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Tandem-repeat DNA sequences appear to be singularly capable of yielding abundant repeat-number mutations with a potentially advantageous distribution of fitness effects. Although knowing the rates and relative proportions of deleterious, neutral and beneficial mutations is fundamental for understanding evolvability, analysis of adaptation routinely overlooks small-effect mutations arising in tandem repeats. Tandem-repeat DNA sequences appear to be singularly capable of yielding abundant repeat-number mutations with a potentially advantageous distribution of fitness effects. Although knowing the rates and relative proportions of deleterious, neutral and beneficial mutations are fundamental for understanding evolvability, analysis of adaptation routinely overlooks small-effect mutations arising in tandem repeats. [ABSTRACT FROM AUTHOR]

In shrimp production, product quality plays a crucial role and determines consumer acceptance. However, there are no studies on its genetic determination. The main purpose of this study was, for first time in Penaeus vannamei, to estimate the additive genetic variation of flesh quality traits in terms of composition and texture, and their genetic correlation with growth and morphological traits. To this end, 388 shrimps from the fourth generation of the PMG-BIOGEMAR© breeding program, belonging to 79 full-sib families, were reared under an extensive industrial culturing system (PRODUMAR, Durán, Ecuador). At the same day, they were harvested and measured for fresh weight. They were kept at −20 °C for later sampling for flesh quality traits, in terms of composition, by Near-Infrared spectroscopy (NIR), and texture by Texture analyzer technologies. Growth and morphological traits were manually measured with a vernier caliper. Low heritabilities were estimated for flesh composition traits (0.01 to 0.07), and low-medium for meat quality traits related to texture (0.01 to 0.37). Medium-high heritabilities were estimated for total length and weight (0.35 and 0.50, respectively), with a very high genetic correlation between both (0.99). Regarding morphological traits, heritabilities ranged from 0.05 to 0.52 for length-related traits, from 0.15 to 0.36 for height-related traits, and from 0.22 to 0.42 for width-related traits. Cephalothorax length showed the highest heritability among all analyzed traits (0.52), with high genetic correlations with growth, flesh composition, and texture traits. The high genetic correlations found between growth and morphometric traits, and both flesh composition and texture traits suggest indirect selection as a successful, undemanding, and cost-effective method to obtain high-quality shrimps under industrial conditions. • High heritability and positive correlations with growth and meat traits were observed for shrimp cephalothorax length • Meat quality showed low heritabilities but high and positive genetic correlations with growth and morphological traits. • High genetic correlations between growth, morphology, and meat quality traits suggest indirect selection in P. vannamei. • Shrimp body hardness showed a medium heritability, which was the highest of all the meat quality traits. [ABSTRACT FROM AUTHOR]

The objective of this study was to estimate genetic parameters of predicted N use efficiency (PNUE) and N losses (PNL) as proxies of N use and loss for Holstein cows. Furthermore, we have assessed approximate genetic correlations between PNUE, PNL, and dairy production, health, longevity, and conformation traits. These traits are considered important in many countries and are currently evaluated by the International Bull Evaluation Service (Interbull). The values of PNUE and PNL were obtained by using the combined milk mid-infrared (MIR) spectrum, parity, and milk yield–based prediction equations on test-day MIR records with days in milk (DIM) between 5 and 50 d. After editing, the final data set comprised 46,163 records of 21,462 cows from 154 farms in 5 countries. Each trait was divided into primiparous and multiparous (including second to fifth parity) groups. Genetic parameters and breeding values were estimated by using a multitrait (2-trait, 2-parity classes) repeatability model. Herd-year-season of calving, DIM, age of calving, and parity were used as fixed effects. Random effects were defined as parity (within-parity permanent environment), nongenetic cow (across-parity permanent environment), additive genetic animal, and residual effects. The estimated heritability of PNUE and PNL in the first and later parity were 0.13, 0.12, 0.14, and 0.13, and the repeatability values were 0.49, 0.40, 0.55, and 0.43, respectively. The estimated approximate genetic correlations between PNUE and PNL were negative and high (from −0.89 to −0.53), whereas the phenotypic correlations were also negative but relatively low (from −0.45 to −0.11). At a level of reliability of more than 0.30 for all novel traits, a total of 504 bulls born after 1995 had also publishable Interbull multiple-trait across-country estimated breeding values (EBV). The approximate genetic correlations between PNUE and the other 30 traits of interest, estimated as corrected correlations between EBV of bulls, ranged from −0.46 (udder depth) to 0.47 (milk yield). Obtained results showed the complex genetic relationship between efficiency, production, and other traits: for instance, more efficient cows seem to give more milk, which is linked to deeper udders, but seem to have lower health, fertility, and longevity. Additionally, the approximate genetic correlations between PNL, lower values representing less loss of N, and the 30 other traits, were from −0.32 (angularity) to 0.57 (direct calving ease). Even if further research is needed, our results provided preliminary evidence that the PNUE and PNL traits used as proxies could be included in genetic improvement programs in Holstein cows and could help their management. [ABSTRACT FROM AUTHOR]

Indirect selection is a useful tool for the selection of complex traits like vase life (VL) of cut carnations. Our objective, therefore, was to assess the relative merit of indirect selection compared to direct selection. Phenotypic and genetic correlations were calculated for traits such as VL, flower diameter (FD) of standard carnation, stem length (SL) and count of flowers (CF) in mini carnations, phenotyped in three different experiments. The experiments are special in that some traits are measured in a second phase. Data were analyzed by bivariate mixed models considering in which phase the trait was measured. Some relevant genetic correlations were found in VL and FD and the traits SL and CF, but our results indicate that indirect selection would show no benefit compared to direct selection. However, the combination of direct and indirect selection could improve breeding of long-lasting cut carnations. [ABSTRACT FROM AUTHOR]

Recent studies with Nile tilapia have shown divergent results regarding the possibility of selecting on morphometric measurements to promote indirect genetic gains in fillet yield (FY). The use of indirect selection for fillet traits is important as these traits are only measurable after harvesting. Random regression models are a powerful tool in association studies to identify the best time point to measure and select animals. Random regression models can also be applied in a multiple trait approach to analyze indirect response to selection, which would avoid the need to sacrifice candidate fish. Therefore, the aim of this study was to investigate the genetic relationships between several body measurements, weight and fillet traits throughout the growth period and to evaluate the possibility of indirect selection for fillet traits in Nile tilapia. Data were collected from 2042 fish and was divided into two subsets. The first subset was used to estimate genetic parameters, including the permanent environmental effect for BW and body measurements (8758 records for each body measurement, as each fish was individually weighed and measured a maximum of six times). The second subset (2042 records for each trait) was used to estimate genetic correlations and heritabilities, which enabled the calculation of correlated response efficiencies between body measurements and the fillet traits. Heritability estimates across ages ranged from 0.05 to 0.5 for height, 0.02 to 0.48 for corrected length (CL), 0.05 to 0.68 for width, 0.08 to 0.57 for fillet weight (FW) and 0.12 to 0.42 for FY. All genetic correlation estimates between body measurements and FW were positive and strong (0.64 to 0.98). The estimates of genetic correlation between body measurements and FY were positive (except for CL at some ages), but weak to moderate (-0.08 to 0.68). These estimates resulted in strong and favorable correlated response efficiencies for FW and positive, but moderate for FY. These results indicate the possibility of achieving indirect genetic gains for FW and by selecting for morphometric traits, but low efficiency for FY when compared with direct selection. [ABSTRACT FROM AUTHOR]

Genetic parameters for carcass and fillet percentage were estimated in 760 European sea bass reared under commercial conditions and slaughtered at 573 days post fertilization (395 g mean body weight). Phenotyped fish were the offspring of 45 sires and 20 dams crossed in a factorial mating design. Pedigrees were re-constructed with 90.7% success using 12 microsatellites. The heritability of fillet yield was moderately low (0.21), while it was high for carcass yield (0.57). Both traits were poorly correlated (− 0.01 to 0.28) making space for their combined improvement. We investigated different predictors derived from measurement of surfaces on digital pictures and ultrasound measurements at several points of the body. The accuracy of the phenotypic prediction was rather low for fillet yield (r 2 = 0.02–0.18), but higher for carcass yield (r 2 = 0.27–0.41). However, genetic correlations of predictors with the traits to predict were reasonably high (up to 0.67 for fillet yield and 0.95 for carcass yield), thus allowing to consider them for performing indirect individual selection instead of sib selection. However, it was difficult to design a predictor that would simultaneously increase fillet yield and carcass yield because of contradicting effects of relative head size, an important component of the predictors which was positively correlated to carcass yield but not to fillet yield. Statement of relevance We estimated phenotypic predictors for processing yields in the European sea bass and estimated their genetic variation and correlations with the traits to predict. This is important to be able to apply indirect selection for processing yields in this species. This showed that although the traits of interest were hardly correlated, it was not possible to find external predictors having a significant positive impacts on both traits (carcass and fillet yield) simultaneously. This highlights the need to study specifically these issues in different species and conditions, as the picture here is very different to the well studied case of rainbow trout for example. [ABSTRACT FROM AUTHOR]

Physiological studies have led to the identification of many traits hypothesized to be useful for breeding improved crop performance. The effect of selection for these traits on yield across breeding populations and across target environments is generally unknown, such that crop breeders may have difficulty in prioritizing evaluation resources among potentially many traits. A simple method to estimate the effect on crop performance from selection on a proposed trait would facilitate trait adoption toward implementation and delivery in improved varieties. The response to indirect selection for different traits can be accurately predicted with nearly-isogenic lines differing for only small regions of the genome and those traits under investigation. An alternative approach better suited to complex, polygenic traits is the assessment of direct and indirect response in ‘tails’ representing phenotypic extremes from a distribution for a target trait. The smaller set of lines representing the two tail groups can then be evaluated more extensively for yield or other expensive and difficult to phenotype traits. Assuming an infinitesimal model appropriate for polygenic traits, we used simulations to understand the influence of population size, proportion of lines sampled in each tail group, trait heritability, and the genotypic correlation between the selection and evaluation trait on the resulting difference between tail means. The power of the tail comparison test was closely related to the heritability of the selection trait and its genotypic correlation with the evaluation trait, demonstrating that the tail comparison test can appropriately evaluate and rank the potential utility of different selection traits. Increasing the entry-mean heritability through multiple environment testing can be coupled with larger population and tail group sizes to increase power and confidence in assessment of both selection and response trait values. We assessed the selection of phenotypic distribution tails for water productivity traits in wheat. Reduced-tillering tails were associated with an average 14% reduction in tiller number and significantly reduced yields (−5%), particularly at wider row-spacings. High vigour tails were associated with a 49% increase in early ground cover, 40% increase in NDVI score, and greater yields (+18%) across all sampled environments. Assessment of population tails across multiple genetic backgrounds will guide selection in commercial breeding programs and facilitate trait delivery in improved cultivars. [ABSTRACT FROM AUTHOR]

The difficulties and costs of measuring individual feed intake in dairy cattle are the primary factors limiting the genetic study of feed intake and utilisation, and hence the potential of their subsequent industry-wide applications. However, indirect selection based on heritable, easily measurable, and genetically correlated traits, such as conformation traits, may be an alternative approach to improve feed efficiency. The aim of this study was to estimate genetic and phenotypic correlations among feed intake, production, and feed efficiency traits (particularly residual feed intake; RFI) with routinely recorded conformation traits. A total of 496 repeated records from 260 Holstein dairy cows in different lactations (260, 159 and 77 from first, second and third lactation, respectively) were considered in this study. Individual daily feed intake and monthly BW and body condition scores of these animals were recorded from 5 to 305 days in milk within each lactation from June 2007 to July 2013. Milk yield and composition data of all animals within each lactation were retrieved, and the first lactation conformation traits for primiparous animals were extracted from databases. Individual RFI over 301 days was estimated using linear regression of total 301 days actual energy intake on a total of 301 days estimated traits of metabolic BW, milk production energy requirement, and empty BW change. Pair-wise bivariate animal models were used to estimate genetic and phenotypic parameters among the studied traits. Estimated heritabilities of total intake and production traits ranged from 0.27±0.07 for lactation actual energy intake to 0.45±0.08 for average body condition score over 301 days of the lactation period. RFI showed a moderate heritability estimate (0.20±0.03) and non-significant phenotypic and genetic correlations with lactation 3.5 % fat-corrected milk and average BW over lactation. Among the conformation traits, dairy strength, stature, rear attachment width, chest width and pin width had significant (P<0.05) moderate to strong genetic correlations with RFI. Combinations of these conformation traits could be used as RFI indicators in the dairy genetic improvement programmes to increase the accuracy of the genetic evaluation of feed intake and utilisation included in the index. [ABSTRACT FROM PUBLISHER]

Faster growth has been the primary goal of the few existing selection programs for Nile tilapia. However, carcass yield (CY) is a major factor for tilapia production chain efficiency. The use of indirect selection for CY is vital because direct data collection is only possible after slaughter. The aim of this study was to estimate heritability and correlation between body weight (BW), CY, height (H), width (W) and corrected length (CL) as functions of standardized ages in Nile tilapia. Bivariate animal model analyses were conducted for all traits at five ages (119, 147, 175, 203 and 231 days) and 16 distinct models for fixed and random effects were compared. Heritability estimates through all ages varied from 0.20 to 0.94 for CY, 0.21 to 0.44 for BW, 0.21 to 0.40 for H, 0.13 to 0.80 for W and 0.19 to 0.48 for CL. All genetic correlation estimates were positive, and those between BW and morphometric traits (0.66–1.00) at all ages, CY and H (0.71) at 119 days, and CY and CL (0.58) at 231 days were high. These results highlight the possibility of achieving high genetic gains with selection for any of these traits. These correlations indicate the possibility of achieving indirect genetic gains for CY and BW by the selection of morphometric traits. Statement of Relevance Novelties on direct and indirect selection for carcass yield. [ABSTRACT FROM AUTHOR]

Terminal drought stress strongly affects wheat grain yield under Mediterranean conditions. Therefore, developing early-heading bread wheat cultivars in these conditions is an important breeding strategy. In the present research, earliness was transferred from the Australian cultivar, Excalibur, to three Iranian cultivars, Roshan, Kalheydari and Mahdavi, in separate backcross (BC) breeding programs from 2012 to 2018. The earliest and latest heading genotypes of each BC 3 population, were selected as near-isogenic lines (NILs). NILs and their parents were assessed under diverse field conditions including rain-fed, moderate drought stress and well-watered conditions in three locations, Kerman, Sepidan and Semirom, during two growing seasons, 2018–2019 and 2019–2020. Breeding for early heading significantly improved earliness in all genetic backgrounds and increased grain yield by 36.4% and 9.6%, in the rain-fed and moderate drought stress conditions, respectively. Whereas, grain yield was not significantly affected by early heading under well-watered conditions. Results showed that breeding for early heading, a highly heritable trait, is an appropriate method to increase grain yield and reduce water consumption under drought stress and well-watered conditions, respectively. Based on these findings, we recommend transferring early heading to high yield late heading commercial cultivars using backcrossing. • For the first time, near isogenic lines of early heading were developed. • Breeding for early heading increased grain yield by 36.4% in rain-fed conditions. • Early heading increased grain yield by 9.6% in moderate drought stress conditions. • Early heading did not affect grain yield under well-watered conditions in Kerman. [ABSTRACT FROM AUTHOR]

Carcass and fillet yields are traits of great economic importance in aquaculture species, including rainbow trout. Headless gutted carcass percentage (HC) is a convenient selection criterion to improve carcass yield given that it is highly genetically correlated with the latter and also with fillet yield. However, HC is a sib trait that cannot be recorded on selection candidates. Consequently, the within-family component of the genetic variance cannot be exploited with traditional pedigree-based BLUP selection. Two alternatives to exploit this component would be to select directly on an indicator trait genetically correlated with HC that can be recorded on live candidates or to apply genomic selection. The objective of this simulation study was to predict the phenotypic gains for HC in rainbow trout breeding programs when four alternative selection strategies are used: i) sib selection for HC, ii) indirect selection for a morphological indicator recorded in vivo; iii) genomic selection for HC; and iv) genomic selection for the indicator. Also, the four strategies were compared in a multitrait selection scenario where body weight was also included in the breeding objective. The different scenarios were compared at the same selection intensity and number of records (2000) for HC (on sibs) and IHC (on candidates). Two different heritabilities for HC (0.55 and 0.25) were considered. For the highest heritability, the phenotypic gain for HC was higher with sib than with indirect selection for both BLUP (1.03 versus 0.98) and genomic selection (1.22 versus 1.04). However, for the lowest heritability, the phenotypic gain for HC was lower with sib than with indirect selection for both BLUP (0.60 versus 0.64) and genomic selection (0.70 versus 0.71). In any case, the differences in phenotypic gains for HC between sib and indirect selection were not large. Therefore, given that sib selection implies extra costs associated with maintaining and genotyping sibs and indirect selection allows higher selection intensity for a given number of fish, indirect selection appears to be a more cost-effective option. The patterns found for single trait selection were maintained when the yield trait (HC or indicator) was selected simultaneously with body weight. We conclude that the optimum approach to improve carcass yield is a combination of genomic and indirect selection in both single and multitrait selection scenarios. • Gains for headless carcass from indirect and sib selection are similar • The highest increase in the phenotypic mean of headless carcass was obtained with genomic selection. • Indirect genomic selection on an indicator of headless carcass is the most profitable option to improve carcass yield • The benefit-cost ratio of indirect genomic selection will increase when including growth in the breeding goal [ABSTRACT FROM AUTHOR]

Abstract: Striga hermonthica is a major constraint to maize (Zea mays L.) production in sub-Saharan Africa. The use of secondary traits that have high heritability and genetic correlation with grain yield can improve the precision with which Striga resistant genotypes are identified. Fifteen early cultivars were evaluated under Striga-infested and Striga-free conditions for 2 years at Mokwa and Abuja, Nigeria. The objective was to examine their performance based on multiple traits under stress and non-stress conditions and analyze the interrelationship among traits using genotype-by-trait (GT) biplot so as to assess the value of traits used in the base index for selection for Striga resistance and improved grain yield (YLD). TZE-W DT STR C4 had the best performance based on multiple traits while TZE-W DT STR C4, TZE-Y DT STR C4, Multicob Early DT, and TZE-W DT STR QPM C0 were the closest to the ideal cultivar when Striga infested. Ears per plant, Striga damage at 8 and 10 weeks after planting, and ear aspect (EASP) were the most reliable traits for selecting for resistant genotypes. Striga emergence count at 8 and 10 weeks after planting were not among the reliable traits identified for selection for improved grain yield and their inclusion in the base index needs to be further verified. EASP had high correlation with grain yield and was one of the most reliable traits for selection for increased grain yield under Striga infestation and should be included in the index. [Copyright &y& Elsevier]

Abstract: Specific breeding for organic systems may help reduce their yield gap relative to conventional systems by exploiting genotype×system (GS) interaction. Likewise, specific breeding for distinct subregions within a region could capitalize on genotype×location (GL) interaction. Grain yield and test weight of common wheat varieties were evaluated under organic and conventional systems in ten locations spanning from northern to southern Italy, with the objectives of: (i) comparing production systems; (ii) investigating the extent of GS and GL interactions and their relationship with genotypic and environmental characteristics; and (iii) preliminarily comparing, in terms of predicted selection gains, different strategies to cope with GS and GL effects. These effects were investigated in the 2-year Data set 1 including seven genotypes. GS effects were also assessed in the annual Data sets 2 and 3 including 13 and 11 genotypes, respectively. The yield reduction of organic systems relative to conventional ones averaged 28% in Data set 1, 29% in Data set 2 and 14% in Data set 3. Organic systems also tended to a modest test weight reduction. Genetic correlations between systems ranged from high to very high (0.88≤ r g ≤0.98) for yield and test weight, owing to nil or limited GS interaction. Broad-sense heritability tended to be higher in conventional systems than organic ones for yield in two data sets (mainly due to lower experimental error) while being similar in the two systems in the other cases. Predicted selection gains suggested nil (yield) or very modest (test weight) advantage of direct selection in organic systems relative to indirect selection in conventional systems, when targeting organic systems. The scope for selection only in conventional systems was reinforced when comparing predicted gains for selection scenarios which target both systems in relation to their foreseeable marketing importance. GL effects for yield and test weight were significant and were modeled by additive main effects and multiplicative interaction analysis. Site classification based on GL effects for yield revealed a larger subregion A including northern and central Italy and a smaller subregion B comprising southern Italy, accordingly with previous, independent studies. Yield selection only in subregion A (with indirect selection gain for subregion B) implied slightly higher predicted gain for A (+4%) and much lower gain for B (−24%) relative to independent, direct selection in each subregion. Selection for specific geoclimatic subregions may have greater importance than selection for specific production systems. [Copyright &y& Elsevier]

Abstract: The plantation silviculture of mahogany (Swietenia spp.) has been severely limited by the attack of the mahogany shoot borer (Hypsipyla spp.), which greatly reduces or nullifies the commercial timber value of attacked trees by causing forking low on the stem. Selection for resistance, including tolerance (the capacity to retain apical dominance after attack), is widely considered to have potential as one element in an integrated pest management system. It has been suggested that the response of young seedlings to a predictive decapitation test might be useful as a means of detecting genotypes with high tolerance. This paper describes a pilot provenance/progeny experiment aimed at exploring this hypothesis. The number of shoots produced in response to attacks in the first year of field growth by Costa Rican material was found to be significantly correlated with response to decapitation in the nursery, on both individual tree and family mean bases. It appears, therefore, that the decapitation test could have a role in early selection for tolerance of Hypsipyla in mahogany. However, the presence of within-provenance genetic variation in response to Hypsipyla attack was not established. [Copyright &y& Elsevier]

Abstract: Ease of measurement of linear size traits is of particular significance in livestock breeding, particularly under village breeding programs where measuring live weight is difficult. In this study, we estimated genetic parameters and realized responses for live weight (LW) and linear size traits using data from an ongoing Menz sheep nucleus selection program. Using the estimated genetic parameters and simulating a nucleus breeding program and a village-based breeding program for Menz sheep, we compared predicted responses from indirect selection on linear size traits and direct selection on LW. Heritability estimates were 0.46, 0.36, 0.27, 0.31, 0.08, 0.48 and 0.23 for LW, wither height, body length, chest girth, pelvic width, tail length and tail circumference, respectively. Genetic correlations of LW with linear size traits ranged from 0.40 for tail length to 0.98 for chest girth. Realized responses in LW resulting from selection for LW and fleece weight in the ongoing Menz sheep selection program ranged from 0.27 to 0.86 kg per generation. Based on estimated genetic parameters, we chose chest girth, wither height and body length for the simulation study. Predicted responses in LW from indirect selection on chest girth, wither height and body length were 94.8% (nucleus program) and 92.6% (village program) of the responses to direct selection. Our results strongly indicate that genetic improvement in LW through indirect selection on linear size traits is possible both under nucleus and village-based breeding programs. Implications of results of simulated selection programs on the ongoing Menz sheep improvement program are discussed. [Copyright &y& Elsevier]

Abstract: A pea breeding strategy is required to cope with the large climatic variation featuring south-European environments. Thirty-seven recent cultivars bred by 21 European or Australian institutions were grown in two climatically contrasting Italian sites (Lodi, subcontinental; Foggia, Mediterranean), two cropping years per site and two sowing times per year, to define various elements of this strategy. The study assessed: (i) the impact of genotype×environment (GE) interaction due to spatial and temporal factors on the consistency of top-yielding cultivars; (ii) the similarity between environments for GE effects and its implications on adaptation strategies; (iii) the extent of genotypic and GE interaction effects, and the relationship with adaptive responses, for various morphophysiological traits; (iv) the adaptation pattern and the combination of adaptive traits featuring three germplasm types, i.e. European spring and winter types, and germplasm selected in Mediterranean environments; (v) the predicted efficiency of direct and indirect selection procedures for grain yield. The geoclimatic area had a major impact on crop yield (5.15t/ha in Lodi vs. 2.52t/ha in Foggia) but tended to affect GE interaction less than time or year of autumn sowing, suggesting to breed for wide adaptation. Top-yielding cultivars as modeled by additive main effects and multiplicative interaction were environment-specific. On average, spring and winter materials outyielded the Mediterranean germplasm but the spring type, characterized by wide entry variation, included most widely- and specifically-adapted top-yielding cultivars. Cold-tolerant spring-type germplasm is preferable to breed for wide adaptation as it may combine high yield potential with adaptation to winter cold and terminal drought and heat stress. Lodging susceptibility, harvest index, onset and duration of flowering, and canopy height at maturity assessed in individual environments showed moderate to fairly high broad-sense heritability on a plot basis (h 2 >0.20) and tended to correlation with yield over test environments (r ≥0.20). An indirect selection index including harvest index and canopy height exhibited about 20% greater predicted efficiency than direct selection for yield when using one selection environment and could be preferred for early selection stages. Direct yield selection in late selection stages should ideally be performed across 2 years in two environments that contrast for geoclimatic area and time of autumn sowing. [Copyright &y& Elsevier]

Abstract: Consumer demand regarding the impacts of conventional agriculture on the environment and human health have spurred the growth of organic farming systems; however, organic agriculture is often criticized as low-yielding and unable to produce enough food to supply the world''s population. Using wheat as a model crop species, we show that poorly adapted cultivars are partially responsible for the lower yields often found in organic farming systems when compared with conventional farming systems. Our results demonstrate that the highest yielding soft white winter wheat genotypes in conventional systems are not the highest yielding genotypes in organic systems. An analysis of variance for yield among 35 genotypes between paired organic and conventional systems showed highly significant (P <0.001) genotype×system interactions in four of five locations. Genotypic ranking analysis using Spearman''s rank correlation coefficient (R S) showed no correlation between genotypic rankings for yield in four of five locations; however, the ranks were correlated for test weight at all five locations. This indicates that increasing yield in organic systems through breeding will require direct selection within organic systems rather than indirect selection in conventional systems. Direct selection in organic systems produced yields 15%, 7%, 31% and 5% higher than the yields resulting from indirect selection for locations 1–4, respectively. With crop cultivars bred in and adapted to the unique conditions inherent in organic systems, organic agriculture will be better able to realize its full potential as a high-yielding alternative to conventional agriculture. [Copyright &y& Elsevier]

Abstract: Cultivar×location interaction for lucerne forage yield across northern Italy is large, repeatable and associated with summer drought-stress level and soil type. The objectives of this study were: (i) to investigate the genotypic factors associated with cultivar adaptive responses to drought-stress and soil factors; (ii) to identify adaptive traits exploitable for selection of widely adapted or specifically adapted material. Aerial dry matter (DM) over 12 harvests and shoot traits of 13 landraces and four varieties were evaluated in four artificial environments created by the factorial combination of drought-stress level (almost nil or high) and soil type (sandy-loam or silty-clay) (Exp. 1). Aerial and root DM over four or five harvests were evaluated in metal containers 55cm×12cm×75cm deep for the factorial combinations of three varieties by two drought-stress levels by two soil types (Exp. 2), or six landraces by two drought-stress levels (Exp. 3). Cultivar×environment interaction was detected for forage yield, plant mortality after the second summer, leaflet size and stem weight. The environments of Exp. 1 reproduced well the variety adaptive responses across agricultural environments. The relationship of cultivar forage yield with shoot traits was environment-specific, i.e.: (i) strictly negative with plant mortality, in no-stress environments (where mortality and plant competition were severe); (ii) positive with stem number per plant and autumn-winter growth, in stress environments; (iii) positive with stem dry weight, in ‘stress/sandy-loam soil’; and (iv) positive with leaflet size, in ‘no-stress/sandy-loam soil’. Cultivars specifically adapted to no-stress or sandy-loam conditions showed consistently greater root DM across three soil layers than material with opposite adaptive response. Entry yields tended to inverse genetic correlation between two environments which represented contrasting geographical subregions and were characterized by different combinations of traits associated with higher yield, i.e.: (i) higher root biomass, lower plant mortality and larger leaflets, for ‘no-stress/sandy-loam soil’; and (ii) more stems per plant and greater autumn-winter growth, for ‘stress/silty-clay soil’. The difficulty of yield-based selection for wide adaptation may hardly be overcome by selection based on adaptive traits. Adaptive trait-based selection for specific adaptation may be envisaged especially for ‘stress/silty-clay soil’ conditions, for which the relevant traits are inexpensive to record, not correlated, and not subject to cultivar×environment interaction. [Copyright &y& Elsevier]

Abstract: Aerobic rice production systems, wherein rice is dry-sown in non-puddled soil and grown as an upland crop, offer large water savings but are subject to severe weed infestation. Weed-competitive cultivars will be critical to the adoption of aerobic rice production by farmers. Breeding weed-competitive cultivars requires an easily used selection protocol, preferably based on traits that can be measured under weed-free conditions. To develop such an indirect selection index for weed competitiveness, 40 rice cultivars were evaluated in aerobic soil conditions in a weed-free environment in 2003 and in weedy environments over 3 years (2001–2003). Broad-sense heritabilities (H) of vegetative and harvest traits and their genetic correlation with weed biomass and yield under weed competition were estimated. All the traits measured under weed-free conditions were closely correlated with the same traits measured under weedy conditions. Crop vigor ratings at 2, 4, and 6 weeks after sowing (WAS), canopy ground cover at 6 WAS, height at 3 and 4 WAS, tillers per plant at 4 and 8 WAS, vegetative crop biomass at 4 and 9 WAS and plant erectness at 3 WAS under weed-free conditions in 2003 were all positively correlated with means for yield under weed competition and negatively with means for weed biomass across three years. In general, traits associated with rapid seedling biomass accumulation were also strongly associated with weed suppression and yield under weed competition. Regression analysis revealed that yield and early vigor under weed-free conditions in a single three-replicate trial could be used together in an indirect selection index, explaining 89% and 48% of variation for yield under weed competition and weed biomass, respectively. The predicted indirect selection efficiencies of weed-free yield and vigor ratings as selection criteria for yield under weed competition and weed biomass were high. Visual vigor rating at 4 WAS is the best vegetative trait as an indirect selection criterion for use together with weed-free yield, but it could be replaced by plant height at 4 WAS without loss in selection effectiveness. [Copyright &y& Elsevier]

Abstract: Drought is the most important limitation to sugar beet (Beta vulgaris L.) production in the UK and other areas dependent on usually insufficient summer rainfall. As increased irrigation is not a viable answer to the problem, an economically and environmentally desirable solution is new varieties with decreased sensitivity to water deficits. However, there is little genotypic information on drought tolerance in sugar beet, and breeders are not equipped to make these selections. The objectives of this study were to assess the degree of genotypic diversity for drought-related morpho-physiological traits and to measure the strength of association between these traits and indicators of crop performance. 46 sugar beet genotypes with diverse genetic backgrounds were tested in three field experiments from 1999 to 2001. Drought was imposed by covering plots with large polythene tunnels, allowing the crop to grow solely on stored soil moisture. Agronomic characters and drought tolerance indices are described in a companion paper [Ober et al., Assessing the genetic resources to improve drought tolerance in sugar beet. Agronomic traits of diverse genotypes under droughted and irrigated conditions. Field Crops Res., in press]. In this report, we show that there were significant genotypic differences for stomatal conductance, succulence index, specific leaf weight, and osmotic adjustment, but not for photosynthetic rate, relative water content or total water use. Patterns of water use within the soil profile differed between genotypes; some extracted more water from deep soil layers. The maintenance of green foliage cover during drought was positively correlated with drought tolerance index, which was negatively correlated with succulence index and scores for wilting and leaf senescence. Droughted sugar yield was positively correlated with soil water extraction and negatively correlated with relative leaf expansion rate measured in late summer. Under irrigated conditions, there was high positive correlation between transpiration rate and sugar yield. Genotype × trait biplots showed superior genotypes with relatively greater expression of combinations of favourable traits. The results suggest that succulence index and wilting score could be used to cull inferior plants in early stages of breeding programs, and green foliage cover and patterns of water use could help identify superior genotypes in elite germplasm. These data should enable tools to be developed for indirect selection of genotypes suited to drought-prone environments. [Copyright &y& Elsevier]

Screening for drought resistance of rainfed lowland rice using drought score (leaf death) as a selection index has a long history of use in breeding programs. Genotypic variation for drought score during the vegetative stage in two dry season screens was examined among 128 recombinant inbred lines from four biparental crosses. The genotypic variation detected for drought score in the dry season was used to examine the reliability of the dry season screening method to estimate relative grain yield of genotypes under different types of drought stress in the wet season.Large genotypic variation for drought score existed in two experiments (A and B). However, there was no relationship between the drought scores of genotypes determined in these two experiments. Different patterns of development and severity of drought stress in these two experiments, i.e. slow development and mild plant water deficit in experiment A and fast development and severe plant water deficit in experiment B, were identified as the major factors contributing to the genotypes responding differently. Larger drought score in the dry season experiments was associated with lower grain yield under specific drought stress conditions in the wet season, but the association was weak to moderate and significant only in particular drought conditions. In most cases, a significant phenotypic and moderate genetic correlation between drought score in the dry season and grain yield in the wet season existed only when both drought score and grain yield of genotypes were affected by similar patterns and severity of drought stress in their respective experimental environments. The dry season environments used to measure genotypic variation for drought score should be managed to correspond to relevant types of drought environment that are frequent in the wet season. The efficiency of using the drought score as an indirect selection criterion for improving grain yield for drought conditions was lower than the direct selection for grain yield, and hence wet season screening with grain yield as a selection criterion would be more efficient. However, using drought score as a selection index, a larger number of genotypes can be evaluated than for wet season grain yield. Therefore, it is possible to apply higher selection intensities using the drought score system, and the selected lines can be further tested for grain yield in the wet season. [Copyright &y& Elsevier]

Over 30 root and shoot growth traits of nine diverse rice cultivars (cvs) grown under competitive conditions were analyzed to exhaustively quantify cv differences and identify which traits most affected rice growth in competition. The cvs included a traditional Oryza glaberrima, CG14, and selections from three isozyme groups of O. sativa: aus, indica, and tropical japonica. Single rice plants were grown in pots with and without nitrogen fertilizer, surrounded by six plants of either barnyardgrass (Echinochloa crus-galli), in trials 1 and 2, or themselves, in trial 3. Growth traits were measured weekly or in harvests at 21 and 48 days after seeding (DAS). Significant differences amongst cvs were found for nearly every response variable, and the most productive cvs lacked uniform growth traits. Total dry mass (DM) was primarily a function of leaf area (LA, m−2 per plant), but height growth rates (HGRs, m per day) at 7 and 21 DAS and tillering ability were also consistently important. Non-destructively measured traits, such as tillering, and HGRs at 7 and 21 DAS, accounted for at least 75% of the variation in DM across all trials. Overall, rice cv growth in competition depended on multiple traits, and in particular was not simply a function of specific leaf area (SLA, m2 g−1 leaf). Early vigor was highly repeatable in both competition and monoculture trials, indicating that it may be used to discriminate between more and less competitive cvs even in monoculture. Therefore, screening lines in standard nurseries for competitiveness against weeds seems possible using non-destructive scoring of plant cover, very early heights (i.e., vigor), tillering ability, and early HGRs. [Copyright &y& Elsevier]

Bean/Cowpea Collaborative Research Support Program (B/C CRSP) scientists have successfully developed integrated consensus maps of the 11 linkage groups (LGs) in both bean (Phaseolus vulgaris L.) and cowpea (Vigna unguiculata L. Walp). The bean map is approximately 1200 cM with some 500 markers and an additional 500 markers shared with other bean maps. The cowpea map spans 2670 cM with over 400 markers. In addition to molecular markers, both maps include map locations of defense genes and phenotypic traits for disease and insect resistance, seed size, color and storage proteins, pod color and those traits associated with the domestication syndrome in bean. Since the bean and cowpea maps were developed independently, LGs with the same number probably refer to non-syntenic groups. Map locations of major resistance genes in bean are revealing gene clusters on LGs B1, B4, B7, and B11 for resistance to bean rust, anthracnose, common bacterial blight and white mold. Gene tagging and marker-assisted selection for disease resistance has progressed to a point where the indirect selection for resistance to a number of major diseases is now routine in bean breeding programs both in the US and overseas. [Copyright &y& Elsevier]

Slaughter yields are traits of high interest especially for fish species sold in processed form like headless carcass or fillets, as well as with regard to increasing consumer preference for easy-to-prepare fish products. However, slaughter yields cannot be measured on live fish and thus their genetic improvement through mass selection is impossible. The usual alternatives are sib selection and/or indirect selection on correlated traits or morphological predictors of slaughter yields. In the present study, we assessed the possibility of using a combination of 3D digitized landmarks and ultrasound measurements in genetic improvement of slaughter yields in common carp. DNA – pedigreed market-size carp (n = 1553 fish) were produced from a partial factorial design of 20 dams and 40 sires. Morphological predictors were recorded in real-time using a 3D digitizer and ultrasound tomography, and combined by multiple linear regression to predict slaughter yields. The 3D model-predicted headless carcass and fillet yields explained 59% and 50%, respectively, of the total phenotypic variation in slaughter yields. Genetic parameters of model-predicted yields and of the best individual predictor (3D_P 2 – ratio between abdominal fillet thickness – E8 and external 3D ventral height) were similar or slightly lower when compared to previous 2D-based predictors (Prchal et al., 2018a, 2018b, 2018c). This was also the case for the expected genetic gain using indirect selection on the same simple predictor for fillet yield improvement (0.48% fillet units for 3D vs. 0.52% for 2D). 3D model-predicted yields and especially simple predictors thus have a solid potential for genetic improvement of slaughter yields in common carp. While they are not better than 2D predictors, they are much more convenient and faster to collect in the field, as they do not imply post-processing of images. These practical aspects should be taken into account in the future carp breeding program. • We studied combination of 3D digitized landmarks and ultrasound measurements. • 3D collection of morphological landmarks do not imply post processing of images. • 3D models / predictors have a solid potential for genetic improvement of slaughter yields. • Future carp breeding strategies have been suggested. [ABSTRACT FROM AUTHOR]

Scrotal circumference of bulls is correlated with pubertal age of female offspring. Hormonal control of reproductive function is similar in males and females, which may result in genetic correlation among different reproductive traits measured in the two sexes. The estimation of heritability and genetic correlations allows for the computation of direct and correlated genetic gains which are important for predicting of outcomes as a result of genetic-based selection. The aim of this study was to estimate genetic parameters and relative efficiency of indirect selection for age at first calving (AFC), stayability (STAY) and scrotal circumference at 365 days of age (SC365) in Nellore cattle. The STAY variable can be defined as the probability of a cow remain in the herd enough time to raise a certain number of calves that pay for her development and maintenance costs. A bivariate Bayesian analysis was used to estimate variance components using a linear-animal model for SC365 and AFC and threshold-linear model for SC365 and STAY and for AFC and STAY. For STAY, the value of 1 was assigned to cows that calved at least three times by 76 months of age; otherwise, the value 0 was assigned. The posteriori means of heritability estimates were 0.29, 0.08 and 0.09 for SC365, AFC and STAY, respectively. Genetic correlations were favorable from a cow productivity perspective between SC365 and AFC, and SC365 and STAY (-0.45 and 0.12, respectively). Indirect selection approaches were more efficient than direct selection for AFC (ERS = 1.87) when animals were selected for SC365. [ABSTRACT FROM AUTHOR]