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Genome‐wide development of intra‐ and inter‐specific transferable SSR markers and construction of a dynamic web resource for yam molecular breeding: Y2MD

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Abstract

Microsatellite markers are widely used in population genetics and breeding. Despite the economic significance of yams in developing countries, there is a paucity of microsatellite markers, and as of now, no comprehensive microsatellite marker database exists. In this study, we conducted genome-wide microsatellite marker development across four yam species, identified cross-species transferable markers, and designed an easy-to-use web portal for the yam researchers. The screening of Dioscorea alata, Dioscorea rotundata, Dioscorea dumetorum, and Dioscorea zingiberensis genomes resulted in 318,713, 322,501, 307,040, and 253,856 microsatellites, respectively. Mono-, di-, and tri-nucleotides were the most important types of repeats in the different species, and a total of 864,128 primer pairs were designed. Furthermore, we identified 1170 cross-species transferable microsatellite markers. Among them, 17 out of 18 randomly selected were experimentally validated with good discriminatory power, regardless of the species and ploidy levels. Ultimately, we created and deployed a dynamic Yam Microsatellite Markers Database (Y2MD) available at https://y2md.ucad.sn/. Y2MD is embedded with various useful tools such as JBrowse, Blast, insilicoPCR, and SSR Finder to facilitate the exploitation of microsatellite markers in yams. This study represents the first comprehensive microsatellite marker mining across several yam species and will contribute to advancing yam genetic research and marker-assisted breeding. The released user-friendly database constitutes a valuable platform for yam researchers.

First insights into the quantitative genetic composition of the female seed yield for an efficient hybrid seed production in wheat (Triticum aestivum L.)

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Abstract

Hybrid breeding of wheat (Triticum aestivum L.) is limited by its self-pollinating nature. Past cross-pollination improvements mostly focused on optimizing male traits. We tested the hybrid seed yield of 100 diverse elite lines treated with a chemical hybridization agent (CHA) and pollinated by non-sterilized male plants in multi-environmental field trials. Plant height and phenological traits of female plants were also assessed. In parallel, control experiments without CHA sterilization were conducted to measure per se yield of the tested material. Hybrid seed yield variation is of quantitative genetic nature, and, despite the large environmental influence, this trait has a strong genotypic component and is highly heritable (h 2 = .77). The lack of correlation between hybrid seed yield and per se yield suggests a non-shared genetic control. Phenological traits and their interactions are important factors explaining together ~1/3 of hybrid seed yield variation. In contrast to plant height and flowering traits, which are influenced by major genetic factors, no significant marker–trait associations were found for the hybrid seed yield, thus suggesting a highly polygenic genetic architecture and the need of larger populations to investigate female hybrid seed yield.

Control of crown rot with potassium carbonate in banana cv. Enano Gigante

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Control of crown rot with potassium carbonate in banana cv. Enano Gigante

Incidence of banana postharvest crown rot caused by artificial infection with Colletotrichum musae can be reduced by 91.6% with treatments of potassium carbonate, a ‘generally recognized as safe’ (GRAS) substance, at 175 mM.


Abstract

The postharvest antifungal activity of potassium carbonate (PC) against crown rot (CR) was investigated in banana cv. Enano Gigante by artificially inoculating with Colletotrichum musae (Cm) and incubating at 25 ± 1°C for 7 days. PC treatments were tested by in vitro and in vivo primary experiments. The in vivo preliminary concentration of 175 mM PC was selected as the most effective and was used in subsequent experiments on the influence of dip temperature on the effectiveness of PC. Curative dip treatments of 175 mM PC at 40°C for 20 min applied alone or combined with low doses of thiabendazole (TBZ) were evaluated on CR. Finally, the effect of PC on banana fruit quality was determined. PC at 150 and 200 mM totally inhibited mycelial growth and conidial germination of Cm. In in vivo primary experiments, 175 mM PC significantly reduced both the incidence (33.3% reduction) and the severity (90.5% reduction) of CR, but only in curative treatments. When the 175 mM PC dip for 20 min was tested at different temperatures, the curative dip at 40°C was the most effective, reducing CR incidence and severity by 91.6% and 98.8%, respectively, and was used for subsequent experiments. PC combined with TBZ at 225 μL L−1 did not improve the curative control effectiveness on CR compared to PC alone. PC did not affect the quality of banana fruit.

Genome‐wide association mapping for field spot blotch resistance in South Asian spring wheat genotypes

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Abstract

Spot blotch caused by Bipolaris sorokiniana ((Sacc.) Shoemaker) (teleomorph: Cochliobolus sativus [Ito and Kuribayashi] Drechsler ex Dastur) is an economically important disease of warm and humid regions. The present study focused on identifying resistant genotypes and single-nucleotide polymorphism (SNP) markers associated with spot blotch resistance in a panel of 174 bread spring wheat lines using field screening and genome-wide association mapping strategies. Field experiments were conducted in Agua Fria, Mexico, during the 2019–2020 and 2020–2021 cropping seasons. A wide range of phenotypic variation was observed among genotypes tested during both years. Twenty SNP markers showed significant association with spot blotch resistance on 15 chromosomes, namely, 1A, 1B, 2A, 2B, 2D, 3A, 3B, 4B, 4D, 5A, 5B, 6A, 6B, 7A, and 7B. Of these, two consistently significant SNPs on 5A, TA003225-0566 and TA003225-1427, may represent a new resistance quantitative trait loci. Further, in the proximity of Tsn1 on 5B, AX-94435238 was the most stable and consistent in both years. The identified genomic regions could be deployed to develop spot blotch-resistant genotypes, particularly in the spot blotch-vulnerable wheat growing areas.

Physiological and hormonal responses of drought‐stressed Eucalyptus seedlings infected with Neofusicoccum kwambonambiense

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Physiological and hormonal responses of drought-stressed Eucalyptus seedlings infected with Neofusicoccum kwambonambiense

Water stress increased Eucalyptus globulus predisposition to Neofusicoccum kwambonambiense infection and may also have promoted a change in the lifestyle of the fungus.


Abstract

The contribution of Eucalyptus globulus plantations to timber production for pulp, paper and energy production may be hampered by climate change. It is expected that Eucalyptus productivity may be affected through drought stress and changes to both pathogen distribution/pathogenicity and host–pathogen interactions. The impact of the fungal pathogen Neofusicoccum kwambonambiense on E. globulus, causing cankers and dieback, is well known but the impact of drought on disease development is still understudied. Our aim was to study the effect of drought on N. kwambonambiense infection by inoculating E. globulus plants under well-watered conditions or with water limitation. Non-infected plants for both water regimes were also analysed. Morphophysiological, biochemical and hormonal parameters were assessed 65 days post-inoculation. Inoculation under conditions of water stress decreased water potential and photosynthetic efficiency and increased abscisic acid, jasmonic acid and lipid peroxidation. Water-stressed infected plants also showed higher fungal colonization and external lesion length in comparison with well-watered inoculated plants. Our results indicate that drought increased E. globulus predisposition to N. kwambonambiense infection and may also have promoted a change in the lifestyle of the fungus. Identifying host–pathogen interaction responses under different stress conditions is necessary to provide knowledge for decision-making in the management of forest systems in general and of Eucalyptus production in particular.

Uncovering the hidden hosts: Identifying inoculum reservoirs for Phytophthora pseudosyringae in Nothofagus forests in Chile

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Uncovering the hidden hosts: Identifying inoculum reservoirs for Phytophthora pseudosyringae in Nothofagus forests in Chile

First study in the Southern Hemisphere on Phytophthora pseudosyringae life cycle in Nothofagus forests and its first detection in Persea lingue leaves.


Abstract

Mortality of Nothofagus trees in native forests in Chile has been observed for more than 30 years. Phytophthora pseudosyringae was identified as the causal agent of partial defoliation and bleeding cankers on Nothofagus obliqua and N. alpina. Nevertheless, to improve the conservation of natural resources it is crucial to determine potential native hosts that may act as inoculum reservoirs. Two N. obliqua stands were visited and all native plant species with symptoms resembling those caused by Phytophthora spp. were examined. Seven isolates from cortical and foliar tissues were isolated and subsequentially identified as P. pseudosyringae. Pathogenicity tests were carried out on eight species from a native forest. P. pseudosyringae caused cankers in N. obliqua, N. dombeyi and Persea lingue. Under natural conditions, no symptoms were detected on leaves of Cryptocarya alba, N. dombeyi, N. obliqua or Peumus boldus, but lesions were formed in inoculation assays under a controlled environment, suggesting that these species may act as hosts. Leaf necrosis in P. lingue was observed in both natural and controlled conditions. P. pseudosyringae can sporulate on lesions of C. alba, N. dombeyi and N. obliqua leaves. In Sophora macrocarpa, sporulation was observed both on asymptomatic tissues and on lesions. The frequent association of S. macrocarpa in the understorey of Nothofagus spp. strengthens the putative role of S. macrocarpa as an inoculum reservoir for epidemic events in Nothofagus. This is the first study carried out in the Southern Hemisphere on the life cycle of P. pseudosyringae in native Nothofagus forests.

Levan differentially primes barley defence against infections by Fusarium graminearum, Rhizoctonia solani and Pyricularia oryzae

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Levan differentially primes barley defence against infections by Fusarium graminearum, Rhizoctonia solani and Pyricularia oryzae

Levan could induce distinct pathways in response to different pathogens.


Abstract

The widespread use of pesticides poses significant challenges to the safety of agricultural products and the ecological environment. Levan-type fructans have the ability to act as an induced resistance stimulus, enhancing plant disease resistance, which aligns with the principles of green development. This study showed that levan polysaccharide, produced by Halomonas smyrnnensis levansucrase, could induce the resistance of barley to Fusarium graminearum much better than inulin-type fructans or low-molecular-weight chitosan oligosaccharide. Three different application methods of levan, namely seed soaking, leaf spraying or their combination, all decreased the necrotic areas caused by F. graminearum and Rhizoctonia solani. When inoculated with F. graminearum, the content of hydrogen peroxide, proline or jasmonic acid and the activities of peroxidase and ascorbate peroxidase in levan-treated barley were higher than those in the control. In contrast, when inoculated with R. solani, the hydrogen peroxide content and peroxidase activity in levan-treated leaves showed a faster induction than the control at the early priming and the content of proline and methyl salicylate was higher than that of the control. Thus, levan induces distinct pathways in response to different pathogens.

Wheat stripe mosaic virus from Brazil and South Africa evolved as distinct subpopulations with low genetic variability

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Wheat stripe mosaic virus from Brazil and South Africa evolved as distinct subpopulations with low genetic variability

Phenotyping and sequencing reveal that wheat stripe mosaic virus (WhSMV) in Brazil is genetically homogeneous constituting a distinct subpopulation, more variable than the South African population.


Abstract

Wheat stripe mosaic virus (WhSMV) is the causal agent of soilborne wheat mosaic disease (SBWMD) in Brazil, which is a serious threat to wheat production in the southern part of the country. WhSMV also occurs in Paraguay and South Africa. The virus is soilborne, transmitted by Polymyxa graminis, and management strategies are mainly based on genetic resistance. Variation in the reaction (type and severity of symptoms) of cultivars has been reported depending on the region and/or year of cultivation, leading wheat breeding programmes to test their materials in several locations, which increases costs and is time-consuming. One hypothesis is that this variation in symptoms is a result of the genetic variability of WhSMV. We assessed the genetic variability and population structure of WhSMV infecting wheat in Brazil and South Africa. In field experiments conducted in different locations in southern Brazil, a consistent reproducibility of symptoms was observed in a set of cultivars, and molecular analysis showed a low degree of genetic variability of the Brazilian viral population. The hypothesis that the variation in SBWMD symptoms in Brazil is due to genetic variability of the virus was thus rejected. Comparison of the Brazilian and South African WhSMV isolates indicated that they comprise distinct subpopulations and that the Brazilian subpopulation is more variable than the South African subpopulation. The lower genetic variability of the South African subpopulation suggests genetic stability or a recent emergence of WhSMV in that region.