Genetic Diversity Of The Pathogen Population And Chemical Control Of Litchi Anthracnose In Hainan Province

Litchi（Litchi chinensis Sonn.）,aspindaceae,is an evergreen fruit tree.It is native to the tropical and subtropical areas of southern China and cultivated in Hainan,Guangdong,Guangxi,Fujian and other six provinces of China.Later,it was introduced to Australia,South Africa,Vietnam,Thailand and Mauritius and widely planted.Litchi anthracnose is an important fungal disease in litchi production.Its harm runs through the process from field planting to post harvest,which seriously limits the development of litchi industry.In this paper,the field disease investigation,typical symptom sample collection,pathogen isolation and purification,pathogen pathogenicity identification,population genetic diversity analysis of different source strains,the correlation between species composition and distribution of pathogens and geographical sources,the selection of field control agents for litchi anthracnose and the addition of different types and concentrations were studied The effects of surfactants on the control of Colletotrichum gloeosporioides in the field and the effects of surfactants on the ripening and colouring of fruits and the residues of chemicals in the peel were studied.1.Total of 217 strains were isolated and purified.Among them,128 strains were Colletotrichum spp.79 strains were identified as pathogens by Koch’s law,and their pathogenicity was different to some extent,but they were different from that of strain sites There was no correla tion between the distribution and the distribution.2.The species and classification of the pathogen of litchi anthracnose were precisely identified.It was clear that the pathogen of litchi anthracnose in Hainan Province was caused by C.caudum and C.gloeosporioides,C.fruticola,C.siamense,C.horii,C.Asiaum,C kahawae subsp.There are 44 strains of C.gloeosporioides,accounting for 55.9%of all strains,C.fruticola,C.HORII,C.asiaum and C.kahawae subsp.,C.musae was first reported on Litchi in China.3.The results showed that genetic information differentiation between and within populations of litchi Colletotrichum in Hainan Province was not significantly correlated with geographical origin.In addition,the environment of each region is different,and the strain has certain genetic differentiation.4.The results of Fungicide Screening test showed that 20%prochloraz EW had the strongest inhibition on C.gloeosporioides in laboratory,EC₅₀ value was 0.0465 mg/L,and the field control effect of the mixed reagent with 50%carbendazim WP was the best,the field control effect was 84.48%,followed by 20%prochloraz EW+50%prochloraz WP,the field control effect was 82.76%.5.In this paper,the addition of 0.025,0.05%assistant fariland 2408 has better effect on the control effect;in the case of using half of the liquid,the control effect has reached more than 90%,significantly improving the control effect of the agent.6.Surfactant can effectively improve the adhesion of chemicals on the surface of leaves,so as to effectively improve the utilization rate of chemicals,improve the effect of chemical control,and reduce the application amount of agents for controlling litchi anthracnose.However,different concentrations of surfactants may delay or inhibit the pigmentation of litchi peel;high concentrations of additives can significantly inhibit the pigmentation of litchi peel,of which 0.1%concentration of additives has the most obvious effect.