The winter wheat (Triticum aestivum L.) producing region of the U.S. Pacific Northwest (PNW) is subject to periods of water deficit during sowing and grain filling. Improving the genetic adaptation of wheat to drought stress represents one of the main objectives of regional breeding programs. One biochemical response to dehydrative stress is the accumulation of a family of proteins called dehydrins, which are believed to protect membranes and macromolecules against denaturation. Although previous studies demonstrated the accumulation of dehydrins in drought‐stressed wheat, little was known about the relation of dehydrin expression to acquisition of drought tolerance in specific varieties adapted to the PNW. We characterized dehydrin accumulation during the exposure of seven cultivars (‘Connie’, ‘Gene’, ‘TAM105’, ‘Rod’, ‘Hiller’, ‘Rhode’, and ‘Stephens’) to progressive drought stress in four separate experiments. The objective was to identify differences in the nature or timing of dehydrin expression in these cultivars and to learn whether dehydrin expression was associated with the acquisition of stress tolerance during seedling development. Expression of a 24‐kDa dehydrin was observed in Connie, TAM105, and Gene after 4 d of stress and at subsequent sampling dates while no dehydrins were detected in nonstress control plants. Dehydrin expression was significantly delayed in the remaining cultivars. The presence of this dehydrin was related to acquisition of drought tolerance characterized by a greater maintenance of shoot dry matter production in Connie, TAM105, and Gene. Although the role of these proteins remains unknown, their association with stress tolerance suggests that dehydrins might be used to improve the adaptation to drought.

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In Argentina, maize (Zea mays L.) hybrids selected for silage production and local adaptation are not available for most temperate regions where silage maize can be produced. This study sought maize landraces that could be used as germplasm sources to enhance forage yield and quality in warm temperate areas and emphasized eight landraces not previously selected for grain yield. These were crossed in a diallel mating design and the 28 F1 population hybrids, the eight parental populations, and four commercial hybrids were evaluated in four environments in Argentina for combining abilities and to determine heterotic patterns among germplasm sources, using a biplot diallel analysis. Significant midparent heterosis (MPH) was observed for ear yield (EY), stover yield (SY), and whole plant yield (WY). General combining ability (GCA) effects were significant for EY, SY, and WY. Specific combining ability (SCA) effects were not significant for any trait. The graphical representation offered by biplot analysis allowed a rapid and effective overview of GCA and SCA effects of the populations, their performance in crosses, as well as grouping patterns of similar genotypes. Significant variation among checks was observed for EY and SY. On average, commercial hybrids had greater EY, but lower SY, than landraces and population hybrids. Some landrace crosses showed superior or similar WY than commercial checks, indicating the breeding potential of the evaluated germplasm.Abbreviations: ATC, average tester coordinate; ED, in vitro digestibility of ear dry matter; EY, ear dry matter yield; GCA, general combining ability; GGE, genotype main effect plus genotype 3 environment interaction; INTA, Instituto Nacional de Tecnología Agropecuaria; LAMP, Latin American Maize Project; MPH, midparent heterosis; NIRS, near infrared reflectance spectroscopy; PC, principal component; PC1, first principal component; PC2, second principal component; SCA, specific combining ability; SD, in vitro digestibility of stover dry matter; SY, stover dry matter yield; WD, in vitro digestibility of whole-plant dry matter; WY, whole-plant dry matter yield.

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