Greenbug resistance in barley landraces from Uzbekistan

Background. The greenbug (Sсhizaphis graminum Rondani) can significantly reduce the yield of barley and other cereals in the southern regions of Russia. Cultivation of resistant varieties can significantly limit the pathogen’s harmfulness. At the same time, specific interaction with the genotypes of the host plant, characteristic of S. graminum, requires a continuous search for new resistance donors to broaden the genetic diversity of barley cultivars. Materials and methods. The resistance of 178 accessions of barley landraces from Uzbekistan to the Krasnodar greenbug population was tested in laboratory experiments. Juvenile plants were infested with aphids of different ages, and when the susceptible control died (cv. ‘Belogorsky’), resistance was assessed on a 0 to 10 (plant death) rating scale. Plants with a damage rate of 1–4 points (up to 30% of the leaf surface being damaged) belonged to the resistant class; damage rate of 5–8 points indicated moderate resistance of plants, and that of 9–10 meant susceptibility. In addition, we assessed the aphid damage of the winter barley cultivar ‘Post’, protected by the previously identified resistance gene Rsg1.Results and conclusions. We identified 52 barley accessions as heterogeneous for the studied trait. In six accessions, plants with high (points 3 to 4) and moderate (5 to 8) resistance were identified; 6 accessions were differentiated into 3 phenotypic classes: resistant, moderately resistant, and susceptible; and in 40 accessions the manifestation of the resistance component varied within 5 to 7 points (from 31 to 60% of the leaf surface being damaged). The distinctly expressed resistance of 12 accessions is controlled by alleles of resistance genes that differ from Rsg1. After selection for resistance, the identified accessions can be used in breeding.

Characterization of RsgWBDC053: A New Greenbug Resistance Gene From Wild Barley (Hordeum Vulgare ssp. Spontaneum)

Greenbug (Schizaphis graminum Rondani) is a destructive insect pest that not only damages plants, but also serves as a vector for many viruses. Host plant resistance is the preferred strategy for managing greenbug. To date, only two greenbug resistance genes, Rsg1 and Rsg2, have been reported in barley, with only the former being deployed in cultivars. To breed cultivars with effective resistance against various greenbug biotypes, additional resistance genes are urgently needed to sustain barley production. Wild barley accession WBDC053 (PI 681777), originating from the Baluchistan region of Pakistan, was previously found to be resistant to several greenbug biotypes. In this study, a recombinant inbred line (RIL) population derived from Weskan × WBDC053 was evaluated for response to greenbug biotype E and genotyped using genotyping by sequencing (GBS). A set of 3,347 high quality GBS-derived single nucleotide polymorphisms (SNPs) were then used to map a greenbug resistance gene in this wild barley accession. Linkage analysis placed the greenbug resistance gene in WBDC053, temporarily designated RsgWBDC053, in a 2.35 Mb interval (0-2,354,645 bp) in the terminal region of the short arm of chromosome 2H. This interval harbors 15 genes with leucine-rich-repeat (LRR) protein domains. An allelism test between WBDC053 carrying RsgWBDC053 and STARS1501B carrying Rsg2 indicated that the former is either allelic or closely linked to the latter. GBS-SNPs 2H_1318811 and 2H_1839499 co-segregated with RsgWBDC053 and were converted to Kompetitive allele specific PCR (KASP) markers, KASP-Rsg053-1 and KASP-Rsg0533-2. The two KASP markers can be used to select for RsgWBDC053, but also have the potential to tag Rsg2 in barley improvement programs.

Resistance of barley cultivars approved for use in Russia to harmful organisms and toxic aluminum ions

Background. The most rational way to reduce barley crop losses from diseases, pests and adverse edaphic factors is cultivation of resistant varieties. The specificity of the host– pathogen interactions necessitates a constant search for new donors of resistance for breeding, and phytosanitary monitoring of cultivars.Materials and methods. The research material comprised 248 barley cultivars included in the State Register of Selection Achievements Admitted for Usage in the Russian Federation – 168 were developed domestically, and 80 by foreign breeders. Their resistance to powdery mildew and leaf rust was studied in under laboratory and field conditions. Barley cultivars distinguished for powdery mildew resistance were analyzed using molecular markers. In the laboratory, barley was screened for greenbug resistance. To study the sensitivity to toxic aluminum ions in barley, we used the laboratory method for the early diagnosis of the trait – the root test method.Results and conclusions. Field and laboratory screening revealed a fairly wide diversity of barley cultivated in Russia in terms of resistance to harmful organisms and the edaphic stressor. It was established that 24 barley cultivars were resistant to powdery mildew, and 14 accessions were carriers of the effective mlo11 allele. Two cultivars manifested combined resistance to powdery mildew and barley leaf rust. In 11 cultivars, a distinct greenbug resistance was revealed. High resistance to toxic aluminum ions according to the root and sprout length indices was observed in 26 cultivars. Accessions with the complex resistance to harmful organisms and the edaphic stressor were identified.

GREENBUG RESISTANCE OF OAT LANDRACES FROM CENTRAL ASIA К ОБЫКНОВЕННОЙ ЗЛАКОВОЙ ТЛЕ

The greenbug (Sсhizaphis graminum) is a dangerous pest of cereals in Southern Russia. Breeding of resistant varieties is an effective and eco-friendly way to control this insect. Its differential interaction with host plants substantiates the search for new resistance donors. We evaluated 276 accessions of oat landraces from Central Asian countries (Kazakhstan, Uzbekistan, Kyrgyzstan, and Turkmenistan) to the Krasnodar population and respective isolated clones of the aphid. We identified two pest resistant accessions from Kazakhstan (k-6945 and k-8691) and found 133 accessions from Kazakhstan being heterogeneous including 77 forms with high and moderate resistance and 56 – with only moderate resistance. All accessions from Uzbekistan and Turkmenistan were susceptible to Sсh. graminum. Accession k-9993 from Kyrgyzstan was heterogeneous in terms of resistance. A wide variation in the damage degree of the most oat forms was mostly due to the virulence heterogeneity of the aphid population. Damage evaluation of 15 accessions from Kazakhstan by Sсh. graminum clones showed that the alleles of greenbug resistance genes of these forms differ from the previously identified Grb1 and Grb3 genes.

GREENBUG RESISTANCE IN OAT ACCESSIONS FROM DAGESTAN AND CAUCASIAN COUNTRIES

Background. The breeding of resistant varieties is an effective way to control greenbug Schizaphis graminum Rondani, an economically important pest of oat and other cereals in southern Russia. The insect-host differential interaction necessitates a constant search for new resistance donors.Materials and methods. One hundred and ninety one accessions (mostly landraces) from the Caucasian countries (Armenia, Azerbaijan and Georgia) as well as from the North Caucasus of the Russian Federation (Dagestan) were assessed for greenbug resistance. The Krasnodar (Gulkevichi District) insect population was used in the experiments. The intact plants were uniformly infested with differentaged aphids in the phase of two leaves by shaking insects onto them. When the susceptible control (cv. Borrus) died, the plant damage score was determined using the scale from 0 (no damage) to 10 (91–100% of the leaf surface damaged, plant’s death). The plants with the score of 1–4 points were classified as resistant, 5–8 moderately resistant, and 9–10 susceptible.Results and conclusions. A local oat accession from Georgia (k-4308) was noted for its high insect resistance. Also, heterogeneity of the studied trait was demonstrated by 38 oats forms, most of which were differentiated into two phenotypic classes, and a wide range of plant damage variation was characteristic of 16 accessions. The specific occurrence of resistant forms was the highest among oat landraces from Azerbaijan: two out of five studied accessions (40%) carry resistance genes with a distinct phenotypic manifestation. They are followed by accessions from Georgia (25%), Armenia (17.3%) and Dagestan (13.8%). After selection for resistance, the identified forms can be used in plant breeding.

Identification and confirmation of greenbug resistance loci in an advanced mapping population of sorghum

SUMMARYGreenbug infestations to sorghum can cause severe and above economic threshold damage in the Great Plains of the United States. The current study was conducted to identify quantitative trait loci (QTLs) and potential candidate genes residing within the QTL region responsible for greenbug resistance in an advanced mapping population. Inter-crossed populations are useful in detecting QTLs tightly linked to genetic markers with high resolution. In the current study, QTLs responsible for greenbug resistance in sorghum were mapped using an inter-cross population derived from two parents, BTx623 (greenbug-susceptible line) and PI 607900 (greenbug-resistant line). Molecular markers for 115 loci were used to construct a linkage map which eventually facilitated tagging portions of the sorghum genome regions responsible for greenbug resistance. The molecular genetic map covered all the chromosomes of sorghum with a total genome length of 963·0 cM. The advanced mapping population revealed and confirmed the location of greenbug resistance loci, which explained a high phenotypic variation from 72·9 to 80·9% of greenbug resistance. The loci for greenbug resistance were mapped to the region flanked by markers Starssbnm 93 and Starssbnm 102 on chromosome 9 with an increased allelic effect from the resistant parent. The locations of these loci were compared with a previous study on QTL analysis using an F2 mapping population. The results from the present study were in agreement with the findings in the F2 QTL analysis and identified QTLs had a better confidence interval. The markers/QTLs identified from the current study can be effectively utilized in marker-assisted selection and map-based cloning experiments.