Anatomy of Rootstocks and Scions in Four Pine Species

Abstract

When performing grafts, it is thought that by using plants of the same species the engraftment rate will be high; when the above is not fulfilled, the grafter, type of graft or the origin of the scions is blamed, but the anatomy of the parts forming the graft is not considered. The aim of this study was to evaluate the anatomy of four pine species used as rootstock and scion to define which species to use as rootstock based on cambium shape and bark thickness. Before grafting, 2-cm stem fractions were cut from plants that were used as rootstocks and scions. The evaluated species were Pinus patula, P. greggii, P. leiophylla and P. teocote. Cuts of 10 μm in thickness were made to determine bark and xylem thickness. Photographs were also taken with a photomicroscope to observe the "shape" of the vascular cambium. The experimental design was completely randomized with a 4x2 factorial arrangement, using 12 measurements as the sample size with four replicates. P. patula had greater bark thickness, while P. leiophylla obtained the greatest xylem thickness. In the images of the anatomical cuts, it was determined that the vascular cambium is continuous for all the species both in rootstock and in scions, but it is only circular in the P. teocote and P. leiophylla rootstocks, and the P. leiophylla scions did not present this feature. Based on the anatomy of the cambium, P. greggii, P. patula and P. teocote scions have greater possibilities of engraftment if they are grafted onto P. teocote and P. leiophylla because the cambium is circular. Tissue anatomy is one of the areas that must be known before making grafts in order to make appropriate decisions regarding the materials to be used.

Interspecific grafting of Pinus patula

“…The highest average value was obtained with the rootstocks of the same species (13 cm), while with P. pseudostrobus, P. ayacahuite, and P. hartwegii, it recorded lower growth differences (30, 78, and 90%, respectively) (Table 2). These results match other intraspecific grafting experiments, where a better response was obtained, as a consequence of the anatomical and histological affinity of the parts of the graft (Castro-Garibay et al, 2017).…”

“…Both species belong to the same subgenus, but to a different subsection. This situation shows that a successful graft is more difficult in some pine species, perhaps as a result of factors related to the cambium characteristics and their internal conduction structures (Castro-Garibay et al, 2017). P. ayacahuite rootstocks recorded the lowest survival rate (Figure 1G).…”

“…In addition, it is highly responsive when cut, which could favor the "succsess" percentage. Consequently, this species could be potentially used as rootstock for P. patula, as a result of the circular and continuous shape of its vascular cambium (Gernandt and Pérez-de la Rosa, 2014;Castro-Garibay et al, 2017). No information on P. patula grafts has been documented on these two rootstock species; therefore, trials to determine its influence on the scion through their interaction must be carried out (Han et al, 2019).…”

“…Low-height grafts can be kept in asexual seed orchards, facilitating their management and cone harvesting ( Jayawickrama et al, 1991). Grafting of P. patula on P. radiata resulted in a lower growth; however, strobile production did not diminish (Castro-Garibay et al, 2017).…”

“…In this case, the survival of the first graft was higher on the hybrid. This type of grafts increases productivity, the capacity to adapt to different environments, and the resistance to pests, diseases, and stress caused by abiotic factors (drought, salinity, excess, or deficit of water); in addition, it accelerates or increases fruiting, improves graft compatibility, or promotes a smaller size that favors the harvesting of cones in asexual seed orchards (Castro-Garibay et al, 2017;Han et al, 2019). In Mexico, grafting has the potential to seek favorable combinations and to improve the compatibility between pine species, because 49 (40%) out of the approximately 120 species of the world can be found in its territory (Gernandt and Pérez-de la Rosa, 2014).…”