*2.1. Plant Material*

Winter triticale cv. "Sekundo" was obtained from the Danko Hodowla Ro´slin Sp. z o.o. (Chory ´n, Poland) plant breeding company. Accession Ak3 of *Aegilops kotschyi* was received by Prof. B. Wojciechowska (Institute of Plant Genetics of the Polish Academy of Sciences, Pozna ´n, Poland; IPG PAS) from a collection of Professor M. Feldman (Weizmann Institute of Science, Rehovot, Israel) and assembled in the genebank of the IPG PAS. All plants were grown and crossed in the greenhouse of the IPG PAS. In the initial study, monosomic addition triticale line (MA2Sk; 2*n* = 43) that carried chromosome 2S<sup>k</sup> derived from triticale-*Aegilops kotschyi* hybrids was used. These plants were crossed with triticale nullisomic plants for chromosomes 2R (N2R, 2*n* = 40); obtained

by Kwiatek et al. [35]. Double monosomic (M2R and M2Sk) F1 plants (2*n* = 42) were identified using GISH, according to Kwiatek et al. [35]. Ditelosomic (Dt2RS and Dt2RL) plants of triticale were generated by Kwiatek et al. [35] by harnessing chromosome fragmentation induced by gametocidal action, in combination with the production of double haploids. Spikes emasculated between April and June of 2018 were used for cross-pollination. The anthers of donor plants were collected, and pollen was transferred onto stigmas by chafing.
