Percentage Of Phenotypic Variance Research Articles

Bipolar patients display stoichiometric imbalance of gene expression in post-mortem brain samples

Bipolar disorder is a severe neuro-psychiatric condition where genome-wide association and sequencing studies have pointed to dysregulated gene expression as likely to be causal. We observed strong correlation in expression between GWAS-associated genes and hypothesised that healthy function depends on balance in the relative expression levels of the associated genes and that patients display stoichiometric imbalance. We developed a method for quantifying stoichiometric imbalance and used this to predict each sample’s diagnosis probability in four cortical brain RNAseq datasets. The percentage of phenotypic variance on the liability-scale explained by these probabilities ranged from 10.0 to 17.4% (AUC: 69.4–76.4%) which is a multiple of the classification performance achieved using absolute expression levels or GWAS-based polygenic risk scores. Most patients display stoichiometric imbalance in three to ten genes, suggesting that dysregulation of only a small fraction of associated genes can trigger the disorder, with the identity of these genes varying between individuals.

Genetic variants of the vitamin D receptor are related to dynapenia in postmenopausal women

BackgroundDynapenia increases with age and in the case of women is possibly influenced by menopause, yet whether vitamin D affects this increase remains controversial. The influence of genetic variants (single nucleotide polymorphisms) of the vitamin D receptor on dynapenia is an understudied area. AimTo analyze the association between genetic variants of the vitamin D receptor gene and dynapenia in a cohort of community-dwelling postmenopausal women. MethodsWe performed a cross-sectional study of 463 women in a university hospital. Grip strength was used as an indicator of dynapenia. Differences in grip strength among single nucleotide polymorphisms rs11568820 and rs2228570 genotypes of the vitamin D receptor gene were assessed after adjusting for confounding variables, and the percentage of phenotypic variance was estimated by linear regression. ResultsDynapenia (grip strength <20 kg) was diagnosed in 178 of the women (38.45 %). A difference in grip strength, corresponding to variants of the vitamin D receptor gene single nucleotide polymorphism rs11568820, was found when using an additive model of inheritance, with lower grip strength for the TT genotype (ANOVA, p = 0.030, close to the 0.025 significance level determined by Bonferroni correction). Assuming a recessive inheritance model for allele T, the between-group difference in grip strength was significant (TT = 19.79 ± 3.10 kg vs. CC/CT = 21.58 ± 3.49 kg, p = 0.008) after adjusting for age, body mass index, comorbidities, and sociodemographic variables. More women with dynapenia had the TT genotype (60.71 %) than the CC or CT genotype (37.01 %) (p = 0.012). ConclusionThis study demonstrates that the TT genotype of the rs11568820 SNP of the vitamin D receptor gene was associated with decreased grip strength in community-dwelling postmenopausal women.

CgSSR marker-based genome-wide association study identified genomic regions for panicle characters and yield in rice (Oryza sativa L.).

To improve production efficiency, positive alleles corresponding to yield-related attributes must be accumulated in a single elite background. We designed and used cgSSR markers, which are superior to random SSR markers in genome-wide association study, to identify genomic regions that contribute to panicle characters and grain yield in this study. As evidenced by the high polymorphic information content value and gene diversity coefficient, the new cgSSR markers were determined to be highly informative. These cgSSR markers were employed to generate genotype data for an association panel evaluated for four panicle characters and grain yield over three seasons. For five traits, 17 significant marker-trait associations on six chromosomes were discovered. The percentage of phenotypic variance that could be explained ranged from 4% to 13%. Unrelated gene-derived markers had a strong association with target traits as well. Trait-associated cgSSR markers derived from corresponding or related genes ensure their utility in direct allele selection, while other linked markers aid in allele selection indirectly by altering the phenotype of interest. Through a marker-assisted breeding approach, these marker-trait associations can be leveraged to accumulate favourable alleles for yield enhancement in rice. © 2022 Society of Chemical Industry.

Genotyping by sequencing-based linkage map construction and identification of quantitative trait loci for yield-related traits and oil content in Jatropha (Jatropha curcas L.).

Jatropha (Jatropha curcas L.) has been considered as a potential bioenergy crop and its genetic improvement is essential for higher seed yield and oil content which has been hampered due to lack of desirable molecular markers. An F2 population was created using an intraspecific cross involving a Central American line RJCA9 and an Asiatic species RJCS-9 to develop a dense genetic map and for Quantitative trait loci (QTL) identification. The genotyping-by-sequencing (GBS) approach was used to genotype the mapping population of 136 F2 individuals along with the two parental lines for classification of the genotypes based on single nucleotide polymorphism (SNPs). NextSeq 2500 sequencing technology provided a total of 517.23million clean reads, with an average of ~ 3.8million reads per sample. We analysed 411 SNP markers and developed 11 linkage groups. The total length of the genetic map was 4092.3cM with an average marker interval of 10.04cM. We have identified a total of 83 QTLs for various yield and oil content governing traits. The percentage of phenotypic variation (PV) was found to be in the range of 8.81 to 65.31%, and a QTL showed the maximum PV of 65.3% for a total seed number on the 6th linkage group (LG). The QTLs detected in this study for various phenotypic traits will lay down the path for marker-assisted breeding in the future and cloning of genes that are responsible for phenotypic variation.

Multi-year analyses on three populations reveal the first stable QTLs for tolerance to rain-induced fruit cracking in sweet cherry (Prunus avium L.)

Rain-induced fruit cracking is a major problem in sweet cherry cultivation. Basic research has been conducted to disentangle the physiological and mechanistic bases of this complex phenomenon, whereas genetic studies have lagged behind. The objective of this work was to disentangle the genetic determinism of rain-induced fruit cracking. We hypothesized that a large genetic variation would be revealed, by visual field observations conducted on mapping populations derived from well-contrasted cultivars for cracking tolerance. Three populations were evaluated over 7–8 years by estimating the proportion of cracked fruits for each genotype at maturity, at three different areas of the sweet cherry fruit: pistillar end, stem end, and fruit side. An original approach was adopted to integrate, within simple linear models, covariates potentially related to cracking, such as rainfall accumulation before harvest, fruit weight, and firmness. We found the first stable quantitative trait loci (QTLs) for cherry fruit cracking, explaining percentages of phenotypic variance above 20%, for each of these three types of cracking tolerance, in different linkage groups, confirming the high complexity of this trait. For these and other QTLs, further analyses suggested the existence of at least two-linked QTLs in each linkage group, some of which showed confidence intervals close to 5 cM. These promising results open the possibility of developing marker-assisted selection strategies to select cracking-tolerant sweet cherry cultivars. Further studies are needed to confirm the stability of the reported QTLs over different genetic backgrounds and environments and to narrow down the QTL confidence intervals, allowing the exploration of underlying candidate genes.

Mapping QTLs associated with chloride accumulation in leaves of oriental tobacco (Nicotiana tabacum L.) using F2:3 population of Basma Seres 31 × SPT 406 cross

Chloride is considered as the most important micronutrient in tobacco production. But excessive amounts of chloride accumulation in leaves of tobacco has many adverse effects on the tobacco quality, such as burning capacity. Identification of quantitative trait loci (QTL) involved in chloride accumulation would be beneficial for the improvement of tobacco quality. The objective of this study was to identify genomic regions associated with chloride accumulation by using a mapping population consists of 225 F2:3 families derived from hybridization between ‘Basma Seres 31’ and ‘SPT 406’ lines. Linkage map was constructed with 23 microsatellite (SSR) and 29 inter simple sequence repeat (ISSR) polymorphic markers which covered 570.8 cM of the tobacco genome. Thirty-four of these polymorphic markers were mapped to 7 linkage groups. Distance between two adjacent markers was 17.3 cM. Composite interval mapping (CIM) was used to identify QTLs controlling chloride accumulation. One QTL for chloride accumulation was identified on linkage group 3. The percentage of phenotypic variance (R2) explained by this QTL was 12.7%. A significant association was not found between ISSR markers and chloride accumulation. The outcome of present effort can be a basis for marker aided selection (MAS) in tobacco breeding programs.

Genome-wide association analysis of root system architecture features and agronomic traits in durum wheat

Root system architecture (RSA) has positive effects on wheat growth and its yield performance. As root features are difficult to manipulate through conventional breeding strategies, marker-trait association (MTA) could be helpful for the improvement of RSA. In the present study, 112 durum wheat genotypes were investigated for several root system features as well as some agronomic traits. The population was genotyped using a 15K SNP and a total of 3321 markers were used in the association analysis. A total of 581 significant marker-trait associations were identified in all of the 14 chromosomes. The percentages of phenotypic variation (R2) of measured traits varied between 8.76 and 24.81%. Out of 581 associated markers, 125 loci were linked with multiple traits. The most significant associations on measured traits were detected for genome B compared to genome A (61% vs 39%). Also, major associated loci existed on chromosomes 1A, 1B, 2B, 3B, and 5B, which could be considered in the future breeding programs to manipulate relevant traits using marker-assisted selection procedures. Among associated SNP markers, most markers were related to the number of days to spike heading (181), anthesis (53), booting (69), physiological maturity (41), water use efficiency (109), and transpiration efficiency (24). Furthermore, the large number of QTLs (167 in total) for RSA and agronomic traits were detected. The highest numbers of QTLs were related to WUE (23), DAS (23), DB (21), and DA (20) than other traits. Among the detected QTLs, 16 QTLs for RSA overlapped with different agronomic traits, as well as 6 QTLs co-located with other RSA traits in at last one trait. These results are helpful for better understanding the genetic basis of root system features and agronomic traits. Furthermore, these results could be valuable for facilitating pyramiding of the ideal alleles using the MAS approach for favorable plant-type and high water use efficiency in the future durum wheat breeding programs.

Mining of favorable alleles for seed reserve utilization efficiency in Oryza sativa by means of association mapping

BackgroundWet direct-seeded rice is a possible alternative to conventional puddled transplanted rice; the former uses less water and reduces labor requirements. Improving seed reserve utilization efficiency (SRUE) is a key factor in facilitating the application of this technology. However, the QTLs controlling this trait are poorly investigated. In this study, a genome-wide association study (GWAS) was conducted using a natural population composed of 542 accessions of rice (Oryza sativa L.) which were genotyped using 266 SSR markers. Large phenotypic variations in SRUE were found in the studied population.ResultsThe average SRUE over 542 accessions across two years (2016 and 2017) was 0.52 mg.mg− 1, ranging from 0.22 mg.mg-1 to 0.93 mg.mg− 1, with a coefficient of variation of 22.66%. Overall, 2879 marker alleles were detected in the population by 266 pairs of SSR markers, indicating a large genetic variation existing in the population. Using general linear model method, 13 SSR marker loci associated with SRUE were detected and two (RM7309 and RM434) of the 13 loci, were also detected using mixed linear model analyses, with percentage of phenotypic variation explained (PVE) greater than 5% across two years. The 13 association loci (P < 0.01) were located on all chromosomes except chromosome 11, with PVE ranging from 5.05% (RM5158 on chromosome 5) to 12% (RM297 on chromosome 1). Association loci RM7309 on chromosome 6 and RM434 on chromosome 9 revealed by both models were detected in both years. Twenty-three favorable alleles were identified with phenotypic effect values (PEV) ranging from 0.10 mg.mg− 1 (RM7309–135 bp on chromosome 9) to 0.45 mg.mg− 1 (RM297–180 bp on chromosome 2). RM297–180 bp showed the largest phenotypic effect value (0.44 mg.mg− 1 in 2016 and 0.45 mg.mg− 1 in 2017) with 6.72% of the accessions carrying this allele and the typical carrier accession was Manyedao, followed by RM297–175 bp (0.43 mg.mg− 1 in 2016 and 0.44 mg.mg− 1 in 2017).ConclusionNine novel association loci for SRUE were identified, compared with previous studies. The optimal parental combinations for pyramiding more favorable alleles for SRUE were selected and could be used for breeding rice accessions suitable for wet direct seeding in the future.

Detection of QTLs for outcrossing-related traits in rice (Oryza sativa L.) by association mapping and the RSTEP-LRT method

The outcrossing traits in rice affect the yield of hybrid rice seed production. In this study, 30 quantitative trait loci (QTLs) were detected in a natural population composed of 522 accessions by using a mixed linear model for the four outcrossing-related traits in 2017 and 2018. We detected 3, 4, 9 and 14 QTLs for flag leaf length (FLL), flag leaf width (FLW), flag leaf angle (FLA) and panicle neck length (PNL), respectively, among which 26 QTLs were novel. The favorable alleles and their carrier varieties were noticed with the largest phenotypic effect value. For FLL, marker allele RM6997-105 bp on chromosome 4 carried by Yue96 cultivar showed the highest phenotypic effect value (PEV), allele RM562-280 bp on chromosome 1 carried by Wanzhongqiu genotype for FLW, allele RM152-375 bp on chromosome 8 in typical carrier variety Zhongzuo93 for FLA and allele RM134-150 bp on chromosome 7 carried by Yue34 cultivar for PNL showed the highest PEVs. Additionally, nine QTLs were detected for the 4 traits with percentage of phenotypic variance explained (PVE) ranging from 16.24% (RM21) to 28.75% (RM5479) using a chromosome segment substitution line (CSSL) population. Among these detected QTLs, qFLL-12 and qFLW-12 showed 19.85% and 19.57% PVE, respectively. Four QTLs (qFLA-10, qFLA-11, qFLA-12.1, qFLA-12.2) detected for FLA showed PVEs ranging from 16.24% to 28.75%. For PNL, qPNL-7, qPNL-12.1, qPNL-12.2 were observed with PVEs of 20.14%, 17.39% and 28.36%, respectively. The favorable allele RM125-145 bp on chromosome 7 for PNL was detected in both the natural population and CSSL population and was carried by Yue38 accession and parent Xiushui79. The detected favorable alleles could be used to improve target traits.

QTL consistency for agronomic traits across three generations and potential applications in popcorn

Favorable agronomic traits are important to improve productivity of popcorn. In this study, a recombinant inbred line (RIL) population consisting of 258 lines was evaluated to identify quantitative trait loci (QTLs) for nine agronomic traits (plant height, ear height, top height (plant height subtracted ear height), top height/plant height, number of leaves above the top ear, leaf area, stalk diameter, number of tassel branches and the length of tassel) under three environments. Meta-analysis was conducted then to integrate QTLs identified across three generations (RIL, F2:3 and BC2F2) developed from the same crosses. In total, 179 QTLs and 36 meta-QTLs (mQTL) were identified. The percentage of phenotypic variation (R2) explained by any single QTL varied from 3.86 to 28.4%, and 24 QTLs with contributions over 15%. Nine common QTLs located in the same or similar chromosome regions were detected across three generations. Five meta-QTLs were identified including QTLs in three independent studies. Seven important mQTLs were composed of 11–26 QTLs for 4–7 traits, respectively. Only 11 mQTLs were commonly identified in the same or similar chromosome regions across agronomic traits, popping characteristics (popping fold, popping volume and popping rate) and grain yield components (ear weight per plant, grain weight per plant, 100-grain weight, ear length, kernel number per row, ear diameter, row number per ear and kernel ratio) by meta-QTL analysis. In conclusion, we identified a list of QTLs, some of which with much higher contributions to agronomic traits should be valuable for further study in improving both popping characteristics and grain yield components in popcorn.

Methods for detecting associations between phenotype and aggregations of rare variants

Although genome-wide association studies have uncovered variants associated with more than 150 traits, the percentage of phenotypic variation explained by these associations remains small. This has led to the search for the dark matter that explains this missing genetic component of heritability. One potential explanation for dark matter is rare variants, and several statistics have been devised to detect associations resulting from aggregations of rare variants in relatively short regions of interest, such as candidate genes. In this paper we investigate the feasibility of extending this approach in an agnostic way, in which we consider all variants within a much broader region of interest, such as an entire chromosome or even the entire exome. Our method searches for subsets of variant sites using either Markov chain Monte Carlo or genetic algorithms. The analysis was performed with knowledge of the Genetic Analysis Workshop 17 answers.

QTL mapping of coleorhiza length in maize (Zea mays L.) under two germination environmental conditions

With 2 figures and 3 tablesAbstractIn our present study, using molecular marker technology, we aimed to identify the genetic factors controlling the length of coleorhiza during seed germination based on a population of recombinant inbred lines (RILs) derived from Xinzi517 × B73. The genetic linkage map was constructed with 255 simple sequence repeat markers, which covered 2399 cM of maize genome with an average mapping distance of 9.4 cM. We detected a total of 10 putative quantitative trait loci (QTLs) using composite interval mapping, among which six QTLs were detected on chromosomes 1, 2, 7 and 9 (10°C, 28 day), whereas four QTLs were detected on chromosomes 1, 2, 3 and 9 (25°C, 7 day). The percentage of phenotypic variance (R2) explained by QTL ranged from 5.18 to 16.67 (10°C, 28 day) and 6.73–11.46 (25°C, 7 day), respectively. These results provided the foundation for detecting additional QTL and discovering more favourable alleles for high vigour seed of maize in future study.

Genetic parameters and genotype × environment interaction for feed efficiency traits in steers fed grower and finisher diets1

The objective of this study was to examine the genetic parameters and genetic correlations of feed efficiency traits in steers (n = 490) fed grower or finisher diets in 2 feeding periods. A bivariate model was used to estimate phenotypic and genetic parameters using steers that received the grower and finisher diets in successive feeding periods, whereas a repeated animal model was used to estimate the permanent environmental effects. Genetic correlations between the grower-fed and finisher-fed regimens were 0.50 ± 0.48 and 0.78 ± 0.43 for residual feed intake (RFI) and G:F, respectively. The moderate genetic correlation between the 2 feeding regimens may indicate the presence of a genotype × environment interaction for RFI. Permanent environmental effects (expressed in percentage of phenotypic variance) were detected in the grower-fed steers for ADG (38%), DMI (30%), RFI (18%), and G:F (40%) and also in the finisher-fed steers for ADG (28%), DMI (35%), metabolic mid-weight (23%), and RFI (10%). Heritability estimates were 0.08 ± 0.10 and 0.14 ± 0.15 for the grower-fed steers and 0.42 ± 0.16 and 0.40 ± 17 for the finisher-fed steers for RFI and G:F, respectively. The dependency of the RFI on the feeding regimen may have serious implications when selecting animals in the beef industry. Because of the higher cost of grains, feed efficiency in the feedlot might be overemphasized, whereas efficiency in the cow herd and the backgrounding segments may have less emphasis. These results may also favor the retention (for subsequent breeding) of cows whose steers were efficient in the feedlot sector. Therefore, comprehensive feeding trials may be necessary to provide more insight into the mechanisms surrounding genotype × environment interaction in steers.

Quantitative trait loci associated with red foliage in Cornus florida L.

The objective of our investigation was to acquire information on the association between molecular markers and foliage color in flowering dogwood in order to improve our understanding of the inheritance of this trait and to make possible early selection of red foliage genotypes in breeding programs. A segregating pseudo-F2 population of 94 individuals of flowering dogwood (Cornus florida L.), together with 255 simple sequence repeat markers, was used to identify putative quantitative trait loci (QTL) for foliage color. Foliage color segregated into green- and red-leaved phenotypes and was visually rated for color on five spring dates over 3 years (2007–2009). Repeated measures single-marker categorical analysis of variance (ANOVA) identified four putative QTL (CF309C, CF792A, CF367B, and CF367C) on three linkage groups. Single-marker categorical ANOVA was then used to determine stability of QTL across dates. We identified different QTL, found a low percentage of phenotypic variance explained by the QTL, and detected QTL instability over time, providing evidence of the complex genetics for red pigment expression in flowering dogwood.

QTL analysis of agronomic traits in recombinant inbred lines of sunflower under partial irrigation

The objective of the present research was to map QTLs associated with agronomic traits such as days from sowing to flowering, plant height, yield and leaf-related traits in a population of recombinant inbred lines (RILs) of sunflower (Helianthus annuus). Two field experiments were conducted with well-irrigated and partially irrigated conditions in randomized complete block design with three replications. A map with 304 AFLP and 191 SSR markers with a mean density of 1 marker per 3.7 cM was used to identify QTLs related to the studied traits. The difference among RILs was significant for all studied traits in both conditions. Three to seven QTLs were found for each studied trait in both conditions. The percentage of phenotypic variance (R2) explained by QTLs ranged from 4 to 49%. Three to six QTLs were found for each yield-related trait in both conditions. The most important QTL for grain yield per plant on linkage group 13 (GYP-P-13-1) under partial-irrigated condition controls 49% of phenotypic variance (R2). The most important QTL for 1,000-grain weight (TGW-P-11-1) was identified on linkage group 11. Favorable alleles for this QTL come from RHA266. The major QTL for days from sowing to flowering (DSF-P-14-1) were observed on linkage group 14 and explained 38% of the phenotypic variance. The positive alleles for this QTL come from RHA266. The major QTL for HD (HD-P-13-1) was also identified on linkage group 13 and explained 37% of the phenotypic variance. Both parents (PAC2 and RHA266) contributed to QTLs controlling leaf-related traits in both conditions. Common QTL for leaf area at flowering (LAF-P-12-1, LAF-W-12-1) was detected in linkage group 12. The results emphasise the importance of the role of linkage groups 2, 10 and 13 for studied traits. Genomic regions on the linkage groups 9 and 12 are specific for QTLs of leaf-related traits in sunflower.

Comparison and analysis of main effects, epistatic effects, and QTL × environment interactions of QTLs for agronomic traits using DH and RILs populations in rice

Two genetic linkage maps based on doubled haploid (DH) and recombinant inbred lines (RILs) populations, derived from the same indica-japonica cross ‘Samgang × Nagdong’, were constructed to analyze the quantitative trait loci (QTLs) affecting agronomic traits in rice. The segregations of agronomic traits in RILs population showed larger variations than those in DH population. A total of 10 and 12 QTLs were identified on six chromosomes using DH population and seven chromosomes using RILs population, respectively. Three stable QTLs including pl9.1, ph1.1, and gwp11.1 were detected through different years. The percentages of phenotypic variation explained by individual QTLs ranged from 8 to 18% in the DH population and 9 to 33% in the RILs population. Twenty-three epistatic QTLs were identified in the DH population, while 21 epistatic QTLs were detected in the RILs population. Epistatic interactions played an important role in controlling the agronomic traits genetically. Four significant main-effect QTLs were involved in the digenic interactions. Significant interactions between QTLs and environments (QE) were identified in two populations. The QTLs affecting grain weight per panicle (GWP) were more sensitive to the environmental changes. The comparison and QTLs analysis between two populations across different years should help rice breeders to comprehend the genetic mechanisms of quantitative traits and improve breeding programs in marker-assisted selection (MAS).

GENETIC EVALUATION OF FUR TRAITS IN NEW ZEALAND WHITE AND CALIFORNIAN RABBITS RAISED ON HIGH AMBIENT TEMPERATURE

An experiment on New Zealand White (NZW) and Californian (CAL) rabbits was carried out to evaluate genetically post­weaning coat traits of these two breeds raised under hot conditions. Data on 24680 and 10549 fibers collected from 1234 NZW and 520 CAL weaned rabbits were used, respectively. At 8 and 12 weeks of age, post-weaning coat traits included average hair length in cm (HL), hair diameter (µm) in down hair (HDD) and guard hair (HDG), medulla diameter (µm) in down hair (MDD) and guard hair (MDG), and medullation percent in down hair (PMD) and guard hair (PMG). Variance components and sire heritabilities were estimated for these traits using Restricted Maximum Likelihood (REML) procedure. Transmitting abilities (TA) for these traits were estimated using a single­trait Animal Model (AM).Most postweaning coat traits in CAL were slightly higher than those in NZW. The estimates at 8 and 12 weeks, respectively were 2.4 and 3.0 cm in NZW vs 2.4 and 3.1 cm in CAL for HL, 12.2 and 18.8 µm in NZW vs 12.2 and 18.9 µm in CAL for HDD, 62.1 and 89.1 µm in NZW vs 62.3 and 88.9 µm in CAL for HDG, 10.2 and 16.4 µm in NZW vs 10.2 and 16.4 µm in CAL for MDD, 51.4 and 78.1 µm in NZW vs 51.5 and 77.8 µm in CAL for MDG, 82.2 and 87.1 % in NZW vs 83.5 and 86.3 % in CAL for PMD, and 82.2 and 87.4 % in NZW vs 82.6 and 80.5 % in CAL for PMG. Percentages of phenotypic variation in NZW and CAL for coat traits at earlier ages were slightly higher than at older ages with exception of HL. Except HL and HDD in both breeds, sire heritabilities for coat traits were low or somewhat moderate. Heritabilities for all coat traits in CAL rabbits at 8 and 12 weeks of age were higher than in NZW: 0.667 and 0.775 in CAL vs 0.357 and 0.392 in NZW for HL, 0.326 and 0.304 in CAL vs 0.401 and 0.246 in NZW for HDD, 0.051 and 0.142 in CAL vs 0.053 and 0.116 in NZW for HDG, 0.046 and 0.356 in CAL vs 0.053 and 0.075 for MDD, 0.058 and 0.174 in CAL vs 0.057 and 0.119 in NZW for MDG, 0.008 and 0.132 in CAL vs 0.052 and 0.031 in NZW for PMD and 0.074 and 0.047 in CAL vs 0.055 and 0.048 in NZW for PMG. The largest differences in TA for most coat traits were recorded in CAL breed and the lowest differences were observed in NZW. In favor of CAL breed at 12 weeks of age, there was a large range in TA between NZW and CAL rabbits with a difference of 2.474 cm for HL, 0.755 µm for HDD, 0.906 µm for HDG, 0.818 µm for MDD, 1.181 µm for MDG, and 1.5 % for PMO. Among coat traits, the largest percent of positive TA was recorded for HDD followed by HL, MDD and MDG, while the lowest percent was recorded for HDG.

Mapping QTLs with epistatic effect and QTL×environmental interaction effect of heading date in rice

A population of 284 recombinant inbred lines(RIL) from the indica-japonica rice cross Lemont×Teqing was used to analyze the main effects,epistatic effects of the QTLs,and QTL by environmental interactions(QEs) controlling heading date(HD).Three QTLs with additive effects for HD were mapped in the chromosome 3,7 and 11,which accounted for 18.86% of the phenotypic variation.The percentage of phenotypic variation was explained by individual additive QTLs ranged from 2.95% to 10.56%.QTL×environmental interaction was detected on qHD7-1,which explained the phenotypic variation of HD with 2.18%.Epistasis analysis indicated that nine pairs of epistasis were detected for heading date.The results indicated that some QTLs were environmentally sensitive and epistasis was important genetic basis for heading date.The information obtained in this study should be very useful for manipulating the QTLs for heading date by molecular MAS.

Seleção fenotípica e assistida por marcadores moleculares de famílias de feijoeiro-comum com alta produtividade

O objetivo deste trabalho foi selecionar famílias de feijoeiro-comum, com alta produtividade de grãos, por meio de seleção fenotípica e de seleção assistida por marcadores moleculares (SAM). Foram avaliadas 394 famílias, de quatro populações, e seus seis genitores, no Município de Lavras, em dois experimentos: um na geração F3:4, na safra das águas de 2005/2006, em látice simples 20x20; e outro na geração F3:5, na safra da seca de 2006, em látice triplo 20x20. Foram estimados parâmetros genéticos e fenotípicos, e foi realizada a genotipagem das famílias, com marcadores microssatélites associados a QTL controladores da produção de grãos, previamente identificados. Também foram realizadas análises de associação por marcas simples, entre os marcadores e a produção de grãos, e foi obtido um índice para a SAM. A ampla variabilidade entre famílias e as altas estimativas de herdabilidade possibilitaram obter elevados ganhos com a seleção fenotípica. Os marcadores explicaram pequena percentagem da variação fenotípica e apresentaram alta interação QTL x ambiente e QTL x população. A SAM gerou baixos ganhos e a coincidência de famílias selecionadas pelas duas metodologias foi baixa, o que evidencia, neste caso, a ineficiência da SAM, principalmente pela pouca disponibilidade de marcadores ligados a QTL.

Genetic control of early events in protoplast division and regeneration pathways in sunflower

Experiments were conducted to identify the genetic factors controlling protoplast division and to determine eventual relations between genetic factors involving organogenesis, somatic embryogenesis and protoplast division in sunflower. The present study involved protoplast culture and two traits: total division per 100 protoplasts (TOTD) and asymmetric division per 100 protoplasts (ASYD) were scored in 52 recombinant inbred lines (RILs) from a cross between PAC-2 and RHA-266. Asymmetric division is an early event in the formation of embryoids from protoplasts. Analysis of variance indicated the existence of highly significant differences among parental genotypes and their RILs. Heritability for the two protoplast division parameters (TOTD and ASYD) was high (0.87 and 0.89, respectively) and genetic gain expressed as percentage of the best parent for 10% of the selected RILs was significant. Twelve putative loci associated with total division per 100 protoplasts were identified. Eleven QTLs were also detected for asymmetric division per 100 protoplasts. The QTLs present high significant LOD scores and sum to a high percentage of phenotypic variance. The percentage of phenotypic variation explained by each QTL ranged from 2% to 24%. Some segments of the linkage groups I, XV and XVII are likely to contain genes important for organogenesis, somatic embryogenesis and protoplast division, as clustering of QTLs for these characters were described. The QTLs identified in these three linkage groups should be involved in cell division and in early events associated with cell differenciation.