Genetic\ agronomic and quality comparisons of two 1AL.1RS. wheat-rye chromosomal translocations

The 1AL.1RS wheat-rye chromosomal translocation originally found in ‘Amigo’ wheat possesses resistance genes for stem rust, powdery mildew and greenbug biotypes B and C, but also has a negative effect on wheat processing quality. Recently, a second 1AL.1RS translocation carrying Gb6 a gene conferring resistance to greenbug biotypes B, C, E, G and I, was identified in the wheat germplasm line ‘GRS1290’. Protein analytical methods, and the DNA polymerase chain reaction were used to identify markers capable of differentiating the 1RS chromosome arms derived from ‘Amigo’ and ‘GRS1201’. The secalin proteins encoded by genes on 1RS chromosome arms differed in ‘Amigo’ and ‘GRS1201’. A 70 kDa secalin was found in the ‘Amigo’ 1AL.1RS, but did not occur in the ‘GRS1201’ 1AL.1RS. Polymorphisms detected by PCR primers derived from a family of moderately repetitive rye DNA sequences also differentiated the two translocations. When ‘GRS1201’ was mated with a non-1RS wheat, no recombinants between 1RS markers were observed. In crosses between 1RS and non-1 RS parents, both DNA markers and secalins would be useful as selectable markers for 1RS-derived greenbug resistance. Recombination between 1RS markers did occur when 1RS from ‘Amigo’ and 1RS from ‘GRS1201’ were combined\ but in such intermatings, the molecular markers described herein could still be used to develop a population enriched in lines carrying Gb6. No differences in grain yield or grain and flour quality characteristics were observed when lines carrying 1RS from ‘Amigo’ were compared with lines with 1RS from ‘GRS1201’. Hence, differences in secalin composition did not result in differential quality effects. When compared with sister lines with 1AL.1AS derived from the wheat cultivar ‘Redland’, lines with ‘GRS1201’ had equal grain yield, but produced flours with significantly shorter mix times, weaker doughs, and lower sodium dodecyl sulphate sedimentation volumes

Nitrogen management and wheat genotype performance in a planting system on narrow raised beds

Wheat ( Triticum aestivum L.) grain production in the Central Highlands of Mexico occurs under rainfed conditions. Traditionally this crop has been planted by conventional means in solid stands combined with heavy tillage and lack of ground cover. These practices have been leading to soil erosion in the sloping lands, frequent drought stress, and water logging after occasional heavy rainstorms in the low lands. To ameliorate those constrains, farmers have started to replace the traditional planting system by the planting system on narrow raised beds. However, information on N management and varieties is needed. This 5-yr study was conducted from 1999 to 2003 to test a set of eight wheat genotypes using a raised-bed system to evaluate their performance as affected by N fertilizer management. Three N rates (40, 70 and 100 kg N ha −1 ) were applied at planting, at the end of tillering-early jointing, and split at planting and at the end of tillering-early jointing. Treatments included an unfertilized check plot. Results indicated that the optimum N fertilizer rate for wheat grain production varies from 0 to 40 kg N ha −1 ) depending upon the variety. Nitrogen timing practices had no effect on grain yield but on N use efficiency (NUE). The split application of 40 kg N ha −1 increased the NUE. Higher N rates reduced the NUE irrespective of the N timing practice. According to the differential performance among varieties, this study showed that the planting system on narrow raised beds is a variety-specific technology. The relative grain yield, stability, and NUE, indicated that Tlaxcala F2000, Nahuatl F2000 and Romoga F96 are the most adequate varieties for the planting system on narrow raised beds in the Central Highlands of Mexico