Survey of spiking in the mouse visual system reveals functional hierarchy.

The anatomy of the mammalian visual system, from the retina to the neocortex, is organized hierarchically1. However, direct observation of cellular-level functional interactions across this hierarchy is lacking due to the challenge of simultaneously recording activity across numerous regions. Here we describe a large, open dataset-part of the Allen Brain Observatory2-that surveys spiking from tens of thousands of units in six cortical and two thalamic regions in the brains of mice responding to a battery of visual stimuli. Using cross-correlation analysis, we reveal that the organization of inter-area functional connectivity during visual stimulation mirrors the anatomical hierarchy from the Allen Mouse Brain Connectivity Atlas3. We find that four classical hierarchical measures-response latency, receptive-field size, phase-locking to drifting gratings and response decay timescale-are all correlated with the hierarchy. Moreover, recordings obtained during a visual task reveal that the correlation between neural activity and behavioural choice also increases along the hierarchy. Our study provides a foundation for understanding coding and signal propagation across hierarchically organized cortical and thalamic visual areas.

Mapping of the stem rust resistance gene Pg13 in cultivated oat.

KEY MESSAGE: The widely deployed, oat stem rust resistance gene Pg13 was mapped by linkage analysis and association mapping, and KASP markers were developed for marker-assisted selection in breeding programs. Pg13 is one of the most extensively deployed stem rust resistance genes in North American oat cultivars. Identification of markers tightly linked to this gene will be useful for routine marker-assisted selection, identification of gene pyramids, and retention of the gene in backcrosses and three-way crosses. To this end, high-density linkage maps were constructed in four bi-parental mapping populations using SNP markers identified from 6K oat Infinium iSelect and genotyping-by-sequencing platforms. Additionally, genome-wide associations were identified using two sets of association panels consisting of diverse elite oat lines in one set and landrace accessions in the other. The results showed that Pg13 was located at approximately 67.7 cM on linkage group Mrg18 of the consensus genetic map. The gene co-segregated with the 7C-17A translocation breakpoint and with crown rust resistance gene Pc91. Co-segregating markers with the best prediction accuracy were identified at 67.7-68.5 cM on Mrg18. KASP assays were developed for linked SNP loci for use in oat breeding.

Characterization of Ethiopian Wheat Germplasm for Resistance to Four Puccinia graminis f. sp. tritici Races Facilitated by Single-Race Nurseries.

In Ethiopia, breeding rust resistant wheat cultivars is a priority for wheat production. A stem rust epidemic during 2013 to 2014 on previously resistant cultivar Digalu highlighted the need to determine the effectiveness of wheat lines to multiple races of Puccinia graminis f. sp. tritici in Ethiopia. During 2014 and 2015, we evaluated a total of 97 bread wheat and 14 durum wheat genotypes against four P. graminis f. sp. tritici races at the seedling stage and in single-race field nurseries. Resistance genes were postulated using molecular marker assays. Bread wheat lines were resistant to race JRCQC, the race most virulent to durum wheat. Lines with stem rust resistance gene Sr24 possessed the most effective resistance to the four races. Only three lines with adult plant resistance possessed resistance effective to the four races comparable with cultivars with Sr24. Although responses of the wheat lines across races were positively correlated, wheat lines were identified that possessed adult plant resistance to race TTKSK but were relatively susceptible to race TKTTF. This study demonstrated the importance of testing wheat lines for response to multiple races of the stem rust pathogen to determine if lines possessed non-race-specific resistance. Copyright © 2019 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Discovery of a Novel Stem Rust Resistance Allele in Durum Wheat that Exhibits Differential Reactions to Ug99 Isolates.

Wheat stem rust, caused by Puccinia graminis f. sp. tritici Eriks. & E. Henn, can incur yield losses in susceptible cultivars of durum wheat, Triticum turgidum ssp. durum (Desf.) Husnot. Although several durum cultivars possess the stem rust resistance gene Sr13, additional genes in durum wheat effective against emerging virulent races have not been described. Durum line 8155-B1 confers resistance against the P. graminis f. sp. tritici race TTKST, the variant race of the Ug99 race group with additional virulence to wheat stem rust resistance gene Sr24 However, 8155-B1 does not confer resistance to the first-described race in the Ug99 race group: TTKSK. We mapped a single gene conferring resistance in 8155-B1 against race TTKST, Sr8155B1, to chromosome arm 6AS by utilizing Rusty/8155-B1 and Rusty*2/8155-B1 populations and the 90K Infinium iSelect Custom bead chip supplemented by KASP assays. One marker, KASP_6AS_IWB10558, cosegregated with Sr8155B1 in both populations and correctly predicted Sr8155B1 presence or absence in 11 durum cultivars tested. We confirmed the presence of Sr8155B1 in cultivar Mountrail by mapping in the population Choteau/Mountrail. The marker developed in this study could be used to predict the presence of resistance to race TTKST in uncharacterized durum breeding lines, and also to combine Sr8155B1 with resistance genes effective to Ug99 such as Sr13 The map location of Sr8155B1 cannot rule out the possibility that this gene is an allele at the Sr8 locus. However, race specificity indicates that Sr8155B1 is different from the known alleles Sr8a and Sr8b.

Kenyan Isolates of Puccinia graminis f. sp. tritici from 2008 to 2014: Virulence to SrTmp in the Ug99 Race Group and Implications for Breeding Programs.

Frequent emergence of new variants in the Puccinia graminis f. sp. tritici Ug99 race group in Kenya has made pathogen survey a priority. We analyzed 140 isolates from 78 P. graminis f. sp. tritici samples collected in Kenya between 2008 and 2014 and identified six races, including three not detected prior to 2013. Genotypic analysis of 20 isolates from 2013 and 2014 collections showed that the new races TTHST, TTKTK, and TTKTT belong to the Ug99 race group. International advanced breeding lines were evaluated against an isolate of TTKTT (Sr31, Sr24, and SrTmp virulence) at the seedling stage. From 169 advanced lines from Kenya, 23% of lines with resistance to races TTKSK and TTKST were susceptible to TTKTT and, from two North American regional nurseries, 44 and 91% of resistant lines were susceptible. Three lines with combined resistance genes were developed to facilitate pathogen monitoring and race identification. These results indicate the increasing virulence and variability in the Kenyan P. graminis f. sp. tritici population and reveal vulnerabilities of elite germplasm to new races.