Study On The Effect Of Different Exogenous Substances And Rootstock Grafting On The Prevention And Control Of Watermelon Continuous Cropping Obstacle

Watermelon（Citrullus lanatus（Thunb.）Matsum.&Nakai.）is a significant horticultural crop in China and globally,ranking first in melon and fruit crop production in China.However,watermelon is not tolerant of continuous cropping,and this is particularly evident in facility cultivation.The main factor responsible for this obstacle is Fusarium wilt.Grafting is a useful technique for managing watermelon wilt disease.However,the use of common rootstocks like pumpkin and gourd during production can negatively impact the quality of watermelon fruit.Immune induction technology is a valuable method for enhancing plant disease resistance and preventing pest and disease outbreaks.Despite this,its application for controlling watermelon wilt disease in fields with continuous cropping is not well-documented.This article examines the impact of different exogenous substances and rootstock grafting,as well as their combinations,on watermelon wilt resistance,growth and development,fruit yield,and quality in fields that are continuously cropped.The primary findings are summarized below:1.Effect of grafting different rootstocks of watermelon self-cross line’M08’,hybrid combination’M08×ZTC’,wild watermelon germplasm’ZTC’and white seeded pumpkin on watermelon in a continuous crop facility.The study’s results indicate that all rootstocks were effective in reducing the disease index of watermelon fusarium wilt in fields with 12years of continuous cropping.The white seed pumpkin rootstock was found to be the most effective,followed by ZTC.Furthermore,the use of white seed pumpkin,ZTC,and M08×ZTC as rootstocks significantly promoted watermelon growth and increased yield by166.50%,67.70%,and 51.55%,respectively.Grafting watermelon onto ZTC rootstock was found to significantly enhance fruit quality,whereas other rootstock grafting methods led to a decline in quality.As a result,it has been determined that using white seed pumpkin rootstock provides distinct benefits in terms of controlling wilt disease and increasing yield.However,it does come at the cost of reduced fruit quality,making it more appropriate for watermelon cultivation in heavy facility continuous cropping land that has been in use for over 10 years.While ZTC rootstock may not have as strong of a resistance to wilt disease as white seed pumpkin,it still has the potential to enhance fruit quality and is well-suited for producing top-quality watermelons in moderate facility continuous cropping fields lasting between 3 to 8 years.Furthermore,ZTC can also be utilized to cultivate exceptional watermelon cultivars or rootstock varieties.2.Effects of melatonin（MT,root irrigation）,methyl jasmonate（MeJA,root irrigation）,calcium chloride（CaCl₂,leaf spray）and their combinations MT+MeJA（M+M）and MT+MeJA+CaCl₂（M+M+C）on watermelon production in continuous crop fields in facilities.The results indicated that all treatments had a significant positive impact on watermelon production.Specifically,they improved the plant’s resistance to wilt disease,supported growth and development,and increased fruit yield and quality.Among the various treatments tested,the M+M and M+M+C treatments demonstrated superior results in terms of wilt resistance,growth and development,fruit yield,and quality,exhibiting an increase of 67.70%and 72.05%on yield,respectively,as compared to the single exogenous treatment.There was no significant difference between the two,suggesting that different combinations of exogenous substances had a synergistic effect.However,when considering convenience and cost-effectiveness,the M+M treatment proves to be the more suitable option for production,as compared to the M+M+C treatment.3.The effect of applying ZTC as rootstock grafting combined with exogenous resistance induction on watermelon production in continuous cropping facilities.The application of ZTC as rootstock grafting combined with MT,MeJA,CaCl₂,M+M,M+M+C treatments can significantly improve the resistance to watermelon wilt,promote watermelon growth and development,and improve fruit yield and quality.The combination of grafting and exogenous substance induced resistance has a certain superimposed effect on Fusarium wilt resistance,but the effect is not significant,and there is no significant superimposed effect on yield and quality.Although the cost of M+M treatment induced by exogenous substances is more than twice that of grafting,it is superior to ZTC rootstock grafting in improving fruit quality,and is also suitable for the production of high-quality and high-end gift watermelons in medium facility continuous cropping fields（3-8 years）.