Knowledge of changes associated with advances in crop productivity is essential for understanding yield‐limiting factors and developing strategies for future improvement. Our objective was to identify plant traits associated with gains in grain yield of winter wheat (Triticum aestivum L.) in the Great Plains. Twelve landmark cultivars and one experimental line were compared with ‘Turkey’ (introduced 1873) at Hutchinson (Clark‐Ost complex soil) and Manhattan (Reading silt loam soil), KS, during 1996–1997 and 1998–1999. Agronomic traits, leaf rust infection (caused by Puccinia recondita Rob. ex Desm. f. sp. tritici), and grain yield and its components were measured. Grain yields ranged from 2718 kg ha−1 for Turkey to 4987 kg ha−1 for the experimental line, with mean genetic gains of 0.16% per year for early genotypes and 0.63% per year for recent genotypes. Kernel number per unit of soil area had the highest phenotypic correlation with grain yield and contributed most to its genetic gain. Gains in spike numbers per unit of soil area and above‐ground biomass also contributed significantly to higher yields of some genotypes. Significant genetic changes over time and correlations with grain yield were observed for early heading, decreased height, and reduced lodging and leaf rust but not for kernel weight. Our results suggested that yield components that form during vegetative phases (spike numbers per unit of soil area and kernels per spike) when conditions for growth are generally favorable are more amenable to genetic improvement than kernel weight, which forms during maturation when moisture and temperature are often unfavorable.

Periodic evaluation of genetic improvement of crop cultivars is useful, both as a demonstration of the importance of plant breeding to the public and as a way of identifying traits or target environments that may require increased efforts by breeders. Evaluation of cultivars from different eras in a common environment is the most direct of the several methods that have been used to estimate breeding progress. Thirty‐five hard red winter wheat (Triticum aestivum L. em. Thell.) cultivars introduced or released between ca. 1874 and 1987 were evaluated in experiments at three locations in Kansas during 1986 and 1987 (three other cultivars were evaluated only in 1987) to estimate genetic progress achieved by hard red winter wheat breeding programs. Linear regression of cultivar means on years of release showed increases of 16.2 kg ha−1 yr−1 in grain yield, 0.4 kg m−3 yr−1 in volume weight, and 0.04 g yr−1 in thousand‐kernel weight. Days to heading and plant height decreased at rates of −0.1 d yr−1 and −0.5 cm yr−1, respectively. There were also significant increases over time in lodging resistance. There was no significant change in biomass yield over time. Rates of genetic improvement varied significantly across evaluation environments, with the greatest gain in grain yield (1.4% of the experiment mean per year) estimated in an epidemic of stem and leaf rust (caused by Puccinia graminis Pers. f. sp. tritici Eriks. & Henn., and P. recondita Rob. ex. Desm. f. sp. tritici, respectively). Moderate gain per year (0.6%) was estimated in the most highly productive environment, lower gain (0.4%) was found under drought stress, and there was no gain when evaluation was conducted under an epidemic of tan spot (caused by Helminthosporium tritici‐ repentis Died.), a foliar disease. High levels of resistance to H. tritici‐repentis had not been incorporated into hard red winter wheat cultivars. No evidence of a yield plateau was found for hard red winter wheat cultivars evaluated under a range of environmental conditions in Kansas.

Winter wheat (Triticum aestivum L.) is frequently subjected to stress that causes early senescence of plants and cessation of grain filling. This research evaluated chemical desiccation for selecting genotypes for tolerance to postanthesis stress and determined the relationship of chemical desiccation tolerance to carbohydrate and N partitioning. Twenty‐eight cultivars with a wide range of stress tolerance and yield potential were treated with 0 and 0.19 mol L‐1 NaCIO3 14 d after anthesis. The 2‐yr study was on a Eudora silt loam (coarse‐silty, mixed, mesic Fluventic Hapludoll); treatments were in randomized‐complete blocks with four replications. Ten cultivars representing a range of treatment responses were evaluated further at two locations on dryland and irrigated Eudora silt loam and Pratt loamy fine sand (sandy, mixed thermic Psammentic Haplustalf) in split plots with three replications. Cultivars that had high kernel weights and early release dates were generally more tolerant of chemical desiccation than cultivars with low kernel weights and recent release dates. Grain yields of chemically desiccated plants under irrigation correlated significantly with yields of untreated plants at one location but not at another location. Losses of dry matter and soluble carbohydrates, but not of N, from stems were related to grain yield response to chemical desiccation. We concluded that chemical desiccation effectively selects for postanthesis stress resistance, and that combining high carbohydrate reserves with efficient translocation to the grain should improve wheat performance in unfavorable environments.

Thirty‐nine genotypes of winter wheat (Triticum aestivum L.) were examined for potential use in tissue culture studies. Tissue cultures were initiated from immature embryos approximately 12 days old on a modified Murashige and Skoog medium containing 1.0 mg 2,4‐dichlorophenoxyacetic acid (2,4‐D)/liter. Cultures were maintained on the same medium with 0.5 mg 2,4‐D/liter. Shoots were initiated by reducing the 2,4‐D to 0.1 mg/liter and complete plants were regenerated by transferring to 2,4,‐D‐free medium. Variability was observed among the wheat genotypes tested for callus induction, regenerable callus formation, response to subculture, and plant regeneration potential. Eighteen genotypes were capable of regenerating plants after four subcultures (90 to 125 days). Cultures from five genotypes remained totipotent after 240 days. Tissue cultures derived from ND 7532 and Roughrider remained totipotent for 420 days. Selection ND7532 demonstrated higher percentage of calli induction and regenerable calli formation, faster in vitro growth rates, and higher frequency of totipotent calli than other genotypes. Plant regeneration from tissue cultures derived from immature embryos is predictable and stable when the appropriate genotype is used. Five hundred thirty‐two plants were regenerated from callus tissue in this study and 510 of these produced seed. It appears that the response in tissue culture of cultivated wheat varies with genotype and that lines with good potential can be identified.

Registration of ' Jagger' Wheat 'Jagger' hard red winter wheat (Triticum aestivum L.) (Reg. no. CV-836, P1 593688) was developed cooperatively by the Kansas Agricultural Experiment Station and the USDA-ARS. It was released to seed producers in 1994. Jagger is an increase from an ?4 head row, reselected again as an Fe head row from the cross KS82W418/' Stephens', made in 1984. Jagger was released because of its high grain yield, strong general disease resistance, and excellent bread-baking quality. Jagger is awned, brown-chaffed, and semidwarf. It is similar in height to 'Karl 92' and 1 d earlier in heading. Its winterhardiness is similar to that of 'Newton' and less than that of 'Scout 66'. Stems of Jagger are white, strong, and hollow; the flag leaf is erect, not twisted, and glabrous. Spikes of Jagger are midlong, oblong, and lax. At maturity, the spikes are inclined. Glumes are tan, with a brown line on the outside edge of the glume and lemma; they are long, wide, and rounded at the shoulder. The beak is narrow, midlong, and acuminate. The kernel is red, hard, and ovate; the germ is midsized; the crease is midwide and shallow, the cheeks are angular; the brush is midsized and has no collar. Jagger has been evaluated as KS84063-9-39-3 in the Kansas Intra-State Nursery since 1992. It was evaluated in the USDA Southern Regional Performance Nursery in 1993 and has been evaluated in the Kansas Variety Performance Tests since 1993. In Kansas tests (40 location-years), Jagger has been 14 and 8% higher in grain yield than Karl 92 and '2163', respectively. It is recommended for all growing areas in Kansas south of Interstate Hwy. 70. Jagger is resistant to stem rust (caused by Puccinia graminis Pers.:Pers.), leaf rust (caused by Puccinia recondita Roberge ex Desmaz.), tan spot [caused by Pyrenophora trichostoma (Fr.) Fckl.], speckled leaf blotch (caused by Septoria tritici Roberge in Desmaz.), wheat soilborne mosaic virus (SBWMV), and wheat spindle streak mosaic virus (WSSMV). It is moderately resistant to glume blotch [caused by Phaeosphaeria nodorum (E. Miiller) Hedjaroude], bacterial streak (caused by Xanthomonas campestris pv. translucens) and cephalosporium stripe (caused by Hymemla cerealis Ellis & Everh.; syn. Cephalosporium gramineum Nisikado & Ikata in Nisikado et al.). Jagger is tolerant to A1 toxicity caused by low soil pH, being equal to 2163 in this regard. Hard wheat milling and bread-making qualities of Jagger are excellent and similar to Karl 92, except that Jagger has slightly lower grain volume weight and requires a shorter dough-mixing time. Cultivar protection of Jagger under the U.S. Plant Variety Protection Act, Public Law 91-577, has been granted (PVP no. 9500324). Breeder seed will be maintained by the Kansas Agric.