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Good crop stand establishment and root system development are essential for optimum grain yield of dryland wheat (Triticum aestivum L.). At present, little is known about the effect of tillage and straw mulch on the root system of wheat under dryland areas in southwestern China. The aim of this study was to evaluate the effect of three tillage treatments (no-till, NT; rotary till, RT; conventional till, CT) and two crop residue management practices (straw mulch, ML; non-straw mulch, NML) on stand establishment, root growth and grain yield of wheat. NT resulted in lower soil cover thickness for the wheat seed, higher number of uncovered seeds, lower percentage of seedling-less ridges and lower tiller density compared to RT and CT; ML resulted in higher tiller density compared to NML. Straw mulching resulted in more soil water content and root length density (RLD) at most of the growth stages and soil depths. The maximum RLD, root surface area density and root dry matter density were obtained under NT. In the topmost 10 cm soil layer, higher RLD values were found under NT than those under RT and CT. There were no significant differences in the yield or yield components of wheat among the tillage treatments in 2011–2012, but NT resulted in a significant higher yield compared to RT and CT in 2012–2013. Grain yield was significantly higher in ML compared to in NML. A strong relationship was observed between the water-use efficiency and the grain yield. Both NT and ML proved beneficial for wheat in term of maintaining higher tiller density, better soil water status and root growth, leading to a higher grain yield and enhanced water-use efficiency, especially in a low rainfall year.

Synthetic hexaploid wheat (SHW) represents a valuable source of new resistances to a range of biotic and abiotic stresses. A recombinant inbred line (RIL) population with 127 recombinant inbred lines derived from a SHW-derived variety Chuanmai 42 crossing with a Chinese spring wheat variety Chuannong 16 was used to map QTLs for agronomic traits including grain yield, grains per square meter, thousand-kernel weight, spikes per square meter, grain number per spike, grains weight per spike, and biomass yield. The population was genotyped using 184 simple-sequence repeat (SSR) markers and 34 sequence-related amplified polymorphism (SRAP) markers. Of 76 QTLs (LOD>2.5) identified, 42 were found to have a positive effect from Chuanmai 42. The QTL QGy.saas-4D.2 associated with grain yield on chromosome 4D was detected in four of the six environments and the combined analysis, and the mean yield, across six environments, of individuals carrying the Chuanmai 42 allele at this locus was 8.9% higher than that of those lines carrying the Chuannong 16 allele. Seven clusters of the yield-coincident QTLs were detected on 1A, 4A, 3B, 5B, 4D, and 7D.

Synthetic hexaploid wheat (SHW), a carrier of multiple elite genes, is an important genetic resource in improvement of common wheat (Triticum aestivum L.). Chuanmai 42 is a wheat cultivar with high-yield potential and resistance to strip rust (Puccinia striiformis f. sp. tritici), which was developed by crossing and backcrossing Syn769 (an elite synthetic hexaploid wheat) with Sichuan commercial wheat cultivars. For understanding the genetic effects of the introgression loci from SHW in Chuanmai 42, a total of 78 introgression loci of SHW were tested in Chuanmai 42 using 1029 simple sequence repeat (SSR) markers. Using 127 recombinant inbred lines (RILs, F8) in Chuanmai 42 (introgression loci) and Chuannong 16 (Chuannong 16 loci) backgrounds, the genetic effects of the introgression loci were evaluated across 6 environments in Sichuan Province, China from 2006 to 2009. One locus from the SHW parent, Barc1183, was detected in Chuanmai 42. It was located on the long arm of chromosome 4D after idenfication using the 4DS and 4DL telosomic lines of Chinese Spring and the 4D(4A) and 4D(4B) substitution lines of Longdon (T. turgidum subsp. durum). This locus had positive effects on increasing tiller number per plant, number of effective spikes, grains per square meter, harvest index, and grain production rate. The average yield of the 6 growing environments was increased by 8.9% when comparing locus Barc1183 in Chuanmai 42 to that in Chuannong 16. Therefore, Barc1183 from SHW is a candidate locus in high-yield breeding of wheat.

Sichuan Province has the largest wheat (Triticum aestivum L.) producing area in Southwest China. It is crucial to understand the quality potential and stability for the major commercial cultivars and to provide guidance to farmers regarding wheat production in this province. Seven representative cultivars were planted in 5 ecological localities of Sichuan under two nitrogen rates from 2006 to 2008. Eight quality traits and 2 end-use production (noodle and bread making) scores were determined. The average of 3-year test weight, grain protein content, wet gluten content, Zeleny sedimentation, falling number, flour water abstraction, dough developing time, stability time, noodle score of dry white Chinese noodle, and bread score were 777 g L−1, 12.3%, 25.1%, 32.9 mL, 326 s, 56.5%, 3.0 min, 4.5 min, 78.5, and 62.2, respectively. In a combined analysis of variance, the effects of genotype, environment, and their interaction were significant for almost all traits tested. For test weight, Zeleny sedimentation, falling number, flour water abstraction, and noodle score of dry white Chinese noodle, the influences between years were greater than differences between locations; whereas, for protein content, wet gluten content, dough developing time, stability time, and bread score, location had a greater influence than year. Increasing nitrogen rate significantly improved most quality traits and raised bread score, but had no influence on noodle score. Stability analysis revealed that Chuanmai 39 was stable for bread quality with the highest bread score value, while Chuanmai 37 was stable for most quality traits with the highest noodle score. This result indicates that Chuanmai 39 and Chuanmai 37 can be favorably used in wheat quality improvement in Sichuan Province.