Meta-analysis of seed weight QTLome using a consensus and highly dense genetic map in Brassica napus L.

KEY MESSAGE: We report here the discovery of high-confidence MQTL regions and of putative candidate genes associated with seed weight in B. napus using a highly dense consensus genetic map and by comparing various large-scale multiomics datasets. Seed weight (SW) is a direct determinant of seed yield in Brassica napus and is controlled by many loci. To unravel the main genomic regions associated with this complex trait, we used 13 available genetic maps to construct a consensus and highly dense map, comprising 40,401 polymorphic markers and 9191 genetic bins, harboring a cumulative length of 3047.8 cM. Then, we performed a meta-analysis using 639 projected SW quantitative trait loci (QTLs) obtained from studies conducted since 1999, enabling the identification of 57 meta-QTLS (MQTLs). The confidence intervals of our MQTLs were 9.8 and 4.3 times lower than the average CIs of the original QTLs for the A and C subgenomes, respectively, resulting in the detection of some key genes and several putative novel candidate genes associated with SW. By comparing the genes identified in MQTL intervals with multiomics datasets and coexpression analyses of common genes, we defined a more reliable and shorter list of putative candidate genes potentially involved in the regulation of seed maturation and SW. As an example, we provide a list of promising genes with high expression levels in seeds and embryos (e.g., BnaA03g04230D, BnaC03g08840D, BnaA10g29580D and BnaA03g27410D) that can be more finely studied through functional genetics experiments or that may be useful for MQTL-assisted breeding for SW. The high-density genetic consensus map and the single nucleotide polymorphism (SNP) physical map generated from the latest B. napus cv. Darmor-bzh v10 assembly will be a valuable resource for further mapping and map-based cloning of other important traits.

Evaluation of grain yield stability of tritipyrum as a novel cereal in comparison with triticale lines and bread wheat varieties through univariate and multivariate parametric methods.

Salinity is a major abiotic stress affecting cereal production. Thus, tritipyrum (x. Tritipyrum), a potential novel salt-tolerant cereal, was introduced as an appropriate alternative for cereal production. The purposes of this study were to evaluate agronomic traits, yield, and yield stability of eight primary tritipyrum lines, five promising triticale lines, and four bread wheat varieties and to screen a stable yielding line. The experiments were conducted in randomized complete block designs with three replicates in three locations during four growing seasons. Analysis of variance in each environment and Bartlett's test for the variance homogeneity of experimental errors were made. Subsequently, separate experiments were analyzed as a combined experiment. The stability of grain yield was analyzed according to Eberhart and Russell's regression method, environmental variance, Wrick's ecovalance, Shokla's stability variance, AMMI, and Tai methods. Genotype × environment interactions (GEI) and environments were significant for the agronomic traits. Stability analysis revealed that combined primary tritipyrum line (Ka/b)(Cr/b)-5 and triticale 4115, 4108, and M45 lines had good adaptability in all environments. The results of the AMMI3 model and pattern analysis showed that the new cereal, tritipyrum, had the most stable response in various environments. The tritipyrum line (Ka/b)(Cr/b)-5 had the best yield performance and general adaptability. Based on Tai's method, the contribution of spike number to the stability of grain yield over different environments was higher than that of other yield components. Also, tritipyrum lines demonstrated higher stability compared with wheat and triticale. Totally, M45 triticale and tritipyrum (Ka/b)(Cr/b)-5 lines were the most stable genotypes with high grain yield. Complementary agronomic experiments may then release a new grain crop of triticale and a new pasture line of combined primary tritipyrum for grain and forage. Moreover, the combined tritipyrum line can be used in bread wheat breeding programs for producing salt-tolerant wheat cultivars.

Genetic control of some plant growth characteristics of bread wheat (Triticum aestivum L.) under aluminum stress.

BACKGROUND: Biomass yield is an important trait for wheat breeding programs. Enhancing the yield of the aerial components of wheat cultivars will be an integral part of future wheat improvement. Aluminum (Al) toxicity is one of the main factors limiting wheat growth and production in acid soils, which occur on up to 50% of the arable lands of the world especially in tropical and subtropical regions. OBJECTIVE: Our objective was to identify quantitative trait loci (QTL) of plant growth characteristics and yield in wheat. METHODS: A recombinant inbred line (RIL) population consisting of 167 lines, derived from a cross between SeriM82 and Babax were evaluated under two Al treatments (+ Al, 800 µM of Al; -Al, 0 µM of Al) in the field based on an alpha lattice design with two replications for two consecutive crop seasons. RESULTS: A total of 40 QTLs including nine putative and 31 suggestive QTLs were found for all traits using the composite interval mapping (CIM) method. By mixed model-based composite interval mapping (MCIM) method, 42 additive QTLs and nine pairs of epistatic effects were detected for studied traits, of which 20 additive and six pairs of epistatic QTLs showed significant QTL × environment interactions. Most of the detected QTLs across environments were stable, and the highest number of stable QTLs was related to A genome. Co-localization of QTL was found on linkage groups (LGs) 2B, 4B, 6A-a, and 7A (CIM method) and 2A-d, and 6A-a (MCIM method). CONCLUSION: These results have implications for selection strategies in biomass yield and for increasing the yield of the aerial part of wheat following further evaluations in various genetic backgrounds and environments.

Mapping QTLs of flag leaf morphological and physiological traits related to aluminum tolerance in wheat (Triticum aestivum L.).

Genetic improvement of aluminum (Al) tolerance is one of the cost-effective solutions to improve plant productivity in acidic soils around the world. This study was performed to progress our understanding of the genetic mechanisms of aluminum tolerance underlying wheat (Triticum aestivum L.) flag leaf morphological and physiological traits. A recombinant inbred line population derived from SeriM82 and Babax was used for mapping quantitative trait loci (QTL) in wheat for tolerance to Al toxicity through 477 DNA markers. Based on a single-locus analysis, 48 QTLs including 16 putative and 32 suggestive QTLs were identified for all studied traits. Individual QTL explained 4.57-11.29% of the phenotypic variance in different environments during both the crop seasons. These QTLs located unevenly throughout the wheat genome. Among them, 52.08%, 29.17%, and 18.75% were in the A, B, and D genomes, respectively. Based on two-locus analysis, 54 additive QTLs and 6 pairs of epistatic effects were detected, among which 29 additive and 5 pairs of epistatic QTLs showed significant QTL × environment interactions. The highest number of stable QTLs was identified on genome A. Determining a number of QTL clusters indicated tight linkage or pleiotropy in the inheritance of different traits. The stable and major QTLs controlling traits in this research can be applied for verification in different environments and genetic backgrounds and identifying superior allelic variations in wheat to increase the performance of selection of high yielding lines adapted to Al stress in breeding programs.