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Optimal breeding zones were developed for white spruce (Picea glauca (Moench) Voss) in Ontario under present and future climate conditions to examine potential shifts due to climate change. These zones were developed by (i) determining a set of candidate breeding zones based on the relationship between measured performance variables and climate and (ii) employing a decision support model to select subsets of breeding zones that maximize geographic coverage subject to a constraint on the maximum number of zones. Current optimal breeding zones were based on 1961-1990 climate normals, and future breeding zones were based on three general circulation model (CGCM2, HADCM3, and CSIRO) predictions of 2041-2070 climate. Based on a maximum adaptive distance of 2.0 least significant difference values between sites within zones, 14 zones were required to cover the Ontario range of white spruce for the 1961-1990 data. Compared with breeding zones of other boreal conifers, current optimal breeding zones for white spruce were quite large, spanning up to 3° latitude and 10°-12° longitude and indicating large distances of effective seed transfer. Of the three general circulation models used to simulate future climate, HADCM3 B2 and CGCM2 B2 predicted 2041-2070 breeding zones that largely coincide with 1961-1990 zones. In contrast, CSIRO B2 indicated much narrower 2041-2070 breeding zones. Resume: Les auteurs ont determine des zones optimales damelioration de lepinette blanche (Picea glauca (Moench) Voss) en Ontario pour les conditions climatiques actuelles et futures afin dexaminer les modifications potentielles dues aux changements climatiques. Ces zones ont ete obtenues (i) en determinant un ensemble de zones candidates damelioration a partir des relations entre les variables de performance et le climat et (ii) en utilisant un modele daide a la decision pour choisir un sous-ensemble de zones damelioration maximisant la couverture geographique avec une contrainte quant au nombre maximal de zones. Les zones optimales actuelles damelioration etaient basees sur les normales climatiques de la periode 1961-1990. Les zones futures damelioration etaient basees sur les predictions de trois modeles de circulation generale (GCM2, HADCM3 et CSIRO) pour le climat de la periode 2041-2070. Avec la restriction que la distance reliee a ladaptation ne depasse pas deux fois la plus petite difference significative entre deux sites dune meme zone, 14 zones sont apparues necessaires pour representer adequatement la distribution de lepinette blanche en Ontario durant la periode 1961-1990. Comparativement aux zones damelioration des autres coniferes boreaux, les zones optimales actuelles dame--lioration pour lepinette blanche etaient relativement grandes, couvrant jusqua 3° de latitude et de 10° a 12° de longitude, impliquant de grandes distances pour le transfert effectif des semences. Parmi les trois modeles de circulation generale utilise s pour simuler le climat futur pour la periode 2041-2070, les modeles HADCM3 B2 et CGCM2 B2 predisaient des zones damelioration largement similaires a celles de la periode 1961-1990. A loppose, le modele CSIRO B2 predisait des zones damelioration beaucoup plus etroites. [Traduit par la Redaction], Introduction Ensuring local adaptation of planted sources is of paramount concern in forest regeneration and tree improvement practices. Tree seeds planted outside of their environmental tolerance limits are unable to [...]

Two big bluestem (Andropogon gerurdii Vitman) strains (Pawnee C3 and Kaw C3) developed by three breeding cycles for increased forage yield and in vitro dry matter digestibility (IVDMD) were compared with the base populations of 'Pawnee' and 'Kaw' in a 3-yr grazing trial. Pastures were seeded in May 1998 near Mead, NE. Experimental units were three 0.4-ha pastures of each strain or cultivar in a randomized complete block design. Pastures were burned and fertilized with ammonium nitrate at 112 kg N [ha.sup.-1] in the spring of 2000, 2001, and 2002 before grazing. Each pasture was continuously stocked with three crossbred yearling steers (Bos taurus) (380 ± 38 kg) in mid-June 2000, 2001, and 2002 to provide a stock density of 7.5 steers [ha.sup.-1]. Pawnee C3 and Kaw C3 produced 16 and 7% more average daily gain (ADG), respectively, than the base populations during the 3-yr study. Additionally, Pawnee C3 and Kaw C3 produced 14 and 5% more total body weight (BW) gain [ha.sup.-1], respectively, than the base populations. Pawnee C3 ADG was 1.30 kg [ha.sup.-1] and produced greater than 455 kg total BW gain [ha.sup.-1] during a drought period in eastern Nebraska. Pawnee C3 pastures produced more available forage with higher IVDMD, cell soluble, cell wall digestibility, and lower lignin concentration than forages from Pawnee pastures. Kaw C3 pastures differed from Kaw pastures by producing forage with greater crude protein concentration. These results demonstrate the productivity of big bluestem pastures in the eastern Great Plains and document the positive livestock response to moderate increases in forage IVDMD. The strains bred for increased yield and IVDMD provided as much as 26% more total BW gain ha-1 at no additional cost. Pawnee C3 was released as the eultivar Bonanza and Kaw C3 was released as 'Goldmine'., BIG BLUESTEM is a [C.sub.4] perennial grass native to North America (Weaver, 1954) and accounts for over 25% of the basal cover and over 40% of the herbaceous biomass of [...]

Heading and photoperiod response are key processes affecting adaptiveness of wheat (Triticum aestivum L.). Few soft white winter (SWW) wheat cultivars of the U.S. Pacific Northwest (PNW) express early heading. Earliness offers several advantages including early harvest, reduced pre-harvest sprouting loss, and increased operational efficiency. The objective of this study was to determine if early heading genotypes warrant greater breeding emphasis. Near-isogenic lines (NILs) were developed by transferring early heading character from Early Blackhull and an Early Blackhull derivative to `Nugaines' (NGN), an adapted PNW SWW cultivar. The NILs comprise a near-continous range of phenotypes that head 0 to 10 d earlier than NGN. The parents and NILs were tested during two to four yr in three diverse field environments. Results showed that genotypes 3 to 7 d earlier than NGN warrant increased breeding emphasis because they had high yield potential across all environments and often had enhanced test weight, kernel weight and harvest index. The earliest NILs had limited yield potential in the cool-moist medium growing season environment, but they had high yield potential in the temperate long-growing season environment. Grain-fill duration of NILs was strongly influenced by environment and only partially associated with heading date. Two early-heading NILs were less sensitive to photoperiod than NGN, but less sensitivity was not a requirement for early heading. Rate of apical meristem development was partially associated with early heading date at the distinct blister-like spikelet stage. Breeding programs centered in cool-moist environments of the PNW should consider increasing emphasis on early heading SWW germplasm., WINTER WHEAT is generally sown in the PNW of the USA between August and November but occasionally between July and February. Heading occurs between the following May and July with [...]

The ecological basis for breeding-system evolution was explored in Ecballium elaterium (L.) A. Rich. (Cucurbitaceae). Two subspecies are parapatric on the Iberian Peninsula: dioicum (dioecious) is found in southern, more arid regions and elaterium (monoecious) is found in northern, wetter regions. Six experimental gardens were set up in three sites that span the climatic gradient of the species' natural range in Spain in order to address two issues: (1) gender specialization in reproductive characters and life history, and (2) ecological specialization of the two subspecies across environments. Overall, the dioecious subspecies outperformed the monoecious subspecies. Monoecious plants, on average, were shorter-lived in all environments. Females of the dioecious subspecies produced similar numbers of female flowers, but more fruits and seeds, than did monoecious plants (cosexuals). The fruits of females contained more, but smaller, seeds than the fruits of cosexuals. Males always produced more male flowers than did cosexuals, disproportionately so with increased plant size (canopy volume); no such disproportionate increase in seed production was found in females. A geographic analysis of gender (proportion of female flowers) in the monoecious plants revealed a striking pattern: dimorphism with increased gender differentiation in drier sites, in contrast to monomorphism with respect to gender in wetter sites. Differences between the subspecies and between habitat types can be related directly to breeding-system differences. The higher overall performance of dioecious plants may be due to enhanced heterozygosity resulting from outcrossing enforced by dioecy. On the other hand, the gender differentiation of the monoecious plants in the drier sites may reflect gender allocation 'decisions' enforced by limited resource availability. Key words: common garden; Cucurbitaceae; dioecy; Ecballium elaterium; gender; monoecy; Spain., INTRODUCTION The breeding system is the single most important determinant of the mating structure of nonclonal plant populations. The mating structure in turn controls the amount and distribution of genetic [...]

Breeding projects work to stabilize productivity without increasing pressures on limited natural resources One of the main goals of agricultural research is to provide an adequate and secure food source [...]

Biochemistry and Physiology 10: 57-93. Texeira, S., and L. Sanint. 1988. Arroz de sequeiro. Agroanalysis 12: 11-16. -----. 1989. Arroz em Minas Gerais situacao atual e contribuicoes dapesquisa. Inf. Agropec. [...]

If intraspecific variation to rising atmospheric [CO.sub.2] exists in soybean [Glycine max (L.) Merr.], such variation could be used to select for optimal, high-yielding cultivars. To quantify the range and determine the basis for variation in seed-yield with increasing [CO.sub.2], eight ancestral and one modern soybean cultivar differing in determinacy, maturity group, and morphology were grown to reproductive maturity at two [CO.sub.2] partial pressures, 40 Pa (ambient) and 71 Pa (elevated). Experiments were replicated three times in temperature controlled glasshouses during 1998 and 1999. Although all cultivars showed a significant increase in seed yield with elevated [CO.sub.2],(~40%) Mandarin, an ancestral indeterminate cultivar, showed a greater relative response of seed yield to increased [CO.sub.2] than did all other cultivars (~80%). The observed variation in seed yield response to [CO.sub.2] was not correlated with any vegetative parameter. At maturity, significant correlations in the relative response of seed yield to [CO.sub.2] were observed for both pod weight per plant and seed weight from branches. The later observation suggests that the sensitivity of seed yield response to [CO.sub.2] was associated with plasticity in the ability to form new seed in axillary branches in a high [CO.sub.2] environment. Genotypic differences in the seed yield response among existing ancestral soybeans suggests that sufficient germplasm is available for breeders to begin selecting lines which maximize soybean yield in response to increasing atmospheric [CO.sub.2]., FEW STUDIES have attempted to utilize genotypic variation in the response to increasing atmospheric [CO.sub.2] as a means to maximize growth or yield within a given agricultural species. Significant variation [...]

Seasonal availability of water is a major consideration in the management and selection of plant materials for irrigated pastures in the Intermountain West, USA. Objectives were to evaluate the forage yield of 10 tall fescue (Festuca arundinacea Schreb.) strains and cultivars across five irrigation levels and to elucidate the effects of the endophytic fungus Neotyphodium coenophialum (Morgan-Jones & Gems) Glenn, Bacon & Hanlin on productivity and trends. A line-source irrigation system was used in a 2-yr study. Significant differences were detected among the tall fescue entries for dry matter yield (DMY), and differences were relatively consistent across water levels (WL) as indicated by the nonsignificant cultivar x WL interaction and significant correlations among WL. Trends in DMY across WL were largely curvilinear; however, linear trends were much more predominant during the late summer and fall. Stability parameters, based on regression of cultivar x WL x year means on their respective WL x year means, differed among cultivars in analyses including all harvests but were relatively uniform (b [approximately equals] 1.0) for most cultivars later in the season. Differences in DMY between `Ky 31' tall fescue infected with the Neotyphodium endophyte and its endophyte-free counterpart confirms earlier reports of the positive effect of this fungal organism on forage yield in tall fescue, particularly in water-limited environments. Seasonal distribution of yield was primarily determined by water availability during the late summer and fall. The relative consistency in DMY of the cultivars across WL indicates that annual yield averaged across levels of water stress would be a logical criterion for selection of germplasm for irrigated pastures in the Intermountain Region., FEDERAL LAND POLICIES have curtailed the use of public lands for livestock grazing in the Semiarid West, particularly in the Intermountain Region. This has led to an increased interest in [...]