Major-effect QTLs Research Articles

Deciphering the genetic basis of agronomic, yield, and nutritional traits in rice (Oryza sativa L.) using a saturated GBS-based SNP linkage map

Developing high-yielding rice varieties that possess favorable agronomic characteristics and enhanced grain Zn content is crucial in ensuring food security and addressing nutritional needs. This research employed ICIM, IM, and multi-parent population QTL mapping methods to identify important genetic regions associated with traits such as DF, PH, NT, NP, PL, YLD, TGW, GL, GW, Zn, and Fe. Two populations of recombinant inbred lines consisting of 373 lines were phenotyped for agronomic, yield and grain micronutrient traits for three seasons at IRRI, and genotyped by sequencing. Most of the traits demonstrated moderate to high broad-sense heritability. There was a positive relationship between Zn and Fe contents. The principal components and correlation results revealed a significant negative association between YLD and Zn/Fe. ICIM identified 81 QTLs, while IM detected 36 QTLs across populations. The multi-parent population analysis detected 27 QTLs with six of them consistently detected across seasons. We shortlisted eight candidate genes associated with yield QTLs, 19 genes with QTLs for agronomic traits, and 26 genes with Zn and Fe QTLs. Notable candidate genes included CL4 and d35 for YLD, dh1 for DF, OsIRX10, HDT702, sd1 for PH, OsD27 for NP, whereas WFP and OsIPI1 were associated with PL, OsRSR1 and OsMTP1 were associated to TGW. The OsNAS1, OsRZFP34, OsHMP5, OsMTP7, OsC3H33, and OsHMA1 were associated with Fe and Zn QTLs. We identified promising RILs with acceptable yield potential and high grain Zn content from each population. The major effect QTLs, genes and high Zn RILs identified in our study are useful for efficient Zn biofortification of rice.

Genomic loci associated with grain yield under well-watered and water-stressed conditions in multiple bi-parental maize populations

Smallholder maize farming systems in sub-Saharan Africa (SSA) are vulnerable to drought-induced yield losses, which significantly impact food security and livelihoods within these communities. Mapping and characterizing genomic regions associated with water stress tolerance in tropical maize is essential for future breeding initiatives targeting this region. In this study, three biparental F3 populations composed of 753 families were evaluated in Kenya and Zimbabwe and genotyped with high-density single nucleotide polymorphism (SNP) markers. Quantitative trait loci maping was performed on these genotypes to dissect the genetic architecture for grain yield (GY), plant height (PH), ear height (EH) and anthesis-silking interval (ASI) under well-watered (WW) and water-stressed (WS) conditions. Across the studied maize populations, mean GY exhibited a range of 4.55–8.55 t/ha under WW and 1.29–5.59 t/ha under WS, reflecting a 31–59% reduction range under WS conditions. Genotypic and genotype-by-environment (G × E) variances were significant for all traits except ASI. Overall broad sense heritabilities for GY were low to high (0.25–0.60). For GY, these genetic parameters were decreased under WS conditions. Linkage mapping revealed a significant difference in the number of QTLs detected, with 93 identified under WW conditions and 41 under WS conditions. These QTLs were distributed across all maize chromosomes. For GY, eight and two major effect QTLs (>10% phenotypic variation explained) were detected under WW and WS conditions, respectively. Under WS conditions, Joint Linkage Association Mapping (JLAM) identified several QTLs with minor effects for GY and revealed genomic region overlaps in the studied populations. Across the studied water regimes, five-fold cross-validation showed moderate to high prediction accuracies (−0.15–0.90) for GY and other agronomic traits. Our findings demonstrate the polygenic nature of WS tolerance and highlights the immense potential of using genomic selection in improving genetic gain in maize breeding.

A Case Study from the Overexpression of OsTZF5, Encoding a CCCH Tandem Zinc Finger Protein, in Rice Plants Across Nineteen Yield Trials

BackgroundDevelopment of transgenic rice overexpressing transcription factors involved in drought response has been previously reported to confer drought tolerance and therefore represents a means of crop improvement. We transformed lowland rice IR64 with OsTZF5, encoding a CCCH-tandem zinc finger protein, under the control of the rice LIP9 stress-inducible promoter and compared the drought response of transgenic lines and nulls to IR64 in successive screenhouse paddy and field trials up to the T6 generation.ResultsCompared to the well-watered conditions, the level of drought stress across experiments varied from a minimum of − 25 to − 75 kPa at a soil depth of 30 cm which reduced biomass by 30–55% and grain yield by 1–92%, presenting a range of drought severities. OsTZF5 transgenic lines showed high yield advantage under drought over IR64 in early generations, which was related to shorter time to flowering, lower shoot biomass and higher harvest index. However, the increases in values for yield and related traits in the transgenics became smaller over successive generations despite continued detection of drought-induced transgene expression as conferred by the LIP9 promoter. The decreased advantage of the transgenics over generations tended to coincide with increased levels of homozygosity. Background cleaning of the transgenic lines as well as introgression of the transgene into an IR64 line containing major-effect drought yield QTLs, which were evaluated starting at the BC3F1 and BC2F3 generation, respectively, did not result in consistently increased yield under drought as compared to the respective checks.ConclusionsAlthough we cannot conclusively explain the genetic factors behind the loss of yield advantage of the transgenics under drought across generations, our results help in distinguishing among potential drought tolerance mechanisms related to effectiveness of the transgenics, since early flowering and harvest index most closely reflected the levels of yield advantage in the transgenics across generations while reduced biomass did not.

Identification of two mutant JASON-RELATED genes associated with unreduced pollen production in potato

Key messageMultiple QTLs control unreduced pollen production in potato. Two major-effect QTLs co-locate with mutant alleles of genes with homology to AtJAS, a known regulator of meiotic spindle orientation.In diploid potato the production of unreduced gametes with a diploid (2n) rather than a haploid (n) number of chromosomes has been widely reported. Besides their evolutionary important role in sexual polyploidisation, unreduced gametes also have a practical value for potato breeding as a bridge between diploid and tetraploid germplasm. Although early articles argued for a monogenic recessive inheritance, the genetic basis of unreduced pollen production in potato has remained elusive. Here, three diploid full-sib populations were genotyped with an amplicon sequencing approach and phenotyped for unreduced pollen production across two growing seasons. We identified two minor-effect and three major-effect QTLs regulating this trait. The two QTLs with the largest effect displayed a recessive inheritance and an additive interaction. Both QTLs co-localised with genes encoding for putative AtJAS homologs, a key regulator of meiosis II spindle orientation in Arabidopsis thaliana. The function of these candidate genes is consistent with the cytological phenotype of mis-oriented metaphase II plates observed in the parental clones. The alleles associated with elevated levels of unreduced pollen showed deleterious mutation events: an exonic transposon insert causing a premature stop, and an amino acid change within a highly conserved domain. Taken together, our findings shed light on the natural variation underlying unreduced pollen production in potato and will facilitate interploidy breeding by enabling marker-assisted selection for this trait.

Mapping of quantitative trait loci for growth traits around the first overwintering period in Songpu mirror carp (Cyprinus carpio L.) cultured in Northeast China

QTL mapping studies of growth traits based on high-density linkage maps in Northeast China has great significance for local enterprises in achieving MAS and improving the selection accuracy of parent fish. Here, we constructed a high-density genetic linkage map with 11,445 single nucleotide polymorphism (SNP) markers in a full-sib F1 family consisting of 120 progenies in Songpu mirror carp (Cyprinus carpio) reared in Northeast China. The consensus map covered 5471.93 centimorgans (cM) across the 50 linkage groups with an average resolution of 0.54 cM. Around the first overwintering period, a total of 15 QTLs for growth traits were identified on five LGs (LG7, LG8, LG14, LG30, and LG41). All of them were responsible for body weight (BW) at both 150 (before overwintering) and 350 (after overwintering) days, explaining 9.8–17.9 % of the phenotypic variation (PV). Two major-effect QTLs were detected on LG30, which explained 16.5 % and 16.4 % (qTL9–30), and 15.8 % and 17.9 % (qTL10–30) of the PV at 150 and 350 days, respectively. In addition, 15 loci were identified for 4 growth traits other than BW at both time points, including 6 loci for body length (BL), 7 loci for body height (BH), 3 loci for body thickness (BT) and 5 loci for head length (HL). These loci explained PV ranging from 15.9 % to 21.2 % for BL, 9.3–19.6 % for BH, 9.6–15.5 % for BT, and 10.6–18.1 % for HL. Nine candidate genes (IGF1b, LEPb, PACAP1a, GHSR1a, PPSS2, IRS1, APOAIb, IRS2b and ADSS1) were identified, five of which were directly related to growth hormone (GH), including IGF1b, PACAP1a, GHSR1a, PPSS2 and IRS1. Notably, three genes (GHSR1a, PPSS2 and IRS1) were derived from two major-effect QTLs (qTL9–30 and qTL10–30). In conclusion, these novel findings may shed light on early selection of growth traits of common carp cultured in Northeast China and other relatively high-latitude regions.

Genetic analysis and exploration of major effect QTLs underlying oil content in peanut.

AhyHOF1, likely encoding a WRI1 transcription factor, plays critical roles in peanut oil synthesis. Although increasing the oil content of peanut to meet growing demand has long been a primary aim of breeding programs worldwide, the mining of genetic resources to achieve this objective has obviously lagged behind that of other oil crops. In the present study, we developed an advanced recombinant inbred line population containing 192 F9:11 families derived from parents JH5 and KX01-6. We then constructed a high-resolution genetic map covering 3,706.382cM, with an average length of 185.32cM per linkage group, using 2840 polymorphic SNPs. Two stable QTLs, qCOA08_1 and qCOA08_2 having the highest contributions to genetic variation (16.1% and 20.7%, respectively), were simultaneously detected in multiple environments and closely mapped within physical intervals of approximately 2.9Mb and 1.7Mb, respectively, on chromosome A08. In addition, combined analysis of whole-genome and transcriptome resequencing data uncovered a strong candidate gene encoding a WRI1 transcription factor and differentially expressed between the two parents. This gene, designated as High Oil Favorable gene 1 in Arachis hypogaea (AhyHOF1), was hypothesized to play roles in oil accumulation. Examination of near-inbred lines of #AhyHOF1/#Ahyhof1 provided further evidence that AhyHOF1 increases oil content, mainly by affecting the contents of several fatty acids. Taken together, our results provide valuable information for cloning the favorable allele for oil content in peanut. In addition, the closely linked polymorphic SNP markers within qCOA08_1 and qCOA08_2 loci may be useful for accelerating marker-assisted selection breeding of peanut.

Genetic mapping identifies genomic regions and candidate genes for seed weight and shelling percentage in groundnut.

Seed size is not only a yield-related trait but also an important measure to determine the commercial value of groundnut in the international market. For instance, small size is preferred in oil production, whereas large-sized seeds are preferred in confectioneries. In order to identify the genomic regions associated with 100-seed weight (HSW) and shelling percentage (SHP), the recombinant inbred line (RIL) population (Chico × ICGV 02251) of 352 individuals was phenotyped for three seasons and genotyped with an Axiom_Arachis array containing 58K SNPs. A genetic map with 4199 SNP loci was constructed, spanning a map distance of 2708.36cM. QTL analysis identified six QTLs for SHP, with three consistent QTLs on chromosomes A05, A08, and B10. Similarly, for HSW, seven QTLs located on chromosomes A01, A02, A04, A10, B05, B06, and B09 were identified. BIG SEED locus and spermidine synthase candidate genes associated with seed weight were identified in the QTL region on chromosome B09. Laccase, fibre protein, lipid transfer protein, senescence-associated protein, and disease-resistant NBS-LRR proteins were identified in the QTL regions associated with shelling percentage. The associated markers for major-effect QTLs for both traits successfully distinguished between the small- and large-seeded RILs. QTLs identified for HSW and SHP can be used for developing potential selectable markers to improve the cultivars with desired seed size and shelling percentage to meet the demands of confectionery industries.

A genome wide association study to dissect the genetic architecture of agronomic traits in Andean lupin (Lupinus mutabilis).

Establishing Lupinus mutabilis as a protein and oil crop requires improved varieties adapted to EU climates. The genetic regulation of strategic breeding traits, including plant architecture, growing cycle length and yield, is unknown. This study aimed to identify associations between 16 669 single nucleotide polymorphisms (SNPs) and 9 agronomic traits on a panel of 223 L. mutabilis accessions, grown in four environments, by applying a genome wide association study (GWAS). Seven environment-specific QTLs linked to vegetative yield, plant height, pods number and flowering time, were identified as major effect QTLs, being able to capture 6 to 20% of the phenotypic variation observed in these traits. Furthermore, two QTLs across environments were identified for flowering time on chromosome 8. The genes FAF, GAMYB and LNK, regulating major pathways involved in flowering and growth habit, as well as GA30X1, BIM1, Dr1, HDA15, HAT3, interacting with these pathways in response to hormonal and environmental cues, were prosed as candidate genes. These results are pivotal to accelerate the development of L. mutabilis varieties adapted to European cropping conditions by using marker-assisted selection (MAS), as well as to provide a framework for further functional studies on plant development and phenology in this species.

Genetic Dissection of Alkalinity Tolerance at the Seedling Stage in Rice (Oryza sativa) Using a High-Resolution Linkage Map.

Although both salinity and alkalinity result from accumulation of soluble salts in soil, high pH and ionic imbalance make alkaline stress more harmful to plants. This study aimed to provide molecular insights into the alkalinity tolerance using a recombinant inbred line (RIL) population developed from a cross between Cocodrie and Dular with contrasting response to alkalinity stress. Forty-six additive QTLs for nine morpho-physiological traits were mapped on to a linkage map of 4679 SNPs under alkalinity stress at the seedling stage and seven major-effect QTLs were for alkalinity tolerance scoring, Na+ and K+ concentrations and Na+:K+ ratio. The candidate genes were identified based on the comparison of the impacts of variants of genes present in five QTL intervals using the whole genome sequences of both parents. Differential expression of no apical meristem protein, cysteine protease precursor, retrotransposon protein, OsWAK28, MYB transcription factor, protein kinase, ubiquitin-carboxyl protein, and NAD binding protein genes in parents indicated their role in response to alkali stress. Our study suggests that the genetic basis of tolerance to alkalinity stress is most likely different from that of salinity stress. Introgression and validation of the QTLs and genes can be useful for improving alkalinity tolerance in rice at the seedling stage and advancing understanding of the molecular genetic basis of alkalinity stress adaptation.

Mapping QTLs for yield and photosynthesis-related traits in three consecutive backcross populations of Oryza sativa cultivar Cottondora Sannalu (MTU1010) and Oryza rufipogon.

Identification of trait enhancing QTLs for yield and photosynthesis-related traits in rice using interspecific mapping population and chromosome segment substitution lines derived from a cross between Oryza sativa and Oryza rufipogon. Wild rice contains novel genes which can help in improving rice yield. Common wild rice Oryza rufipogon is a known source for enhanced photosynthesis and yield-related traits. We developed BC2F2:3:4 mapping populations using O. rufipogon IC309814 with high photosynthetic rate as donor, and elite cultivar MTU1010 as recurrent parent. Evaluation of 238 BC2F2 families for 13 yield-related traits and 208 BC2F2 families for seven photosynthesis-related physiological traits resulted in identification of significantly different lines which performed better than MTU1010 for various yield contributing traits. 49 QTLs were identified for 13 yield traits and 7 QTLs for photosynthesis-related traits in BC2F2. In addition, 34 QTLs in BC2F3 and 26 QTLs in BC2F4 were also detected for yield traits.11 common QTLs were identified in three consecutive generations and their trait-increasing alleles were derived from O. rufipogon. Significantly, one major effect common QTL qTGW3.1 for thousand grain weight with average phenotypic variance 8.1% and one novel QTL qBM7.1 for biomass were identified. Photosynthesis-related QTLs qPN9.1, qPN12.1, qPN12.2 qSPAD1.1 and qSPAD6.1 showed additive effect from O. rufipogon. A set of 145 CSSLs were identified in BC2F2 which together represented 87% of O. rufipogon genome. In addition, 87 of the 145 CSSLs were significantly different than MTU1010 for at least one trait. The major effect QTLs can be fine mapped for gene discovery. CSSLs developed in this study are a good source of novel alleles from O. rufipogon in the background of Cottondora Sannalu for rapid improvement of any trait in rice.

Dissecting the genetic basis of bioactive metabolites and fruit quality traits in blueberries (Vaccinium corymbosum L.).

Blueberry is well-recognized as a healthy fruit with functionality derived largely from anthocyanin and chlorogenic acid. Despite their importance, no study to date has evaluated the genetic basis of these bioactives in blueberries and their relationship with fruit quality traits. Hence, to fill this gap, a mapping population including 196 F1 individuals was phenotyped for anthocyanin and chlorogenic acid concentration and fruit quality traits (titratable acidity, pH, and total soluble solids) over 3 years and data were used for QTL mapping and correlation analysis. Total soluble solids and chlorogenic acid were positively correlated with glycosylated anthocyanin and total anthocyanin, respectively, indicating that parallel selection for these traits is possible. Across all the traits, a total of 188 QTLs were identified on chromosomes 1, 2, 4, 8, 9, 11 and 12. Notably, four major regions with overlapping major-effect QTLs were identified on chromosomes 1, 2, 4 and 8, and were responsible for acylation and glycosylation of anthocyanins in a substrate and sugar donor specific manner. Through comparative transcriptome analysis, multiple candidate genes were identified for these QTLs, including glucosyltransferases and acyltransferases. Overall, the study provides the first insights into the genetic basis controlling anthocyanins accumulation and composition, chlorogenic acid and fruit quality traits, and establishes a framework to advance genetic studies and molecular breeding for anthocyanins in blueberry.

Identification of QTLs linked with watermelon fruit and seed traits using GBS-based high-resolution genetic mapping

Watermelon is an economic horticultural crop of the Cucurbitaceae family. An in-depth genetic understanding of fruit and seed associated traits is important for the effective breeding of watermelon. In the present study, we conducted genotyping by sequencing (GBS)-based high-resolution genetic mapping and performed QTL mapping of twelve horticultural traits using segregated mapping populations (F2 and F2:3) derived from the breeding of two contrasting inbred parent lines. The developed genetic linkage map comprised of 6,164 SNP loci and 1,004 bins, which spanned a total genetic length of 1,261.13 cM with an average interval of 1.26 cM (329.31 kb) between adjacent whole-genome markers. Overall, a total of 34 QTLs were identified, and 16 QTLs exhibited moderate and major-effect QTLs; however, 25 were novel QTLs that were not identified in earlier studies. The mapped genetic loci of RC, RSP, and FFC traits were identified as closely overlapping with previously reported loci and exhibited delimited genetic intervals located on chromosomes 8, 6, and 4, respectively. The identified novel QTL (qfd2.1) of FD and QTL (qfl2.1) of FL were tightly localized with QTL (qfsi2.1) of FSI over chromosome 2, but a minor QTL (qfw3.2) positioned on chromosome 3 was consistent with previously published QTLs (qfd3.1, qfl3.1, and qfsi3.1) of fruit shape. A total of five minor-effect QTLs (qbcc2.1, qbce2.1, qbce2.2, qbcc5.1, and qbce5.1) identified in the novel genetic region which controlled the average Brix content of edible fruit. The seed width QTL (qsw10.1) was found to be localized with 20-seed weight QTL (q20swt10.1) on chromosome 10. The collected phenotypic dataset of two environmental experiments across the two years also revealed highly significant correlations among fruit and seed traits. Hence, we concluded that our GBS-based identified novel QTLs positions would expand powerful molecular breeding prospects for the genetic improvement of quality-related traits of watermelon.

Mapping of fruit apex shape related QTLs across multi-genetic backgrounds in cucumber (Cucumis sativus L.)

The shape of fruit apex is critical to appearance quality in cucumber (Cucumis sativus L.), of which the genetic basis was poorly understood, and the use of marker-assisted breeding for fruit apex improvement is not available yet. In this study, the variation of fruit apex in different cucumber ecotypes was evaluated by fruit apex angle (variation coefficient from 7.1% to 15.7%) and fruit apex index (variation coefficient from 8.8% to 22.6%). Fruit apex associated QTLs were mapped by using 145 F2:3 families and 155 F2:6 population that were derived from the cross of different ecotype cucumbers. Phenotyping of the mapping populations were conducted in four experiments in 2 years. Four major-effect QTLs, Bfal4.1, Bfai4.1, Bfad6.1 and Bfai6.1 were consistently and reliably detected across two environments which could explain 11.6% - 33.6% phenotypic variations (R2) in the F2:3 families. Three major-effect QTLs, Ofai4.1 (R2 = 13.4%–15.5%), Ofal4.1 (R2 = 10.7%–12.8%), and Ofad6.1 (R2 = 11.6%–12.4%) were stably detected in the F2:6 population in two experiments. Bfai4.1, Bfal4.1, Ofai4.1 and Ofal4.1 were integrated to be consensus QTL fa4.1, within which 11 candidate genes were predicted. Bfai6.1 and Bfad6.1 were integrated to be consensus QTL fa6.1. QTL interaction analysis showed that Bfai6.1 has epistatic effect with Bfai4.1. This study revealed two reliable major-effect fruit apex related QTLs across multi-genetic backgrounds and environments in cucumber. The possible candidate genes regulating the shape of fruit apex, and the relationship between cell division and fruit apex morphogenesis were discussed.

Identification of QTL Combinations that Cause Spikelet Sterility in Rice Derived from Interspecific Crosses

BackgroundThe exploitation of useful genes through interspecific and intersubspecific crosses has been an important strategy for the genetic improvement of rice. Postzygotic reproductive isolation routinely occurs to hinder the growth of pollen or embryo sacs during the reproductive development of the wide crosses.ResultIn this study, we investigated the genetic relationship between the hybrid breakdown of the population and transferred resistance genes derived from wide crosses using a near-isogenic population composed of 225 lines. Five loci (qSS12, qSS8, qSS11, ePS6-1, and ePS6-2) associated with spikelet fertility (SF) were identified by QTL and epistatic analysis, and two out of five epistasis interactions were found between the three QTLs (qSS12, qSS8 and qSS11) and background marker loci (ePS6-1 and ePS6-2) on chromosome 6. The results of the QTL combinations suggested a genetic model that explains most of the interactions between spikelet fertility and the detected loci with positive or negative effects. Moreover, the major-effect QTLs, qSS12 and qSS8, which exhibited additive gene effects, were narrowed down to 82- and 200-kb regions on chromosomes 12 and 8, respectively. Of the 13 ORFs present in the target regions, Os12g0589400 and Os12g0589898 for qSS12 and OS8g0298700 for qSS8 induced significantly different expression levels of the candidate genes in rice at the young panicle stage.ConclusionThe results will be useful for obtaining a further understanding of the mechanism causing the hybrid breakdown of a wide cross and will provide new information for developing rice cultivars with wide compatibility.

Comparative evolution of vegetative branching in sorghum.

Tillering and secondary branching are two plastic traits with high agronomic importance, especially in terms of the ability of plants to adapt to changing environments. We describe a quantitative trait analysis of tillering and secondary branching in two novel BC1F2 populations totaling 246 genotypes derived from backcrossing two Sorghum bicolor x S. halepense F1 plants to a tetraploidized S. bicolor. A two-year, two-environment phenotypic evaluation in Bogart, GA and Salina, KS permitted us to identify major effect and environment specific QTLs. Significant correlation between tillering and secondary branching followed by discovery of overlapping sets of QTLs continue to support the developmental relationship between these two organs and suggest the possibility of pleiotropy. Comparisons with two other populations sharing S. bicolor BTx623 as a common parent but sampling the breadth of the Sorghum genus, increase confidence in QTL detected for these two plastic traits and provide insight into the evolution of morphological diversity in the Eusorghum clade. Correspondence between flowering time and vegetative branching supports other evidence in suggesting a pleiotropic effect of flowering genes. We propose a model to predict biomass weight from plant architecture related traits, quantifying contribution of each trait to biomass and providing guidance for future breeding experiments.

Construction of a high-density genetic map and QTL analysis for yield, yield components and agronomic traits in chickpea (Cicer arietinum L.).

Unravelling the genetic architecture underlying yield components and agronomic traits is important for enhancing crop productivity. Here, a recombinant inbred line (RIL) population, developed from ICC 4958 and DCP 92–3 cross, was used for constructing linkage map and QTL mapping analysis. The RIL population was genotyped using a high-throughput Axiom®CicerSNP array, which enabled the development of a high-density genetic map consisting of 3,818 SNP markers and spanning a distance of 1064.14 cM. Analysis of phenotyping data for yield, yield components and agronomic traits measured across three years together with genetic mapping data led to the identification of 10 major-effect QTLs and six minor-effect QTLs explaining up to 59.70% phenotypic variance. The major-effect QTLs identified for 100-seed weight, and plant height possessed key genes, such as C3HC4 RING finger protein, pentatricopeptide repeat (PPR) protein, sugar transporter, leucine zipper protein and NADH dehydrogenase, amongst others. The gene ontology studies highlighted the role of these genes in regulating seed weight and plant height in crop plants. The identified genomic regions for yield, yield components, and agronomic traits, and the closely linked markers will help advance genetics research and breeding programs in chickpea.

The Effect of Pesticide Application on QTLs Controlling Traits in Barley

Among cereals, barley (Hordeum vulgare L.) ranks fourth in consumption worldwide. Among barley breeding goals, one can refer to gene mapping, studying their inheritance, and saturated genetic linkage maps. Problems with pesticide applications include reduced genetic diversity, reduced nitrogen fixation, and destruction of the habitat of especially endangered species. The effect of pesticide application on the emergence of QTLs expressing traits in experimental barley was investigated using 104 barley F2:4 families from Badia × Kavir cross. A total of 25 QTLs were mapped for all traits. In non-using pesticides, 12 QTLs were identified for peduncle length, stem diameter, flag leaf length, and awn length. It was found that qFL-4 has major effects on flag leaf length. or using the pesticide, 13 QTLs were detected that QTLs related to stem diameter, grain weight, flag leaf length explained a high percentage of phenotypic variation. The results of this study showed that pesticide application affects the expression of some genes in barley. Besides, major-effect trait-controller QTLs and their associated markers can be used in marker-assisted selection (MAS) programs.

Shortlisting putative candidate genes underlying qDTY1.1, a major effect drought tolerant QTL in rice (Oryza sativa L.).

Drought is one of the major constraints affecting rice (Oryza sativa L.) productivity and production. Conventional breeding is leading to slow progress in developing drought tolerant varieties. In this context, mapping consistent major effect QTLs and unraveling molecular basis of those QTLs will pave way for deployment of those QTLs into breeding applications. Out of more than 2500 drought tolerance related QTLs, hardly 5 to 10 QTLs have been put into breeding applications due to larger QTL window, lack of tightly linked markers and lack of knowledge on candidate genes underlying QTLs. In this present study, in silico analysis was carried out to characterize a major effect QTL qDTY1.1 region on chromosome 1 for its gene content, drought responsiveness of genes in the QTL window and metabolic functions. Out of 352 genes residing in the qDTY1.1 window, 50% of the genes were found to be drought responsive. Bioinformatics search identified precise drought responsive expression pattern of 100 genes in the QTL window. Fifty seven genes were found to be up regulated and forty three genes were found to be down regulated. The qDTY1.1 region is found to contain 23 drought responsive transcription factors such as WRKY, bZIP, NAC, AP2 and C2H2. These drought responsive genes are confirmed for the possession of drought responsive cis elements like DRE, ABRE, MYB and MYC.

A Hitchhiker\u2019s guide to the potato wart disease resistance galaxy

Key messageTwo novel major effect loci (Sen4 and Sen5) and several minor effect QTLs for potato wart disease resistance have been mapped. The importance of minor effect loci to bring full resistance to wart disease was investigated. Using the newly identified and known wart disease resistances, a panel of potato breeding germplasm and Solanum wild species was screened. This provided a state-of-the-art “hitch-hikers-guide” of complementary wart disease resistance sources.Potato wart disease, caused by the obligate biotrophic soil-born fungus Synchytrium endobioticum, is the most important quarantine disease of potato. Because of its huge impact on yield, the lack of chemical control and the formation of resting spores with long viability, breeding for resistant varieties combined with strict quarantine measures are the only way to efficiently and durably manage the disease. In this study, we set out to make an inventory of the different resistance sources. Using a Genome-Wide Association Study (GWAS) in the potato breeding genepool, we identified Sen4, associated with pathotypes 2, 6 and 18 resistance. Associated SNPs mapped to the south arm of chromosome 12 and were validated to be linked to resistance in one full-sib population. Also, a bulked segregant analysis combined with a Comparative Subsequence Sets Analysis (CoSSA) resulted in the identification of Sen5, associated with pathotypes 2, 6 and 18 resistance, on the south arm of chromosome 5. In addition to these two major effect loci, the GWAS and CoSSA allowed the identification of several quantitative trait loci necessary to bring full resistance to certain pathotypes. Panels of varieties and Solanum accessions were screened for the presence of Sen1, Sen2, Sen3, Sen4 and Sen5. Combined with pedigree analysis, we could trace back some of these genes to the ancestral resistance donors. This analysis revealed complementary resistance sources and allows elimination of redundancy in wart resistance breeding programs.

Genetic determinants for agronomic and yield-related traits localized on a GBS-SNP linkage map from a japonica x indica cross in rice

Rice is an important cereal for human consumption. Identification of QTLs for important agronomic traits with high resolution is essential to the identification of genes and marker-assisted breeding to improve rice productivity. A genotyping by sequencing (GBS)-based high-resolution SNP linkage developed in a recombinant inbred lines (RIL) population of a japonica (Bengal) × indica (Pokkali) cross was used for QTL analysis of traits such as days to heading, plant height, panicle length, flag leaf length, 1000 kernel weight, number of unfilled grains, number of filled grains, grain width, grain length, and awns using interval mapping and inclusive composite interval mapping approaches. Among the 102 additive QTLs identified for the ten traits, 23 QTLs were major effect QTLs. A chromosomal region flanking the sd-1 gene colocalized the QTLs for plant height, panicle length, and flag leaf length, suggesting possible pleiotropic effects on the expression of these traits. Our study not only reduced confidence intervals of previously identified QTLs but also validated several known genes for heading date (Hd1), panicle length (APO1), grain width (GW2, GW5) and awn length (An-1). Furthermore, candidate genes for several agronomic traits were identified. Annotations of genes within novel QTLs for yield-related traits revealed that RCN4 (LOC_Os06g45460), expansin precursor (LOC_Os02g51040), and RGB1 (LOC_Os03g46650) are promising candidates for yield enhancement. Our study provided genetic insights into the important agronomic and yield enhancing traits through identification of QTLs and candidate genes for future validation and molecular breeding to improve rice yield potential.