Effects Of Nitrogen Nutrition On Infection Of TYLCV And Competitive Displacement Of Invasive Whiteflies,Bemisia Tabaci

Nitrogen nutrition is an indispensable nutrient element for plant growth,but it can also promote the development of insect pests.The whitefly,Bemisia tabaci?Hemiptera:Aleyrodidae?,is an important agricultural pest on many vegetable crops including tomato,it is also the vector of geminiviruses,particularly the genus Begomovirus.Bemisia tabaci is a fast-changing species complex including more than30 cryptic species,among them,Middle East Asia Minor 1?MEAM1?and Mediterranean?MED?are two worldwide invasive species with serious damage to many crops.Nowadays,nitrogen fertilizer is often over-used in tomato production,but the effects of nitrogen nutrition on infection of begomovirus and competitive displacement between cryptic speceies is less known.In this study,we used two tomato cultivars named"Hezuo 903"and"Beiying"to test the effects of nitrogen nutrition on Tomato yellow leaf curl virus?TYLCV?infection and competitive displacement between MEAM1 and MED cryptic species,in order to provide reference for the rational application of nitrogen fertilizer.The main results are as follows:?1?High nitrogen nutrition promotes virus accumulation of TYLCV in tomato,but the result varies with different infection timeWe set three nitrogen nutrition concentrations,low?5 mM?,media?10 mM?and high?15 mM?and used two virus inoculation methods?injection with agrobacterium infectious cloning infiltration and viruliferous whitefly transmission?in the test system.Moreover,the infection time of TYLCV was set either before or after nitrogen application.When tomato plants were treated with different concentrations of nitrogen nutrition for 10 d,then the virus inoculation was performed.The results showed that the heights of tomato plants were significantly affected by nitrogen nutrition treatments,with the order of 10 mM>5 mM>15 mM.Although the infection rate?whitefly vector method?was the lowest in 10 mM treatment,the virus accumulation under this treatment was the highest.When virus inoculation was done first and then followed by nitrogen nutrition treatment after two days,the growth of tomato plants treated with 5 mM nitrogen utrition solution was the best,followed by 10 mM and 15 mM,respectively.However,the relative expression of TYLCV was the highest in the weak-growing tomato plants treated with high concentration of nitrogen nutrition solution,the accumulation of virus always showed following trend,15 mM>10 mM>5 mM,when inoculated with virus for 10 d,20 d,and 30 d respectively.?2?Nitrogen nutrition showed no significant effect on competitive displacement between MEAM1 and MED cryptic species of Bemisia tabaci he competition between MEAM1 and MED was achieved on“Hezuo 903” omato plants treated with two concentrations of nitrogen nutrition solution starting at the ratio of 1:1.The results showed that,no matter which nitrogen concentration?8mM and 16 mM?,MEAM 1 always occupied competitive superiority,the proportion of MEAM 1 in the whole population of whitefies had exceeded 90%in the 4^th eneration,both revealing a trend of replacement to MED.Meanwhile,the gender ratio increased as the rearing process,but there was no significant difference between8 mM and 16 mM nitrogen solution treatment.In addition,the competition experiments were also performed in a plastic house with three treatments:no nitrogen supplement,optimized nitrogen supplement and traditional nitrogen supplement.However,due to complex climate environment,no valuable data were obtained.