| Capsicum annuum L.is a perennial herbaceous plant of the genus Capsicum L.in the Solanaceae family,belonging to the subclass Asteridae and the class Magnolia.It is named after its origin in Qiubei County,Yunnan Province and is a famous specialty of Qiubei County,also known as "Qiubei Xiaojiao".Qiubei peppers are favored by consumers due to their bright appearance,slender body,pure taste,rich nutrition and trace elements.However,in recent years,it has been found that during the cultivation of Qiubei peppers in Wenshan,there has been a sudden whitening of the fruits during the harvest period,which has led to a sharp decline in the yield and quality of Qiubei peppers,causing significant economic losses.However,there is currently limited research on this type of post harvest albinism in Qiubei peppers,which may be caused by a combination of multiple pathogenic bacteria.The causes and types of the disease are not clear,and there is a lack of effective prevention and control measures in production.In order to identify the pathogenic factors of Qiubei pepper albinism,this study collected samples of Qiubei pepper albinism pathogen from the Qiubei region of Yunnan province,isolated and purified the pathogen,and observed its colony morphology characteristics and microscopic observations using biological morphology identification methods,combined with ITS and TEF-1 α Sequence joint analysis is used to construct a phylogenetic tree for molecular biology identification.Pathogenicity of pathogenic bacteria is determined according to Koch’s rule,and drug resistance testing is performed on the most virulent strains.The research results obtained are as follows:1.This study observed the morphological characteristics of the colonies and isolated and purified strains with single spores.Based on the similarity in morphological characteristics,8 strains were selected,namely LNZ-2,LNZ-5,XBP-6,XBP-9,GAN-2,GAN-3,GAN-4,GAN-6.Morphological observations were conducted on them,and the results showed that the initial colonies of the 8 strains were all white,and the conidia were elongated and slightly curved in a sickle shape.2.Pathogen strains were obtained by conventional tissue isolation method,combined with morphological observation and molecular biological identification,and through conserved sequence ITS and translation extension factor 1(TEF-1 α)A phylogenetic tree constructed jointly and tested for pathogenicity according to Koch’s law.The results showed that XBP-6,XBP-9,and GAN-6 formed a branch with F.proliferatum,LNZ-5 and GAN-2 had the closest evolutionary distance with F.oxysporum,LNZ-2 and GAN-4 formed a branch with F.equiseti,and GAN-3 formed a branch with F.solani.Combining morphological observation and molecular biology identification,it is determined that the albinism of Qiubei pepper is caused by the infection of pathogenic fungi F.oxysporum,F.equiseti,F.proliferatum,and F.solani,with the strongest pathogenicity being F.oxysporum.3.Ten fungicides were tested for their antibacterial toxicity against the most pathogenic strain of GAN-2,Fusarium oxysporum.The resistance tests of the ten fungicides showed that:(1)when the concentration of oxysporin was 268 mL/L,the maximum antibacterial rate was 90.2%,followed by chloramphenicol and thiophanazole methyl,with concentrations of 2800 mL/L and 1600 mL/L,the antibacterial rates were 89.8% and 88.8%;At a concentration of 31.25 mL/L,the minimum inhibitory rate was 28.9%,followed by a concentration of 23 mL/L of azoxystrobin,with an inhibitory rate of 37.6%.(2)Isocarbamide has the strongest antibacterial effect on GAN-2,with a highly significant control effect,with an EC50 of 1.83 mL/L,followed by prochloraz with an EC50 of 2.05 mL/L.However,pyrazolidinolate has a poor inhibitory effect on the tested strain,with an EC50 of105.69 mL/L.In addition to obtaining two strong fungicides,isochloraz and prochloraz,for the prevention and treatment of GAN-2 strains,this study also found that fungicides such as chlorpyrifos and difenoconazole are sensitive to GAN-2strains.These achievements will provide a basis for further research on new fungicides.The above research can lay a foundation for further exploring the occurrence patterns and control techniques of northern pepper albinism in the future,and also provide a theoretical basis for studying new fungicides for Qiubei pepper albinism. |
