Quantification of the drought tolerance of wheat (Triticum spp.) genotypes is of interest to physiologists investigating traits associated with adaptation to dry conditions and to breeders developing cultivars for dry areas. The objective of this research was to assess drought tolerance in terms of minimal depression of yield in dry compared with favorable environments (drought susceptibility index, S) with a superiority measure (P) based on the sum across environments of the mean‐squared differences between genotype yield and the maximum yield in each environment. Twenty‐five hexaploid (T. aestivum L.) and 16 tetraploid (T. turgidum L. var. durum) wheat genotypes were grown in separate experiments under dry and irrigated conditions on a Swinton loam (Aridic Haploboroll) soil. There was year‐to‐year variation in S within genotypes and changes in genotype ranking within years. No single cause for this variability was identified. The S index did not differentiate between potentially drought‐tolerant genotypes and those that had low yield potential from other causes. P was correlated with mean yield in both the hexaploid (−0.96**) and tetraploid (−0.94**) groups (both significant at P = 0.01). However, P was strongly influenced by high yield environments; this was alleviated by standardization of the yield data. Although P appears to be a possible method to quantify average superiority of genotypes across locations, its suitability requires further assessment. There seems to be no simple technique to quantify drought tolerance that would assist physiologists in choosing genotypes in which to evaluate putative drought tolerance mechanisms.

Wheat is Canada's largest crop with most of the production in the western Canadian prairie provinces of Manitoba, Saskatchewan and Alberta. Since wheat production started in western Canada, over 100 yr ago, market classes of hexaploid spring bread wheat (Triticum aestivum L.) were the dominant type of wheat, although production of durum wheat [Triticum turgidum L. ssp. durum (Desf.) Husn.)] has grown significantly over this period, and hexaploid winter wheat was grown on a relatively small portion of the wheat area. Within hexaploid wheat there has been diversification into a number of market classes based on different end-use quality criteria. The predominant spring bread wheat class has been the Canada Western Red Spring (CWRS) class. A few cultivars were grown extensively over a long period of time, such as the CWRS wheat Thatcher, which was the dominant cultivar from 1939 to 1968, and Kyle, which was the leading Canada Western Amber Durum (CWAD) cultivar from 1988 to 2004. Other cultivars dominated particular wheat classes for many years such as Glenlea, Canada Western Extra Strong (CWES) spring wheat and Norstar, Canada Western Red Winter (CWRW) wheat. The reasons for newer cultivars replacing older cultivars include improvements in grain yield, resistance to stem rust (Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E. Henn.), leaf rust (Puccinia triticina Eriks.), and other diseases, resistance to wheat stem sawfly (Cephus cinctus Nort.), enhanced end-use quality, and other agronomic characteristics such as lodging resistance. Cultivars with improved pest resistance were often rapidly adopted, such as Thatcher and Selkirk, in response to the stem rust epidemics in the 1930s and 1950s, and Rescue and Lillian in response to wheat stem sawfly epidemics in the 1940s and 2000s. Improved grain yield led to the rapid increase of many cultivars including Marquis in the 1910s and 1920s, Neepawa, Wascana and Wakooma in the 1970s, AC Barrie in the 1990s, and Superb in the 2000s. Increased breeding efforts recently have led to many more highly adapted cultivars and subsequently more diverse wheat production. Wheat classes and cultivars in the prairies continue to improve and diversify to meet the challenges of the marketplace and the production concerns of wheat growers. Key words: Rust, fusarium head blight, cereal quality, protein

. 1990. Nitrogen and phosphorus uptake, translocation, and utilization efficiency of wheat in relation to environment and cultivar yield and protein levels. Can. J. Plant Sci. 70: 965-9'7'7 . A field study was carried out in four environments to determine the effects of available water and cultivar on N and P uptake, translocation, and utilization efficiency of wheat (Triticum spp.) cultivars with varying grain yield potential and protein concentration.Two common wheat (Z aestivum L.) cultivars, Neepawa and HY320, and two durum (7. turgidumL. var. durum) cultivars, DT367 and Wakooma, were studied. HY320 and DT367 had highel grain yield potentials and lower protein concentrations than Neepawa and Wakooma. Total plant N and P uptake was proportional to available water, and was strongly associated with dry matter accumulation. From 6'7 to 102% of plant N and 64-1 00 % of P present at harvest had been accumulated by anthesis. Postanthesis uptake of N and P was greater under moist than under dry environments. There were few cultivar difTerences in uptake ofN or P, and any differences observed were related to variations in plant dry matter. Nitrogen harvest index ranged from 71 to 85% and P harvest index ranged from 8l to 93%. Both indices responded to environment in the same way as grain harvest index; there were no cultivar differences for either N or P harvest index. From 59 to 79% of N and 75 to 87% of P present in vegetative tissues at anthesis was translocated to the grain; translocation did not vary among cultivars. The efTiciency of utilization of N and P in production of harvest biomass and grain was directly proportional to water availability and was greater in the high yield cultivars HY320 and DT367 than in Neepawa and Wakooma. There was no evidence that selection for N uptake, translocation. or utilization efficiency would be useful in wheat breeding.

No abstract

Adult plant resistance (APR) to leaf rust and stripe rust derived from the wheat (Triticum aestivum L.) line PI250413 was previously identified in RL6077 (=Thatcher*6/PI250413). The leaf rust resistance gene in RL6077 is phenotypically similar to Lr34 which is located on chromosome 7D. It was previously hypothesized that the gene in RL6077 could be Lr34 translocated to another chromosome. Hybrids between RL6077 and Thatcher and between RL6077 and 7DS and 7DL ditelocentric stocks were examined for first meiotic metaphase pairing. RL6077 formed chain quadrivalents and trivalents relative to Thatcher and Chinese Spring; however both 7D telocentrics paired only as heteromorphic bivalents and never with the multivalents. Thus, chromosome 7D is not involved in any translocation carried by RL6077. A genome-wide scan of SSR markers detected an introgression from chromosome 4D of PI250413 transferred to RL6077 through five cycles of backcrossing to Thatcher. Haplotype analysis of lines from crosses of Thatcher × RL6077 and RL6058 (Thatcher*6/PI58548) × RL6077 showed highly significant associations between introgressed markers (including SSR marker cfd71) and leaf rust resistance. In a separate RL6077-derived population, APR to stripe rust was also tightly linked with cfd71 on chromosome 4DL. An allele survey of linked SSR markers cfd71 and cfd23 on a set of 247 wheat lines from diverse origins indicated that these markers can be used to select for the donor segment in most wheat backgrounds. Comparison of RL6077 with Thatcher in field trials showed no effect of the APR gene on important agronomic or quality traits. Since no other known Lr genes exist on chromosome 4DL, the APR gene in RL6077 has been assigned the name Lr67.

Germination of wheat (Triticum spp) kernels prior to harvest reduces the economic value of grain . Losses attributable to pre-harvest sprouting could be reduced by developing sprouting tolerant (ST) cultivars if heritable variation exists for this trait . Objectives of this study were to compare various assays that measure ST, seed dormancy (SD), and alpha-amylase activity, and to divide the total variation for these traits into parts relating to genetic differences, genotype-year interaction, and residual variation . Twenty-six hexaploid wheat genotypes (Triticum aestivum L.) (eight red-kennelled and eighteen white-kernelled), and three white-kernelled tetraploid wheat genotypes (T turgidum L . var. durum) were subjected to various assays that measure ST, SD, and alpha-amylase production using artificial wetting treatments . Genotype effects accounted for 44% to 90% of the phenotypic variation . The genetic component of variation, when expressed as a proportion of the total variation, was 2 to 6 times greater than the proportion attributable to error . Heritability expressed on a genotype mean basis was highly significant for all variables and ranged from 0.59 to 0 .93 . The phenotypic correlation for any ST or SD trait or alpha-amylase activity measured on samples collected at two dates (Tl and T2 = T1 + 14 days) was highly significant and positive . The phenotypic correlation matrix among assays performed on the unthreshed spikes, germination tests and alpha-amylase activity at both Tl and T2 were positive and highly significant . Increased ST is an attainable objective, and direct selection for ST using an artificial wetting treatment is an appropriate breeding strategy .

Wheat functions as a complex wellintegrated organism with adaptation to many environments. Traits of wheat may be correlated to each other in a positive or a negative manner. The direction of the correlation is independent of breeding objectives and may change from one production environment to another. Grain yield is correlated positively with time to maturity in environments without terminal stress. The negative correlation between grain yield and grain protein concentration exemplifies an undesirable relationship in a wheat quality type in which protein concentration is positively correlated with bread loaf volume. However, this same correlation has an advantage to those end-products that are favored by low protein concentration such as confectionary products. To shift the negative correlation between grain yield and protein concentration requires assembling a more photosynthetically efficient, nitrogen-use efficient and\or water-use efficient genotype in combination or separately. Simultaneous selection for quantitative and quality traits is a breeding strategy, which with the inclusion of marker assisted selection, can shift undesirable correlations.

. 2002. Physiological characteristics of recent Canada Western Red Spring wheat cultivars: Yield components and dry matter production. Can. J. Plant Sci. 82: 299-306. Genetic yield gains have been difficult to achieve within the Canada Western Red Spring (CWRS) wheat (Triticum aestivum L.) class because of stringent quality requirements and a short growing-season environment with low precipitation and high temperatures. Understanding the physiological basis of yield gains may provide breeders with better insight in selecting parents and screening tools to identify desirable genotypes. The objective of the present study was to compare four new CWRS wheat cultivars with two older cultivars, Neepawa and Marquis, for yield components and dry matter production. When grown at Swift Current, SK, for 3 yr, the average yield for the group of new cultivars was 34.3% higher than that of Marquis (P < 0.01), and 5.9% higher than that of Neepawa (P = 0.10). The new cultivars, as a group, had significantly increased kernel weight, kernels per spike, yield per spike, and spike-filling rate relative to either of the older cultivars. When cultivars were compared individually, all four of the new cultivars had significantly higher yield per spike and spike-filling rate than Neepawa or Marquis, suggesting that these factors may be closely related to the increased yields of the newer cultivars. The trend toward higher kernel weight and kernels per spike suggests that the new cultivars have increased the sink size of each tiller. The number of spikes per plant and the length of the grainfilling period do not appear to be associated with the increased yield. Harvest index of the group of new cultivars, while significantly higher than that of Marquis, has not increased significantly compared to Neepawa, probably because this group is similar in height to Neepawa. L'étude devait comparer quatre nouveaux cultivars de BRPOC à deux autres, plus anciens (Neepawa et Marquis), sur le plan du rendement et de la matière sèche produite. Cultivées à Swift Current (Saskatchewan) pendant trois ans, les nouvelles variétés ont donné un rendement moyen de 34,3 % supérieur à celui de Marquis (P < 0,01) et de 5,9 % plus élevé que celui de Neepawa (P = 0,10). Collectivement, les nouveaux cultivars se démarquent par un poids d'amandes sensiblement plus élevé, par un nombre accru de grains par épi, par un meilleur rendement par épi et par un meilleur taux de remplissage du grain que les deux cultivars plus anciens. Quand on les compare individuellement à ces derniers, on constate que chacun des quatre cultivars a un rendement par épi et un taux de remplissage du grain sensiblement plus élevés que ceux de Neepawa et de Marquis, signe que ces facteurs sont peut-être étroitement associés au rendement supérieur des nouveaux cultivars. La tendance vers un poids d'amandes plus élevé et un nombre accru de grains par épi donne à penser que les nouveaux cultivars possèdent un plus grand puits d'assimilat dans leurs talles. Le nombre d'épis par plant et la durée de ...