Identification of powdery mildew resistance loci in wheat by integrating genome-wide association study(GWAS) and linkage mapping

Wheat powdery mildew(Blumeria graminis f.sp.tritici, Bgt) is a disease of increasing importance globally due to the adoption of high yielding varieties and modern sustainable farming technologies.Growing resistant cultivars is a preferred approach to managing this disease, and novel powdery mildew resistance genes are urgently needed for new cultivar development.A genome-wide association study was performed on a panel of 1292 wheat landraces and historical cultivars using 5011 single nucleotide polymorphism(SNP)markers.The association panel was evaluated for reactions to three Bgt inoculants, OKS(14)-B-3-1, OKS(14)-C-2-1, and Bgt15.Linkage disequilibrum(LD) analysis indicated that genome-wide LD decayed to 0.1 at 23 Mb, and population structure analysis revealed seven subgroups in the panel.Association analysis using a mixed linear model(MLM) identified three loci for powdery mildew resistance on chromosome 2 B, designated QPm.stars-2BL1,QPm.stars-2BL2, and QPm.stars-2BL3.To evaluate the efficacy of GWAS in gene discovery,QPm.stars-2BL2 was validated using F2 and F2:3 populations derived from PI420646 × OK1059060-126135-3.Linkage analysis delimited the powdery mildew resistance gene in PI 420646 to an interval where QPm.stars-2BL2 was located, lending credence to the GWAS results.QPm.stars-2BL1 and QPm.stars-2BL3, which were associated with four SNPs located at 457.7–461.7 Mb and two SNPs located at 696.6–715.9 Mb in the Chinese Spring reference IWGSC RefSeq v1.0, respectively, are likely novel loci for powdery mildew resistance and can be used in wheat breeding to improve powdery mildew resistance.

Effects of Ovarian Preservation Time on in vitro Maturation and in vitro Fertilization of Oocytes from Slaughtered Sheep

[Objectives] The aim was to study the effects of ovarian preservation time on in vitro fertilization of oocytes from slaughtered sheep. [Methods] The collected ovaries were randomly and evenly divided into four groups. They were preserved in physiological saline containing penicillin（ 100 IU/ml） and streptomycin（ 100 μg/ml） at 15-20 ℃ for 0（ Control）,6,12 and 18 h,respectively. Then,the oocytes were subjected to in vitro fertilization. [Results]The maturation rates,cleavage rates and blastocyst rates of the oocytes preserved for 6 and 12 h showed no significant differences compared with those of the oocytes preserved for0 h（ 72. 03%,70. 87% vs. 73. 68%; 74. 12%,72. 60% vs. 74. 49%; 22. 22%,20. 75% vs. 23. 29%）（ P 〉 0. 05）. There were also no significant differences in maturation rate,cleavage rate or blastocyst rate between the oocytes preserved for 18 and 0 h（ P 〉 0. 05）. [Conclusions] Within a certain rage（ 0-18 h）,storage time of ovary at 15-20 ℃ does not affect the continued development of oocytes from slaughtered sheep.

Next generation of neurological therapeutics:Native and bioengineered extracellular vesicles derived from stem cells

Extracellular vesicles(EVs)-based cell-free therapy,particularly stem cell-derived extracellular vesicles(SC-EVs),offers new insights into treating a series of neurological disorders and becomes a promising candidate for alternative stem cell regenerative therapy.Currently,SC-EVs are considered direct therapeutic agents by themselves and/or dynamic delivery systems as they have a similar regenerative capacity of stem cells to promote neurogenesis and can easily load many functional small molecules to recipient cells in the central nervous system.Meanwhile,as non-living entities,SC-EVs avoid the uncontrollability and manufacturability limitations of live stem cell products in vivo(e.g.,low survival rate,immune response,and tumorigenicity)and in vitro(e.g.,restricted sources,complex preparation processes,poor quality control,low storage,shipping instability,and ethical controversy)by strict quality control system.Moreover,SC-EVs can be engineered or designed to enhance further overall yield,increase bioactivity,improve targeting,and extend their half-life.Here,this review provides an overview on the biological properties of SC-EVs,and the current progress in the strategies of native or bioengineered SC-EVs for nerve injury repairing is presented.Then we further summarize the challenges of recent research and perspectives for successful clinical application to advance SC-EVs from bench to bedside in neurological diseases.

Heritability estimates for seed yield and its components in Cynodon dactylon var. dactylon (L.) Pers.

Bermudagrass[Cynodon dactylon var.dactylon(L.)Pers.]is a major warm-season turf and forage grass worldwide.Seed yield is an important trait targeted for improvement in bermudagrass breeding programs because of the increased interest in seed-propagated cultivars.Understanding the nature of genetic variation for seed yield and its components in bermudagrass would aid the development of seed-propagated cultivars.The objective of this study was to estimate the genetic variation and narrow-sense heritability for seed yield and its two major components,inflorescences prolificacy and seed set percentage in bermudagrass.Twenty-five half-sib families and their respective clonal parents were evaluated at two Oklahoma locations,Perkins and Stillwater(Oklahoma,USA),over two years.Half-sib families were different for seed yield,inflorescences prolificacy and seed set percentage,indicating the expression of additive genes in controlling these traits.Family×location effects were observed for seed set percentage and seed yield.All three traits showed family×year interaction effects.There was a significant family×location×year interaction in inflorescences prolificacy and seed set percentage.Narrow-sense heritability estimates for seed yield was 0.18 based on variance component analysis among half-sib families and ranged from 0.26 to 0.68 based on parent-offspring regressions,indicating genetic complexity of seed yield.Heritability estimates were moderate(0.30−0.55)for inflorescences prolificacy and moderate to relatively high(0.41−0.78)for seed set percentage.The results indicate that sufficient magnitudes of additive genetic variation for seed set percentage and inflorescence prolificacy permit positive response to selection and conventional progeny-based genotypic evaluation is necessary for seed yield improvement.Citation:Tan C,Wu Y,Taliaferro CM,Bell GE,Martin DL,et al.2022.Heritability estimates for seed yield and its components in Cynodon dactylon var.