# Behavior of Different Grafting Strategies Using Automated Technology for Splice Grafting Technique
###### Abstract
Despite being a relatively recent technique, the splice grafting process has developed exponentially, especially when applied to solanaceae, and has been widely described and defined in much of the literature [25; 26; 27; 28; 29]. In the splice graft technique, the rootstock is cut (straight or beveled) below or above the cotyledons. A pronounced cutting angle creates more surface area than a flat cut, allowing more cells on the cut surfaces of the rootstock and scion to be in contact and, thus, fuse better. When cutting above the cotyledons, it is necessary to remove the rootstock regrowth throughout the life of the plant, whereas a  
Figure 1: Common grafting methods to join scion and rootstock for solanaceae. Highlights the use of splice grafting technique. It is widely used as it is efficient and easy to execute. 1 Hole grafting, 2 cleft grafting, 3 splice grafting. graft below the cotyledons can facilitate the rooting of the scion because of its proximity to the ground, so that the grafted scion can bridge the rootstock, casting adventitious roots while completely removing the meristemal tissue from the rootstock [30]. The shoot is also bevel-cut with a complementary angle and a stem height that guarantee a similar diameter at the union. Both parts must be placed in close contact, holding together the union with a grafting clip or other passive device that ensures pressure between the cut surfaces of the rootstock and the shoot. One must make sure that the cambium area between the two seedlings is well aligned, ensuring good contact between the shoot and the rootstock's vascular system [28; 31]. One advantage of the splicing method is that it allows grafting with smaller plants, which reduces pre-graft growing times and the space required in the growing chambers [22; 32]. The first recorded splice graft tests were developed with graft tubes in the late 1950s, but these tubes were neither elastic nor had the side opening that they have today [33]. In the early 1990s, elastic tubes were developed and applied, very similar to those used nowadays, and, thus, achieved grafting times 2 to 3 times faster than the conventional method used up until then [34; 35; 36]. To ensure fusing between the plants, in the graft union, one can use a ceramic or bamboo pin fixed inside the stem, glue or adhesive plastic tape, and a clamp or an elastic clip in the form of a tube with or without a side slit [9; 37; 38]. In most countries today, there is standardized use of elastic tube-shaped clips with a longitudinal opening and side wings that facilitate handling and clip opening when positioning (Figure 2). Once the clips are in place, they tighten and fasten the seedlings securely during their healing phase. The use of graft pins has been common in south-east Asian countries but limited to those areas where the grafting clip use is not possible or they are not available, because of the added difficulty involved in the insertion operation. Using grippers is more common for thick stems such as cucurbitaceae; they are also significantly more expensive elements compared to tube-shaped clips. The grippers also need to be removed manually, whereas the tube clips will release by themselves as the plant grows (if they have a longitudinal opening); if they are closed tubes, they are manufactured using a material that expands as the stem thickness increases and degrades naturally over time [39]. Moreover, using tube-shaped elastic clips ensures a smoother grip and more distributed pressures, as well as minimizing water loss from the graft wounds [40]. The use of transparent film around such thin stems makes handling and placement difficult, especially when grafting is carried out manually. The use of instant glue has been adopted in some automated processes [41], or simply to support other grafting techniques to further secure the union [42]. The grafting techniques developed over the last century for vegetable cultivation have been varied and adapted to particular environments, media, and the technical skills available for their application [10].