Although cold acclimation in cereals involves the expression of many cold-regulated genes, genetic studies have shown that only very few chromosomal regions carry loci that play an important role in frost tolerance. To investigate the genetic relationship between frost tolerance and the expression of cold-regulated genes, the expression and regulation of the wheat homolog of the barley cold-regulated gene cor14b was studied at various temperatures in frost-sensitive and frost-tolerant wheat genotypes. At 18/15°C (day/night temperatures) frost-tolerant plants accumulated cor14b mRNAs and expressed COR14b proteins, whereas the sensitive plants did not. This result indicates that the threshold temperature for induction of the wheat cor14b homolog is higher in frost-resistant plants, and allowed us to use this polymorphism in a mapping approach. Studies made with chromosome substitution lines showed that the polymorphism for the threshold induction temperature of the wheat cor14b homolog is controlled by a locus(i) located on chromosome 5A of wheat, while the cor14b gene was mapped in Triticum monococcum on the long arm of chromosome 2A m . The analysis of single chromosome recombinant lines derived from a cross between Chinese Spring/Triticum spelta 5A and Chinese Spring/Cheyenne 5A identi®ed two loci with additive eects that are involved in the genetic control of cor14b mRNA accumulation. The ®rst locus was tightly linked to the marker psr911, while the second one was located between the marker Xpsr2021 and Frost resistance 1 (Fr1).

and, to some extent, conflicting mechanisms. Traits related to drought resistance, such as small plant size, re-Future climate changes are expected to increase risks of drought, duced leaf area, and early maturity, lead to reduced total which already represent the most common stress factor for stable seasonal evapotranspiration. Prolonged stomatal closure barley (Hordeum vulgare L.) production in Mediterranean areas. It is important, therefore, to evaluate if there are needs of specific allows plants to limit water loss but also reduces dry matter adaptive measures in selecting genotypes for these more stressful production (Karamanos and Papatheohari, 1999). These environments. Our objective was to study diversity of yield perfortraits, however, are associated with a lower yield potential mance under rainfed (R) and irrigated (I) conditions in 89 barley (Fischer and Wood, 1979). Furthermore, assimilate accugenotypes of different origin, growth habit, and year of release, repremulation in the stems before anthesis is advantageous if senting a sample of cultivars grown in Europe. The experiment was drought occurs during the following phases, but it could conducted at Foggia (southern Italy) for 3 yr. For each trial, a water reduce spike weight at anthesis (Slafer and Araus, 1998). stress index (WSI) was calculated on the basis of the daily potential Thus, traits related to drought resistance and to high and actual evapotranspiration in the growing season, estimated by yield potential should be alternatively favored in cereal Thornthwaite's method. The WSI explained most of the variation in breeding programs, based on the ideotype for a target yield (R 2 ϭ 0.89**) among years and treatments. We examined, using the yield vs. WSI regression, the behavior of a given genotype across area and a specific type of stress. According to some trials. The intercept and slope values were used as measures of yield authors, yield in low and high yielding environments potential and adaptability under drought, respectively. Several cultican be considered as separate traits which are not necesvars showing high yield potential and minimal genotype ϫ environsarily maximized by identical sets of alleles (Falconer, ment (GE) interaction were identified. Notably, they were character-1990), consequently plant breeding strategies should be ized by a high slope of the yield vs. WSI regression. Furthermore, different when targeting stress and nonstress environwithin the range of water stress here examined, high yield potential ments (Ceccarelli et al., 1991; Ceccarelli et al., 1998). played a preeminent role in the performance of these barley geno-

Representative, broad and diverse collections are a primary resource to dissect genetic diversity and meet pre-breeding and breeding goals through the identification of beneficial alleles for target traits. From 2,500 tetraploid wheat accessions obtained through an international collaborative effort, a Global Durum wheat Panel (GDP) of 1,011 genotypes was assembled that captured 94–97% of the original diversity. The GDP consists of a wide representation of Triticum turgidum ssp. durum modern germplasm and landraces, along with a selection of emmer and primitive tetraploid wheats to maximize diversity. GDP accessions were genotyped using the wheat iSelect 90K SNP array. Among modern durum accessions, breeding programs from Italy, France and Central Asia provided the highest level of genetic diversity, with only a moderate decrease in genetic diversity observed across nearly 50 years of breeding (1970–2018). Further, the breeding programs from Europe had the largest sets of unique alleles. LD was lower in the landraces (0.4 Mbp) than in modern germplasm (1.8 Mbp) at r2 = 0.5. ADMIXTURE analysis of modern germplasm defined a minimum of 13 distinct genetic clusters (k), which could be traced to the breeding program of origin. Chromosome regions putatively subjected to strong selection pressure were identified from fixation index (Fst) and diversity reduction index (DRI) metrics in pairwise comparisons among decades of release and breeding programs. Clusters of putative selection sweeps (PSW) were identified as co-localized with major loci controlling phenology (Ppd and Vrn), plant height (Rht) and quality (gliadins and glutenins), underlining the role of the corresponding genes as driving elements in modern breeding. Public seed availability and deep genetic characterization of the GDP make this collection a unique and ideal resource to identify and map useful genetic diversity at loci of interest to any breeding program.

Over the past 70 years, the world has witnessed extraordinary growth in crop productivity, enabled by a suite of technological advances, including higher yielding crop varieties, improved farm management, synthetic agrochemicals, and agricultural mechanization. While this ''Green Revolution'' intensified crop production, and is credited with reducing famine and malnutrition, its benefits were accompanied by several undesirable collateral effects (Pingali, 2012). These include a narrowing of agricultural biodiversity, stemming from increased monoculture and greater reliance on a smaller number of crops and crop varieties for the majority of our calories. This reduction in diversity has created vulnerabilities to pest and disease epidemics, climate variation, and ultimately to human health (Harlan, 1972).The value of crop diversity has long been recognized (Vavilov, 1992). A global system of genebanks (e.g., www.genebanks. org/genebanks/) was established in the 1970s to conserve the abundant genetic variation found in traditional ''landrace'' varieties of crops and in crop wild relatives (Harlan, 1972). While preserving crop variation is a critical first step, the time has come to make use of this variation to breed more resilient crops. The DivSeek International Network (https://divseekintl. org/) is a scientific, not-for-profit organization that aims to accelerate such efforts.

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