C. James Peterson

Dehydrin expression and drought tolerance in seven wheat cultivars

rarely receives additional moisture during emergence. The lack of precipitation during seedling emergence The winter wheat (Triticum aestivum L.) producing region of the represents a major cropping risk to producers. ConseU.S. Pacific Northwest (PNW) is subject to periods of water deficit during sowing and grain filling. Improving the genetic adaptation of quently, there is need to improve the genetic tolerance wheat to drought stress represents one of the main objectives of of wheat to drought at the seedling stage. regional breeding programs. One biochemical response to dehydrative Plant breeding efforts to improve drought tolerance stress is the accumulation of a family of proteins called dehydrins, would be aided by the identification of biochemical which are believed to protect membranes and macromolecules against markers associated with improved field performance denaturation. Although previous studies demonstrated the accumulaunder drought conditions. Dehydrins, also known as tion of dehydrins in drought-stressed wheat, little was known about late embryogenesis abundant (LEA) D11 (Dure, 1993) the relation of dehydrin expression to acquisition of drought tolerance proteins represent potential markers. Dehydrins are in specific varieties adapted to the PNW. We characterized dehydrin members of a family of proteins that are expressed after accumulation during the exposure of seven cultivars (‘Connie’, ‘Gene’, ‘TAM105’, ‘Rod’, ‘Hiller’, ‘Rhode’, and ‘Stephens’) to progressive plants are exposed to stresses with a dehydrative compodrought stress in four separate experiments. The objective was to nent. This family of proteins is characterized by the identify differences in the nature or timing of dehydrin expression in presence of a consensus amino acid sequence (EKK these cultivars and to learn whether dehydrin expression was associGIMDKIKELPG) near the carboxy terminus (Close ated with the acquisition of stress tolerance during seedling developet al., 1993). Dehydrins can be detected by means of ment. Expression of a 24-kDa dehydrin was observed in Connie, antibodies prepared against this consensus sequence TAM105, and Gene after 4 d of stress and at subsequent sampling (Close et al., 1993) and have been identified in at least dates while no dehydrins were detected in nonstress control plants. 30 diverse plant species including wheat (Campbell and Dehydrin expression was significantly delayed in the remaining cultiClose, 1997). vars. The presence of this dehydrin was related to acquisition of drought tolerance characterized by a greater maintenance of shoot An association between tolerance to stresses with a dry matter production in Connie, TAM105, and Gene. Although the dehydrative component (drought, freezing, or salinity) role of these proteins remains unknown, their association with stress and the expression of dehydrin proteins has been obtolerance suggests that dehydrins might be used to improve the adaptaserved in some crop species. Houde et al. (1992) found tion to drought. that the expression of a specific dehydrin (WSC120) accompanied the development of freezing tolerance in eight species of Gramineae. Tolerance to chilling temperatures during emergence was correlated with the M wheat-producing regions of the world are expression of a 35-kDa dehydrin in two genetically simisubject to water deficits during some part of the lar cowpea [Vigna ungiculata (L.) Walp] sublines that growing season (Moustafa et al., 1996). The impacts of differed in their expression of this dehydrin (Ismail et al., these water deficits on grain development and yield 1997). Lim et al. (1999) also found a positive association depend on their severity and the stage of plant growth between cold hardiness and a dehydrin protein in Rhoduring which they occur. Seedling emergence is one dodendron. Danyluk et al. (1998) showed that the stage of growth that is sensitive to water deficit. In WCOR410 dehydrin protein accumulated near the Mediterranean environments like the PNW, dry condiplasma membrane during cold acclimation of wheat and tions during emergence and early growth along with low suggested that this accumulation protected the integrity temperatures during winter and high temperatures and of the plasma membrane when plants were subjected increasing water demands at the end of spring, result to stress. Zhu et al. (2000) reported increased expression in low yields because of the inability of plants to produce of dehydrin genes during the development of freezing adequate dry matter (Regan et al., 1992). Many productolerance in a more tolerant barley (Hordeum vulgare ing regions of the world, including the PNW are subL.) cultivar Dicktoo relative to that which occurred in jected to water deficits during the seedling stage since ‘Morex’, a less tolerant variety. Cellier et al. (1998), winter wheat is sown during autumn into dry soil and using two sunflower (Helianthus annuus L.) inbred lines, one tolerant and one susceptible to drought stress, showed a higher accumulation of mRNA transcripts Cesar G. Lopez, Catedra de Mejoramiento Vegetal, Facultad de Ciencias Agrarias, Universidad Nacional de Lomas de Zamora, Ruta 4 corresponding to HaDhn1 and HaDhn2 genes in the Km. 2, Llavallol, 1832, Buenos Aires, Argentina; Gary M. Banowetz, tolerant line that was associated with cellular turgor USDA/ARS, 3450 S.W. Campus Way, Corvallis, OR 97331; C. James maintenance under drought stress. Peterson, Department of Crop and Soil Science, Oregon State UniverAlthough genotypic differences in dehydrin expressity, Corvallis, OR 97331-3002; Warren E. Kronstad (deceased), Department of Crop and Soil Science, Oregon State University, Corvallis, sion have been demonstrated in responses to cold and OR 97331. Received 8 July 2002. *Corresponding author banowetg@ drought tolerance, it is important to study the expression ucs.orst.edu). of dehydrins in relation to changes in leaf water potential when seedlings are exposed to drought. The purpose Published in Crop Sci. 43:577–582 (2003).

Wheat dehydrin accumulation in response to drought stress during anthesis

The winter wheat (Triticum aestivum L.) producing region of the US Pacific Northwest (PNW) is often subject to water deficits at sowing and during grain filling. Improved genetic adaptation of wheat cultivars to drought stress is one objective of breeding efforts in the region. Consequently, there is interest in identifying molecular markers associated with drought tolerance. Dehydrins, a family of proteins that accumulate in response to dehydrative stress, may provide a suitable marker for use in breeding programs. Seven cultivars (Connie, Gene, TAM105, Rod, Hiller, Rhode and Stephens) were evaluated in two experiments in which dehydrin accumulation and their association to stress tolerance during grain filling were characterized during progressive drought stress. A24-kDa dehydrin was present in leaves at each sampling date in all seven cultivars. Quantitative differences in accumulation of this protein were observed between cultivars on the third sampling date (4 d of stress). This differential accumulation was associated with stress tolerance characterized by a lower yield reduction and a lowered rate of decrease in leaf water potential in Connie, TAM105 and Gene. In contrast to leaves, an increased number of dehydrins were observed in grains under stress and non-stress treatments. Despite the number of dehydrins detected, there was no apparent association between drought stress and dehydrin expression in grains. Although the specific role of these proteins remains unknown, their association with stress tolerance suggests that dehydrins have utility in improving adaptation to drought and as markers for drought tolerance.

Identification of Wheat Lines Possessing the 1AL.1RS or 1BL.1RS Wheat-Rye Translocation by Near-Infrared Reflectance Spectroscopy

ABSTRACT Wheat-rye chromosomal translocations, particularly those involving the short arm of rye chromosome 1R, have been used during the past 25 years to instill resistance to plant pathogens and insects and improve the hardiness, adaptation, and yield of wheat. Unfortunately, the presence of the 1AL.1RS or 1BL.1RS rye translocations in wheat has been shown to impart inferior dough handling and baking characteristics. Although numerous analytical techniques (e.g., HPLC, monoclonal antibody tests, high-performance capillary electrophoresis) have been developed for detecting these translocations, the complexity of the analytical procedures restricts their use to research and analytical laboratories. The purpose of this study was to examine the potential of diffuse reflectance near-infrared spectroscopy, a well-accepted technique in the grain industry, for detecting 1RS-containing genotypes. This research used three independent groups of wheat samples, ranging in genetic diversity from sister lines derived ...

Quantitative trait loci analysis for resistance to Cephalosporium stripe, a vascular wilt disease of wheat.

Cephalosporium stripe, caused by Cephalosporium gramineum, can cause severe loss of wheat (Triticum aestivum L.) yield and grain quality and can be an important factor limiting adoption of conservation tillage practices. Selecting for resistance to Cephalosporium stripe is problematic; however, as optimum conditions for disease do not occur annually under natural conditions, inoculum levels can be spatially heterogeneous, and little is known about the inheritance of resistance. A population of 268 recombinant inbred lines (RILs) derived from a cross between two wheat cultivars was characterized using field screening and molecular markers to investigate the inheritance of resistance to Cephalosporium stripe. Whiteheads (sterile heads caused by pathogen infection) were measured on each RIL in three field environments under artificially inoculated conditions. A linkage map for this population was created based on 204 SSR and DArT markers. A total of 36 linkage groups were resolved, representing portions of all chromosomes except for chromosome 1D, which lacked a sufficient number of polymorphic markers. Quantitative trait locus (QTL) analysis identified seven regions associated with resistance to Cephalosporium stripe, with approximately equal additive effects. Four QTL derived from the more susceptible parent (Brundage) and three came from the more resistant parent (Coda), but the cumulative, additive effect of QTL from Coda was greater than that of Brundage. Additivity of QTL effects was confirmed through regression analysis and demonstrates the advantage of accumulating multiple QTL alleles to achieve high levels of resistance.

Unexpectedly Good Soft Wheat Quality from a Hard × Soft Cross

ABSTRACT The soft-grained progeny of a recombinant inbred line (RIL) population was characterized for a comprehensive set of quality traits and associated quantitative trait loci (QTLs). The population was derived from the cross Tubbs (soft grained) × NSA 98-0995 (hard grained) and was grown in two crop years in Corvallis, Oregon. Transgressive segregation was observed for all of the studied traits. Hardness index was significantly correlated with several important traits related to the absorption capacity of the flour for diagnostic aqueous solvents. Five lines with a desired combination of superior soft wheat quality traits were also identified. Fifteen QTLs were detected on nine wheat chromosomes for eight traits. The observed transgressive segregation was useful, because RILs with potentially above average soft wheat quality were unexpectedly identified in this hard × soft cross. The QTLs identified in this study could be useful in marker-assisted selection for future preselection of progeny from Tubb...