Broad-sense Heritability Estimates Research Articles

Genetic Variability and Character Association Analysis for Yield and Its Related Traits in Rain Fed Lowland Rice (<i>Oryza sativa </i>L.)<i> </i>Genotypes at Teppi and Fogera, Ethiopia

In Ethiopia, rice variety development started very recently and is mainly dependent on the introduction breeding materials in which characterization and understanding of the genetic variability of genotypes is the critical step. Knowledge of the extent of genetic variability and interrelationships of yield and yield components is pre-request for designing an effective selection-based rice improvement programs for evolving high yielding rice genotypes. Therefore, this study was carried out with all objectives of assessing genetic variation for yield and yield related traits in lowland rice genotypes. Thirty-six selected lowland rice genotypes were evaluated in simple lattice design with two replications during 2017 cropping season and data on 15 quantitative morphological traits were collected and subjected to various statistical analysis. Combined analysis of variance across location revealed significant location, genotype and genotype × location interaction effects for the traits evaluated at p ≤0.01. The phenotypic coefficient of variation was high for un fertile tiller per plant (88.16 %), followed by infertile grain per panicle (50.66%), and grain yield (21.57%), and the genotypic coefficient of variation was high for un fertile tiller per plant (50.38 %), followed by infertile grain per panicle (27.22%), and culm length (17.7%). The estimate of broad sense heritability ranges from 15.2% for biological yield to 91.5% for plant height. The expected genetic advance as present of mean varied from 5.42% for biological yield to 59.3% for unfertile tiller per plant. Phenotypic and genotypic correlation revealed grain yield had a a significant and positive association with primary branches per panicle (rp=0.4, rg=0.7), fertile grain per panicle (rp=0.5, rg=0.72) and harvest index (rp=0.76, rg=0.73) at both genotypic and phenotypic. Path coefficient analysis of grain yield revealed that harvest index, total tiller per plant and thousand grain weights showed positive phenotypic direct effect. A Positive direct effect was found for total tiller per plant, harvest index and biological yield at genotypic level. The present study indicated sufficient genetic variability for the characters studied in rain fed low land rice genotype, which will create opportunity for future improvement. To have full scale data, further study at various locations and years with the help of molecular techniques should be done.

Evaluation of 10 Edamame Breeding Lines to Determine Yield, Agronomic, and Seed Composition Traits

Edamame is a vegetable soybean (Glycine max) that is harvested at the R6 growth stage. Although it is relatively new to America, the acreage and market demand of edamame have steadily increased. Developing new cultivars that are more adapted to local environments and crop management systems is significantly important to promoting specialty crop production and meeting the market requirements. In this study, 10 edamame breeding lines and four check cultivars were evaluated during 2020–23 to determine the potential production in the southeastern United States. Among genotypes, there were significant differences in the fresh pod and mature seed yields and agronomic and seed composition traits that were investigated. The year effects and genotype × year interactions were also significant in most cases. Fresh pod and mature seed yields were not significantly correlated with most of other agronomic traits and seed compositions. Over 4 years, the fresh pod yield averaged 11,227.5 kg·ha−1 (range, 9800.1–13,154.3 kg·ha−1), and the mature seed yield averaged 2814.7 kg·ha−1 (range, 2029.2–3175.2 kg·ha−1). The average 100-seed weight of 14 genotypes was 26.9 g (range, 23.1–30.1 g), and the average seed size of nine breeding lines was larger than that of the check. Maturity occurred on average 153.3 days after planting (range, 147.1–159.5 days). Based on dry weight, seed protein, oil, and sucrose contents had averages of 43.5%, 18.7%, and 5.0%, respectively. The estimates of broad-sense heritability were medium to high (66.82%–94.90%) for most of the traits, whereas the heritability estimates for fresh pod yield and duration from flowering to maturity were relatively low (23.44%–42.29%). Several breeding lines exhibited good yield, larger seed size, and higher contents of protein, oil, and oleic acid, suggesting the potential of release and commercial production.

Genetic variability in macadamia rootstocks and their effects on early vigor traits of ‘HAES 741′

Early vigor in tree crops is crucial as it accelerates orchard establishment and enhances resilience to environmental stresses. Rootstocks play an essential role in determining vigor of tree crops. Macadamia is propagated through grafting, however research into rootstocks is rare. This study evaluated a range of macadamia rootstocks including cultivars, standard rootstocks, breeding selections and wild germplasm, focusing on their effects on early vigor (age 4). Phenotypic variability in the scion ‘HAES 741′ was assessed using 24 accessions of seedling and cutting rootstocks over 4 years (2018–2021), analyzing 7 early vigor traits and growth rates. Principal coordinate analysis and cluster analysis revealed high genetic diversity among accessions, clustering into 4 groups. Significant rootstock effects on early vigor were observed. Broad-sense heritability estimates of rootstock effects were moderate for scion height (H2=0.48) and total height (H2=0.44), holding promise for improvement through selection. Positive correlations among scion growth traits, particularly trunk circumference, (rg= 0.50 to 0.99) suggested their potential as indicators of early vigor. The strong genetic correlations for canopy area (rg = 0.84) and canopy volume (rg = 0.63) between scions of grafted trees and the ungrafted trees of the same rootstock accessions reflect the possibility of trait transmission from rootstock to scion. Among the studied rootstocks, ‘BHI1’, ‘BHY2’ and ‘BHI3’ imparted the highest early vigor. Compared with the current industry standard rootstocks ‘H2’ and ‘Beaumont’, the least vigorous rootstocks ‘Mjan1’ and ‘BDW3’ showed reductions of 18 % and 47% in tree height, 54 % and 74% in trunk circumference and 97 % and 210 % in canopy volume respectively. These findings suggest promising rootstock candidates for high performing orchard systems, although ongoing evaluation until maturity is crucial.

Genetic characterization and mapping of the shell-strength trait in peanut.

Shell strength is an important trait in peanuts that impacts shell breakage and yield. Despite its significance, the genetic basis of shell strength in peanuts remains largely unknown, and the current methods for rating this trait are qualitative and subjective. This study aimed to investigate the genetics of shell strength using a segregating recombinant-inbred-line (RIL) population derived from the hard-shelled cultivar 'Hanoch' and the soft-shelled cultivar 'Harari'. Initially, a quantitative method was developed using a texture analyzer, focusing on the proximal part of isolated shells with a P/5 punching probe. This method revealed significant differences between Hanoch and Harari. Shell strength was then measured in 235 RILs across two distinct environments, revealing a normal distribution with some RILs exhibiting shell strength values beyond those of the parental lines, indicating transgressive segregation. Analysis of variance indicated significant effects for the RILs, with no effects of block or year, and a broad-sense heritability estimate of 0.675, indicating a substantial genetic component. Using an existing genetic map, we identified three QTLs for shell strength, with one major QTL (qSSB02) explaining 18.7% of the phenotypic variation. The allelic status of qSSB02 corresponded significantly with cultivar designation for in-shell or shelled types over four decades of Israeli peanut breeding. Physical and compositional analyses revealed that Hanoch has a higher shell density than Harari, rather than any difference in shell thickness, and is associated with increased levels of lignin, cellulose, and crude fiber. These findings provide valuable insights into the genetic and compositional factors that influence shell strength in peanut, laying a foundation for marker-assisted selection in breeding programs focused on improving pod hardness in peanuts.

English

Coffee breeding programs aim at developing superior genotypes, which entail exploring the genetic variability existing in conilon/robusta coffee. This study aimed at examining the variability and estimate genetic param of physical and physiological nature in Coffea canephora seeds in order to provide bases for the selection of genotypes for superior seeds quality. Forty-three C. canephora genotypes were evaluated for 11 physical and physiological seed traits. Estimates of genetic param, environmental variance, phenotypic variance, genotypic variance, broad-sense heritability, variation index and Pearson's correlation were obtained. The Dissimilarity between genotypes was obtained by generalized Mahalanobis distance. The dendrogram was constructed using unweighted pair group method with arithmetic mean (UPGMA). C. canephora genotypes presented high germination potential and exhibited genetic diversity for all seed traits, with estimates of genetic variance greater than environmental variance. Heritability reached values above 96.0% and all genetic variation indices found were higher than unity. The UPGMA hierarchical method grouped the genotypes in three groups. The physical traits (circumference, area and roundness) were those that contributed the most to explaining the dissimilarity between genotypes. Genotypes Alecrim, AP, Bamburral, Z39 and Tardio C were the most divergent. The results revealed the presence of genetic variability between C. canephora genotypes and greater genetic than environmental influence on the characters of seeds, indicating that selection for the studied traits showed favorable conditions in terms of immediate gain.

Genome-wide study of drought tolerance traits in wild jujube

BackgroundWild jujube trees in Ningxia, China, demonstrate exceptional drought tolerance. The identification of quantitative trait loci (QTLs) associated with drought resistance and linked genes could significantly enhance molecular breeding efforts for this species. This study involved the measurement of nine drought resistance indicators were measured in 150 wild jujube trees from five regions in Ningxia. Genome-wide association studies (GWAS) were carried out using a range of mixed linear models to pinpoint SNP markers linked to drought resistance.ResultsThe coefficients of variation for the nine leaf traits in wild jujube trees ranged from 14.76 to 62.17%, with broad-sense heritability estimates falling between 0.84 and 0.99. Through GWAS analysis, a total of 12 significant SNPs and 162 potential genes associated with drought resistance were detected. This SNPs explained phenotypic variance ranging from 20.74 to 50.37%. Gene Ontology (GO) functional annotation highlighted five crucial candidate genes‒ZjMYB44, ZjUCLOC, ZjDnaJ50, ZjUCHL22 and ZjHSFB‒linked to drought tolerance in wild jujube. These genes demonstrated a positive correlation with drought tolerance within the wild jujube population.ConclusionsOur findings indicate that these five genes likely play a pivotal role in conferring drought tolerance in wild jujubes. This study offers new insights to support the development of drought-resistant jujube varieties, thereby contributing to sustainable agricultural practices and bolstering food security in arid regions.

Genetic diversity, population structure, and a genome-wide association study of sorghum lines assembled for breeding in Uganda.

Sorghum is an important source of food and feed worldwide. Developing sorghum core germplasm collections improves our understanding of the evolution and exploitation of genetic diversity in breeding programs. Despite its significance, the characterization of the genetic diversity of local germplasm pools and the identification of genomic loci underlying the variation of critical agronomic traits in sorghum remains limited in most African countries, including Uganda. In this study, we evaluated a collection of 543 sorghum accessions actively used in Ugandan breeding program across two cropping seasons at NaSARRI, Uganda, under natural field conditions. Phenotypic data analysis revealed significant (p<0.01) variation among accessions for days to 50% flowering, plant height, panicle exsertion, and grain yield, with broad-sense heritability (H²) estimates of 0.54, 0.9, 0.81, and 0.48, respectively, indicating a high genetic variability for these traits. We used a newly developed genomic resource of 7,156 single nucleotide polymorphism (SNP) markers to characterize the genetic diversity and population structure of this collection. On average, the SNP markers exhibited moderately high polymorphic information content (PIC = 0.3) and gene diversity (He = 0.3), while observed heterozygosity (Ho = 0.07) was low, typical for self-pollinating crops like sorghum. Admixture-based models, PCA, and cluster analysis all grouped the accessions into two subpopulations with relatively low genetic differentiation. Genome-wide association study (GWAS) identified candidate genes linked to key agronomic traits using a breeding diversity panel from Uganda. GWAS analysis using three different mixed models identified 12 genomic regions associated with days to flowering, plant height, panicle exsertion, grain yield, and glume coverage. Five core candidate genes were co-localized with these significant SNPs. The SNP markers and candidate genes discovered provide valuable insights into the genetic regulation of key agronomic traits and, upon validation, hold promise for genomics-driven breeding strategies in Uganda.

The world as I see it: genetic and environmental influences on primal world beliefs in a large Swedish twin sample

ABSTRACT Beliefs about the general character of the world – called primals – have received much attention in recent years. Primals (e.g. believing that the world is safe) are associated with psychological and social outcomes, such as personality traits, character strengths and life satisfaction. We performed the first study of genetic and environmental influences on primals, and explored phenotypic associations between primals and the big five personality traits, in a large (~9000) population-wide Swedish twin sample. Correlations between primals and personality traits were low to moderate. Broad-sense heritability estimates of primals ranged between 21% and 49%, suggesting that genetic factors contribute significantly to people’s beliefs about the general character of the world. In contrast, we found little support for shared environmental effects (e.g. rearing environment). Conclusively, we demonstrate that primals and personality are related, yet distinct, constructs and that individual differences in primals depend on both genetic and non-shared environmental factors.

Identifying dryland-resilient chickpea genotypes for autumn sowing, with a focus on multi-trait stability parameters and biochemical enzyme activity

BackgroundChickpea is a key pulse crop grown in the spring in dryland regions. The cold resistance potential of chickpeas allows for the development of genotypes with varying sowing dates to take advantage of autumn and winter rainfall, particularly in dryland regions. In this study, we assessed grain yield, plant height, 100-seed weight, days to maturity, and days to flowering of 17 chickpea genotypes in five autumn-sown dryland regions from 2019 to 2021. Additionally, the response of selected chickpea genotypes to cold stress was examined at temperatures of -4 °C, 4 °C, and 22 °C by analyzing biochemical enzymes.ResultsMixed linear model of ANOVA revealed a significant genotype × environment interaction for all traits measured, indicating varying reactions of genotypes across test environments. This study reported low estimates of broad-sense heritability for days to flowering (0.34), days to maturity (0.13), and grain yield (0.08). Plant height and seed weight exhibited the highest heritability, with genotypic selection accuracies of 0.73 and 0.92, respectively. Moreover, partial least square regression highlighted the impactful role of rainfall during all months except of October, November, and February on grain yield and its interaction with environments in autumn-planted chickpeas. Among the genotypes studied, G9, G10, and G17 emerged as superior based on stability parameters and grain yield. In particular, genotype G9 stood out as a promising genotype for dryland regions, considering both MTSI and genotype by yield*trait aproaches. The cold assay indicated that − 4 °C is crucial for distinguishing between susceptible and resistant genotypes. The results showed the important role of the enzymes CAT and GPX in contributing to the cold tolerance of genotype G9 in autumn-sown chickpeas.ConclusionsSignificant G×E for agro-morphological traits of chickpea shows prerequisite for multi-trial analysis. Chickpea`s direct root system cause that monthly rainfall during plant establishment has no critical role in its yield interaction with dryland environment. Considering the importance of agro-morphological traits and their direct and indirect effects on grain yield, the utilization of multiple-trait stability approches is propose. Evaluation of chickpea germplasm reaction against cold stress is necessary for autumn-sowing. Finally, autumn sowing of genotype FLIP 10–128 C in dryland conditions can led to significant crop performance.

Genetic variability and trait associations in bread wheat (Triticum aestivum L.) genotypes under drought-stressed and well-watered conditions

Drought is one of the most important yield-limiting abiotic stresses threatening wheat production and productivity. Development of wheat genotypes with enhanced grain yield under drought-stressed conditions depend on the extent of genetic variation present for drought tolerance-related traits. This study was carried out to determine the level of genetic variation and associations of yield and yield attributing traits among 196 bread wheat genotypes under drought-stressed and well-watered conditions. The genotypes were evaluated under greenhouse and field conditions and phenotyped for yield and yield-related traits. The genotypes varied significantly for the traits under both conditions. Grain yield ranged from 2.13 to 3.74 t ha−1 and from 2.52 to 5.06 t ha−1 under drought-stressed and well-watered conditions, respectively. Under both conditions, variances due to genotype were higher than environment and genotype × environment interaction variances for all the traits. Estimates of phenotypic coefficient of variation (PCV) were higher than genotypic coefficient of variation (GCV) for all the traits under both conditions, with both PCV and GCV being highest for kernel weight spike−1 and lowest for spike fertility. Under both conditions, broad-sense heritability estimates ranged from moderately high to very high, accompanied with high genetic advance as a percentage of the mean. Fertile spikelets spike−1, one thousand kernel weight, kernel weight spike−1, biomass yield and harvest index manifested high positive genotypic and phenotypic correlations and positive direct effects on grain yield under both conditions. The first five principal components accounted for 78.4% (well-watered) and 76.0% (drought-stressed) of the variation among the genotypes. The 196 genotypes were delineated into six major clusters under both water conditions, with clusters 3 (well-watered) and cluster 5 (drought-stressed) containing genotypes with the highest ability to tolerate drought stress. Genotypes Alidoro, Bolo, Dinknesh, ETBW8491 and ETBW172938 had high stable yields under both conditions. The identified traits and genotypes were drought tolerant and could be exploited to develop novel genotypes for drought stress tolerance.

Evaluation of Cotton Cultivars and Breeding Lines for Tolerance to Monosodium Methanearsonate (MSMA) Under Field Conditions

Monosodium methanearsonate (MSMA) is an organic arsenical herbicide used to control weeds such as grasses and nutsedges in Upland cotton (Gossypium hirsutum) production. Transient crop injury, yield reduction, and maturity delays have been observed in commercial Upland cotton. It is unknown if genetic variation in MSMA tolerance in cotton exists. In this field study, seven replicated tests were conducted in the same field to compare MSMA tolerance among 212 commercial cotton cultivars and advanced breeding lines. The tests were sprayed over the top at the 4-true-leaf stage, and seedlings were assessed for crop injury severity on a scale of 0 (no injury) to 5 (death). Significant genotypic variation in MSMA tolerance was detected in three tests, and broad-sense heritability estimates for MSMA tolerance ranged from 0.476 to 0.846 with a mean of 0.712, indicating that most phenotypic variation in MSMA tolerance is heritable. Nine tested G. barbadense genotypes, including seven commercial Pima cultivars and two Sea-Island cotton lines, exhibited minimal crop injury with severity ratings of 0.40 to 0.83 (except for one cultivar with 1.33). Among the remaining 203 Upland cotton genotypes with crop injury ratings ranging from 0.90 to 3.67, five commercial transgenic cultivars and 38 public breeding lines exhibited various levels of MSMA tolerance. The results represent the first study in germplasm evaluation for MSMA tolerance and identify a set of tolerant cotton genotypes that can be selected in cotton production or used to develop new cultivars for commercial cotton production.

Genome-wide association study for yield and quality of granulated cassava processed product.

The starchy storage roots of cassava are commonly processed into a variety of products, including cassava granulated processed products (gari). The commercial value of cassava roots depends on the yield and quality of processed products, directly influencing the acceptance of new varieties by farmers, processors, and consumers. This study aims to estimate genetic advance through phenotypic selection and identify genomic regions associated and candidate genes linked with gari yield and quality. Higher single nucleotide polymorphism (SNP)-based heritability estimates compared to broad-sense heritability estimates were observed for most traits highlighting the influence of genetic factors on observed variation. Using genome-wide association analysis of 188 clones, genotyped using 53,150 genome-wide SNPs, nine SNPs located on seven chromosomes were significantly associated with peel loss, gari yield, color parameters for gari and eba, bulk density, swelling index, and textural properties of eba. Future research will focus on validating and understanding the functions of identified genes and their influence on gari yield and quality traits.

Self-reported neurocognitive complaints in the Swiss HIV Cohort Study: a viral genome-wide association study.

People with HIV may report neurocognitive complaints, with or without associated neurocognitive impairment, varying between individuals and populations. While the HIV genome could play a major role, large systematic viral genome-wide screens to date are lacking. The Swiss HIV Cohort Study biannually enquires neurocognitive complaints. We quantified broad-sense heritability estimates using partial 'pol' sequences from the Swiss HIV Cohort Study resistance database and performed a viral near full-length genome-wide association study for the longitudinal area under the curve of neurocognitive complaints. We performed all analysis (i) restricted to HIV Subtype B and (ii) including all HIV subtypes. From 8547 people with HIV with neurocognitive complaints, we obtained 6966 partial 'pol' sequences and 2334 near full-length HIV sequences. Broad-sense heritability estimates for presence of memory loss complaints ranged between 1% and 17% (Subtype B restricted 1-22%) and increased with the stringency of the phylogenetic distance thresholds. The genome-wide association study revealed one amino acid (Env L641E), after adjusting for multiple testing, positively associated with memory loss complaints (P = 4.3 * 10-6). Other identified mutations, while insignificant after adjusting for multiple testing, were reported in other smaller studies (Tat T64N, Env *291S). We present the first HIV genome-wide association study analysis of neurocognitive complaints and report a first estimate for the heritability of neurocognitive complaints through HIV. Moreover, we could identify one mutation significantly associated with the presence of memory loss complaints. Our findings indicate that neurocognitive complaints are polygenetic and highlight advantages of a whole genome approach for pathogenicity determination.

Evaluation of Genetic Variability for Yield Improvement in Bitter Gourd (Momordica charantia L.) Genotypes

The degree of genetic variability found in any particular germplasm is a major factor in determining the best breeding program or technique to be used. Exploitation of the natural genetic variability present within a crop species can aid in meeting the rising demand through the identification and modification of the adaptive and productive genes present. Breeders thus identify natural genetic variability as the key to crop improvement. The present investigation was undertaken at the Experimental field of Urban Technological Park Habbak, Srinagar, Jammu and Kashmir during kharif-2022. To investigate several aspects of genetic variability, including mean, range, PV, GV, PCV, GCV, heritability, genetic gain, and genetic advance among the genotypes, the experiment was set up in a Randomized Block Design with three replications and a plant spacing of 2×1 m for thirty genotypes. For every character under study, it was discovered that the estimates of the phenotypic coefficient of variation were marginally greater than the respective genotypic coefficient of variation, indicating a possible involvement of environment in the expression of these traits. Fruit yield hectare-1 (q) exhibited the largest genotypic and phenotypic coefficient of variation (39.788 and 38.970). For yield hectare-1 (q), high heritability and high genetic gain (0.95 and 78.62) were observed. This suggests that additive gene effects are most likely the cause of the heritability and increases the likelihood that this characteristic would be fixed by selection. For every characteristic, the estimates of broad sense heritability were high. All these factors help in selection of better parents for the development of commercial varieties/hybrids. Considering the potential nutritional and economic benefits of bitter gourd (Momordica charantia L.), there is an imperative necessity to isolate such breeding lines having desirable traits, high yield potential along with better quality.

Genome-wide association studies reveals new candidate genes associated with resistance to Striga gesneroides in Cowpea [Vigna unguiculata (L.) Walp.] accessions from sub-Saharan Africa

Parasitic plant Striga gesneroides reduces cowpea productivity in sub-Saharan Africa, leading to substantial yield losses. This weed is the major reason for land abandonment by many farmers. While various methods have been proposed for managing Striga invasion and parasitism, host-plant resistance remains the most effective and affordable option for small-scale farmers in the sub-region. This study aims to expedite the improvement of Striga resistance breeding through marker-assisted selection by identifying genomic regions and candidate genes associated with Striga resistance indicator traits using association mapping. A panel of 188 cowpea accessions assembled from five gene banks in West Africa were phenotyped for two years under Striga-infested and non-infested research conditions. These accessions were equally genotyped using the medium-density genotyping of the Diversity Arrays Technology sequencing (DArTseq) platform to obtain marker information. High broad-sense heritability estimates were observed for Striga resistance status (SRS), number of Striga per plot (NSPlot), and Pod weight (PW) while low heritability estimates were observed for fodder weight (FW) and Plant Aspect (PASP). Twenty-four SNP markers were identified across SRS, NSPlot, FW, PASP, and PW under Striga-infested conditions. Under non-infested conditions, 17 SNPs were identified across FW, PASP, and PW. Gene annotation of the significant SNPs revealed candidate genes such as ubiquitin ligase activity, cell wall reinforcement protein, and pathogenesis-related protein. These genes function in plant growth regulation, development, and defense mechanisms. This study offers valuable insights for marker selection, validation, and deployment in cowpea improvement for Striga resistance in SSA.

Genetic Variation and Heritability for Hydrogen Cyanide in Fresh Cassava Roots: Implications for Low-Cyanide Cassava Breeding.

Breeding for low-hydrogen-cyanide (HCN) varieties is a major objective of programs targeting boiled cassava food products. To enhance the breeding of low-HCN varieties, knowledge of genetic variation and trait heritability is essential. In this study, 64 cassava clones were established across four locations and evaluated for HCN using three HCN assessment methods: one with a 1 to 9 scale, on with a 0 ppm to 800 ppm scale, and a quantitative assay based on spectrophotometer readings (HCN_Spec). Data were also collected on the weather variables precipitation, relative humidity, and temperature. Highly significant differences were observed among clones (p < 0.001) and locations (p < 0.001). There was also significant clone-environment interactions, varying from p < 0.05 to p < 0.001. Locations Arua and Serere showed higher HCN scores among clones and were associated with significantly higher (p < 0.001) mean daily temperatures (K) and lower relative humidity values (%) across 12 h and 18 h intervals. Within locations, HCN broad sense heritability estimates ranged from 0.22 to 0.64, while combined location heritability estimates ranged from 0.14 to 0.32. Relationships between the methods were positive and strong (r = 0.75-0.92). The 1 to 9 scale is more accurate and more reproducible than either the 0 to 800 ppm scale or spectrophotometric methods. It is expected that the information herein will accelerate efforts towards breeding for low-HCN cassava varieties.

Evaluation of shoot-growth variation in diverse carrot (Daucus carota L.) germplasm for genetic improvement of stand establishment.

Carrot (Daucus carota L.) is a high value, nutritious, and colorful crop, but delivering carrots from seed to table can be a struggle for carrot growers. Weed competitive ability is a critical trait for crop success that carrot and its apiaceous relatives often lack owing to their characteristic slow shoot growth and erratic seedling emergence, even among genetically uniform lines. This study is the first field-based, multi-year experiment to evaluate shoot-growth trait variation over a 100-day growing season in a carrot diversity panel (N=695) that includes genetically diverse carrot accessions from the United States Department of Agriculture National Plant Germplasm System. We report phenotypic variability for shoot-growth characteristics, the first broad-sense heritability estimates for seedling emergence (0.68 < H2 < 0.80) and early-season canopy coverage ( 0.61 < H2 < 0.65), and consistent broad-sense heritability for late-season canopy height (0.76 < H2 < 0.82), indicating quantitative inheritance and potential for improvement through plant breeding. Strong correlation between emergence and canopy coverage (0.62 < r < 0.72) suggests that improvement of seedling emergence has great potential to increase yield and weed competitive ability. Accessions with high emergence and vigorous canopy growth are of immediate use to breeders targeting stand establishment, weed-tolerance, or weed-suppressant carrots, which is of particular advantage to the organic carrot production sector, reducing the costs and labor associated with herbicide application and weeding. We developed a standardized vocabulary and protocol to describe shoot-growth and facilitate collaboration and communication across carrot research groups. Our study facilitates identification and utilization of carrot genetic resources, conservation of agrobiodiversity, and development of breeding stocks for weed-competitive ability, with the long-term goal of delivering improved carrot cultivars to breeders, growers, and consumers. Accession selection can be further optimized for efficient breeding by combining shoot growth data with phenological data in this study's companion paper to identify ideotypes based on global market needs.

Evaluation of non-additive genetic effects on carcass and meat quality traits in Korean Hanwoo cattle using genomic models

The traditional genetic evaluation methods generally consider additive genetic effects only and often ignore non-additive (dominance and epistasis) effects that may have contributed to genetic variation of complex traits of livestock species. The available dense single nucleotide polymorphisms (SNPs) panels offer to investigate the potential benefits of including non-additive genetic effects in the genomic evaluation models. Data from 16 971 genotyped (Illumina Bovine 50 K SNP chip) Korean Hanwoo cattle were used to estimate genetic variance components and prediction accuracy of genomic breeding values (GEBVs) for four carcass and meat quality traits: carcass weight (CWT), eye muscle area (EMA), back fat thickness (BFT) and marbling score (MS). Five different genetic models were evaluated through including additive, dominance and epistatic interactions (additive by additive, A × A; additive by dominance, A × D and dominance by dominance, D × D) successively in the models. The estimates of additive genetic variances and narrow sense heritabilities (ha2) were found similar across the evaluated models and traits except when additive interaction (A × A) was included. The dominance variance estimates relative to phenotypic variance ranged from 1.7–3.4% for CWT and MS traits, whereas, they were close to zero for EMA and BFT traits. The magnitude of A × A epistatic heritability (haa2) ranged between 14.8 and 27.7% in all traits. However, heritability estimates for A × D and D × D epistatic interactions (had2 and hdd2) were quite low compared to haa2 and were contributed only 0.0–9.7% of the total phenotypic variation. In general, broad sense heritability (hG2) estimates were almost twice (ranging between 0.54 and 0.68) the ha2 for all of the investigated traits. The inclusion of dominance effects did not improve the prediction accuracy of GEBV but improved 2.0–3.0% when epistatic effects were included in the model. More importantly, rank correlation revealed that partitioning of variance components considering dominance and epistatic effects in the model would enable to re-rank of top animals with better prediction of GEBV. The present result suggests that dominance and epistatic effects could be included in the genomic evaluation model for better estimates of variance components and more accurate prediction of GEBV for carcass and meat quality traits in Korean Hanwoo cattle.

Morpho-agronomıc varıabılıty, herıtabılıty and genetıc advance studıes ın sesame (sesamum ındıcum L.) In nıgerıa

The study explored morpho-agronomic and biochemical traits to assess variability level and the degree of genetic diversity in 15 Sesame accessions. Data were subjected to analysis of variance, multivariate analyses, and genetic parameters were estimated. Significant differences (P &lt; 0.05) existed among the accessions in all the characters. Four components with a cumulative variation of 85.7% were extracted. Substantial broad sense heritability estimates and high genetic gain were observed in secondary branches (97.8%; 719.4%), primary branches (96.1%;142,5%), capsules per plant (97.8%; 141.1%), single plant seed yield (86.87%; 46.03%), capsule length (99.16%; 32%), and 500 seed weight (95.15%; 34.12%). It may be inferred that a considerable level of variability existed among the accessions studied and charcters like branching habit, capsules per plant, capsule length and single plant seed yield could be considered for selection in breeding for superior genotypes. Bangladesh J. Bot. 53(1): 75-81, 2024 (March)

Genetic analysis of cassava brown streak disease root necrosis using image analysis and genome-wide association studies.

Cassava brown streak disease (CBSD) poses a substantial threat to food security. To address this challenge, we used PlantCV to extract CBSD root necrosis image traits from 320 clones, with an aim of identifying genomic regions through genome-wide association studies (GWAS) and candidate genes. Results revealed strong correlations among certain root necrosis image traits, such as necrotic area fraction and necrotic width fraction, as well as between the convex hull area of root necrosis and the percentage of necrosis. Low correlations were observed between CBSD scores obtained from the 1-5 scoring method and all root necrosis traits. Broad-sense heritability estimates of root necrosis image traits ranged from low to moderate, with the highest estimate of 0.42 observed for the percentage of necrosis, while narrow-sense heritability consistently remained low, ranging from 0.03 to 0.22. Leveraging data from 30,750 SNPs obtained through DArT genotyping, eight SNPs on chromosomes 1, 7, and 11 were identified and associated with both the ellipse eccentricity of root necrosis and the percentage of necrosis through GWAS. Candidate gene analysis in the 172.2kb region on the chromosome 1 revealed 24 potential genes with diverse functions, including ubiquitin-protein ligase, DNA-binding transcription factors, and RNA metabolism protein, among others. Despite our initial expectation that image analysis objectivity would yield better heritability estimates and stronger genomic associations than the 1-5 scoring method, the results were unexpectedly lower. Further research is needed to comprehensively understand the genetic basis of these traits and their relevance to cassava breeding and disease management.