Utilizing a Preplant Soil Test for Predicting and Estimating Root Rot Severity in Sugar Beet in the Central High Plains of the United States.

Aphanomyces cochlioides and Rhizoctonia solani are important soilborne pathogens causing root diseases that are primary constraints to sugar beet production in Nebraska, Colorado, and Wyoming. These types of diseases are difficult to control because they are often not noticed until substantial damage has already occurred. Efforts to manage them would be more effective if techniques were available that were more predictive than reactive. Therefore, a preplant soil test was developed to estimate the relative pathogen populations in the soil and to predict potential root disease problems later in the growing season. Preplant soil samples collected from fields to be sown with sugar beet were planted with a susceptible cultivar and tests were conducted for 1 month in the greenhouse. A preplant disease index was developed based on the time period during the test that seedlings became infected and was calculated on a 0-to-100 scale. Disease index values were compared with yields obtained from the same fields after harvest. Analysis of data collected for 5 years (2003 to 2007) with analysis of covariance revealed a strong relationship between the preplant disease index values and recoverable sucrose and root yields but not sucrose concentration. Results indicated that, for each unit increase in the preplant disease index, root yield decreased by 0.27 metric tons (270 kg) per hectare (P < 0.05, R2 = 0.44) and recoverable sucrose decreased by 49 kg/ha (P < 0.05, R2 = 0.45). We concluded that this preplant soil test can accurately predict root disease potential due to R. solani and A. cochlioides, and has the potential to help producers make effective management decisions in production fields using the index procedure. This soil assay has additionally provided new information on the biology, incidence, and distribution of root pathogens in production fields throughout the Central High Plains.

Systemic distribution of viral antigen in alpacas persistently infected with bovine pestivirus.

Recently, confirmed occurrences of persistent bovine viral diarrhea virus (BVDV) infection in North American alpacas have raised concerns about the role of persistently infected (PI) alpacas in transmission of virus among herds, yet only limited pathological descriptions of persistent infections in alpacas have been reported. The objective of this study was to characterize BVDV antigen distribution in 10 PI alpacas of varying age and to compare viral antigen distribution and localization in tissues of PI alpacas with 5 PI calves of varying age. Ocular dysplasia was evident in 1 PI alpaca, constituting the first reported congenital ocular lesion in PI alpacas. Viral antigen was widely distributed in alpaca tissues and was prominent in neurons, endothelial cells, and vascular tunica media myocytes but had limited distribution in lymphoid tissues and moderate distribution in epithelium of several organ systems of alpacas. Macrophages in the alpaca gastrointestinal system submucosa and lymph node medullary sinuses often had prominent labeling. In addition, only 1 alpaca had antigen labeling in the bone marrow in contrast to PI cattle. Labeled cells in calf tissues were more widely distributed, occurring prominently in lymphoid and epithelial tissues. Common features of the 2 host species were widespread antigen labeling and absence of lymphoid depletion.

Prediction of genetic values of quantitative traits with epistatic effects in plant breeding populations.

Though epistasis has long been postulated to have a critical role in genetic regulation of important pathways as well as provide a major source of variation in the process of speciation, the importance of epistasis for genomic selection in the context of plant breeding is still being debated. In this paper, we report the results on the prediction of genetic values with epistatic effects for 280 accessions in the Nebraska Wheat Breeding Program using adaptive mixed least absolute shrinkage and selection operator (LASSO). The development of adaptive mixed LASSO, originally designed for association mapping, for the context of genomic selection is reported. The results show that adaptive mixed LASSO can be successfully applied to the prediction of genetic values while incorporating both marker main effects and epistatic effects. Especially, the prediction accuracy is substantially improved by the inclusion of two-locus epistatic effects (more than onefold in some cases as measured by cross-validation correlation coefficient), which is observed for multiple traits and planting locations. This points to significant potential in using non-additive genetic effects for genomic selection in crop breeding practices.

Chemical and sensory properties of beef of known source and finished on wet distillers grains diets containing varying types and levels of roughage.

Beef knuckles (n = 160) were obtained from source-verified cattle finished on 30% wet distillers grains plus solubles enriched with varying levels of alfalfa hay (4 or 8%), corn silage (6 or 12%), or corn stalks (3 or 6%) based on NDF. Proximate analysis, pH, oxidation-reduction potential, fatty acid composition, and sensory analysis were conducted on the rectus femoris muscle to determine if roughage inclusion, in conjunction with wet distillers grains plus solubles and cattle source, affects beef flavor with particular interest in liver-like off-flavor. Proximate analysis, fat content, and oxidation-reduction potential were unaffected (P ge;0.129) by diet or source. For s.c. adipose tissue, cattle from Nebraska (NE) had greater amounts of MUFA (P = 0.048) and unsaturated fatty acids (P = 0.068) but less SFA (P = 0.065) when compared with cattle from South Dakota. Diet affected s.c. adipose tissue levels of 15:0, 17:0, and n-3 fatty acids in which cattle from NE finished on the low corn stalk diet had (P < or =0.050) lower levels. Cattle from NE had (P < or = 0.049) greater i.m. adipose proportions of 13:0 and CLA. Dietary effects (P < or = 0.050) were observed for i.m. adipose tissue proportions of 16:0, 18:1(n-9), 18:2(n-6), 20:4(n-6), 22:5(n-3), MUFA, PUFA, and n-6 fatty acids. Sensory analysis revealed that cattle from NE were (P < or = 0.023) less juicy and had less bloody notes when compared with cattle from South Dakota. Cattle finished on the low alfalfa diet were (P < or = 0.014) more tender and juicy but had more bloody notes. No (P ge; 0.670) dietary or source effects were noted for liver-like off-flavor. Subcutaneous amounts of 18:2(n-6 trans) (r = -0.17) were inversely related to the incidence of liver-like off-flavor, whereas 20:1(n-9) (r = 0.21), CLA cis-9, trans-11 (r = 0.16) were directly related. Data from this study indicate that type and level of roughage inclusion and cattle source have minimal effects on fatty acid profiles and sensory properties of the musculus rectus femoris. However, individual fatty acids of s.c. and i.m. adipose tissue were significantly correlated with liver-like off-flavor.

Virulence Diversity of the Common Bean Rust Pathogen Within and Among Individual Bean Fields and Development of Sampling Strategies.

There is a dearth of information on pathogen variation within an individual field. In this study, virulence diversity of Uromyces appendiculatus, cause of bean rust, within individual fields was investigated. From six bean fields in the United States, Honduras, Dominican Republic, and South Africa, 380 U. appendiculatus isolates were differentiated into 65 virulence phenotypes on bean lines containing Andean- and Middle American-derived rust resistance genes. Race variation among bean rust isolates from different geographic regions was found, and virulence phenotypes found in fields from tropical and subtropical regions were more virulent and diverse than those found in fields from temperate regions. The variance components between fields was greater than the variance within a field based on mean disease score on 12 differentials but the variance components within a field were greater than the variances between fields based on number of virulence phenotypes. This is the first report that multiple site samples are needed to represent the fungal virulence diversity in a diseased field. In developing sampling plans, the entire cost of sampling one field is higher than the cost of taking more samples; therefore, to estimate virulence diversity variation, we recommend selecting fewer fields and collecting more samples per field.

Unsaturated fatty acids and sodium affect the liver-like off-flavor in cooked beef.

Beef knuckles (n = 60) were chosen from a population of 328 knuckles to test a selection procedure and determine the potential causes of liver-like off-flavor. In phase I, 2 independent panelists were allowed to smell the aromas or smell and taste samples of cooked beef to determine the presence or absence of the liver-like off-flavor and off-flavor intensity. The panelists tested knuckles from 5 feedlots, but only identified 29 as having an off-flavor. A kappa statistic was generated to assess the level of agreement of the 2 panelists that indicated the panelists moderately or substantially agreed when judgments were based on smell exclusively or smelling and tasting, respectively. Although the agreement was acceptable (kappa = 0.57 and 0.76), there was not enough variation in the liver-like off-flavor and off-flavor intensity for the 2 panelists to detect differences compared with an independent sensory panel. Phase II identified factors that led to the development of the liver-like off-flavor in beef. The M. rectus femoris from knuckles identified from phase I were used. Sensory analysis, proximate composition, heme iron, mineral content, and fatty acid analyses were conducted. Stepwise regression was used to identify factors contributing to the liver-like off-flavor. Specifically, Na, 16:1, cis 18:1(n-7), 20:2(n-6), and 20:3(n-6) fatty acids explained (P = 0.021) 46% of the variation of the liver-like off-flavor. Although previously reported as playing a role in the development of the liver-like off-flavor, iron, heme iron, and pH had no effect in this study.

Consumer sensory acceptance and value of wet-aged and dry-aged beef steaks.

To determine sensory preference and value of fresh beef steak differing in aging technique, strip steaks were evaluated by consumers in Denver (n = 132 consumers) and Chicago (n = 141 consumers). Wet-aged Choice strip loins were matched with dry-aged Choice strip loins, whereas wet-aged Prime strip loins were matched with dry-aged Prime strip loins. Dry-aged strip loins were commercially aged in air in a controlled environment for 30 d and vacuum-aged for 7 d during shipping and storage. Wet-aged strip loins were vacuum-packaged and aged for 37 d in a 1 degrees C cooler. Pairs of strip loins were matched to similar Warner-Bratzler shear force values and marbling scores. Twelve sensory evaluation panels (of 12 scheduled panelists each) were conducted over a 3-d period in each city. Individual samples from a pair of steaks were evaluated by the panelists for sensory traits. Bids were placed on the samples after sensory traits were obtained utilizing a variation of the Vickery auction with silent, sealed bids. No significant differences for sensory traits of flavor, juiciness, tenderness, or overall acceptability were detected between wet-aged Choice samples and dry-aged Choice samples. Although wet-aged Choice samples were numerically superior for all sensory traits, consumers placed similar bid values (P = 0.12) on wet- and dry-aged Choice samples ($3.82 per 0.45 kg and $3.57 per 0.45 kg, respectively). Wet-aged Prime samples were rated more desirable (P < 0.001) for flavor, tenderness, and overall acceptability than dry-aged Prime samples. Wet-aged Prime samples were valued at $4.02 per 0.45 kg, whereas dry-aged Prime samples brought $3.58 per 0.45 kg (P = 0.008). Consumers (29.3%) who preferred the dry-aged Choice samples over the wet-aged Choice samples were willing to pay $1.99/0.45 kg more (P < 0.001) for dry-aged samples. The consumers who preferred the wet-aged Choice over the dry-aged Choice samples (39.2%) were willing to pay $1.77/0.45 kg more (P < 0.0001). Consumers who preferred wet-aged Prime over dry-aged Prime samples (45.8%) paid $1.92/0.45 kg more (P < 0.0001). Consumers who preferred dry-aged Prime samples (27.5%) were willing to pay $1.92/0.45 kg more than for the wet-aged Prime samples. Although more consumers preferred wet-aged samples, markets do exist for dry-aged beef, and consumers are willing to pay a premium for this product.

Consumer sensory acceptance and value of domestic, Canadian, and Australian grass-fed beef steaks.

To determine US consumer acceptance and value of beef from various countries, 24 taste panels of consumers (n = 273 consumers) were conducted in Denver and Chicago. Two pairs of strip steaks were evaluated for flavor, juiciness, tenderness, and overall acceptability on eight-point hedonic scales. One pair consisted of an Australian grass-fed strip steak and a domestic strip steak, whereas the other pair included Canadian and domestic strip steaks. The pairs were matched to similar Warner-Bratzler shear values and marbling scores to decrease variation associated with tenderness and juiciness. A variation of the Vickery auction was used to obtain silent, sealed bids on steaks (0.45 kg) from the same strip loins sampled in the taste panel. Consumers gave higher (P < 0.001) scores for flavor, juiciness, tenderness, and overall acceptability for domestic steaks compared with Australian grass-fed steaks. Domestic steaks averaged 3.68/0.45 dollars kg, whereas consumers placed an average value of 2.48/0.45 dollars kg on Australian grass-fed steaks (P < 0.001). Consumers rated Canadian steaks numerically lower for juiciness (P = 0.09) and lower (P < 0.005) for flavor, tenderness, and overall acceptability than domestic samples. Consumers placed an average value of 3.95/0.45 dollars kg for domestic steaks and 3.57/0.45 dollars kg for Canadian steaks (P < 0.01). Consumers (19.0%) who preferred Australian grass-fed steaks over domestic steaks paid 1.38/0.45 dollars kg more (P < 0.001), whereas consumers (29.3%) who favored the Canadian steaks over the domestic steaks paid 1.37/0.45 dollars kg more (P < 0.001) for the Canadian steaks. A majority of US consumers seem to be accustomed to the taste of domestic beef and prefer domestic steaks to beef from Australia grass-fed and Canadian beef.

Consumer visual preference and value for beef steaks differing in marbling level and color.

To determine visual preference and value for fresh beef steaks differing in marbling level and color, consumers in Chicago and San Francisco (n = 124 per city) evaluated two pairs of steaks in a retail case. Steaks differing in marbling level (Modest/Moderate vs. Slight) and color (bright, cherry-red vs. dark red) were purchased at retail stores in each city. Consumers selected their preferred steak in each pair, described their selection criteria, and provided the price they were willing to pay for each of the four steaks. There was a difference in visual preference in each city, with most consumers preferring (P < 0.01) low (Slight) over high (Moderate/Modest) marbling; however, more (P < 0.01) consumers in Chicago (86.7%) preferred low marbling than in San Francisco (67.0%). Selection criteria were categorized into five groups: marbling, fat, color, appearance, and palatability. Marbling was mentioned by 65.4% of consumers who preferred high marbling, whereas 64.9% of consumers who preferred low marbling mentioned fat as a selection criterion. Bright, cherry-red color was preferred by a higher (P < 0.01) percentage of consumers in both Chicago and San Francisco (67.6 and 76.5%, respectively). Color was mentioned both by consumers who preferred bright, cherry-red color (64.8%) and those who preferred dark red color (63.9%). All preference groups were willing to pay more for their preferred steak (P < 0.01), but consumers who preferred low marbling were willing to pay more (P < 0.01) for their preferred steak than consumers who preferred high marbling. Consumers who preferred bright, cherry-red color were willing to pay more (P < 0.01) for their preferred steak than consumers who preferred dark red color. Consumers who preferred low marbling seemed to desire lean products, and consumers who preferred high marbling seemed to desire products with high eating quality. In this study, consumers were willing to pay more to purchase their preferred product; however, most consumers preferred low marbling and bright, cherry-red color.

Consumer sensory acceptance and value for beef steaks of similar tenderness, but differing in marbling level.

To determine consumer sensory acceptance and value of beef steaks differing in marbling level (high = upper USDA Choice and low = USDA Select), but similar in Warner-Bratzler shear value, consumers in Chicago and San Francisco (n = 124 per city) evaluated two matched pairs of high- and low-marbled strip steaks, and had the opportunity to participate in a silent, sealed-bid auction to purchase steaks from the same strip loins as the samples. Consumers who purchased steaks also evaluated the steaks when prepared in their homes. Based on overall acceptability ratings, consumers were categorized into three groups: 1) those who consistently found high marbling more acceptable, 2) those who consistently found low marbling more acceptable, and 3) those who were indifferent. Consumers who evaluated at least one high-marbled and one low-marbled sample in their home were included in an evaluation environment analysis (n = 50). High-marbled steaks were rated higher (P < 0.01) in juiciness, flavor, and overall acceptability than low-marbled steaks. In Chicago, consumers tended to bid more (P < 0.10) for high-marbled steaks, whereas consumers in San Francisco did not. Consumers who found high-marbled steaks more acceptable and those who found low-marbled steaks more acceptable were willing to pay more (P < 0.01) for the more acceptable product. Consumers who evaluated high- and low-marbled samples in both the laboratory and home environments rated high- and low-marbled samples similar (P > 0.10) in flavor, juiciness, tenderness and overall acceptability when evaluating the steaks in their homes. In addition, these consumers were willing to pay similar (P > 0.10) amounts for high- and low-marbled samples in both environments. Overall, consumers found high-marbled steaks to be more acceptable than low-marbled steaks in flavor and overall acceptability when tenderness differences were minimized in the laboratory environment. Consumers were willing to pay more for their preference, whether that preference was for high-marbled or low-marbled steaks.

A comparison of consumer sensory acceptance and value of domestic beef steaks and steaks from a branded, Argentine beef program.

To determine consumer sensory acceptance and value of branded, Argentine (grass-finished, aged 30+ d) and domestic (U.S. grain-finished beef, aged 9 d) strip loins were paired based on similar Warner-Bratzler shear force values (P = 0.34) and similar marbling levels (P = 0.82). Consumers in Chicago, IL, and San Francisco, CA (n = 124 per city), evaluated one pair of Argentine and domestic steaks, and had the opportunity to participate in a silent, sealed-bid auction to purchase steaks matching the taste panel samples. Consumers were categorized into three groups based on overall acceptability ratings: 1) those who found Argentine steaks more acceptable, 2) those who found domestic steaks more acceptable, and 3) those who were indifferent. Consumers rated domestic steaks higher (P < 0.05) in juiciness, tenderness, flavor, and overall acceptability. Consumers in both Chicago and San Francisco were willing to pay more (P < 0.05) for domestic steaks (0.86 dollars and 0.52 dollars per 0.45 kg, respectively). In both cities, consumers who found Argentine samples more acceptable were willing to pay more (P < 0.05) for Argentine steaks (0.74 dollars per 0.45 kg in Chicago and 1.82 dollars per 0.45 kg in San Francisco), and consumers who found domestic samples more acceptable were willing to pay more (P < 0.05) for domestic steaks (1.66 dollars per 0.45 kg in Chicago and 1.34 dollars per 0.45 kg in San Francisco). Consumers who were indifferent were willing to pay similar (P = 0.99) amounts for Argentine and domestic steaks. Although some consumers found Argentine beef more acceptable than domestic beef (19.7 and 16.5% in Chicago and San Francisco, respectively) and were willing to pay more for it, most consumers found domestic beef to be more acceptable (59.0% in Chicago and 61.5% in San Francisco) and were willing to pay more to obtain a more acceptable product.

Phenotypic and Genotypic Characterization of Uromyces appendiculatus from Phaseolus vulgaris in the Americas.

Populations of 90 Uromyces appendiculatus isolates were collected from throughout the Americas and evaluated for virulence on 19 standard bean rust differentials, and also on 12 landraces of Phaseolus vulgaris from South and Central America. The landrace differentials represented geographical centers of bean domestication. Three groups were observed. Two groups were isolates from centers of bean domestication and a third heterogeneous group comprised isolates from countries in South and Central America. Molecular analysis using random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) was also conducted on these isolates. Cluster analysis of the molecular profiles showed three groups that corresponded to those obtained by virulence tests. These results show a clear differentiation of the pathogen population along similar lines as its host and suggest parallel evolution in the bean rust pathosystem.

Virulence of Puccinia triticina on Wheat in Nebraska during 1997 and 1998.

Urediniospore isolates of Puccinia triticina were obtained from wheat leaf collections made in three wheat-growing regions in Nebraska in 1997 and in four regions in 1998. Using 16 Thatcher lines that are near-isogenic for leaf rust resistance, 17 virulence phenotypes were found among 121 single uredinial isolates in 1997, and 42 virulence phenotypes were found among 178 isolates in 1998. The most prevalent phenotype in 1997 was MDRR (virulent on Lr1, 3, 3ka, 10, 11, 18, 23, 24, and 30). In 1998, virulence phenotypes MDRR and MDRM (virulent on Lr1, 3, 3ka, 10, 11, 23, 24, and 30) were the most prevalent. In both years, virulence frequency was above 80% to genes Lr1, 3, 3ka, 10, 11, 23, 24, and 30 and below 21% to Lr2a, 17, and 26. Virulence frequency to Lr2c was 37% in 1997 and 22% in 1998. No virulence was found to Lr9, 16, or 21 in either year. New virulence phenotypes were detected in 1998 that were not found in 1997. In 1998, virulence was less frequent on Lr2a, 2c, 3ka, 18, 24, and 26 and more frequent on Lr17 than in 1997.

Effects of Mesocyclops longisetus (Copepoda:Cyclopidae) on mosquitoes that inhabit tires: influence of litter type, quality, and quantity.

A 59-week study was conducted to evaluate the impact of adult Mesocyclops longisetus populations on larval mosquito species inhabiting tires. Greater than 90% reduction of number of 1st and 2nd instars was recorded by 4 wk with 90% reduction of number of 3rd and 4th instars after 7 wk. Reduced control was noted with the onset of cooler winter water temperature. Overall. a 52% reduction in the number of 1st and 2nd instars was achieved, and a 57% reduction was noted in number of 3rd- and 4th-instar mosquito larvae. Cooler temperatures resulted in a decline of adult Mesocyclops, which resulted in reduced larval control. Significantly greater numbers of Mesocyclops adults were collected in tires with either new litter or heavy amounts of litter regardless of litter type. Lastly, litter type, either oak leaves or pine needles, did not influence mosquito reduction or abundance of Mesocyclops populations.

Flow cytometric analyses of lymphocyte subsets in peripheral blood and lymphoid tissues of gnotobiotic calves during primary acute postnatal infections of bovine viral diarrhea virus.

Eight 1-day-old gnotobiotic calves were exposed to one of 2 noncytopathic isolates of bovine viral diarrhea virus (ncp-BVDV 7937 and ncp-BVDV 126) and 2 similar calves were not infected and served as controls. Phenotypic analyses of peripheral blood mononuclear leukocytes at 3, 7, and 10 days postinfection (PI), and cell preparations of thymus, Peyer's patch, mesenteric lymph node, spleen, and bone marrow collected at necropsy, 10 days PI, were conducted using flow cytometric techniques on cells stained by an indirect fluorescent antibody assay using monoclonal antibodies specific for mononuclear leukocyte subsets. Significant fluctuations in specific subsets of peripheral blood mononuclear leukocytes were observed in calves exposed to ncp-BVDV 7937 on day 3 PI (cells expressing MHC class II), day 7 PI (B-cells), and day 10 PI (B cells and cells expressing MHCII). Significant phenotypic differences between groups were also detected in cell preparations from Peyer's patch and thymus. Calves exposed to ncp-BVDV 7937 had a significantly higher percentage of B cells than calves exposed to ncp-BVDV 126 and calves not exposed to BVDV. Calves exposed to ncp-BVDV 126 had a significantly higher percentage of CD2 (BoCD2) positive T cells than calves not exposed to BVDV. Fragility of thymic cell preparations was attributed to infection with virus. These results highlight the importance of the tropism of BVDV for cells of the bovine immune system and its role as a significant immunosuppressive agent capable of predisposing affected animals to infection with other agents.

Comparing test cultivars using reliability functions of test-check differences from on-farm trials.

An approach to selection is proposed that is based on the probabilities that a test cultivar outperforms a check by more than an amount d in a future environment. The function that gives these probabilities for all possible values of d is called the reliability function. When d=0, the value of the reliability function is the probability that the test cultivar outperforms the check. The method is illustrated using data from on-farm maize (Zea mays L.) strip test trials grown cooperatively by Pioneer Hi-bred International and farmers. Results indicate that reliability functions are useful for evaluating how test cultivars perform relative to a check across a range of environments since the location, slope and shape of the reliability function may be used to describe a test cultivar's performance, similarity to the check and stability, and identify environments where the test cultivar has performance problems.

Comparison of six commercially available transport media for maintenance of Serpulina (Treponema) hyodysenteriae.

Two anaerobic (A1 and A2), 1 selective (S1), and 3 conventional (C1, C2, and C3) transport media formulations were compared for their capacity to maintain the viability of Serpulina (Treponema) hyodysenteriae. Initial experiments compared the recovery of S. hyodysenteriae from pure cultures held in each transport medium for 0.5, 1, 2, 3, 5, and 7 days at -40 C, 4 C, 25 C, and 36 C. Subsequent experiments compared each transport medium for maintenance of S. hyodysenteriae in fecal specimens obtained from experimentally infected pigs after holding for up to 7 days at 25 C. In each experiment, the viability of S. hyodysenteriae in each transport medium incubated at each temperature and for each period was determined by inoculating the transport medium onto either trypticase soy agar with 5% sheep blood or selective BJ agar and incubating at 42 C anaerobically. Viability and fecal flora contamination were evaluated blindly after 2-, 4-, and 6-day incubation periods. At -40 C, recovery of viable S. hyodysenteriae from pure culture did not differ among the transport media from 0.5 to 7 days, and all of the transport media consistently maintained the viability of the spirochetes for 7 days. At 4 C, the anaerobic and selective transport media maintained the viability of pure cultures of S. hyodysenteriae significantly better than did the conventional transport media group at day 7 (P = 0.019). At the same temperature, the anaerobic media maintained viability better than did the conventional media at 5 days (P less than 0.042).(ABSTRACT TRUNCATED AT 250 WORDS)

Choosing plant cultivars based on the probability of outperforming a check.

A major consideration in most plant breeding programs is the development of cultivars that have high probabilities of outperforming the check cultivar in a broad range of environments. Methods are presented for estimating and testing hypotheses regarding these probabilities, which are termed reliabilities. Reliabilities are shown to be directly related to several commonly used stability parameters. Data from international maize yield trials are used to illustrate and evaluate the repeatability of the approach. Results indicate that reliabilities can be useful aids to plant breeders since they (1) are easy to understand and compute, (2) are indices that weigh the importance of the difference in performance relative to stability, and (3) are potentially useful as genetic parameters since they are generally repeatable across randomly sampled sets of environments.

Expected utility maximization and selection of stable plant cultivars.

In most plant breeding programs, selection of the best commercially suitable cultivars for a target group of environments is based on information obtained from evaluation trials cultivated in a sample of environments. Information on the performance of cultivars collected in a sample of environments can only be approximate and, consequently, selection of the best cultivar involves choosing among cultivars that respond uncertainly in many environments. The agronomic and/or economic value of a cultivar across environments may be considered the general or overall utility of the cultivar. Data from a sample of environments therefore provides only an estimate of any cultivar's overall utility, with the overall goal of selection among all cultivars being the maximization of the expected utility. Within this frame-work, expected utility maximization, an approach to decision making that has been well developed in the disciplines of economics and statistics, can assist the plant breeder in making such decisions. This research was initiated (1) to determine how expected utility maximization might be used to develop indices that are useful for selecting broadly adapted plant cultivars, and (2) to determine how the breeder's preferences might affect choice of the best cultivar. The data used in this research were from USDA Regional Soybean Tests. The results indicated that expected utility maximization, which explicitly incorporates into the selection rule the plant breeder's preferences regarding stability, can be a useful aid in the selection of stable plant cultivars.

CSF ion composition and manipulation during thermoregulation in an avian species, Gallus domesticus.

1. At thermoneutrality (28 degrees C), CSF Na+:Ca2+ in hens was 61.66; under thermal stress (39 degrees C), it changed to 59.38 (30 min), 62.58 (3 hr), and 52.44 (10 hr); no change in ratio occurred at 15 degrees C. 2. ICV Ouabain and/or EGTA increased body temperature (TR) but not respiration rate (RR) at 39 degrees C. 3. At 28 degrees C, Ouabain decreased, and EGTA increased, TR and RR. 4. Ca2+ may be more critical than Na+ in thermoregulation. 5. Heat stress appears to stimulate Na+-transport mechanisms other than Na+-ATPase. 6. RR appears to be a function of TR, not of ion balance.