Elite,transformable haploid inducers in maize

The introduction of alleles into commercial crop breeding pipelines is both time consuming and costly.Two technologies that are disrupting traditional breeding processes are doubled haploid(DH)breeding and genome editing(GE).Recently,these techniques were combined into a GE trait delivery system called HI-Edit(Haploid Inducer-Edit).In HI-Edit,the pollen of a haploid inducer line is reprogrammed to deliver GE traits to any variety,obviating recurrent selection.For HI-Edit to operate at scale,an efficient transformable HI line is needed,but most maize varieties are recalcitrant to transformation,and haploid inducers are especially difficult to transform given their aberrant reproductive behaviors.Leveraging marker assisted selection and a three-tiered testing scheme,we report the development of new Iodent and Stiff Stalk maize germplasm that are transformable,have high haploid induction rates,and exhibit a robust,genetically-dominant anthocyanin native trait that may be used for rapid haploid identification.We show that transformation of these elite‘‘HI-Edit”lines is enhanced using the BABYBOOM and WUSCHEL morphogenetic factors.Finally,we evaluate the HI-Edit performance of one of the lines against both Stiff Stalk and non-Stiff Stalk testers.The strategy and results of this study should facilitate the development of commercially scalable HI-Edit systems in diverse crops.

Reactions of Triticum urartu accessions to two races of the wheat yellow rust pathogen

Triticum urartu(AA,2n=2x=14),a wild grass endemic to the Fertile Crescent(FC),is the progenitor of the A subgenome in common wheat.It belongs to the primary gene pool for wheat improvement.Here,we evaluated the yellow rust(caused by Puccinia striiformis f.sp.tritici,Pst)reactions of 147 T.urartu accessions collected from different parts of the FC.The reactions varied from susceptibility to strong resistance.In general,there were more accessions with stronger resistance to race CYR33 than to CYR 32.In most cases the main form of defense was a moderate resistance characterized by the presence of necrotic/chlorotic lesions with fewer Pst uredinia on the leaves.Forty two accessions displayed resistance to both races.Histological analysis showed that Pst growth was abundant in the compatible interaction but significantly suppressed by the resistant response.Gene silencing mediated by Barley stripe mosaic virus was effective in two T.urartu accessions with different resistance responses,indicating that this method can expedite future functional analysis of resistance genes.Our data suggest that T.urartu is a valuable source of resistance to yellow rust,and represents a model for studying the genetic,genomic and molecular basis underlying interaction between wheat and Pst.

Genetic Analysis of Chromosomal Loci Affecting the Content of Insoluble Glutenin in Common Wheat

In common wheat, insoluble glutenin （IG） is an important fraction of flour glutenin macropolymers, and insoluble glutenin content （IGC） is positively associated with key end-use quality parameters. Here, we present a genetic analysis of the chromosomal loci affecting IGC with the data collected from 90 common wheat varieties cultivated in four environments. Statistical analysis showed that IGC was controlled mainly genetically and influenced by the environment. Among the major genetic components known to affect end-use quality, 1BL/1RS translocation had a significantly negative effect on IGC across all four environments. As to the different alleles of Glu-A1, -B1 and -D1 loci, Glu-Ala, Glu-Blb and Glu-Dld exhibited relatively strong positive effects on IGC in all environments. To identify new loci affecting IGC, association mapping with 1355 DArT markers was conducted. A total of 133 markers were found associated with IGC in two or more environments （P 〈 0.05）, ten of which consistently affected IGC in all four environments. The phenotypic variance explained by the ten markers varied from 4.66% to 8.03%, and their elite alleles performed significantly better than the inferior counterparts in enhancing IGC. Among the ten markers, wPt-3743 and wPt-733835 reflected the action of Glu-D1, and wPt-664972 probably indicated the effect of GIu-A1. The other seven markers, forming three clusters on 2AL. 3BL or 7BL chromosome arms, represented newly identified genetic determinants of IGC. Our work provided novel insights into the genetic control of IGC, which may facilitate wheat end- use quality improvement through molecular breeding in the future.