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Stripe rust caused by Puccnina striiformis (Pst) is an economically important disease attacking wheat all over the world. Identifying and deploying new genes for Pst resistance is an economical and long-term strategy for controlling Pst. A genome-wide association study (GWAS) using single nucleotide polymorphisms (SNPs) and functional haplotypes were used to identify loci associated with stripe rust resistance in synthetic-derived (SYN-DER) wheats in four environments. In total, 92 quantitative trait nucleotides (QTNs) distributed over 65 different loci were associated with resistance to Pst at seedling and adult plant stages. Nine additional loci were discovered by the linkage disequilibrium-based haplotype-GWAS approach. The durable rust-resistant gene Lr34/Yr18 provided resistance in all four environments, and against all the five Pst races used in this study. The analysis identified several SYN-DER accessions that carried major genes: either Yr24/Yr26 or Yr32. New loci were also identified on chr2B, chr5B, and chr7D, and 14 QTNs and three haplotypes identified on the D-genome possibly carry new alleles of the known genes contributed by the Ae. tauschii founders. We also evaluated eleven different models for genomic prediction of Pst resistance, and a prediction accuracy up to 0.85 was achieved for an adult plant resistance, however, genomic prediction for seedling resistance remained very low. A meta-analysis based on a large number of existing GWAS would enhance the identification of new genes and loci for stripe rust resistance in wheat. The genetic framework elucidated here for stripe rust resistance in SYN-DER identified the novel loci for resistance to Pst assembled in adapted genetic backgrounds.

Stripe (yellow) rust caused by Puccinia striiformis f. sp. tritici (Pst) is a major disease in many wheat growing regions. The objective of this study was to characterise stripe rust resistance in a common wheat landrace PI388231, originated from Sindh province of Pakistan, which confers high to moderate levels of resistance against Pst pathotypes prevalent in Pakistan. A recombinant inbred line (RIL) population was developed by crossing PI388231 with the susceptible parent Avocet ‘s’. Screening of this population with Pakistani Pst pathotype 574212 in glasshouse indicated the presence of a single gene and the locus was temporarily named YrPak. Bulked segregant analysis using the targeted genotyping-by-sequencing (tGBS) platform located YrPak on the short arm of chromosome 5B. YrPak-linked SNPs were converted into kompetitive-allele specific PCR (KASP) markers and were genotyped on the parents. Five KASP markers sunKASP_330, sunKASP_334, sunKASP_335, sunKASP_338 and sunKASP_341 that showed clear clustering between parents were tested on the entire RIL population. Markers sunKASP_338 and sunKASP_341 flanked YrPak. The markers sunKASP_338 and sunKASP_341 amplified alleles alternate to those linked with YrPak in 86% and 83% of wheat cultivars tested, respectively. This population segregated for two adult plant resistance genes in addition to YrPak. The presence of pleiotropic locus Yr46/Lr67/Sr55 was confirmed using the gene specific marker TM10_67T and the second gene remains unknown.

The deficiency of micronutrients and low organic matter (OM) status of soils are major hurdles in the optimum crop yield achievements. Humic substances can play an imperative role in the micronutrient bioavailability and improved crop yield by ameliorating the physicochemical soil properties. consumed as fresh food and in processed form. However, its susceptibility towards micronutrient deficiency causes a significant reduction in yield. That is why a current study was done to examine the influence of different potassium humate (KH) levels, i.e., 0, 5, 10, and 15 kg ha−1 with micronutrients mixture (MC), i.e., 0, 50 (Zn = 2.50, B = 0.75, Fe = 2.50 kg ha−1), 75 (Zn = 3.75, B = 1.125, Fe = 3.75 kg ha−1) and 100% (Zn = 5.0, B = 1.5, Fe = 5.0 kg ha−1) on the yield, biomass, harvesting index and uptake of the micronutrients in tomato. The results showed that increasing the level of K-humate significantly improved the yield (7.4 and 7.17%), total biomass (6.38 and 6.59%), and harvesting the index (0.46 and 0.76%) of tomato. It also enhanced Fe uptake but did not affect B and Zn concentrations in the tomato fruit at 100% MC + 15 kg ha−1 KH over control in the autumn and spring seasons. In conclusion, both levels of K-humate 10 and 15 kg ha−1 and MC 75 and 100% effectively enhance the yield, biomass, harvesting the index, and micronutrients (B, Zn, and Fe) uptake in tomatoes.

Wheat stem rust, a devastating disease of wheat and barley caused by the fungal pathogen Puccinia graminis f. sp. tritici, was largely eradicated in Western Europe during the mid-to-late twentieth century. However, isolated outbreaks have occurred in recent years. Here we investigate whether a lack of resistance in modern European varieties, increased presence of its alternate host barberry and changes in climatic conditions could be facilitating its resurgence. We report the first wheat stem rust occurrence in the United Kingdom in nearly 60 years, with only 20% of UK wheat varieties resistant to this strain. Climate changes over the past 25 years also suggest increasingly conducive conditions for infection. Furthermore, we document the first occurrence in decades of P. graminis on barberry in the UK . Our data illustrate that wheat stem rust does occur in the UK and, when climatic conditions are conducive, could severely harm wheat and barley production. Clare Lewis et al. report the first identification in nearly 60 years of a cultivated wheat plant infected with the fungal pathogen Puccinia graminis f.sp. tritici (wheat stem rust) in the United Kingdom. They find that only 20% of UK wheat varieties are resistant to this strain and urge growers to resume resistance breeding programs.

Yellow rust populations of Pakistan were characterised for their virulence pathotypes/races and pathogenetic variation using seedling evaluation of differential genotypes under glasshouse conditions in Murree (6000 feet above sea level). Differential genotypes comprised a world set, an European set, near isogenic lines and the universally susceptible bread wheat cultivar “Morocco”. Over the two-year study a total of 18 race groups were identified. Out of these 18 race groups, several (68E0, 64E0, 66E0, 70E0, 6E0, 71E0, 6E0, 2E0, 67E0, and 68E16) were found previously. The new race group 70E32 found probably evolved because of mutation from the previously existing 70E16. Virulence frequencies of yellow rust (Yr) resistance genes were also determined on near isogenic lines. The highest virulence frequencies (%) were found for Yr7 (88%), Yr9 (57%), Yr18 (70%), and Yr24 (69%). Virulence frequencies were low for Yr 1 (4%), Yr5 (7%), Yr10 (10%) and Yr15 (4%). Our studies indicated that virulence existed for alm...

Four neem (Azadirchta indica A.Juss) products namely crude neem seed oil, nimbokil, crude neem seed oil terpenoid extract and neem leaf decoction were tested for their in vitro activity against mycelial growth, sporangial germination and sporangial production of Phytophthora infestans. All the products were found highly effective against the different life stages of the fungus. The compounds were evaluated both with and without being heat sterilized along the medium. The heat sterilized compounds were comparatively less effective as compared to the ones which were used without heat sterilization. The results show that neem products have potential for the management of potato late blight disease.