ORIGINAL PAPER Cold-hardening of winter triticale (x Triticosecale Wittm.) results in increased resistance to pink snow mould Microdochium nivale (Fr., Samuels & Hallett) and genotype-dependent chlorophyll fluorescence modulations Gabriela Gole ˛biowska Maria We ˛dzony Received: 23 December 2008 / Revised: 24 April 2009 / Accepted: 22 July 2009 / Published online: 28 August 2009 Ó Franciszek Go ´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako ´w 2009 Abstract The resistance of triticale (x Triticosecale Wittm.) to infection of snow mould Microdochium nivale (Fr., Samuels & Hallett) was examined under different temperature pre-treatment regimes. The results of labora- tory ‘‘cold chamber’’ resistance tests correlated with the breeders’ report from field experiments. Studied genotypes differed substantially in their resistance to infection. Two cultivars: ‘Magnat’ (susceptible) and ‘Hewo’ (relatively resistant) were further studied as a plant model to test the role of pre-hardening and cold-hardening induction of resistance expression. Both model cultivars were suscep- tible to M. nivale infection without cold pre-treatment and gained genotype-depended level of resistance after 4 weeks treatment at 4°C, moreover the resistance grew gradually. Simultaneously to the resistance tests, the measurements of chlorophyll fluorescence parameters were taken. The results showed that higher vitality index Rfd of cold- hardened triticale seedlings correlated with increased pink snow mould resistance while differences in other parame- ters of fluorescence were not distinctly significant. Estab- lishment of Rfd in 4 weeks hardened triticale seedlings could be used for a large scale screening of breeding material in order to select potentially resistant genotypes. Such analyses have not been reported for triticale before. Keywords Winter triticale  Microdochium nivale  Cross-tolerance  Cold-hardening  Chlorophyll fluorescence Introduction According to regular reports, pink snow mould resulted from Microdochium nivale infection is one of the most serious diseases of winter cereals and grasses in moderate and cold climatic areas (Tronsmo et al. 2001; Pron ´czuk et al. 2003). The resistance of the most important cereal cultivars to this pathogen is not satisfactory. Moreover, there is no efficient crop protection strategy against this pathogen, fungicides used so far are very harmful to the environment and many of them are recently banned in Europe. M. nivale infects also the man-made hybrid cereal, winter triticale (x Triticosecale Wittm.) (Cichy and Mac ´kowiak 1993; Wakulin ´ski and Chelkowski 1993). Triticale genome is composed of R genome of rye (Secale cereale) and A and B genomes of wheat (Triticum sp.), although fragments of D wheat genome are sometimes present as translocations (Ryo ¨ppy 1997). The economic importance of triticale has been growing fast but both quality and quantity of its yield are regularly under the threat of pathogenic infection. According to Nakajima and Abe (1996); Ergon et al. (1998) and Tronsmo et al. (2001), cold-hardening is the most important factor switching on cereal defence respon- ses to M. nivale infection. The maximal resistance was detected exclusively in cold-hardened plants (Ho ¨mmo 1996; Laroche et al. 1997) but genotypes differ in their ability to obtain cold-induced resistance expression (Ho ¨mmo 1994; Tronsmo 1994; Pulli et al. 1996). Relation between frost resistance and snow mould resistance remains indistinct (Ergon et al. 1998). Despite several preceding Communicated by B. Barna. G. Gole ˛biowska (&)  M. We ˛dzony Institute of Plant Physiology, Polish Academy of Sciences, Niezapominajek 21, 30-239 Krakow, Poland e-mail: golebiowska@ifr-pan.krakow.pl G. Gole ˛biowska  M. We ˛dzony Pedagogical University of Cracow, Podchora ˛ _ zych 2, 30-084 Krakow, Poland 123 Acta Physiol Plant (2009) 31:1219–1227 DOI 10.1007/s11738-009-0357-5