Vernalization requirement is a key component in determining the overall fitness of developmental patterns of barley to its environment. We have used previously reported markers and spring-sown growth habit nursery to characterize the genotypes of barley germplasm in an applied barley breeding ground to establish a baseline of information required to understand the relationship between adaptation of autumn-sown barley germplasm in diverse regions with warm (W), moderate (M), or cold climates (C). This study revealed that twenty entries were detected with the presence of the vernalization critical region in VRN-H1 locus and complete presence of the three geneclusters ZCCT-Ha, -Hb, and -Hc in VRN-H2 locus represented as genotype vrn-H1/Vrn-H2 (V1w/V2w). Of these genotypes, 17 entries showed winter growth habit whereas the remaining three revealed facultative growth habit indicating reduced vernalization requirements possibly due to VRN-H3 and photoperiod sensitivity loci as compared to the landmark winter growth habit entries in this group. Twenty-four entries were detected with the lack of vernalization critical region in VRN-H1 locus but complete presence of the three geneclusters ZCCT-Ha, -Hb, and -Hc in VRN-H2 locus represented as genotype Vrn-H1/Vrn-H2 (V1s/V2w). However, only half of these germplasms were identified with spring growth habit in spring-sown nursery, and the rest of the germplasms in this group revealed facultative growth habits due to possible variation in the length of deletion in VRN-H1. Four germplasms showed vernalization insensitive phenotype due to the lack of a functional ZCCT-Ha and/or ZCCT-Hb alleles in VRN-H2 and the deletion in the vernalization critical region of VRN-H1. These germplasms revealed acomplete spring type growth habit. Only one entry showed reduced vernalization requirement solely due to the deletion in functional ZCCT-Hb allele in VRN-H2 and not due to the deletion in the vernalization critical region of VRN-H1. 1. Introduction Increases in yield and adaptation of cereals rest on life cycle adjustments to environmental constraints explained, in part, by the transition from vegetative to reproductive growth, flowering, and maturity [1, 2]. Optimal fitness of developmental patterns to the environment takes place when the crop utilizes most of inputs from the environment on the one hand and on the other hand escapes from deleterious effects of the adverse environmental conditions (i.e., frost stress and late maturity) [3], [4] leading to superior crop performance and yield potential [3]. Barley is a temperate
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