Formation And Germination Characteristics Of Different Spore Types Of Fusarium Oxysporum F. Sp. Medicaginis

Alfalfa（Medicago sativa）is currently the most widely planted and most important perennial forage in our country and the world.Alfalfa fusarium wilt is caused by Fusarium oxysporum f.sp.Medicaginis（Fom）.Seriously affect the yield and quality of forage,lead to grassland decline,and then affect the development of alfalfa industry.F.oxysporum can produce three types of spores:microconidia,macroconidia and chlamydospore,which play an important role in the occurrence and cycle of disease.The number of spores and germination status directly affect the occurrence and degree of damage of the disease.However,studies on these three sporulation and germination characteristics are currently lacking.In this paper,the formation conditions,germination characteristics and formation mechanism of different types of spores of Fusarium oxysporum f.sp.medicaginis（Fom）were studied in order to reveal the formation and germination mechanism of different types of spores.New methods of disease control provide theoretical basis.The main findings are as follows:1.F.oxysporum strains（T6,T7,T8 and T9）had significant differences（P<0.05）in the number of sporulations on the four media（PDA,PDB,CMC and SNA）,PDA and PDB media were significantly（P<0.05）higher than those in CMC and SNA media.In the three media of PDB,CMC and SNA,the four strains all formed a large number（>94%）of microconidia;the proportion of macroconidia formed in the CMC medium was the highest,and the T9 strain was cultured in the CMC medium The highest proportion of macroconidia was formed at two weeks（5.63%）.When the four strains were cultured for 0 to 8 hours,SNA medium had a significant effect on promoting conidia germination（P<0.05）;after 24 hours of culture,both PDB and SNA medium could significantly promote the germination of conidia（P<0.05）.2.Since the formation of chlamydospores was observed in the above media,the existing methods were further referenced and improved.Glucose double-salt liquid medium（Glucose 2.0mg/L,KH₂PO₄ 1.0g/L,Mg SO₄·7H₂O 0.5g/L）can quickly and effectively induce mycelia to form a large number of chlamydospores in a stationary state.When sucrose and glucose are used as carbon sources,it is beneficial to the germination of chlamydospores and the growth of germ tubes.when sodium nitrate is used as nitrogen source,it can promote the germination of chlamydospores,and when ammonium chloride and potassium nitrate are used as nitrogen sources,it is beneficial to growth of chlamydospores germ tubes.3.By observing the formation of conidia and chlamydospores,two representative time points of three days and seven days were selected to collect the conidia and chlamydospore samples of T6 and T9 strains for transcriptome analysis.Through GO,COG and KEGG metabolic pathway enrichment analysis of DEGs,the results showed that amino acid synthesis and metabolism were significantly related to the formation of conidia and chlamydospores.In addition,the pathway"ABC transporter synthesis"and"glyoxylate and dicarboxylic acid metabolism"were significantly enriched during the formation of conidia;the pathway"peroxidase synthesis"during the formation of chlamydospores was significantly enriched.