Warren E. Kronstad

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).

Breadmaking quality of selected durum wheat genotypes and its relationship with high molecular weight glutenin subunits allelic variation and gluten protein polymeric composition.

ABSTRACT Twenty-seven durum wheat genotypes originating from different geographical areas, all expressing LMW-2 at Glu-B3, and five bread wheats were evaluated for flour mixing properties, dough physical characteristics, and baking performance. Gluten polymeric composition was studied using size-exclusion HPLC of unreduced flour protein extracts. As a group, durum wheats had poorer baking quality than bread wheats in spite of higher protein and total polymer concentrations. Durum wheats exhibited weaker gluten characteristics, which could generally be attributed to a reduced proportion of SDS-unextractable polymer, and produced less extensible doughs than did bread wheats. However, substantial variation in breadmaking quality attributes was observed among durum genotypes. Better baking performance was generally associated with greater dough extensibility and protein content, but not with gluten strength related parameters. Extensibility did not correlate with gluten strength or SEHPLC parameters. Genotype...

Expression and inheritance of tolerance to waterlogging stress in wheat

Approximately 10 million hectares of wheat (Triticum aestivum L.) globally experience medium toserious waterlogging. The inheritance of waterloggingtolerance was determined in reciprocal crosses ofthree tolerant (Prl/Sara, Ducula and Vee/Myna), andtwo sensitive (Seri-82 and Kite/Glen) spring breadwheat lines. Parents, F1, F2, F3, and backcrossgenerations were studied under field conditions in Cd.Obregon, State of Sonora, Mexico. Flooding was appliedwhen plants were at the three-leaf and first-internodestages. Basins were drained after 40 days of flooding.Leaf chlorosis was used as a measure of waterloggingtolerance. The sensitive by sensitive cross, Seri-82 × Kite/Glen, showed the highest mean values forpercentage leaf chlorosis and area under chlorosisprogress curve (AUCPC), and the lowest mean values forplant height, biomass, grain yield, and kernel weight.The F3 of the cross between the two tolerant parentsDucula and Vee/Myna had the lowest mean values forpercentage leaf chlorosis and AUCPC, and the highestmean values for plant height, biomass, and grainyield. The expression of waterlogging tolerance wasnot influenced by a maternal effect. The F1 hybridswere intermediate for leaf chlorosis, indicating thattolerance was additive. Quantitative analysis alsoindicated that additive gene effects mainly controlledwaterlogging tolerance in these crosses. Segregationratios of F3 lines indicated that up to four genescontrolled waterlogging tolerance in these crosses,with two genes adequate to provide significanttolerance. Early-generation selection for tolerancewould be effective in these populations.

Associations and genetics of three components of slow rusting in leaf rust of wheat

SummaryForty F6 lines, the two parental lines, and a susceptible check cultivar of wheat (Triticum aestivum L.) were inoculated in the young flag leaf stage with leaf rust (Puccinia recondita f.sp. tritici) and evaluated for latent period, receptivity, and uredinium size in a greenhouse experiment. Genotypic (rg) and phenotypic (rp) correlations between latent period and uredinium size were −0.81 and −0.62, respectively. A negative correlation (rg=−0.50, rp=−0.41) was found between latent period and receptivity and a positive correlation (rg=0.28, rp=0.26) between uredinium size and receptivity was found. Area under the disease progress curve (AUDPC) and final rust severity (FRS) obtained from a subsequent field study with common entries were negatively correlated with latent period and positively correlated with uredinium size. Correlations of receptivity with both AUDPC and FRS were not significant. The distributions of F6 family mean uredinia size and latent period were continuous between slow rusting and fast rusting parents: however, the distribution for receptivity was discrete. Narrow-sense heritability estimates were 63%, 57%, and 47% for uredinium size, latent period, and receptivity, respectively. Estimates of the minimum number of effective factors were three for latent period and three or four for the uredinium size and receptivity. The components are controlled by closely linked genes or due to pleotropic effects of the same gene.

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.

COMPORTAMIENTO AGRONOMICO Y DE CALIDAD DE VARIEDADES DE TRIGO CHILENAS SEMBRADAS EN EL NOROESTE DEL PACÍFICO, ESTADOS UNIDOS.

Cinco cultivares de trigo de pan fueron seleccionados en el presente estudio, los cuales representaban diferentes fuentes de variacion genetica, los cuales se diferenciaron por habito de crecimiento, caracteristicas agronomicas y de calidad. El objetivo del trabajo fue evaluar el comportamiento de diferentes fuentes de germoplasma cuando son sembrados en condiciones ambientales similares. Trigos provenientes de Estados Unidos (Kansas y Oregon) y de Chile fueron evaluados bajo la condicion ambiental del noroeste del Pacifico en los Estados Unidos (Corvallis, Oregon, 44° 30?N, 123° 30?W). Los resultados mostraron diferencias significativas para fecha de espigadura, altura de planta, peso de grano y rendimiento en grano. No se observaron diferencias para indice de cosecha. Los materiales chilenos fueron mas tardios en espigar y superiores en rendimiento. Para parametros de calidad (peso de grano, dureza de grano, volumen de sedimentacion y proteina del grano), el trigo de Kansas fue superior a los trigos chilenos.