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Channel catfish (Ictalurus punctatus) and blue catfish (Ictalurus furcatus) are two economically important freshwater aquaculture species in the United States, with channel catfish contributing to nearly half of the country's aquaculture production. While differences in economic traits such as growth rate and disease resistance have been noted, the extent of transcriptomic variance across various tissues between these species remains largely unexplored. The hybridization of female channel catfish with male blue catfish has led to the development of superior hybrid catfish breeds that exhibit enhanced growth rates and improved disease resistance, which dominate more than half of the total US catfish production. While hybrid catfish have significant growth advantages in earthen ponds, channel catfish were reported to grow faster in tank culture environments. In this study, we confirmed channel fish's superiority in growth over blue catfish in 60-L tanks at 10.8 months of age (30.3 g and 11.6 g in this study, respectively; p < 0.001). In addition, we conducted RNA sequencing experiments and established transcriptomic resources for the heart, liver, intestine, mucus, and muscle of both species. The number of expressed genes varied across tissues, ranging from 5,036 in the muscle to over 20,000 in the mucus. Gene Ontology analysis has revealed the functional specificity of differentially expressed genes within their respective tissues, with significant pathway enrichment in metabolic pathways, immune activity, and stress responses. Noteworthy tissue-specific marker genes, including lrrc10, fabp2, myog, pth1a, hspa9, cyp21a2, agt, and ngtb, have been identified. This transcriptome resource is poised to support future investigations into the molecular mechanisms underlying environment-dependent heterosis and advance genetic breeding efforts of hybrid catfish. [ABSTRACT FROM AUTHOR]

Before the 2020–2021 school year, policymakers and parents confronted the uncertain trade-offs implied by the health, educational, and economic consequences of offering instruction remotely, in person, or through a hybrid of the two. Most public schools in the United States chose remote-only instruction, and enrollment fell dramatically (i.e., a loss 1.1 million K–12 students). We examine the impact of these choices on public-school enrollment using panel data that combine district-level information on enrollment and instructional mode. We find offering remote-only instead of in-person instruction reduced enrollment by 1.1 percentage points (i.e., 42% greater disenrollment). The disenrollment effects of remote instruction are concentrated in kindergarten and, more modestly, elementary schools. We do not find evidence that hybrid instruction had an impact. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) has been a focus of scientific research and breeding for over a century. It is also one of the most economically important crops in the world, with a value of approximately US$50 billion per year in the United States alone. Additionally, maize has long been the model species of choice for the study and exploitation of hybrid vigor, and it continues to be one of the world's most efficient converters of photosynthetic energy into starch. This review discusses the history and future of maize predictive breeding in the context of both genotype centric methods, and those focusing on genotype × environment × management interactions. Current prediction challenges are highlighted, as well as important advances in technology, methods, datasets, interdisciplinary collaborations, and scientific culture that will enable accelerated progress in predictive maize (and other crop species) breeding for years to come. [ABSTRACT FROM AUTHOR]

Abundant evidence supports the benefits accrued to the Florida panther (Puma concolor coryi) population via the genetic introgression project implemented in South Florida, USA, in 1995. Since then, genetic diversity has improved, the frequency of morphological and biomedical correlates of inbreeding depression have declined, and the population size has increased. Nevertheless, the panther population remains small and isolated and faces substantial challenges due to deterministic and stochastic forces. Our goals were 1) to comprehensively assess the demographics of the Florida panther population using long‐term (1981–2015) field data and modeling to gauge the persistence of benefits accrued via genetic introgression and 2) to evaluate the effectiveness of various potential genetic management strategies. Translocation and introduction of female pumas (Puma concolor stanleyana) from Texas, USA, substantially improved genetic diversity. The average individual heterozygosity of canonical (non‐introgressed) panthers was 0.386 ± 0.012 (SE); for admixed panthers, it was 0.615 ± 0.007. Survival rates were strongly age‐dependent (kittens had the lowest survival rates), were positively affected by individual heterozygosity, and decreased with increasing population abundance. Overall annual kitten survival was 0.32 ± 0.09; sex did not have a clear effect on kitten survival. Annual survival of subadult and adult panthers differed by sex; regardless of age, females exhibited higher survival than males. Annual survival rates of subadult, prime adult, and old adult females were 0.97 ± 0.02, 0.86 ± 0.03, and 0.78 ± 0.09, respectively. Survival rates of subadult, prime adult, and old adult males were 0.66 ± 0.06, 0.77 ± 0.05, and 0.65 ± 0.10, respectively. For panthers of all ages, genetic ancestry strongly affected survival rate, where first filial generation (F1) admixed panthers of all ages exhibited the highest rates and canonical (mostly pre‐introgression panthers and their post‐introgression descendants) individuals exhibited the lowest rates. The most frequently observed causes of death of radio‐collared panthers were intraspecific aggression and vehicle collision. Cause‐specific mortality analyses revealed that mortality rates from vehicle collision, intraspecific aggression, other causes, and unknown causes were generally similar for males and females, although males were more likely to die from intraspecific aggression than females. The probability of reproduction and the annual number of kittens produced varied by age; evidence that ancestry or abundance influenced these parameters was weak. Predicted annual probabilities of reproduction were 0.35 ± 0.08, 0.50 ± 0.05, and 0.25 ± 0.06 for subadult, prime adult, and old adult females, respectively. The number of kittens predicted to be produced annually by subadult, prime adult, and old adult females were 2.80 ± 0.75, 2.67 ± 0.43, and 2.28 ± 0.83, respectively. The stochastic annual population growth rate estimated using a matrix population model was 1.04 (95% CI = 0.72–1.41). An individual‐based population model predicted that the probability that the population would fall below 10 panthers within 100 years (quasi‐extinction) was 1.4% (0–0.8%) if the adverse effects of genetic erosion were ignored. However, when the effect of genetic erosion was considered, the probability of quasi‐extinction within 100 years increased to 17% (0–100%). Mean times to quasi‐extinction, conditioned on going quasi‐extinct within 100 years, was 22 (0–75) years when the effect of genetic erosion was considered. Sensitivity analyses revealed that the probability of quasi‐extinction and expected time until quasi‐extinction were most sensitive to changes in kitten survival parameters. Without genetic management intervention, the Florida panther population would face a substantially increased risk of quasi‐extinction. The question, therefore, is not whether genetic management of the Florida panther population is needed but when and how it should be implemented. Thus, we evaluated genetic and population consequences of alternative genetic introgression strategies to identify optimal management actions using individual‐based simulation models. Releasing 5 pumas every 20 years would cost much less ($200,000 over 100 years) than releasing 15 pumas every 10 years ($1,200,000 over 100 years) yet would reduce the risk of quasi‐extinction by comparable amount (44–59% vs. 40–58%). Generally, releasing more females per introgression attempt provided little added benefit. The positive effects of the genetic introgression project persist in the panther population after 20 years. We suggest that managers contemplate repeating genetic introgression by releasing 5–10 individuals from other puma populations every 20–40 years. We also recommend that managers continue to collect data that will permit estimation and monitoring of kitten, adult, and subadult survival. We identified these parameters via sensitivity analyses as most critical in terms of their impact on the probability of and expected times to quasi‐extinction. The continuation of long‐term monitoring should permit the adaptation of genetic management strategies as necessary while collecting data that have proved essential in assessing the genetic and demographic health of the population. The prospects for recovery of the panther will certainly be improved by following these guidelines. © 2019 The Authors. Wildlife Monographs published by Wiley Periodicals, Inc. on behalf of The Wildlife Society. [ABSTRACT FROM AUTHOR]

Understanding fitness level among various breeds is essential for sustainable meat goat production. Research on the relative fitness of Boer F1 does and straightbred base breed has been limited. Meat goat does of various genotypes (Boer, Kiko, Spanish, Boer × Kiko reciprocal F1 crosses, and Boer × Spanish reciprocal F1 crosses) were studied to evaluate breed effects on doe fitness traits and the expression of heterosis over 7 production years. The herd was semi-intensively managed under humid subtropical pasture. Doe age affected (P < 0.05) various traits. Boer × Kiko does were heavier (P < 0.05) than Boer does at fall breeding, but Boer × Spanish does did not differ (P > 0.05) from Boer does for breeding weight. The body weights of Boer × Spanish and Boer × Kiko crosses did not differ (P > 0.05) from the weights of their respective Kiko and Spanish base cohorts at breeding, kidding, or weaning. Boer does had lower (P < 0.05) kidding rate (KR) and weaning rate (WR) than the other breeds and crosses. Boer × Kiko and Kiko were similar for KR and WR. Boer × Spanish and Spanish were also similar for KR and WR. However, the combined group of Boer F1 does had lower (P < 0.01) KR and WR than the combined purebred biotype group of Kiko and Spanish does. Boer does weaned smaller (P < 0.05) litter sizes per doe exposed compared with Kiko, Spanish, Boer × Kiko, and Boer × Spanish does with the latter four doe breedtypes not differing from each other. The combined Boer F1 doe group weaned smaller (P < 0.05) litter sizes per doe exposed than the combined purebred group of Kiko and Spanish does. Boer × Kiko dams had higher (P < 0.05) fecal egg counts at parturition than Kiko dams. Significant heterosis was observed for reproductive traits within each of the 2-breed diallels. Boer F1 does exhibited reproductive output similar to or lower than Kiko and Spanish straightbred does and higher than Boer straightbred does. [ABSTRACT FROM AUTHOR]

The Spooner Agricultural Research Station operated the only dairy sheep research flock in North America through 2016. The original nondairy ewe flock was "bred up" to a crossbred dairy flock through the use of rams and semen of the East Friesian (EF) and Lacaune (LA) dairy breeds. The objective of this study was to determine the environmental and nonadditive genetic effects that influence performance of dairy ewes. The traits analyzed were 180 d adjusted milk (180d MY), fat (180d FY), and protein (180d PY) yields, percentage fat (%F) and protein (%P) in milk, lactation average somatic cell score (LSCS), and number of lambs born per ewe lambing (NLB). The univariate repeatability models included the fixed effects of year of lambing, age, weaning system (except for the trait of NLB), individual breed composition, and individual retained heterosis along with the random additive genetic, permanent environmental, and residual effects. Estimates of heritability were moderate for 180d MY (0.32 ± 0.04), 180d FY (0.26 ± 0.04), and 180d PY (0.29 ± 0.04), high for %F (0.54 ± 0.04) and %P (0.61 ± 0.04), and low for LSCS (0.12 ± 0.03) and NLB (0.08 ± 0.02). Ewes that reared their lambs had lower (P < 0.01) 180d MY, 180d FY, 180d PY, %F, and %P and higher (P < 0.001) LSCS than ewes that had their lambs removed shortly after parturition. Relative to nondairy breeding, EF and LA breeding had positive (P < 0.001) effects on 180d MY, 180d FY, and 180d PY, but a negative (P < 0.03) effect on %P. Purebred EF ewes were predicted to have lower (P < 0.001) %F than purebred LA or nondairy ewes. Purebred LA ewes were predicted to have a higher (P < 0.001) LSCS than purebred EF or nondairy ewes. Purebred EF ewes were expected to be more (P < 0.001) prolific than purebred LA or nondairy ewes. Individual retained heterosis had a favorable (P < 0.01) effect on 180d MY, 180d FY, 180d PY, and NLB. Knowledge of the factors affecting dairy ewe performance are important for dairy sheep producers to make more informed husbandry and breeding decisions. [ABSTRACT FROM AUTHOR]

Understanding the genetic relationships among broad-based populations is a good starting point for breeding programs. These utilize introduction and adaptation of tropical and temperate populations to broaden the genetic resources for genetic improvement. A diallel of 16 maize populations adapted to the northern U.S. Corn Belt was used to estimate population genetic parameters. These were used to assess genetic diversity and assign the populations to heterotic groups. Using the general combining ability ( g) estimates, 19 agronomic and grain quality traits showed large contribution on the variability of the first two principal components. All traits were used to characterize the genetic similarities among the populations. The cluster analysis formed three groups and a singleton based on genetic distances (GD) of g estimates. The specific heterosis ( s) estimates for grain yield were used to assign the 16 populations to heterotic groups, since there was a positive correlation between GD and s. Four heterotic groups were established. These showed a good agreement with that formed using GD. The heterotic grouping agreed with genetic background information and heterotic group's specific and general combining ability estimates. The EARLYGEM 21 populations with exotic background were assigned to a unique heterotic group. They showed high heterosis when crossed with a tropical population and populations belonging from other heterotic groups. The heterotic groupings among the 16 populations validated former heterotic groups, and new heterotic patterns were created. These results will increase breeding efficiency in developing new cultivars for the northern U.S. Corn Belt. [ABSTRACT FROM AUTHOR]

• Hybrid rice yield declined in response to a high heat event at anthesis and grainfill. • Single grain mass decreased with temperature but increased with CO 2. • Elevated CO 2 concentration did not compensate for effects of high heat. • Grain chalk expression increased as much as 40% at highest temperature levels. Changing climate conditions are influencing quality and yield of the United States rice (Oryza sativa L.) export industry. The occurrence of high heat episodes, along with rising atmospheric carbon dioxide (CO 2), is of particular concern for as-yet uncharacterized hybrid varieties. A popular rice hybrid was grown in soil-plant-atmosphere-research (SPAR) chambers under two CO 2 levels (450 or 740 ppm) and subjected to one of three day/night temperature regimes during anthesis and grainfill: a control temperature (T) (0C) of 28/22°C, and a +4° (4C) or +8°C (8C) increase. There was little difference in biomass between 0 and 4C levels; however, yields at the 8C level declined by over 50%, by about 28 or 34 g plant−1°C−1 for ambient or elevated CO 2 grown rice, respectively. There was little difference in fraction of biomass allocated among leaf, stem or panicle at 0 or 4C, but the proportion declined by about 31% to the panicles at 8C. Total productive tiller numbers and grainfill percentages were similar across CO 2 levels at each T treatment such that yield declines were associated primarily with a decrease in grain number and mass. Slightly higher values for yield and harvest index were observed under elevated CO 2 at the 3 T levels which was attributed to an average 10 mg increase in single grain weight. An interaction of CO 2 and T on chalk content was observed, with expression at the +4°C treatment 11% higher for elevated versus ambient CO 2 ; however, chalk expression was similar for CO 2 levels at the +8°C treatment. Breeding efforts associated with climate resiliency should consider traits associated with hybrid vigor as well as high temperature resistance for grain sterility and quality factor responses. [ABSTRACT FROM AUTHOR]

The article focuses on a study to determine heterosis and breed genetic effects for carcass quantity, quality and palatability traits of steers produced from striaghtbred and crossbred of Romosinuano, Brahman and Angus bulls and cows. It informs that Romosinuano steers had some quality and palatability advantage relative to Brahman but did not provide a clear superior alternative to Brahman for U.S. producers. It discusses the results which states that Romosinuano-Angus estimates was smallest.

The genetic basis of heterosis in maize has been investigated in a number of studies but results have not been conclusive. Here, we compare quantitative trait loci (QTL) mapping results for grain yield, grain moisture, and plant height from three populations derived from crosses of the heterotic pattern Iowa Stiff Stalk Synthetic × Lancaster Sure Crop, investigated with the Design III, and analyzed with advanced statistical methods specifically developed to examine the genetic basis of mid-parent heterosis (MPH). In two populations, QTL analyses were conducted with a joint fit of linear transformations Z1 (trait mean across pairs of backcross progenies) and Z2 (half the trait difference between pairs of backcross progenies) to estimate augmented additive and augmented dominance effects of each QTL, as well as their ratio. QTL results for the third population were obtained from the literature. For Z2 of grain yield, congruency of QTL positions was high across populations, and a large proportion of the genetic variance (~70%) was accounted for by QTL. This was not the case for Z1 or the other two traits. Further, almost all congruent grain yield QTL were located in the same or an adjacent bin encompassing the centromere. We conclude that different alleles have been fixed in each heterotic pool, which in combination with allele(s) from the opposite heterotic pool lead to high MPH for grain yield. Their positive interactions very likely form the base line for the superior performance of the heterotic pattern under study. [ABSTRACT FROM AUTHOR]

The overall motivation for the development of an information system for beef cattle improvement is the belief that knowledge of breeding values and heterosis effects allows one to determine the consequences of alternative selection and mating options. With this information, livestock managers can easily shift populations in a desirable direction. The foundation principles for establishing a sound breeding program, including the prediction of animal performance for economically relevant traits and their incorporation into a single index of aggregate economic merit, have been well established over the last half century. Rather than this goal-based approach, the industry adopted a data-driven approach to the production of genetic evaluations that has been characterized by an overemphasis on the evaluation of productive traits, notably BW at various ages, with inadequate regard for other economically important traits, such as reproduction, animal health, and feed requirements. Production of evaluations is breed association centered, and this has delayed the introduction of national across-breed evaluations for all breeds and crosses of cattle. The computational aspects of producing evaluations are now migrating from land-grant universities to breed associations, but not yet to a single entity. The introduction of genomic information in the form of high-density SNP panels will introduce threats, challenges, and new opportunities for the production of evaluations, and represents the largest force to alter the structure of the beef improvement industry since the advent of AI. The use of evaluations has, until recently, stopped short of the provision of index merit as a basis for selection. Accordingly, the value propositions associated with annual improvement or the selection of alternative sires has not been well communicated. Technology, along with economic and other issues related to stakeholder acceptance, will collectively determine the future nature of the industry in terms of the production and use of evaluations. [ABSTRACT FROM AUTHOR]

Increasing the yield of alfalfa (Medicago sativa L.) is a desirable breeding goal. The objective of this experiment was to test the hypothesis that hybrids between nondormant-derived alfalfa germplasm selected for winter hardiness and semidormant germplasm will express heterosis for yield. Four semidormant cultivars and four nondormant-derived populations were handcrossed in a half-diallel mating design to form population hybrids. Both seeded and transplanted trials were grown in Iowa between 2003 and 2005. Total biomass yield was measured at four harvests each year. The nondormant-derived germplasm produced lower yields than the semidormant cultivars. The hybrids between groups were intermediate to the parents with little evidence of heterosis in any environment or for any harvest during the year. Although particular crosses produced high yields in certain environments, no general heterotic pattern was observed between the two proposed groups. A Gardner and Eberhart Analysis III indicated the presence of variation for both general combining ability and specific combining ability effects of approximately equal magnitude among these eight populations. The nondormant germplasm sources used here do not form a new heterotic group for midwestern U.S. alfalfa breeding programs. [ABSTRACT FROM AUTHOR]

The origin of U.S. Corn Belt corn (Zea mays L.), heterotic groups, and heterotic patterns becomes less obvious with more cycles of breeding. Heterosis is poorly understood; simple curiosity cries out for more information. I endeavor to shed light on the effect of adaptedness and heterosis on U.S. Corn Belt corn. I relate pertinent happenings in the phenomenal increase in U.S. corn production. I briefly review the origins of Northern Flint and Southern Dent races of corn and two major, persistent open-pollinated cultivars; and how corn hybridization was preceded and eased by hybrid species of the horse (Equus spp.). I discuss heterotic groups and patterns. The objective of U.S. corn breeding has been to adapt a tropical crop to a temperate climate. Adaptedness is important. Open-pollinated cultivars emphasized local adaptation, but some cultivars were more popular, widely grown, and better adapted over a broad geographic region. Hybrid seed corn companies grew larger by selling more widely adapted hybrids that favored germplasm from the more popular, widely grown, better adapted open-pollinated cultivars containing more genes for adaptedness. I examine morphological differences between inbred parents of a widely adapted hybrid. Relatively constant percentage of heterosis of well-adapted hybrids over years is due to seasonal climate affecting hybrids and their parent inbreds in a like manner because of their selection for adaptedness. Adaptedness has been more important than heterosis in the U.S. corn yield and production increases. Adaptedness in analogous heterotic species hybrids of the genus Equus, where body size is female dominant, apparently discriminates for body size between mules and hinnies that have virtually identical genotypes—adaptedness determines superiority over and above heterosis. [ABSTRACT FROM AUTHOR]

The influence of different levels of adjusted fat thickness (AFT) and HCW slaughter end points (covariates) on estimates of breed and retained heterosis effects was studied for 14 carcass traits from serially slaughtered purebred and composite steers from the US Meat Animal Research Center (MARC). Contrasts among breed solutions were estimated at 0.7, 1.1, and 1.5 cm of AFT, and at 295.1, 340.5, and 385.9 kg of HCW. For constant slaughter age, contrasts were adjusted to the overall mean (432.5 d). Breed effects for Red Poll, Hereford, Limousin, Braunvieh, Pinzgauer, Gelbvieh, Simmental, Charolais, MARC I, MARC II, and MARC III were estimated as deviations from Angus. In addition, purebreds were pooled into 3 groups based on lean-to-fat ratio, and then differences were estimated among groups. Retention of combined individual and maternal heterosis was estimated for each composite. Mean retained heterosis for the 3 composites also was estimated. Breed rankings and expression of heterosis varied within and among end points. For example, Charolais had greater (P < 0.05) dressing percentages than Angus at the 2 largest levels of AFT and smaller (P < 0.01) percentages at the 2 largest levels of HCW, whereas the 2 breeds did not differ (P ≥ 0.05) at a constant age. The MARC III composite produced 9.7 kg more (P < 0.01) fat than Angus at AFT of 0.7 cm, but 7.9 kg less (P < 0.05) at AFT of 1.5 cm. For MARC III, the estimate of retained heterosis for HCW was significant (P < 0.05) at the lowest level of AFT, but at the intermediate and greatest levels estimates were nil. The pattern was the same for MARC I and MARC III for LM area. Adjustment for age resulted in near zero estimates of retained heterosis for AFT, and similarly, adjustment for HCW resulted in nil estimates of retained heterosis for LM area. For actual retail product as a percentage of HCW, the estimate of retained heterosis for MARC III was negative (-1.27%; P < 0.05) at 0.7 cm but was significantly positive (2.55%; P < 0.05) at 1.5 cm of AFT. Furthermore, for MARC III, estimates of heterosis for some traits (fat as a percentage of HCW as another example) also doubled in magnitude depending on different levels of AFT end point. Rational exploitation of breeds requires special attention to use of different end points and levels of those end points, mainly for fat thickness. [ABSTRACT FROM AUTHOR]

Foxtail millet [Setaria italica (L.) P. Beauv.] is a largely self-pollinating species that is used as a warm-season annual in the USA. Nearly all cultivars of this species grown in the USA are selections from land races. This research was undertaken to determine whether sufficient high-parent heterosis is expressed in foxtail millet for grain yield and other key traits to justify the development and use of varietal crosses. Seven diverse parents and 21 F2s and 21 F3s produced from biparental crosses were evaluated in five environments in 1996. Genotype × environment interaction was highly significant for grain yield, but the highest yielding entries were high-yielding in each environment. High-parent heterosis for grain yield was detected in 18 of 21 F2s. On the basis of the estimate of average heterosis, which was highly significant in every environment, the expected yield of the F1 generation was 68% greater than the average yield of the parental cultivars. This high level of heterosis for grain yield suggested that varietal crosses or other types of cultivars in which there exists a relatively high amount of heterozygosity would provide a significant yield benefit over nonhybrid cultivars. Although significant heterotic effects were observed for each of the other traits, additive effects were more important. Significant correlations between traits of the estimates of additive and/or variety heterosis effects suggested that at least some of the genes controlling grain yield, plant height, and spike length were either the same or in coupling phase linkage. [ABSTRACT FROM AUTHOR]

There are currently no policy guidelines for treating hybrids under the U.S. Endangered Species Act (ESA). We considered the scientific basis for determining whether hybridized populations should be included as part of the westslope cutthroat trout (Oncorhynchus clarki lewisi) unit considered for listing under the ESA. Westslope cutthroat trout are threatened by genomic extinction because of widespread introgressive hybridization with introduced rainbow trout (O. mykiss) and Yellowstone cutthroat trout (O. c. bouvieri). Experimental results suggest that first-generation hybrids between westslope cutthroat trout and rainbow trout have reduced fitness. However, hybridization may spread even when hybrids have severely reduced fitness because the production of hybrids is unidirectional—that is, all the progeny of a hybrid will be hybrids. In addition, heterosis resulting from the sheltering of deleterious recessive alleles in early-generation hybrids may increase the effective rate of introgression. However, such short-term increases in fitness may disrupt important long-term adaptations of native populations. The loss of these adaptations will be difficult to detect because some local adaptations might only be apparent during periodic episodes of extreme environmental conditions, such as winter storms, drought, or fire. Thus, rapid spread of hybridization could result in the loss of local adaptations in native populations of westslope cutthroat trout and decrease their probability of long-term persistence. Protection of populations with some admixture would protect sources of spreading hybridization. Treatment of hybrids in conservation planning depends primarily on the amount of evolutionary divergence between the hybridizing taxa and the geographical extent of introgression. We recommend that only nonhybridized populations be included as westslope cutthroat trout in the unit to be considered for listing. Populations of unknown status should be protected until more information about these populations becomes available. [ABSTRACT FROM AUTHOR]

Protein meal and oil are the two commodities produced from soybean [Glycine max (L.) Merr.] that give the crop its value. Increasing seed concentrations of either or both may add value. Objectives of this study were to investigate the effectiveness of recurrent halfsib selection for increased seed oil, to evaluate the effect of tester oil content on selection response, and to investigate testcross heterosis and inbreeding depression for seed oil content. A recurrent half-sib selection system was devised for soybean and selection for increased oil content was conducted in a population for seven and three cycles using a high and a low-oil tester, respectively. The base population was a high-oil composite with gray pubescence (tt) that was segregating for nuclear genetic ms[sub 1] male sterility. In summer, the base population was planted in single plant hills and bordered with the tester (Ms[sub 1]Ms[sub 1]TT) in a random mating block in North Carolina. About 100 to 200 random male-sterile plants with hybrid seeds were harvested. Half-sib families derived from each male-sterile plant were then grown in Puerto Rico in winter. At maturity, seeds from tawny plants (tester hybrid) were used to identify half-sib families with high-oil content. Corresponding gray plant hybrids from sib matings within the population were bulked to start the next cycle of selection. Random progenies from the base populations and selected progenies from each cycle of selection were evaluated in a replicated field experiment at three locations in North Carolina. Cycle × tester hybrids and cycle x cycle sib hybrids were also included in the tests. The results showed that oil content was significantly increased at a rate of 1.1 ± 0.2 g kg[sup -1] cycle[sup -1] in the highoil tester populations but not in the low-oil tester populations. The realized heritability estimate for the high-oil tester population was 0.12 ± 0.03. Evidence of heterosis indicated that some dominance effects on oil content existed. Dominance effects may affect the evaluation accuracy of the genotypes being tested. A high-oil tester and high-oil populations may have many common alleles resulting in less dominance and more additive effects in their hybrids. Consequently, a high-oil tester can lead to better evaluation and selection precision, compared with a low-oil tester which could mask additive effects and reduce selection precision. [ABSTRACT FROM AUTHOR]

Examines the increase of forage yield heterosis of alfalfa in the U.S. Advantages of semihybrid breeding systems; Heterotic pattern of Medicago sativa species; Use of sativa-falcata heterosis for alfalfa breeding.

Presents a study which evaluated the advantage of hybrid cultivars and the magnitude of heterosis in spring canola in Northern Idaho. Details on the increase of spring canola in the Pacific Northwest; Methodology used to conduct the study; Results of the study.

• Eastern (Kansas) and Western (California) populations of Hippodamia convergens are genetically structured and phenotypically different. • Here we test their genotypic and phenotypic variation in utilization of pea aphids in a common garden setting. • Eastern and Western populations are genetically structured. • Eastern and Western populations do not outcompete each other in pea aphid utilization. • Additionally, Eastern, Western, and Hybrid populations do not outcompete each other in pea aphid utilization. The convergent lady beetle (Hippodamia convergens) is a generalist natural enemy that is utilized extensively in augmentative biological control across the United States. Recent studies have pointed to both genetic and phenotypic differences in Western (California) versus Eastern (Kansas) populations of the species. Here we investigate (1) genetic population structure, and (2) phenotypic differences in the utilization of pea aphids at temperatures that resemble the Western United States in (a) Eastern versus Western populations, (b) F1 Eastern X Western hybrids versus their progenitor populations, and investigate the effects of competition between (c) Eastern and Western populations. We found no differences in final pupal weight, or the net weight gain ratio through larval development from the third instar to pupal stage, despite genetic population structure. Our study points towards plastic response and effectiveness in feeding phenotypes of Eastern and Western populations of H. convergens , and the absence of hybrid vigor and heterozygote advantages in hybrids. [ABSTRACT FROM AUTHOR]