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  • Author or Editor: J. Díaz de León x
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Mapping of quantitative trait loci (QTL) was carried out in a set of 114 RILs of the International Triticeae Mapping Initiative (ITMI) mapping population under salt stress. Seedling population was grown during 8 days, under salt treatment (Hoagland’s ½ strength + 110 mM NaCl, EC 12.4 mS/cm) and normal treatment (Hoagland’s ½ strength, EC 0.9 mS/cm). We calculated starch degradation, measuring the dry weight of the grains on the 4th, 6th and 8th days of culturing. Formation of biomass was calculated measuring leaf and root length on the 4th, 6th and 8th days of culture. Interval mapping resulted in 13 QTLs, 2 major QTLs (LOD> 3) and 11 minors QTLs (LOD> 2). A total of 10 QTLs were associated with saline treatment and 3 QTLs at normal treatment. The data show that a high percentage of QTLs were in chromosomes 2B (3, 23.0%), and 1A (3, 23.0%), followed by 4D (2, 13.6%).

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Quantitative Trait Loci (QTL) mapping was carried out in a set of 114 lines of the International Triticeae Mapping Initiative (ITMI) mapping population for null nitrogen fertilization during two agricultural cycles. We quantified phenologic parameters (days to: ear emergency time, flowering time) and components of yield (number of plants and ears, plant height, leaf area, length and weight of ear, spikelet number, number and total weight of grains and by third in the ear, weight of thousand grains and total yield). Interval mapping resulted of 138 QTLs, of which 47 were catalogued as major QTLs (LOD ≥ 3.0) and 91 as minor QTLs (LOD 2.0 >0 2.9). The QTLs were distributed in 14 of the 21 chromosomes of wheat. The data showed that a high percentage of QTLs were in chromosomes 2D (49 or 35.5%), followed by 5A (22 or 15.9%), 1B (10 or 7.2%).

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Wheat improves some traits when inoculated with Azospirillum. However, inconsistent results have been observed in field experiments. The ability of Azospirillum brasilense Cd to adhere to wheat was tested in a germplasm panel consisting of a number of bread wheat cultivars, synthetic hexaploids, synthetic derivatives, and a partial set of single chromosome substitution lines to determine the plant genetic role. Seeds of genotypes were grown in modified Hoagland's medium at seedling stage and then roots were inoculated with the bacteria and adhered cells were counted. The majority of the bread wheat cultivars and synthetic derivatives and some of the synthetic hexaploids were able to support bacterial adhesion. Neither the age of the seedling nor the imposition of either salinity stress or nitrogen starvation had any effect on the extent of adhesion. A pedigree analysis revealed that the root-adhered A. brasilense cultivars shared common ancestor(s), and the substitution line analysis suggested that the genes underlying the trait were located on chromosomes 5D and 6D. The present results are consistent with the notion that the D genome is the source of genetic variation for the capacity of A. brasilense to adhere to the seedling roots.

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Cereal Research Communications
Authors: J. Díaz De León, R. Escoppinichi, R. Zavala-Fonseca, T. Castellanos, M. Röder and A. Mujeeb-Kazi

To determine limits of tolerance, provide information about genetic diversity, and explore potential as progenitors for a salt-tolerant wheat improvement program, we collected several landraces and genotypes reputed to be salt-tolerant. Salt tolerance was tested by irrigation with a diluted solution of seawater with 12 dS.m −1 electrical conductivity for two years. Phenotypic parameters of percent of emergence, days to flowering to spike emergence, and physiological maturity were not significantly affected. Leaf area was sensitive to salt stress and inhibited about 30%. Plant height was inhibited 30%, while spike length and number of grains per spike were not. Total yield of Shorawaki and Kharchia landraces confirmed their reputation as salt-tolerant. Cultivars Mepuchi, Pericu, Calafia, WH157, and SNH-1 were inhibited at a moderate level of tolerance; cultivars Cochimí, Lu26S, and KRL 1–4 were inhibited, as was the control cultivar Oasis by up to 50%. To amplify microsatellites from genomes A, B, and D, 33 pairs of primers were used. The microsatellite WMS169-6A was highly polymorphic, with 10 different alleles distinguishing the genotype set. Also, the short arm of chromosome 4D microsatellites were amplified and found to be monomorphic, which suggests highly conserved alleles. The other microsatellites had variable polymorphism. In total, 120 alleles were obtained and used to define genetic diversity. The resulting dendrogram showed that landraces Shorawaki and Kharchia are distantly grouped from all other cultivars, as well as the cultivar Chinese Spring. Strikingly, KRL1–4, a derivative of Kharchia, did not show a close relationship to its source. The geographic origin did not influence pair-wise combinations. However, pedigree did influence pair-wise combinations.

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The parents (the landrace Chinese spring (CS) and a synthetic hexaploids (S6x)) and 17 derived single chromosome substitution lines (SL) were grown in parallel in the field under non-saline (1.0 dSm−1) and saline (12.0 dSm−1) conditions, and evaluated for a set of phenotypic traits. The performance of CS indicated it to have borderline salinity tolerance with respect to all of the traits except for leaf area (for which it behaved in as a salinity sensitive type). The SL 4D was early in booting, ear emergence, flowering and maturity, while 5D and 2B SLs were both late. The 2B SL produce 33% more ears than CS. The 5D SL under-performed with respect to ear weight, grain number per ear, grain weight per ear and 1000-grain weight both under non-saline and saline conditions. Under saline conditions, four SLs (1A>5A>1D>2B) outperformed Cs for ear length, and six SLs (1D>6A>4B>3A>3B>3D) showed an improved grain weight. The grains produce by the 2B SL were smaller than those of CS. Leaf area developed better in four SLs (4D>2B>1A>7D) than in CS.

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