Design And Synthesis Of Active Small Molecules Against Passion Fruit Mosaic Disease And Analysis Of Their Effects On Fruit Qualit

Passiflora edulia Sims is rich in nutrients and has a sweet and fragrant taste,which is deeply loved by consumers.With the widespread planting of passion fruit in China,its diseases have spread through methods such as seedling introduction,sales,and cutting sowing,and have occurred in various provinces.Among them,Passiflora edulia Sims is one of the main viral diseases of passion fruit plants,which is a key cause of reduced yield and quality of passion fruit in China,and seriously affects the development of the passion fruit industry.At present,due to the lack of effective drugs and targeted treatment methods,the prevention and control effect of passion fruit mosaic disease is not satisfactory.This study designed and synthesized plant derived chromosomal ketone active small molecules,and screened highly active small molecules resistant to cucumber mosaic virus（CMV）through half leaf blight method.And through field control experiments,the control effect of highly active small molecules of chromophores on passion fruit mosaic disease and their impact on the quality of passion fruit were studied.At the same time,the disease resistance mechanism of small molecules of chromophores was preliminarily explored,providing a basic theoretical basis for exploring the disease resistance mechanism of passion fruit mosaic disease in the later stage and cultivating resistant varieties of passion fruit.The main research content and results are as follows:This study is based on passionfruit mosaic disease,using the plant active component chromone as the lead structure,introducing amide and 1,3,4-thiadiazole sulfone active fragments,and designing and synthesizing 14 novel chromone derivatives containing amide and 1,3,4-thiadiazole sulfone structures.Their structures were characterized by ¹H NMR,¹³C NMR,and H RMS.Determine the inhibitory activity of the target compound against CMV using the half leaf blight method.The bioassay results showed that the compounds 6-fluoro-N-（5-（（ethylsulfonyl）-1,3,4-thiadiazo l-2-yl）-4-chromane-2-carboxamide（A3）and 6-chloro-N-（5-ethyl sulfonyl group）-1,3,4-thiadiazole 2-yl）-4-chromane-2-carboxamide（A15）had the best protective and therapeutic activities against CMV,with the protective activities of57.69%and 56.13%respectively,which were better than Ningnanmycin（50.13%）and Tofos（42.08%）;The therapeutic activity was 51.73%and 52.39%,respectively,which was equivalent to the effect of Ningnanmycin（51.35%）and better than that of Toflufos（40.78%）.This study investigated the prevention and control effects of passionfruit mosaic disease by using Ningnanmycin and Toflufos as positive controls,clear water（CK）as negative controls,and A3 and A15 active small molecules for field control experiments.The results showed that A3 and A15 pesticides can to some extent reduce the occurrence of passionfruit mosaic disease,with an average prevention and control effect of 41.29%,which is equivalent to Ningnanmycin（39.78%）,Compared to toxic fluorophosphorus（37.07%）,the relative average prevention effect of small molecule A15 with chromone activity is 37.62,which is equivalent to toxic fluorophosphorus.By measuring the leaf and fruit quality of Passion Fruit,it was found that A3 and A15 pesticides can reduce the impact of Passion Fruit mosaic disease on Passion Fruit leaves,resulting in an increase in chlorophyll,total phenols,soluble protein,and soluble sugar content.At the same time,it enhances the appearance and quality of Passion Fruit,and increases the content of soluble solids,soluble sugar,and vitamin C and other nutrients in Passion Fruit,Alleviated the impact of mosaic disease on fruit growth and development.The resistance mechanism of A3 was analyzed by sequencing the transcriptome treated with A3 spray and CK.The results showed that there were 752 differentially expressed genes in A3 treatment compared with CK,including 246 up-regulated genes and 406 down-regulated genes.The GO annotation results of differentially expressed genes indicate that differentially expressed genes are enriched into 150 GO functions,mainly involving responses to stimuli,oxidation-reduction processes,and cellular processes in biological processes.The cellular components involved are mainly cytoplasm,membrane,plastid,etc.Molecular functions mainly involve catalytic activity and binding.The KEGG metabolic pathway results indicate that differentially expressed genes are mainly involved in metabolic pathways such as thiamine metabolism,porphyrin and chlorophyll metabolism,and photosynthatis antenna proteins.Analysis of differentially expressed genes related to disease resistance revealed that the main pathways involved in disease resistance are plant hormone signaling,phenylpropanoid biosynthesis,and glycerol phospholipid metabolism.The key upregulated genes include PYL,GPAT,HCT,and POD,while the key downregulated genes include PP2C.