Theor Appl Genet (2009) 118:1465–1476 DOI 10.1007/s00122-009-0995-4 123 ORIGINAL PAPER Genes and traits associated with chromosome 2H and 5H regions controlling sensitivity of reproductive tissues to frost in barley Andrew Chen · Jason Reinheimer · Anita Brûlé-Babel · Ute Baumann · Margaret Pallotta · GeoVrey B. Fincher · Nicholas C. Collins Received: 31 October 2008 / Accepted: 13 February 2009 / Published online: 7 March 2009  Springer-Verlag 2009 Abstract Frost at Xowering can cause signiWcant damage to cereal crops. QTL for low temperature tolerance in reproductive tissues (LTR tolerance) were previously described on barley 2HL and 5HL chromosome arms. With the aim of identifying potential LTR tolerance mechanisms, barley Amagi Nijo £ WI2585 and Haruna Nijo £ Galleon populations were examined for Xowering time and spike morphology traits associated with the LTR tolerance loci. In spring-type progeny of both crosses, winter alleles at the Vrn-H1 vernalization response locus on 5H were linked in coupling with LTR tolerance and were unexpectedly asso- ciated with earlier Xowering. In contrast, tolerance on 2HL was coupled with late Xowering alleles at a locus we named Flt-2L. Both chromosome regions inXuenced chasmogamy/ cleistogamy (open/closed Xorets), although tolerance was associated with cleistogamy at the 2HL locus and chasmog- amy at the 5HL locus. LTR tolerance controlled by both loci was accompanied by shorter spikes, which were due to fewer Xorets per spike on 5HL, but shorter rachis inter- nodes on 2HL. The Eps-2S locus also segregated in both crosses and inXuenced spike length and Xowering time but not LTR tolerance. Thus, none of the traits was consistently correlated with LTR tolerance, suggesting that the tolerance may be due to some other visible trait or an intrinsic (bio- chemical) property. Winter alleles at the Vrn-H1 locus and short rachis internodes may be of potential use in barley breeding, as markers for selection of LTR tolerance at 5HL and 2HL loci, respectively. Introduction Frost at anthesis or early grain Wll can damage cereal crops by causing Xoret sterility or shriveled grains. Frost damage to reproductive tissues is most limiting in areas experienc- ing subtropical/Mediterranean climates such as in Australia, West Asia and North Africa, where cereals mature during winter when conditions are most favorable for growth but occasional night time frost events in the order of ¡1 to ¡5°C occur (Single 1985; Fujita et al. 1992; Reinheimer et al. 2004). In these areas, the choice of sowing date is constrained both by the higher probability of frost early in the season and by the hot and dry conditions that typically limit growth late in the season. In temperate regions, mid to late spring freezes may also cause spike damage to winter wheat crops which Xower during spring and summer (Livingston and Swinbank 1950; Paulsen and Heyne 1983; Cromey et al. 1998; Whaley et al. 2004). Agronomic prac- tices, such as clay delving or optimization of sowing time, can be employed to reduce frost damage at Xowering Communicated by J. Snape. Electronic supplementary material The online version of this article (doi:10.1007/s00122-009-0995-4) contains supplementary material, which is available to authorized users. A. Chen · J. Reinheimer · U. Baumann · M. Pallotta · G. B. Fincher · N. C. Collins (&) Australian Centre for Plant Functional Genomics (ACPFG), School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA 5064, Australia e-mail: nick.collins@acpfg.com.au J. Reinheimer Plant Breeding Unit, Australian Grain Technologies, Roseworthy Campus, Roseworthy, SA 5371, Australia A. Brûlé-Babel Department of Plant Science, University of Manitoba, 66 Dafoe Road, 222 Agriculture Building, Winnipeg, MB R3T 2N2, Canada