Subsoil tillage enhances wheat productivity,soil organic carbon and available nutrient status in dryland fields

Tillage practices during the fallow period benefit water storage and yield in dryland wheat crops.However,there is currently no clarity on the responses of soil organic carbon(SOC),total nitrogen(TN),and available nutrients to tillage practices within the growing season.This study evaluated the effects of three tillage practices(NT,no tillage;SS,subsoil tillage;DT,deep tillage)over five years on soil physicochemical properties.Soil samples at harvest stage from the fifth year were analyzed to determine the soil aggregate and aggregate-associated C and N fractions.The results indicated that SS and DT improved grain yield,straw biomass and straw carbon return of wheat compared with NT.In contrast to DT and NT,SS favored SOC and TN concentrations and stocks by increasing the soil organic carbon sequestration rate(SOCSR)and soil nitrogen sequestration rate(TNSR)in the 0-40 cm layer.Higher SOC levels under SS and NT were associated with greater aggregate-associated C fractions,while TN was positively associated with soluble organic nitrogen(SON).Compared with DT,the NT and SS treatments improved soil available nutrients in the 0-20 cm layer.These findings suggest that SS is an excellent practice for increasing soil carbon,nitrogen and nutrient availability in dryland wheat fields in North China.

Positional cloning of PmCH1357 reveals the origin and allelic variation of the Pm2 gene for powdery mildew resistance in wheat

Powdery mildew, caused by the biotrophic fungus Blumeria graminis f. sp. tritici(Bgt), is a prevalent disease in common wheat(Triticum aestivum L.) and causes serious yield losses worldwide. We used a map-based approach to clone the major broad-spectrum powdery mildew resistance gene Pm CH1357 from wheat breeding line CH1357. Pm CH1357 was mapped to a 526 kb region containing only Traes CS5 D01 G044600. The Traes CS5 D01 G044600 sequence of the susceptibility allele in Taichung 29(TC29) was identical to that in Chinese Spring, whereas the sequence of the resistance allele in CH1357 was identical to Pm2a previously cloned from the germplasm Ulka/*8Cc. The susceptibility allele in TC29 contained a 7 bp deletion in exon 1, resulting in loss of 856 of the 1277 amino acids in the predicted nucleotide-binding domain leucine-rich repeat containing Pm2a protein.Pm CH1357/Pm2a sequence was also isolated from the Chinese wheat landraces and cultivars that were previously reported to possess the resistance gene Pm2b, Pm2c,PmLX66, or PmND399. The Pm CH1357/Pm2a resistance allele was present in 10 of 495 accessions in core germplasm and contemporary cultivars from China and the USA. A newly developed diagnostic marker for the 7 bp In Del in the resistance gene can be used to eliminate the susceptibility allele in wheat breeding programs.

Allele mining of wheat ABA receptor at Ta PYL4 suggests neo-functionalization among the wheat homoeologs

ABA receptors(PYR/PYL/RCAR)play a central role in the water loss control of plants.A previous report indicated that TaPYL4 is a critical gene in wheat that improves grain production under drought conditions and increases water use efficiency.In this study,we analyzed the sequence polymorphisms and genetic effects of TaPYL4s.Based on isolated TaPYL4 genes from chromosomes 2A,2B and 2D,three haplotypes were detected in the promoter region of TaPYL4-2A,and two haplotypes were present in TaPYL4-2B and TaPYL4-2D,respectively.Marker/trait association analysis indicated that TaPYL4-2A was significantly associated with plant height in 262 Chinese wheat core collection accessions,as well as the drought tolerance coefficient(DTC)for plant height in 239 wheat varieties from Shanxi Province in multiple environments.However,the frequencies of favored drought-tolerant haplotype TaPYL4-2A-Hap2 were considerably low,accounting for only 10%,and lines with this certain Hap could be reserved in the breeding program.TaPYL4-2B was significantly associated with grain number,and the favored haplotype TaPYL4-2B-Hap1 was the dominant allele of above 90% in the collection.For TaPYL4-2D,there were no significant differences in these traits between the two haplotypes in either of the two panels.These results indicate that variation might lead to functional differentiation among the homoeologs and the haplotypes had undergone artificial selection during breeding.Two molecular markers developed to distinguish these haplotypes could be used for breeding in water-limited regions.

Alternate row mulching optimizes soil temperature and water conditions and improves wheat yield in dryland farming

Straw mulching allows for effective water storage in dryland wheat production. Finding a suitable straw mulching model that facilitates wheat growth was the objective of this study. A 2-year field experiment was conducted to investigate the effects of two straw mulching patterns （FM, full coverage within all the rows; HM, half coverage within alternate rows） and two mulching rates （4.5 and 9.0 t ha^-1） on soil moisture, soil temperature, grain yield, and water use efficiency （WUE） of winter wheat in northern China, with no mulching （M0） as the control. Results showed that mulching increased the soil water storage in all growth stages under high mulching rates, with a stronger effect in later growth stages. Water storage under the HM model was greater in later stages than under the FM model. Soil water content of HM groups was higher than that of FM groups, especially in surface soil layers. Evapotranspiration decreased in mulched groups and was higher under high mulching rates. Aboveground biomass during each growth stage under the HM model was higher than that under M0 and FM models with the same mulched rate, leading to a relatively higher grain yield under the HM model. Mulching increased WUE, a trend that was more obvious under HM9.0 treatment. Warming effect of soil temperature under the HM pattern persisted longer than under the FM model with the same mulching rates. Accumulated soil temperature under mulched treatments increased, and the period of negative soil temperature decreased by 9-12 days under FM and by 10-20 days under HM. Thus, the HM pattern with 9.0 t ha^-1 mulching rate is beneficial for both soil temperature and water content management and can contribute to high yields and high WUE for wheat production in China.

Analysis of three types of resistance gene analogs in Pm U region from Triticum urartu

Resistance gene analog(RGA) screening of mapped disease-resistant genes not only helps to clone these genes but also helps to develop efficient molecular markers for resistance breeding. The present study focused on the PmU region located on chromosome 7 Au L of Triticum urartu, and recently, a nucleotide binding site(NBS)-encoding gene, Pm60, was cloned from the same chromosome arm. In this research, NBS, protein kinase(PK), and ATP-binding cassette(ABC), the three disease resistance-related gene families, were analyzed within PmU region by using informatics tools, and an expression experiment was conducted to verify their functions in vivo. Comparative genomic analysis revealed that 126 RGAs were included on chromosome 7 Au L, and 30 of the RGAs as well as Pm60 were found in the Pm U region. Transcriptome database analysis of T. urartu revealed 14 PmU-RGAs with expression data, and three PmU-NBSs exhibited significant changes in expression after inoculation with Blumeria graminis f. sp. tritici(Bgt); TRIUR314879 was up-regulated, while TRIUR300450 and TRIUR306270 were down-regulated. Cluster analysis showed that these three PmU-NBSs were clustered far from the cloned wheat resistance genes. Then, qRT-PCR was performed to investigate the expression of 14 PmU-RGAs and Pm60 after inoculation with Bgt race E09; the results showed that Pm60 was specifically expressed in UR206 which carrying PmU, but not in susceptible UR203; while TRIUR314879 was significantly up-regulated and TRIUR300450 was downregulated in UR206 after inoculation. These results indicated that PmU is Pm60, and TRIUR314879 and TRIUR300450 may also be involved in the defense against Bgt.

Characterization of a new hexaploid triticale 6D(6A) substitution line with increased grain weight and decreased spikelet number

Hexaploid triticale(×Triticosecale,AABBRR)is an important forage crop and a promising energy plant.Transferring D-genome chromosomes or segments from common wheat(Triticum aestivum)into hexaploid triticale is attractive in improving its economically important traits.Here,a hexaploid triticale 6D(6A)substitution line Lin 456 derived from the cross between the octoploid triticale line H400 and the hexaploid wheat Lin 56 was identified and analyzed by genomic in situ hybridization(GISH),fluorescence in situ hybridization(FISH),and molecular markers.The GISH analysis showed that Lin 456 is a hexaploid triticalewith 14 rye(Secale cereale)chromosomes and 28 wheat chromosomes,whereas non-denaturing fluorescence in situ hybridization(ND-FISH)and molecular marker analysis revealed that it is a 6D(6A)substitution line.In contrast to previous studies,the signal of Oligo-pSc119.2 was observed at the distal end of 6DL in Lin 456.The wheat chromosome 6D was associatedwith increased grain weight and decreased spikelet number using the genotypic data combined with the phenotypes of the F2 population in the three environments.The thousand-grain weight and grain width in the substitution individuals were significantly higher than those in the non-substitution individuals in the F2 population across the three environments.We propose that the hexaploid triticale 6D(6A)substitution line Lin 456 can be a valuable and promising donor stock for genetic improvement during triticale breeding.