fast and frequent formation of spontaneous haustoria greatly hinders full understanding of haustorium formation in root hemiparasites.In this study,seedlings of Pedicularis kansuensis Maxim.,a facultative root hemiparasitic species in Orobanchaceae observed to produce many spontaneous haustoria,were grown in autoclaved water agar in the absence of any known haustoriuminducing stimulants.We aimed to test the temporal and developmental pattern of spontaneous haustorium formation.Also,effects of sucrose supply and root contact on spontaneous haustorium formation were tested.Spontaneous haustoria were observed starting from six days after germination,much earlier than previously reported root hemiparasites.A majority of the spontaneous haustoria formed on lateral roots.Percentage of seedlings with spontaneous haustoria was 28.8% when grown on water agar plates,with a mean of four haustoria per seedling two weeks after germination.Haustorium formation by seedlings grown in water agar amended with 2% sucrose was more than twice of those without sucrose amendment.Singly grown seedlings were able to develop spontaneous haustoria at similar levels as those grown with another conspecific seedling.In view of the fast and abundant formation of spontaneous haustoria,P.kansuensis may be developed as an excellent experimental system in future investigations for unraveling endogenous regulation of haustorium initiation and development in root hemiparasitic plants.
基金Grants 148/2012,144/2013 and 71/2015“Lichinomycetes i Sverige”from the Swedish Taxonomy Initiative(Svenska artprojektet)administered by the Swedish Species Information Center(ArtDatabanken)Grant 2016-03589 from the Swedish Research Council(VR).
文摘Here,we show that Lichinodium(Lichinaceae,Lichinomycetes,Ascomycota)constitutes a formerly unrecognized lineage within the Leotiomycetes,thus being the first lichenized lineage recognized in the superclass Sordariomyceta(Leotiomycetes,Laboulbeniomycetes and Sordariomycetes).To infer the position of Lichinodium,we constructed two multilocus phylogenies based on six and five gene regions(nuLSU rDNA,nuSSU rDNA,mtSSU rDNA,RPB1,RPB2 and MCM7)including main Pezizomycotina groups in the first analysis and focusing secondly on a comprehensive selection of Sordariomyceta.The results show that Lichinodium is sister to Leotiaceae.We discuss the morphological and ecological similarities between Lichinodium and other Leotiomycetes,and describe the new order Lichinodiales and family Lichinodiaceae.The sister relationship between Sordariomycetes and Laboulbeniomycetes is here supported as it is the relationship between this clade and the Leotiomycetes.The results also support the polyphyly of Helotiales,the recognition of the Leotiales in a strict sense or the inclusion of the Triblidiales in Leotiomycetes.The photobionts of Lichinodium were sequenced for two genetic markers(rbcLX and 16S rDNA)and identified as Rhizonema,a recently described genus of filamentous cyanobacteria belonging to Nostocaceae.TEM studies revealed that the mycobiont-cyanobiont interface in Lichinodium does not produce haustoria,thus differing from a typical Lichinomycete(e.g.Ephebe).
