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.

Preharvest sprouting of wheat (Triticum aestivum L.) is associated with inadequate seed dormancy. Although abscisic acid (ABA) has often been suggested to play a central role in developing seed, its involvement in dormancy of mature seed lacks firm experimental evidence and endogenous ABA levels are not well correlated with germinability. We examined genotypic and temporal variation in wheat seed and embryo germination responses to ABA and determined whether differential sensitivity of embryos to ABA extended to growth of embryo-derived calli. Germination of Parker 76 caryopses, which have little slormancy at maturity, was only slightly inhibited by ABA, whereas germination of Clark's Cream, a highly dormant genotype, was greatly inhibited. Responsiveness of caryopses to ABA and dormancy of seeds decreased concurrently during afterripening. Germination of embryos excised from dormant and nondormant seeds was more responsive to ABA but otherwise was similar to that of caryopses, indicating that differential response to ABA occurs in the embryo. Growth of calli derived from immature embryos of two sprouting-susceptible wheat genotypes exceeded growth of calli from Clark's Cream, but no distinct differences in response to ABA among the genotypes were apparent. We concluded that the action of ABA is similar in developing and mature seeds, that genotypic and temporal variation in embryo responsiveness to endogenous ABA may be involved in dormancy, and that ABA probably acts in concert with other endogenous constituents. maturation and then decrease dramatically during desiccation (5,12,17,18). Seed dormancy differs markedly among genotypes at maturity but is temporal, and a variable period of afterripening or stratification is necessary for seeds to become fully germinable (1). As in other species, the level of endogenous ABA is poorly correlated with dormancy of mature seeds (5,12,17).Germination responses of mature wheat caryopses and embryos to exogenous compounds are better correlated with seed dormancy than is the level of endogenous ABA (8, 9, 1 1, 15-18). Genotypic differences in dormancy parallel inhibition of excised embryos by catechin tannin and ABA (15) and by a ubiquitous endogenous compound (8) that is likely tryptophan (9). The effect of the latter is reinforced by exogenous ABA and countered by gibberellic acid (11,16). Loss of dormancy and diminished responsiveness of excised embryos to exogenous inhibitors coincide during afterripening (8,9,11,16). Thus, any role of ABA in dormancy may depend more on changes in perception of the inhibitor by the embryo than on content of the inhibitor in the caryopsis.The present study investigated differential response as an alternative mechanism by which ABA might regulate dormancy of mature wheat seed. Seed lots with extreme ranges in dormancy were used to ascertain whether intact caryopses, excised embryos, and calli from embryo explants varied in responsiveness to ABA and to determine if the effect persisted during afterripening to explain genotypic and...

Photosynthesis is highly sensitive to high temperature stress, an important problem in many regions during reproductive growth of wheat (Triticum aestivum L.). Our objective was to evaluate chlorophyll fluorescence, which indirectly measures photosynthetic efficiency, as a screening criterion for high temperature tolerance in wheat. Six genotypes differing in adaptation to the southern Great Plains were tested in two controlled environments and in the field. Plants in controlled environments were subjected to 37/25 °C and 25/20 °C day/night regimes during grain filling and at different developmental stages from late boot to 10 d after anthesis. The field experiment was planted during late winter to increase the probability of high temperature stress after anthesis. Initial (Fo), variable (Fv), and maximum fluorescence (Fm) were measured using a portable fluorometer on flag leaves of intact plants. Fluorescence parameters differed significantly among genotypes in controlled environments and field conditions. Relative stability of Fv was positively related to yield when high temperature treatment was applied to all genotypes after anthesis. The Fv and grain yield were negatively correlated in controlled environments but positively and not significantly correlated in the field. Genotypes in the high Fv group were also in the high yield group. Chlorophyll fluorescence, especially Fv, may be a useful tool for screening wheat of similar maturity for high temperature tolerance during reproductive growth, but the technique should be used with other criteria that might indicate resistance to stress.

Improvement of crop tolerance to high temperature is hindered by the lack of information on genetic control of the trait. Objectives of this research were to characterize inheritance of high temperature tolerance based on chlorophyll fluorescence measurements and to estimate combining ability effects in wheat (Triticum aestivum L.). A diallel cross, including reciprocals, of six wheat genotypes was analyzed for high temperature tolerance based on chlorophyll fluorescence. Vernalized F1 plants and parents were initially placed in controlled environment chambers at 25/20 °C day/night temperatures. One‐half of the plants were exposed to a high temperature stress of 40 °C (16‐h day)/27 °C (8‐h night) 10 d after the earliest genotypes flowered. Initial (Foe), variable (Fv), and maximum chlorophyll fluorescence (Fm) were measured on dark‐adapted flag leaves of plants 3 and 7 d after initiation of stress. Analysis revealed significant general combining ability effects and maternal effects. Significant specific reciprocal effects indicated cytoplasmic and nuclear interactions in the response to high temperature. The combination of positive specific reciprocal effects and high general combining ability effect for the female parent conferred a high level of stability for Fv in the stress environment. Recurrent selection may be an appropriate method of accumulating genes that favor high temperature tolerance based on chlorophyll fluorescence measurements in wheat.

Hybrid hard winter wheats (Triticum aestivum L.) have shown superior grain yield potential in regional performance trials during the last decade. Evidence for enhanced yield stability, combined with enhanced yield potential, would facilitate wider acceptance of hybrid wheat by growers. Hybrid and pureline yield stability and environmental responsiveness were compared with the use of data from the