Prevention and Control of Gentiana macrophylla Pall Root Rot Disease

The root rot is a major disease affecting yield of Gentiana macrophyl a pal , reducing yield or even causing total crop failure. This research introduced the occurrence characteristics and various control techniques of root rot of Gentiana macrophyl a pal , in order to provide references for farmers.

First Report of Fusarium striatum Causing Root Rot Disease of Panax notoginseng in Yunnan,China

Panax notoginseng is a traditional Chinese medicinal plant.Root rot of P.notoginseng is one of the most serious diseases affecting P.notoginseng growth and causes wilted leaves,fewer lateral roots and rotten roots.Root rot is a soil-borne disease,and mainly occurs from June to August in Yunnan Province when the temperatures are high and the air is humid.In this study,the endophytic fungal genus Fusarium isolate E-2018.1.22-#3.2 was obtained from a P.notoginseng embryo.Fusarium isolate E-2018.1.22-#3.2 was identified as Fusarium striatum based on morphological characteristics and molecular analysis.The fungus was found to have conidiophores and macroconidia,and its ITS,LSU and TEF-1αgenes shared 100%,99.2%and 99%identities with the homologous genes of Fusarium striatum,respectively.Isolate F.striatum E-2018.1.22-#3.2 can cause root rot symptoms,including black,soft roots,fewer lateral roots and leaf wilt,in 93%of the experimental P.notoginseng plants,and could be re-isolated,fulfilling Koch’s postulates.When the P.notoginseng plants were treated with the fungicide pyraclostrobin,isolate F.striatum E-2018.1.22-#3.2 was unable to cause root rot.We have therefore demonstrated that F.striatum E-2018.1.22-#3.2 is able to cause root rot disease in P.notoginseng.This is the first report of root rot disease caused by F.striatum on P.notoginseng in China.

Effects of Torreya grandis Root Rot on Seedling Growth and Screening of Its Chemical Control Agents

[Objectives]This study was conducted to prevent the occurrence of root rot disease in Torreya grandis and improve the yield and quality of T.grandis.[Methods]One-year-old and two-year-old seedlings of Torreya grandis‘Xifei’and‘Cufei’were inoculated with the root rot pathogen Fusarium fujikuroi,and the changes in photosynthesis,chlorophyll content,malondialdehyde,and defense enzyme system(superoxide dismutase,peroxidase,and catalase)activity in leaves of T.grandis seedlings were investigated using water as a control.Meanwhile,the control effects of 80%carbendazim wettable powder,64%metalaxyl·mancozeb wettable powder,430 g/L tebuconazole suspension and 30%difenoconazole·cyproconazole EC on root rot in T.grandis were investigated.[Results]After inoculation with the pathogen F.fujikuroi,the net photosynthetic rates and transpiration rates in leaves of T.grandis‘Xifei’and‘Cufei’decreased,and the contents of chlorophyll decreased,while the contents of malondialdehyde increased,and the contents of superoxide dismutase and catalase increased with time.However,peroxidase showed a high activity in T.grandis‘Cufei’only,but a trend of"increasing-decreasing-increasing"in T.grandis‘Xifei’.Among the four chemical control agents,64%metalaxyl·mancozeb wettable powder had the best control effect on root rot of T.grandis caused by the pathogenic fungus F.fujikuroi.[Conclusions]The net photosynthetic rate,transpiration rate,chlorophyll content,malondialdehyde content,superoxide dismutase activity and catalase activity could all be used as screening indicators for T.grandis varieties resistant to root rot.Meanwhile,64%metalaxyl·mancozeb wettable powder could be used as a control agent for root rot on T.grandis.

Formulation of Biofungicides from Cymbopogon citratus and Tithonia diversifolia: Evaluating Its Antimicrobial Activities against Pythium myriotylum, the Causal Agent of Root Rot of Xanthosoma sagittifolium (L.) Schott

Three fungicide formulations, namely M1, M2 and M3, were prepared from sodium bicarbonate, citronella essential oil and sunflower slurry. The stability of M1, M2 and M3 formulations was determined based on pH, temperature, order of incorporation of the inputs and storage time. The most stable formulations were used for antagonistic tests on Pythium myriotylum. The Minimum Inhibitory Concentration (MIC) was used for the greenhouse tests and the mode of action was determined in vitro. The study showed that the order of incorporation of the inputs “Essential Oil-Tween 80-Bicarbonate-Slurry” (EO-T80-B-S) promotes stability. M1 and M2 are stable at 4°C, 25°C, 37°C and 40°C temperatures and have a pH of 7 and 8 respectively. The Minimum Inhibitory Concentration of M1 and M2 is 1% on P. myriotylum. M1 and M2 act on Pythium by membrane lysis, inhibiting proton pumps and inhibiting protein synthesis. The formulations M1 and M2 reduce the incidence of root rot disease in cocoyam plants growth in the greenhouse. M1 and M2 are potential candidates for improvement of cocoyam seedlings production in Cameroon.

Characterization and functional analysis of gerbera plant defensin(PDF)genes reveal the role of GhPDF2.4 in defense against the root rot pathogen Phytophthora cryptogea

Gerbera(Gerbera hybrida),a major fresh cut flower crop,is very susceptible to root rot disease.Although plant defensins(PDFs),a major group of plant antimicrobial peptides,display broad-spectrum antifungal and antibacterial activities,PDF genes in gerbera have not been systematically characterized.Here,we identified and cloned nine PDF genes from gerbera and divided them into two classes based on phylogenetic analysis.Most Class Ⅰ GhPDF genes were highly expressed in petioles,whereas all Class Ⅱ GhPDF genes were highly expressed in roots.Phytophthora cryptogea inoculation strongly upregulated all Class II GhPDF genes in roots and upregulated all Class Ⅰ GhPDF genes in petioles.Transient overexpression of GhPDF1.5 and GhPDF2.4 inhibited P.cryptogea infection in tobacco(Nicotiana benthamiana)leaves.Transient overexpression of GhPDF2.4,but not GhPDF1.5,significantly upregulated ACO and LOX gene expression in tobacco leaves,indicating that overexpressing GhPDF2.4 activated the jasmonic acid/ethylene defense pathway and that the two types of GhPDFs have different modes of action.Prokaryotically expressed recombinant GhPDF2.4 inhibited mycelial growth and delayed the hyphal swelling of P.cryptogea,in vitro,indicating that GhPDF2.4 is a morphogenetic defensin.Moreover,the addition of GhPDF2.4 to plant culture medium alleviated the root rot symptoms of in vitro-grown gerbera seedlings and greatly reduced pathogen titer in P.cryptogea-inoculated gerbera roots in the early stages of treatment.Our study provides a basis for the use of GhPDFs,especially GhPDF2.4,for controlling root rot disease in gerbera.