RESEARCH ARTICLE OPEN ACCESS Spanish Journal of Agricultural Research 20 (4), e0903, 10 pages (2022) eISSN: 2171-9292 https://doi.org/10.5424/sjar/2022204-19567 INIA-CSIC Early detection of graft-incompatibility in hawthorn (Crataegus azarolus L.) trees on apple, pear, and quince rootstocks Emel Kacal 1 , Oguzhan Caliskan 2 , Gokhan Ozturk 1 , Ibrahim Gur 1 , Hakki Kocal 1 , Omer F. Karamursel 1 , Derya Kilic 2 and María-Ángeles Moreno 3 1 Fruit Research Institute, Isparta, Türkiye. 2 Department of Horticulture, Faculty of Agriculture, Hatay Mustafa Kemal University, Hatay, Türkiye. 3 Department of Pomology, Estación Experimental de Aula Dei-CSIC, 50059 Zaragoza, Spain. iD iD iD iD iD iD iD iD Abstract Aim of study: This study was conducted to determine the usability of some clonal rootstocks of apple (MM 106 and MM 111), pear (Fox 11), and quince (Quince A) for hawthorn trees propagation. Area of study: Fruit Research Institute, Isparta and Hatay Mustafa Kemal University, Hatay, Türkiye. Material and methods: ‘Sultan’ hawthorn cultivar was budded on the following clonal rootstocks: pear Fox 11, quince A, and apple MM 106 and MM 111. Plants of hawthorn seedlings (Crataegus azarolus L.) budded with ‘Sultan’ cv. were used as control. External visual diagnosis of the scion-rootstock graft combinations was performed by observing visual symptoms in budded trees growing in nursery conditions, as well as anatomic and histological investigations of the in- compatibility in the laboratory. Main results: In this study, healthy scion development and callus tissue in the graft region were formed in the seed- ling rootstock as well as on Fox11 and Quince A clonal rootstocks. In contrast, MM 106 and MM 111 apple rootstocks showed incompatibility symptoms, with insufficient scion vigor and unstructured callus tissue development. Research highlights: ‘Tanslocated’ and ‘located’ graft incompatibility symptoms were observed in Sultan/MM 106 and Sultan/MM 111 combinations. Further studies are necessary to confirm the early good compatibility found in nursery conditions, testing the effect of those clonal rootstocks from different species (Fox11 and Quince A) on vigor, yield, and fruit quality traits in orchard conditions. Additional key words: clonal rootstock; histology; vigor; translocated incompatibility; localized incompatibility. Citation: Kacal, E; Calıskan, O; Ozturk, G; Gur, I; Kocal, H; Karamursel, OF; Kılıc, D; Moreno, MA (2022). Early detection of graft-incompatibility in hawthorn (Crataegus azarolus L.) trees on apple, pear, and quince rootstocks. Span- ish Journal of Agricultural Research, Volume 20, Issue 4, e0903. https://doi.org/10.5424/sjar/2022204-19567. Received: 13 May 2022. Accepted: 10 Oct 2022. Copyright © 2022 CSIC. This is an open access article distributed under the terms of the Creative Commons Attri- bution 4.0 International (CC BY 4.0) License. Funding: The authors received no specific funding for this work. Competing interests: The authors have declared that no competing interests exist. Correspondence should be addressed to Oguzhan Caliskan: ocaliskan@mku.edu.tr; caliskanoguzhan@gmail.com Introduction Türkiye is one of the origin areas of hawthorn and con- tains more than 30 hawthorn species (Crataegus spp.) in different ecological regions. These regions have at least one primary species and other secondary or several com- mon species with local genotypes (Ercisli et al., 2015; Caliskan et al., 2016; Donmez & Ozderin, 2019). The hawthorn fruits are commonly consumed either in fresh or processed form such as juice and jam, due to their charac- teristic flavor (astringent, sweet, and floral). In addition, a high content of several macro-and micro-elements, and beneficial effects on health have been reported (Gundogdu et al., 2014; Caliskan, 2015; Wu et al., 2020). The ‘Sultan’ hawthorn cultivar (Crataegus azarolus L.) has been suc- cessfully released due to its large fruit, high eating quality, and rich aroma compounds (Çalışkan et al., 2018; Dursun et al., 2021), reaching high prices in the local markets. It is grown in regular orchards for fresh fruit consumption in the eastern Mediterranean region of Türkiye, and new