Hi, this is Pinky Devi Ph.D. student in Dr. Carol Miles vegetable horticulture program at Washington state. About one of our vegetable grafting research study that is optimizing watermelon grafting to enhance grafting efficiency. Grafting has become a common practice for watermelon production worldwide to mitigate again biotic stresses like soil-borne diseases and abiotic stresses like temperature extreme soil salinity acceptor.
Verticillium wilt is an example of soil-borne disease that decreases the production of watermelon all over the world. This disease is caused by the fungi called Verticillium dahlia that can persist in the soil for up to 14 years and it has over 400 hostile species. In case of watermelon there is no genetic resistance and also there is no effective chemical control method. These two pictures are from a field which is necessarily infested with verticillium dahlia where you can see almost that non-grafted watermelon plant and there is a very healthy grafted watermelon plant, and these two pictures were taken from the same field on the same day. Therefore, to take advantage of the grafting in North America, the most commonly used grafting method is one cutting cotyledon grafting method. In this method first we cut the rootstock at about 60-degree angle with one cotyledon remaining on the plant. The angled cut should also remove the apical meristem in the remaining cotyledon. Then we cut the cyan at about 60-degree angle below the cotyledon where its diameter matches that of the rootstock. Then we join the two cut stems together with a commercially available grafting clip. For additional support, we can put a plastic straw. However, the watermelon grafting technique is not widely adopted in the wide United States due to two reasons, one high labor cost, second the cost of the grafted plants.
One of the major concern related to this problem is root stock regrowth. If we do not remove the meristematic tissue lies below at the base of the remaining catheter that eventually grow as re-growth and compete with the scion for water and nutrient and eventually that of the grafted plants. To avoid this issue, we need to scout the plants in the greenhouse and as well as in the field, which is very time consuming and labor-intensive method.
Therefore, our study objective was to develop splice grafting technique for watermelon where both the cotyledons are removed to increase grafting efficiency and reduce cost of the grafted plants. However, the major concern with a splice grafting technique for watermelon is the low survival rate. Therefore, we tested the external application of sucrose in combination with commercially available anti-transparent solution applied to the root stock seedling before grafting to see if it can increase the survival of the splice grafted watermelon plants. In this method after rootstocks are treated with the treatments, we first cut the rootstock at about 63-degree angle just below both the cotyledons then we cut the cyan and about 60-degree angle below both the cotyledons then we join both the cut stem together with a commercially available grafting clip. Immediately after grafting, we placed our grafted plants in a healing chamber with control environment following a site-specific protocol. We recorded the survival of these splice grafted plant still 21 days after grafting and found that plants that received sucrose in combination with anti-transparent solution that had higher survival which was 91 percent. As compared to the plants which were only treated with the water was 25 percent.
More study we can conclude that Drench application of sucrose solution in combination with commercial anti-transparent solution to root stock seedlings before grafting can definitely increase the survival of splice grafted watermelon. Splice grafting technique can increase the grafting efficiency as it takes lesser time as compared to the commonly grafting techniques that used for watermelon production. Splice grafting could also potentially decrease the cost of the grafted plants as would as it would eliminate the extra attention that is required to eliminate the root stock rate growth which eventually decreased the labor cost that’s involved in watermelon grafting technique.
In 2019 we also evaluated the fruit maturity and quality of splice grafted in one cut lead and grafted watermelon at Hermiston agriculture resource and extension center and found that the splice gifted watermelon retained the same food quality as one cotyledon grafted watermelon and non-grafted watermelon. However more studies are required in the field setting under varying environmental conditions. If you want to know more about this whole study you can go through our publication in Hort Science which I have given details here. This research study was conducted at WSU Mount Vernon northwestern research and extension center, and it was funded by United States department of agriculture specialty crop resource initiative grant. Thank you for watching this video.