| The bottle gourd(Lagenaria siceraria)is widely grown in tropical and subtropical regions worldwide.Parts of this plant are consumed as a vegetable,and it is used as rootstock for the cultivation of several Cucurbitaceae crops,including watermelon,cucumber,and various melons to improve their disease resistance.However,watermelon grafted with bottle gourd can be severely damaged by viruses,like cucumber green mottle mosaic virus(CGMMV)and zucchini yellow mosaic virus(ZYMV).CGMMV is a notorious threat in cucurbit production.Bottle gourd is very sensitive to CGMMV;also,the virus is seed-borne.Thus,it will be easy to transmit virus to scions,such as watermelon.ZYMV is a widespread virus that causes huge yield losses in cucurbit crops.Utilizing resistance in cultivars or rootstocks is an ideal approach to control viral diseases.Though there is a long history of grafting for bottle gourd,few studies about resistance to viruses on this crop were being reported.In a previous study,we obtained 2444 M3 bottle gourd lines treated by Ethyl Methane Sulphonate(EMS).In the present study,we tried to screen some resistance against CGMMV and ZYMV by mechanical inoculation.After the primary screening,the resistance or high tolerance for some different lines retested under different conditions.The main findings are as follows:1-Multiple responses to be observed for CGMMV infection,including immune 11.38 %-partial resistance 13.91 %-high tolerance 34.00 %-tolerant 33.71 %,and susceptible M3 lines susceptible with 6.99 %,in total 2444 M3 lines bellow 20℃.It meant these M3 lines could be used as materials to research the resistant mechanisms to CGMMV.Although we did not obtain the completed resistance,mutation-induced by EMS still be considered as a practical approach to creating novel resistance to CGMMV.2-The 35 M3 lines were immune to ZYMV in different conditions.We obtained the M4 seeds of312-6 and 177-8 lines and then verified the immunity to ZYMV further.The results were an agreement to M3.It suggested the resistant loci had been homozygous and could be applied in breeding.The 13M3 lines which showed fewer symptoms considered have partial resistance-high tolerance-tolerance to ZYMV.3-In the study,we found in a total of 121 M4 that the incidence CGMMV seed-borne at the seedling stage was 50.41 %.These infected seedlings showed symptoms until 40 days of growth at the control condition.We conclude that this may be useful to reduce losses on bottle gourd by CGMMV as a vegetable.We inoculated 34 individuals,being CGMMV seed-borne,with ZYMV,and detected both viruses at 30 dpi.The results showed CGMMV was undetectable in all tested lines,except for wide-type.We suggested that the inoculation with ZYMV occurred antagonistic to inhibit or eliminate CGMMV seed-borne in these lines.Also,we suggest that these immune lines may have inducing resistant gene/s with antagonistic against both viruses occurred high immunity compared with susceptible lines that showed ZYMV may antagonistic to CGMMV,such led to inhibit CGMMV seed-borne,and made these lines resistant to CGMMV seed-borne.Synergistic may be on the wild-type that showed positive results for both viruses with severity symptoms.We inoculated some of M3,M4 lines,and wild-types with CGMMV firstly,and then ZYMV or ZYMV firstly,and then CGMMV.The results did not show ZYMV in both cases of inoculation,and CGMMV was detected in all the plants.We suggest that antagonism between unrelated viruses(CGMMV,ZYMV)led to inhibit ZYMV multiplication in bottle gourd as new findings to control one virus risk with mixed inoculation at the growth chamber.These findings will help to further research the mechanisms of host defense and breed new resistant varieties to the virus.It has practical value to reduce the loss of yields in cucurbits caused by viruses and damage to the environment by the chemical. |
