Studies On The Transcriptional Analysis Of Resistance Response Of Watermelon To Meloidogyne Incognita And Induced Control By Red-light

With the increase of protected cultivation area and the successive years of continuous cropping,the loss caused by the Meloidogyne incognita to watermelon production continues to increase.Therefore,it is of great significance to explore the mechanism of watermelon resistance to M.incognita and to seek for the prevention and control of M.incognita.In this study,on the one hand,we compared the infection process of M.incognita in the resistant and susceptible watermelon materials,and the transcriptome technique was used to preliminarily analyze the defensive control mechanism of watermelon to the M.incognita.It provides scientific support for disease-resistance gene mining and selection of disease-resistant varieties;On the other hand,We compared the effect of red-light treatment on the growth of resistant and susceptible watermelon materials infected by M.incognita,and revealed the mechanism of red light-induced resistance of watermelon to M.incognita from the physiological and biochemical points of view.It provides a scientific basis for the pest control methods that use red-light to induce crop resistance.The main results of this study are as follows:1.We compared the development of root knots and nematodes at different stages of the watermelon resistant material 'hongzi watermelon' and the susceptible material 'M16' after inoculation with M.incognita.We found this result: Feeding sites were initially established in the resistant materials of M.incognita after 2 days of inoculation;There were no significant difference in the root-knot size and the M.incognita development of the resistant and susceptible materials;The root knot diameter and nematode body width of 'M16' were significantly higher than that of 'hongzi watermelon' after 8-30 days of inoculation(P<0.01).The M.incognita in 'M16' has developed to adult stage after 15 days of inoculation,and they can lay eggs and complete the entire life cycle after 30 days;While the M.incognita in 'hongzi watermelon' develop very slowly,and it only developed to the third and fourth instar larval stage after 30 days of inoculation.These results suggest that the disease-resistant material'hongzi watermelon' mitigates the damage by inhibiting the development of M.incognita,and its disease resistance mechanism needs to further dig deeper at the molecular level.2.Through the transcriptome sequencing of the roots of the resistant and susceptible watermelons at different stages after infection with M.incognita,an average of 45,386,159 Clean reads were obtained for each sample.Unigene functional annotation was performed after assembly.20,156 Unigenes were annotated to functional databases such as GO,KEGG,and COG.A total of 2,942 differentially expressed genes(DEGs)related to the M.incognita were obtained through analysis DEGs of the resistant and susceptible watermelons,of which 1194 were specifically expressed in ‘hongzi watermelon' and 958 were specific in 'M16'.The bioinformatics analysis of these DEGs showed that the related processes involving nematode resistance include active oxygen clearance,cellulose,lignin,cloth synthesis,and ABA signaling.In these processes,the expression of many key genes was positively correlated with resistance to M.incognita.In the early stage of nematode infection,the genes related to cellulose,lignin,and phenylpropane synthesis in hongzi watermelon' started to be expressedimmediately.The thickening of cell walls effectively inhibited the infection of nematodes;At the critical and late stages of the colonization of M.incognita,the expression levels of related genes such as transcription and protein regulation,ABA signaling,and reactive oxygen species scavenging in ‘ hongzi watermelon' increased,and they are involved in the defense against nematodes.The synthesis-related genes of the key insect-resistant secondary metabolite DIMBOA were consistently inhibited in 'M16'after infection with M.incognita,making plants susceptible to disease.There are also some key genes whose expression is negatively correlated with resistance to M.incognita.For example,'M16' after infection with M.incognita,photosynthetic process-related genes are abundantly expressed,and this process may be hijacked by nematodes to facilitate the growth and development of nematodes,and causes plants to get sick.The qRT-PCR method was used to verify the transcriptome results,demonstrated the consistency of the two results.3.We compared the effects of watermelon growth and root-knot nematode infestation on the resistant and the susceptible watermelon after red-light treatment,and found that:The resistant and sensitive watermelon plants infected by the nematodes surpass the normal plants from the plant height,the shoot fresh weight,and the root fresh weight,after the red-light fills at night.The red-light treatment also reduced the root knot index of the plant.The preliminary mechanism of red-light induced watermelon resistance to M.incognita was studied by measuring the activity of protective enzyme related to watermelon root resistance.The activities of phenylalanine ammonia-lyase(PAL)and peroxidase(POD)of the two materials were significantly higher than those of the control,and the activity of superoxide dismutase(SOD)was significantly reduced,but the PAL of 'hongzi watermelon'was found.The activities of POD,POD and SOD were all greater than that of 'M16';the activity of polyphenol oxidase(PPO)did not change significantly.The results showed that red-light treatment activated the protective enzymes related to resistance in watermelon,inhibited the normal development of M.incognita,and alleviated the harm of southern root knot nematode to watermelon.