Genetic variability and association of characters in linseed (Linum usitatissimum L.) plant grown in central Ethiopia region

Linseed is one of the most important oil seed crop in the central highlands of Ethiopia for which yield enhancement is the major breeding purposes and genotypic variability is important for selection in any breeding programs. However, shortage of improved varieties’ that provides optimum seed yield is one of the major constraints of the crop. Therefore, this study was carried out to assess the genetic variability and association among quantitative traits of 36 linseed genotypes. The experiment was conducted in 2018 main cropping season by using simple lattice design. The analysis of variances reveled highly significant difference among the genotype for most of traits considered in present study. High phenotypic and genotypic coefficient of variation was recorded for tiller per plant, harvest index, oil yield (kg ha⁻¹), and seed yield (ton ha-1) number of capsules per plant. High heritability along with genetic advance was observed for seed yield (tones ha-¹), oil yield (kg ha-¹) harvest index which indicates selection of these traits at early generation would be effective. Oil yield (kg ha⁻¹) harvest index and number of capsules plant ⁻¹ showed highly significant positive with seed yield (ton ha⁻¹). Cluster analysis revealed that 36 linseed genotypes were grouped into two clusters and four genotypes remain ungrouped. The maximum inter clusters distance was observed between clusters II and the local check. The data set was reduced into four significant principal components (PCs) that comprise (80%) of the variance. The first PC accounted for 34% of the variances that implies greater proportion of variable information explained by PC1. The traits, which contributed more to PC1, were seed yield per plant, primary branches per plant, secondary branches per plant and plant height showed positive association and had positive direct effect on seed yield. This indicates that any improvement of oil yield and harvest index would result in substantial increase on seed.     

Breeding Potential of Some Exotic Tomato Lines: A Combined Study of Morphological Variability,Genetic Divergence,and Association of Traits

Tomato (Solanum lycopersicum L.) is called ‘the poor man’s orange’ due to its low price and improved nutritional values. An experiment was conducted to study the breeding potential of some exotic tomato lines by assessing various qualitative and quantitative traits conferring yield and quality attributes. Among the qualitative traits, greater variability was observed for growth type, stem hairiness, and fruit shape and size. A determinate growth habit was observed in the genotype AVTO9802 while the genotype AVTO0102 produced yellow color fruits. A significant (p ≤ 0.01) variation was also observed for the studied quantitative traits. Based on yield and traits attributed to yield, the genotypes AVTO0314, GPB0107, GPB0120 and AVTO9802 were selected as promising genotypes. The differences between the genotypic and phenotypic coefficients of variation (GCV and PCV) of the studied quantitative traits were very low. This suggests that the apparent variation was mainly due to the genotypes. The higher GCV and PCV values were observed for the number of primary branches plant⁻¹ (NPB), number of fruits cluster⁻¹ (NFC), individual fruit weight (IFW) and total soluble solids (TSS). High heritability was recorded for all quantitative traits in a broad sense. However, the individual fruit diameter showed the highest heritability (99.56). The highest (102.75) genetic advance (GA) was observed for the number of fruits plant⁻¹ (NFP). High heritability coupled with high GA as percentage of mean were recorded for the traits NFP, NFC, fruit yield plant⁻¹ (FYP) and IFW. FYP showed a significant positive correlation with NFC (0.714***) and a negative correlation with days to the first harvest (−0.539***) and plant height (−0.492**). Principal component analysis revealed that the first four components explained 78.5% of the total variation among the genotypes. Thus, the promising genotypes (AVTO0314, GPB0107, GPB0120, AVTO9802 and AVTO0102) isolated from this study can be used for developing high-yielding and high-quality tomato varieties.     

Exploration of Genetic Pattern of Phenological Traits in Wheat (<i>Triticum aestivum</i> L.) under Drought Stress

Drought is the major detrimental environmental factor for wheat (Triticum aestivum L.) production. The exploration of genetic patterns underlying drought tolerance is of great significance. Here we report the gene actions controlling the phenological traits using the line × tester model studying 27 crosses and 12 parents under normal irrigation and drought conditions. The results interpreted via multiple analysis (mean performance, correlations, principal component, genetic analysis, heterotic and heterobeltiotic potential) disclosed highly significant differences among germplasm. The phenological waxiness traits (glume, boom, and sheath) were strongly interlinked. Flag leaf area exhibits a positive association with peduncle and spike length under drought. The growing degree days (heat-units) greatly influence spikelets and grains per spike, however, the grain yield/plant was significantly reduced (17.44 g to 13.25 g) under drought. The principal components based on eigenvalue indicated significant PCs (first-seven) accounted for 79.9% and 73.9% of total variability under normal irrigation and drought, respectively. The investigated yield traits showed complex genetic behaviour. The genetic advance confronted a moderate to high heritability for spikelets/spike and grain yield/plant. The traits conditioned by dominant genetic effects in normal irrigation were inversely controlled by additive genetic effects under drought and vice versa. The magnitude of dominance effects for phenological and yield traits, i.e., leaf twist, auricle hairiness, grain yield/plant, spikelets, and grains/spike suggests that selection by the pedigree method is appropriate for improving these traits under normal irrigation conditions and could serve as an indirect selection index for improving yield-oriented traits in wheat populations for drought tolerance. However, the phenotypic selection could be more than effective for traits conditioned by additive genetic effects under drought. We suggest five significant cross combinations based on heterotic and heterobeltiotic potential of wheat genotypes for improved yield and enhanced biological production of wheat in advanced generations under drought.     

Phenotypic variation in the agronomic and morphological traits of <Emphasis Type="Italic">Pisum sativum</Emphasis> L. Germplasm obtained from different parts of the world

A total of 286 genotypes were collected from 39 countries of the world and were evaluated to determine the phenotypic diversity for 17 quantitative traits. Higher degree of coefficient of variation were recorded for grain yield⁻⁵ (52.46%), biomass⁻⁵ (45.73%), fresh pod width-10 (47.24%), dry pod weight⁻¹⁰ (40.33%), plant height⁻¹ (35.25%), harvest index (32.70%) and number of branches⁻⁵. Cluster-II clearly reflected that late genotypes were having lightest pods weight, shortest pod width, and pod length; low grain yield, biomass and harvest index. Width, and pod length; low grain yield, biomass and harvest index. While genotypes in Cluster-III were in contrast to Cluster-II having heaviest pods weight, longest pods width and length, highest grain yield, biomass and harvest index. Higher PC₋₁ values have been determined for days to flower initiation which consequently were contributing weighed positive to days to pods picking, days to flower completion, days to dry pod appearance, days to plant harvesting while negatively contributed to yield producing traits, indicating that late flowering pea germplasm emphasizes more on the vegetative growth and was low yielding. However, higher PC₋₂ values have been obtained for number of branches⁻⁵, grain yield and biomass while lower values for days to flowering, days to pods picking, days to flower completion, days to dry pod appearance and days to plant harvesting confirming the fact that early genotypes were high yielding.     

Responses of rice (Oryza sativa L.) genotypes to different levels of submergence

The study aims at identifying some submergence-tolerant rice genotypes through morphological and molecular characterization and their genetic variability analysis. Ten rice genotypes including two submergence-tolerant checks, two susceptible varieties and six advanced lines were evaluated for submergence tolerance in the laboratory and in the field during January–December 2015. The experiment was conducted in the field following randomized complete block design in a two-factor arrangement using five replications. Ten characters, viz. days to flowering, plant height, tiller number plant^?1, effective tiller plant^?1, and yield plant^?1 etc. were studied for four treatments. A significant genotype × environment interaction was observed for all traits studied in this experiment. The yield was reduced for all genotypes at a different level of submergence stress compared to control. Binadhan-11, Binadhan-12, RC 249 and RC 251 showed tolerance, whereas RC 192, RC 193 and RC 225 showed moderate tolerance in submerged condition. The phenotypic coefficient of variance (PCV) was higher than the genotypic coefficient of variance (GCV) in all the studies traits. High heritability (75–97%) was found for all traits. High heritability along with high genetic advance was found for days to flowering (45.55) and plant height (40.05). Molecular characterization of the used genotypes was done with three SSR markers viz. RM 24, and submergence specific SC3 and SUB1. SC3 was found reliable for detection of submergence tolerant genotypes due to the highest gene diversity (0.840) compared to others. The banding pattern of the submergence specific markers SC3 and SUB1 identified in Binadhan-11, Binadhan-12, RC 192, RC 193, RC 225, RC 227, RC 249, and RC 251, which possess the SUB1 gene. Finally, clustering also separates the tolerant genotypes from the susceptible by dividing them into different clusters. The identified genotypes might be useful for the breeding programme for the development of submergence tolerant as well as resistant rice variety in Bangladesh.     

Genetic structure of Chrysanthemum genotypes from Iran assessed by AFLP markers and phenotypic traits

Chrysanthemum is popular worldwide as cut flower, potted plant and perennial garden plant. This study used amplified fragment length polymorphism and phenotypic traits to assess genetic diversity and population structure in Chrysanthemum. Results for the phenotypic traits of ray floret number, tubular floret number, flower number, pedicel length, leaflet number on pedicel and days to visible flower bud had high level (i.e., >30 %) evaluations for genotypic coefficient of variation and phenotypic coefficient of variation; thus, heritability for various phenotypic traits ranged from 45.30 to 94.55 %. Phenotypic data clustered the genotypes into four separate groups. Twenty-five primer combinations were used for molecular analysis. On average, each primer combination produced 83.96 polymorphic DNA bands, ranging from 33 to 122 bands. Polymorphic percentage (99.3 %), polymorphism information content (0.43) and Shannon’s information index (0.45) evaluated high levels of genetic variation in the tested genotypes. The Neighbor-Joining (NJ) method grouped genotypes into six clusters, which were in part confirmed by principal coordinate analysis. A Bayesian structure analysis identified four clusters, in which 30 individuals were maintained within the admixed clusters. Results from this study provide appropriate information applicable to designing effective breeding programs and other analyses associated with future studies of Chrysanthemum.     

Rice (<i>Oryza sativa</i> L.) Breeding among Hassawi Landrace and Egyptian Genotypes for Stem Borer (<i>Chilo agamemnon</i> Bles.) Resistance and Related Quantitative Traits

Rice stem borer (Chilo agamemnon Bles.) is a primary insect pest of rice and is a major limiting factor to rice production. Breeding for insect-resistant crop varieties has been an economic way of integrated pest management (IPM) as it offers a viable and ecologically acceptable approach. This study was aimed to evaluate rice genotypes for their resistance against rice stem borer. Seven parental genotypes with twenty one F1 crosses were evaluated for genotypic variation in field experiments. Analysis of variance revealed significant differences for the studied traits in almost all crosses and parents. In addition, the mean squares of parents versus their crosses were signifi- cant for stem borer resistance and other associated traits. Moreover, both general combining ability (GCA) and specific combining ability (SCA) variances were highly significant for all characters studied in the F1 generation. Based on GCA, 4 genotypes (Sakha101, Gz6903-3-4-2-1, Gz9577-4-1-1 and Hassawi) exhibited highly significant negative values for stem borer resistance (–0.53, –1.06, –0.18 and –0.49, respectively) indicating they are the best combiners for stem borer resistance. Based on SCA analysis, nine cross combinations showed highly significant negative effects for stem borer resistance. Similarly, the cross Giza178 Hassawi was the best combination with significantly highest value for early maturity. In addition, seven crosses showed highly significant negative SCA for plant height trait. On the other hand, for panicle length, number of primary branches/panicle, panicle weight and 1000-grain weight, seven, four, eight and six crosses showed highly significant positive SCA, respectively. The result further revealed that the non-additive dominance genetic variance was higher than the additive variance for all evaluated traits indicating that non-additive genetic variances have a role in their inheritance. The broad-sense heritability estimates were high for all the studied traits. The stem borer resistance was significantly correlated with panicle weight and 1000-grain weight, which also showed a highly significant correlation with grain yield/plant. Thus these traits can be effectively employed in a breeding program to confer resistance against stem borer infestation in rice. It was further supported by biplot analysis, which clustered these potentially important traits into two quadrants showing their importance in any future breeding program to control stem borer infestation. This study has contributed valuable information for evaluation of genetic diversity in the local rice germplasm and its utilization in futuristic rice genetic improvement programs.     

Identification of QTLs for Yield and Associated Traits in F₂ Population of Rice

Identification of quantitative trait loci (QTLs) controlling yield and yield-related traits in rice was performed in the F₂ mapping population derived from parental rice genotypes DHMAS and K343. A total of 30 QTLs governing nine different traits were identified using the composite interval mapping (CIM) method. Four QTLs were mapped for number of tillers per plant on chromosomes 1 (2 QTLs), 2 and 3; three QTLs for panicle number per plant on chromosomes 1 (2 QTLs) and 3; four QTLs for plant height on chromosomes 2, 4, 5 and 6; one QTL for spikelet density on chromosome 5; four QTLs for spikelet fertility percentage (SFP) on chromosomes 2, 3 and 5 (2 QTLs); two QTLs for grain length on chromosomes 1 and 8; three QTLs for grain width on chromosomes1, 3 and 8; three QTLs for 1000-grain weight (TGW) on chromosomes 1, 4 and 8 and six QTLs for yield per plant (YPP) on chromosomes 2 (3 QTLs), 4, 6 and 8. Most of the QTLs were detected on chromosome 2, so further studies on chromosome 2 could help unlock some new chapters of QTL for this cross of rice variety. Identified QTLs elucidating high phenotypic variance can be used for marker-assisted selection (MAS) breeding. Further, the exploitation of information regarding molecular markers tightly linked to QTLs governing these traits will facilitate future crop improvement strategies in rice.     

Laboratory-and Field-Phenotyping for Drought Stress Tolerance and Diversity Study in Lentil (<i>Lens culinaris</i> Medik.)

Drought susceptibility and low genetic variability are the major constraints of lentil (Lens culinaris Medik.) production worldwide. Development of an efficient pre-field drought phenotyping technique and identification of diversified drought tolerant lentil genotype(s) are therefore vital and necessary. Two separate experiments were conducted using thirty diverse lentil genotypes to isolate drought tolerant genotype(s) as well as to assess their diversity. In both of the experiments, significant (p ≤ 0.01) variation in genotype (G), treatment (T) and G X T was observed for most of the studied traits. In experiment I, genotypes were examined for drought tolerance at the seedlings stage under hydroponic conditions by assessing root and shoot traits. Among the 30 genotypes studied, BM-1247, BM-1227 and BM-502 were selected as highly tolerant to drought stress as they showed maximum seedling survivability and minimum reduction in growth parameters under drought stress. In experiment II, the genotypes were assayed for diversity and drought stress tolerance based on morphological traits grown under field condition. Drought stress caused a substantial reduction in yield attributing traits, however, the genotypes BM-1247, BM-981, BM-1227 and BM-502 were categorized as drought tolerant genotypes with less than 20% yield reduction. The field screening result of drought stress tolerance was coincided well with the results of laboratory screening. Genetic divergence study reflected the presence of considerable diversity among the genotypes. Considering laboratory and field screening results, the genotypes, BM-1247, BM-1227, BM-981 and BM- 502 were selected as the best drought tolerant genotypes. This information can be exploited for further breeding in developing drought tolerance in lentil.     

Genetic variability,character association and divergence studies in <Emphasis Type="Italic">Jatropha curcas</Emphasis> for improvement in oil yield

Key message

Variability in traits of 15, diverse 6-year-old candidate plus trees of Jatropha curcas was determined to identify the best gain heritable traits correlating with oil yield for Jatropha improvement.

Abstract

Study was carried out on 15 6-year-old candidate plus trees of Jatropha curcas adapted on semi-arid wasteland with an objective to assess variation in morphological, physiological and oil quality characters. Heritable and non-heritable components of the total variability of the characters were determined by genotypic (GCV) and phenotypic (PCV) co-efficient of variation, heritability and genetic advance (GA) and the best gain traits for Jatropha improvement through selection and breeding were assessed. Further, association among the traits were assessed and germplasm were separated into different clusters. Significant variation was found among the different genotypes for all the characters. The photosynthetic and transpiration rate correlated with oil content, seed and oil yield. The chlorophyll pigments correlated positively with the photosynthetic rate and oil content. The seed oil content varied considerably from 27.68 % (JCN01) to 37.49 % (JCN14) and had high heritability, but it had low PCV and GCV and moderate GA. The oil yield plant^?1 had high genetic variability and varied significantly from 0.07 (JCN15) to 0.47 kg plant^?1 (JCN09/IC 565733). Though the different fatty acids differed significantly with different germplasm and also had high heritability, they had low PCV, GCV and GA. Seed weight, fruit weight, seed weight fruit^?1 and seed yield plant^?1 strongly correlated with oil yield and had moderate to high GCV, PCV, coupled with high heritability and GA. Germplasm were separated into four distinct clusters with a maximum inter distance found between cluster II and IV, and minimum between cluster I and III. The study helped to identify the superior germplasm among diverse genotypes of J. curcas that can serve as parents with desirable characters like high oil yield, low stomatal conductance and high water use efficiency for further breeding purposes.

     

Functional Analysis of the Genotypic Differences in Response of Pea (<i>Pisum sativum</i> L.) to Calcareous-Induced Iron Deficiency

Lime-induced iron chlorosis is a major nutritional disorder causing severe plant growth and yield reduction in the calcareous soils of Tunisia. The understanding the behavior of key metabolic functions of peas on calcareous soils, the identification of useful traits of tolerance, and the exploration of the genotypic differences in response to this constraint remain the most efficient approaches due to their coast, environmental benefits, and sustainability. For this purpose, a greenhouse experiment was conducted on three pea genotypes (Alexandra: Alex, Douce de provence: DP, and Merveille de Kelvedon: MK) cultivated on calcareous soil (Fe-deficient) and fertile soil (control). Plant growth, SPAD index, iron nutrition and distribution, photosynthesis, and antioxidant enzymes were deeply analyzed to discriminate genotypic differences. Calcareous-induced iron deficiency reduced SPAD index, plant growth, net photosynthesis, and tissue Fe content against a significant stimulation of the oxidative stress indicators, H₂O₂ and Malondialdehyde (MDA). Moreover, we reported a significant induction of SOD and CAT activity in shoots and roots of the Alexandra genotype. Fe use efficiency increased on calcareous soil and clearly discriminated the studied genotypes. Alexandra genotype was found to be the most tolerant to lime-induced iron chlorosis. This genotype protects its tissues against oxidative stress by stimulating enzyme activities (SOD and CAT) and develops significant efficiency of Fe uptake, translocation to shoots and use when cultivated on calcareous soil.     

Quantitative trait loci mapping of yield and related traits using a high-density genetic map of maize

Improving grain yield is the ultimate goal of the maize-breeding programs. In this study, analyses of conditional and unconditional quantitative trait locus (QTL) and epistatic interactions were used to elucidate the genetic architecture of yield and its related traits. A total of 15 traits of a recombinant inbred line population, including yield per plant (YPP), seven ear-related traits, and seven kernel-related traits, were measured in six different environments. Based on the genetic linkage map constructed using 2091 bins as markers, 56 main-effect QTLs for these traits were identified. These QTLs were distributed across eight genomic regions (bin 1.06, bin 4.02/4.05/4.08, bin 5.04, bin 7.04, bin 8.08, and bin 9.04), within the marker intervals of 85.45–6260.66 kb, and the phenotypic variance explained ranging from 5.69 to 11.56 %. One gene (GRMZM2G168229) encoding SBP-box domain protein was located in the small interval of qKRN4-3 and may be involved in patterning of kernel row number. Seventeen conditional QTLs identified for YPP were conditioned on its related traits and explained 6.18–23.15 % of the phenotypic variance. Conditional mapping analysis revealed that qYPP4-1, qYPP6-1, and qYPP8-1 are partially influenced by YPP-related traits at the individual QTL level. Digenic epistatic analysis identified 12 digenic interactions involving 22 loci across the whole genome. In addition, conditional digenic epistatic analysis identified 14 digenic interactions involving 21 loci. This study provides valuable information for understanding the genetic relationship between YPP and related traits and constitutes the first step toward the cloning of the relevant genes.     

家蚕二化性杂交品种部分数量性状遗传参数的初步评估

采用完全随机设计法根据10头老熟幼虫体重、全茧重、茧层量、茧层率（%）、存活率、万蚕茧层量和茧丝长等指标,对两对二化性家蚕Bombyx mori L. 杂交品系（SH6×NB₄D₂和CSR₂×CSR₄）杂交一代的22个子代个体进行了遗传参数估算,以缩小优质蚕品种的候选范围,并且计算出直接筛选的参数,如遗传力和遗传进度等,使这些信息可用于以筛选高产新品种为目的的育种和选择过程中。杂交子代2, 4, 5, 6, 7, 10, 14, 16, 19和20号个体在这几个指标中表现出显著的优越性。全茧重、万蚕茧层量和茧丝长的遗传力和遗传进度较大,可以简单地从表现型的差异对这些性状进行选择并取得遗传性状改良。其他几个指标(10头老熟幼虫体重、茧层量、茧层率(%)和存活率)的遗传力和遗传进度较低,对这些性状进行直接选择来改良品种的效果较差。     

Genetic variability,character association and path analysis of oil yield and its component characters in Cymbopogon sp.

Seeking an opportunity for genetic improvement in aromatic grasses lead to an explorative study on the aspects of genetic variability, character association and path analysis between essential oil yield/plot and its contributing traits in twenty five genotypes of Cymbopogon sp. collected from different agro-climatic zones of India, grown in RBD with three replicates. Highly significant differences between genotypes were recorded for the traits that were brought under study. High genotypic and phenotypic coefficients of variation coupled with high heritability and moderate to high genetic advance over mean were recorded in geraniol content, citral content and geranyl acetate content indicating predominance of additive gene effects controlling these traits. Correlation and path analysis revealed that oil content, herb yield/plot and geranyl acetate content are overriding traits among all other growth and yield parameters, therefore more emphasis should be laid upon them while designing selection indices for improvement of essential oil yield.     

Estimation of Genetic Divergence and Character Association Studies in Local and Exotic Diversity Panels of Soybean (<i>Glycine max</i> L.) Genotypes

The availability of favorable genetic diversity is a thriving vitality for the success of a breeding program. It provides a firm basis of selecting superior breeding lines for the development of high yielding crop genotypes. In this context, present investigation aimed to generate information on genetic divergence and character association in a diversity panel of 123 local and exotic soybean genotypes. Analysis of variance revealed significant response of the evaluated genotypes based on studied attributes. It depicted the probability of selecting desirable soybean genotypes by focusing on character association studies and genetic diversity analysis. Correlation analysis revealed that seed yield per plant showed high positive correlation with 100-seed weight followed by pods per plant and plant height. Furthermore, path coefficient analysis exposed that pods per plant had maximum direct contribution in seed yield per plant followed by 100-seed weight, days to flowering and SPAD measurement. Genotype named “G-10” showed maximum yield per plant followed by 24607, G-52, 24593, Arisoy, 24566, 17426, A-3127, 24570 and 24567. Genetic diversity analysis grouped the evaluated germplasm into 17 clusters. All clusters showed zero intra-cluster variability; while inter-cluster divergence ranged from 9.00 to 91.11. Cluster V showed maximum inter-cluster distance with cluster XII followed by that of between V and VIII. Moreover, cluster IV with superior genotypes (G-10, 24607, 24593 and 24566), VI (17426 and 24567), XIII (24570) and X (Arisoy and G-52) showed above mean values for most of the studied characters. Overall, the results of hybridization between the superior genotypes of these cluster pairs might be useful for soybean breeding with improving agronomic traits and adaptability.     

Improvement of Early Maturing and Climate Resilient Chickpea (<i>Cicer arietinum</i> L.) Cultivars Suitable for Multiple Environments in Bangladesh

Ensuring food security for the rapidly increasing population and changing climatic scenarios are requisites for exploiting the genetic divergence of food crops. A study was undertaken to sort out an early maturing chickpea variety for fitting easily between rice-rice cropping systems in the Eastern Indo-Gangetic Plain of Bangladesh. The trial was comprised of eight elite lines of chickpea and executed at various localities in Bangladesh from 2014– 15 to 2017–18. The result explored the chickpea genotype, BARI Chola-11 remained superior to the rest of the elite genotypes for having a short maturity period (100–106 days), and lesser days to 50% flowering (47– 55 days). The same genotype was recorded to have robust vegetative and reproductive yield attributes including plant height (49–57 cm), podsplant⁻¹ (37–50), and optimum 100 seed weight (19.5–20.6 g). Owing to better yield attributes, BARI Chola-11 resulted in the maximum seed yield (1200–1500 kg ha⁻¹ ) of chickpea and might be recommended for general adoption in the region for boosting nutritional security status through improved productivity under changing climate.     

Association mapping of seed quality traits using the Canadian flax (Linum usitatissimum L.) core collection

Key message

The identification of stable QTL for seed quality traits by association mapping of a diverse panel of linseed accessions establishes the foundation for assisted breeding and future fine mapping in linseed.

Abstract

Linseed oil is valued for its food and non-food applications. Modifying its oil content and fatty acid (FA) profiles to meet market needs in a timely manner requires clear understanding of their quantitative trait loci (QTL) architectures, which have received little attention to date. Association mapping is an efficient approach to identify QTL in germplasm collections. In this study, we explored the quantitative nature of seed quality traits including oil content (OIL), palmitic acid, stearic acid, oleic acid, linoleic acid (LIO) linolenic acid (LIN) and iodine value in a flax core collection of 390 accessions assayed with 460 microsatellite markers. The core collection was grown in a modified augmented design at two locations over 3 years and phenotypic data for all seven traits were obtained from all six environments. Significant phenotypic diversity and moderate to high heritability for each trait (0.73–0.99) were observed. Most of the candidate QTL were stable as revealed by multivariate analyses. Nine candidate QTL were identified, varying from one for OIL to three for LIO and LIN. Candidate QTL for LIO and LIN co-localized with QTL previously identified in bi-parental populations and some mapped nearby genes known to be involved in the FA biosynthesis pathway. Fifty-eight percent of the QTL alleles were absent (private) in the Canadian cultivars suggesting that the core collection possesses QTL alleles potentially useful to improve seed quality traits. The candidate QTL identified herein will establish the foundation for future marker-assisted breeding in linseed.     

The Physiological Mechanisms Underlying N₂-Fixing Common Bean (<i>Phaseolus vulgaris</i> L.) Tolerance to Iron Deficiency

Iron is an essential element for plants as well as all living organisms, functioning in various physiological and biochemical processes such as photosynthesis, respiration, DNA synthesis, and N₂ fixation. In the soil, Fe bioavailability is extremely low, especially under aerobic conditions and at high pH ranges. In contrast, plants with nodules on their roots that fix atmospheric nitrogen need much more iron. To highlight the physiological traits underlying the tolerance of N₂-fixing common bean to iron deficiency, two genotypes were hydroponically cultivated in a greenhouse: Coco nain (CN) and Coco blanc (CB). Plants were inoculated with an efficient strain of Rhizobium tropici, CIAT899, and received a nutrient solution added with 0 µM Fe (severe Fe deficiency, SFeD), 5 µM Fe (moderate Fe deficiency, MFeD) or 45 µM Fe (control, C). Several physiological parameters related to photosynthesis and symbiotic nitrogen fixation were then analyzed. Iron deficiency significantly reduced whole plant and nodule growth, chlorophyll biosynthesis, photosynthesis, leghemoglobin (LgHb), nitrogenase (N₂ase) activity, nitrogen, and Fe nutrition, with some genotypic differences. As compared to CB, CN maintained better Fe allocation to shoots and nodules, allowing it to preserve the integrity of its photosynthetic and symbiotic apparatus, thus maintaining the key functional traits of the plant metabolism (chlorophyll biosynthesis and photosynthesis in shoots, leghemoglobin accumulation, and nitrogenase activity in root nodules). Plant growth depends on photosynthesis, which needs to be supplied with sufficient iron and nitrogen. Fe deficiency stress index (FeD-SI) and Fe use efficiency (FeUE) are two physiological traits of tolerance that discriminated the studied genotypes.     

Evaluation of genetic behavior of some Egyption Cotton genotypes for tolerance to water stress conditions

Water stress is a critical abiotic stress for plant reduction in arid and semiarid zones and, has been discovered to be detrimental to the development of seedlings as well as the growth and physiological characteristics of many crops such as cotton. The objectives of our study were to determine the combining ability and genetic components for five quantitative traits [(leaf area (LA), leaf dry weight (LDW), plant height (PH), fiber length (2.5 percent SL), and lint cotton yield/plant (LCY/P)] under water shortage stress, a half diallel cross between six cotton genotypes representing a wide range of cotton characteristics was evaluated in RCBD with four replications. The genotype mean squares were significant for all traits studied, demonstrating significant variation among genotypes for all characters under water shortage stress. LCY/P had the highest phenotypic and genotypic correlation co-efficient with PH, LDW, and LA shortage. The highest direct effect on lint cotton yield was exhibited by leaf area (3.905), and the highest indirect effects of all traits were through LA, with the exception of 2.5 percent SL, which was through LDW. The highest dissimilarity (Euclidean Distance) between parental genotypes was between G.87 and G.94, followed by G.87 and Menoufi. G.94 was also a well-adapted genotype, and the combinations G.87 x G.94 and G.87 x Menoufi may outperform their parents. The combining ability analysis revealed highly significant differences between parental GCA effects and F1 crosses SCA effects. The variation of GCA and SCA demonstrated the assurance of additive and non- additive gene action in the inheritance of all traits studied. In terms of general combining ability (GCA) effects, parental genotype G.94 demonstrated the highest significant and positive GCA effects for all traits studied, with the exception of 2.5 percent SL, where G.87 revealed the highest significant and positive GCA effects. The effects of specific combining ability (SCA) revealed that the cross (G.87 x2G.94) revealed stable, positive, and significant SCA for all of the studied traits.     

Genomic selection in soybean: accuracy and time gain in relation to phenotypic selection

Genomic selection (GS) can potentially accelerate genetic improvement of soybean [Glycine max L. (Merrill)] by reducing the time to complete breeding cycles. The objectives of this study were to (1) explore the accuracy of GS in soybean, (2) evaluate the contribution of intrapopulational structure to the accuracy of GS, and (3) compare the efficiencies of phenotypic selection and GS in soybean. For this, phenotypic and genotypic data were collected from 324 soybean genotypes (243 recombinant inbred lines and 81 cultivars) and GS was performed for five yield related traits. BayesB methodology with a 10-fold cross-validation was used to compute accuracies. The GS accuracies were evaluated for grain yield, plant height, insertion of first pod, days to maturity, and 1000-grain weight at eight locations. We found that GS can reduce the time required to complete a selection cycle in soybean, which can lead to increased production of this commercially important crop. Furthermore, genotypic accuracy was similar regardless of population structure correction.