Establishing breeding house of superior sandalwood in Gunung Sewu, Indonesia: preserving the 27 selected genotypes grafted onto two types of rootstocks

Ratnaningrum YWN, Faridah E, Utama INS, Prastyo B. 2022. Establishing breeding house of superior sandalwood in Gunung Sewu, Indonesia: preserving the 27 selected genotypes grafted onto two types of rootstocks. Biodiversitas 23: 3488-3497. Developing methods for vegetative propagation of sandalwood (Santalum album Linn.) is important for the mass production of selected genotypes. Previous research has selected the superior genotypes of sandalwood in Gunung Sewu based on seed production, crossing-ability, santalol content and/or the rare alleles characters. This study estimates the grafting compatibility of 27 selected genotypes of sandalwood, which are grafted onto two types of rootstock. In the peak rainy season in February 2021, scions were picked from the 27 genotypes originating from four landraces (Imogiri, Bejiharjo, Bleberan and Petir) in Gunung Sewu. Scions were then grafted onto two types of rootstock using the top-cleft technique. The first rootstock type is the 8 months old seedlings of the red-big-flower sandalwood variant planted in a polybag (Type 1); while the second one is the root-suckers that emerged from horizontal roots (Type 2). Results revealed Petir genotypes as the most surviving scions (100% in Type 2 and 75% in Type 1 rootstock), followed by those originating from Imogiri. All four genotypes originating from Petir (Pt1, Pt2, Pt3 and Pt4) achieved the highest scores in most of the parameters observed. The Type 2 rootstock survived more grafts (57%) compared to those of Type 1 (49%). The number of shoots and the height increment of grafting showed significant differences. The top-cleft grafting technique is considered effective in conserving the superior genotypes of sandalwood and to provide a copy of those genotypes for materials of the crossing units. The use of Petir and Imogiri genotypes as the scions, and the red-big flower variant root-suckers as the rootstocks, are highly recommended for the best grafting success.