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A new genus and species of Cryphonectriaceae causing stem cankers on plantation eucalypts in South Africa

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A new genus and species of Cryphonectriaceae causing stem cankers on plantation eucalypts in South Africa

A causal agent of a stem canker disease on eucalypts discovered in KwaZulu-Natal province is clarified as a new genus in the Cryphonectriaceae, for which the name Xanthoporthe myrticola is provided.


Abstract

Fungi in the Cryphonectriaceae are important canker pathogens of woody shrubs and trees in the Melastomataceae and Myrtaceae (Myrtales). During 2021 disease surveys in KwaZulu-Natal (South Africa) plantations, a serious stem canker disease was discovered on species of Eucalyptus and Corymbia. The cankers had structures on their surfaces typical of fungi in the Cryphonectriaceae. The aims of the study were to identify the fungus associated with the disease and to test its pathogenicity. Morphological characteristics of both sexual and asexual structures and phylogenetic analyses based on partial sequences of the conserved nuclear large subunit (LSU) ribosomal DNA, the internal transcribed spacer (ITS) regions including the 5.8S gene of the ribosomal DNA operon, and two β-tubulin (BT1/BT2) regions were used for identification purposes. Phylogenetic analyses of the sequence data and morphological characteristics supported the establishment of a new genus in the Cryphonectriaceae, for which the name Xanthoporthe myrticola gen. et sp. nov. is provided. Pathogenicity trials showed that isolates were pathogenic on tested Eucalyptus grandis and hybrids as well as Corymbia henryi. The results suggest that this is an emerging pathogen that could influence the sustainability of plantation forestry in South Africa.

Barley powdery mildew control in Western Australia and beyond

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Barley powdery mildew control in Western Australia and beyond

This review discusses the challenging nature of barley powdery mildew and management strategies used in Western Australia, and the wider context of how scientists and breeders have responded to epidemics.


Abstract

Australia is one of the largest barley exporters in the world, with Western Australia accounting for some 40% of national production. The crop is predominantly grown in the south and south-west of the state in winter and spring, where temperate conditions and higher rainfall levels are more suited to barley than northern and eastern regions. Between 2007 and 2013, prolonged outbreaks of barley powdery mildew (BPM) occurred. This was brought about by a combination of the extensive use of susceptible cultivars and an over-reliance on a small number of single mode-of-action demethylation inhibitor fungicides, which select for mutations in the C14α-demethylase (Cyp51A) gene. This review highlights the steps taken to reduce losses to BPM, breeding efforts to introduce resistance into cultivars and the success of pre-breeding research to find new and durable resistance genes. We also draw comparisons with powdery mildew in Australian wheat, where similar factors are leading to substantial outbreaks.

Passionfruit severe leaf distortion virus: Expanded host range, response of Passiflora spp. plants to infection and transmission by Bemisia tabaci MEAM1

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Passionfruit severe leaf distortion virus: Expanded host range, response of Passiflora spp. plants to infection and transmission by Bemisia tabaci MEAM1

Passion fruit severe leaf distortion virus was not transmitted by Bemisia tabaci to plants of three out of 13 Passiflora species tested. Only P. malacophylla plants grafted onto PSLDV-infected passion fruit plants were not infected.


Abstract

Passionfruit severe leaf distortion virus (PSLDV) is a begomovirus transmitted by Bemisia tabaci Middle East-Asia Minor 1 (MEAM1), associated with severe disease in passion flowers. This study aimed to evaluate the reaction of plants of different species of Passiflora to infection with PSLDV, expand the known host range of the virus and determine the minimum virus acquisition and inoculation access periods and the time of virus retention by B. tabaci MEAM1. Plants of Passiflora cincinnata, P. mucronata and P. malacophylla were not infected with PSLDV through transmission with B. tabaci MEAM1. When healthy plants of these species were fork grafted onto PSLDV-infected plants of P. edulis, only plants of P. malacophylla remained uninfected and the virus was not detected by PCR, suggesting immunity to this begomovirus. Plants of Datura stramonium, Nicotiana benthamiana, N. clevelandii, N. tabacum ‘Xanthi’, Solanum lycopersicum (tomato cv. Compack) and several varieties of Manihot esculenta (cassava cvs IAC 118-96, IAC 6-01, Paranavaí, IAC 576, IAC 90 and IAC 14) were susceptible to infection with PSLDV through transmission with B. tabaci MEAM1. Adults of B. tabaci MEAM1 acquired PSLDV after 1 h of feeding on PSLDV-infected plants of D. stramonium. They transmitted the virus to healthy plants after feeding on these plants for 1 h, although with low transmission rates. The retention time of PSLDV in the vector was 14 days.

Phylogenetic, metabolic and pathogenic characteristics of Alternaria alternata strains from wheat in China

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Phylogenetic, metabolic and pathogenic characteristics of Alternaria alternata strains from wheat in China

Alternaria alternata dominated in wheat grains from China with high toxin production capacity and distinct pathogenicity to wheat and apple.


Abstract

Alternaria is an important toxigenic fungal genus endangering the quality of cereal grains. No data are available in the literature regarding the composition of Alternaria species in wheat from the main wheat-cultivating regions of China. In this study, a total of 282 strains were isolated from wheat kernels collected in various provinces. Phylogenetic characterization was performed using two informative loci, ASA10 and ASA19, demonstrating that all strains belonged to A. alternata. A low molecular diversity was observed, which did not appear to be influenced by geographic origin. The secondary metabolite profile of the strains was evaluated in rice culture. Altertoxin I was synthesized at a high concentration by the majority of the strains, while the accumulation of altenuene was lower in both frequency and level than that of alternariol and its derivative. A. alternata did not cause readily observable symptoms on wheat spikes after spraying of the conidia at anthesis, but a higher quantity of altertoxin I and Alternaria DNA were detected in inoculated grains. Artificial inoculations of apple fruit showed that all examined strains were capable of causing typical rot symptoms and producing all four toxins to a certain degree. The widespread occurrence of A. alternata on wheat grains and its ability to synthesize various toxic metabolites may pose a serious hazard for both growers and consumers.

A Bayesian optimization R package for multitrait parental selection

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Abstract

Selecting and mating parents in conventional phenotypic and genomic selection are crucial. Plant breeding programs aim to improve the economic value of crops, considering multiple traits simultaneously. When traits are negatively correlated and/or when there are missing records in some traits, selection becomes more complex. To address this problem, we propose a multitrait selection approach using the Multitrait Parental Selection (MPS) R package—an efficient tool for genetic improvement, precision breeding, and conservation genetics. The package employs Bayesian optimization algorithms and three loss functions (Kullback–Leibler, Energy Score, and Multivariate Asymmetric Loss) to identify parental candidates with desirable traits. The software's functionality includes three main functions—EvalMPS, FastMPS, and ApproxMPS—catering to different data availability scenarios. Through the presented application examples, the MPS R package proves effective in multitrait genomic selection, enabling breeders to make informed decisions and achieve strong performance across multiple traits.

Optimization of concentration parameters for maximizing bacteriophage recovery value using response surface methodology: A case study on determining the optimal concentration parameters for Erwinia amylovora EA1T1.B3 phage

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Optimization of concentration parameters for maximizing bacteriophage recovery value using response surface methodology: A case study on determining the optimal concentration parameters for Erwinia amylovora EA1T1.B3 phage

Response surface methodology combined with a three-factor central composite design optimized recovery in phage concentration, achieving a maximum recovery rate of 85.37% with 18% PEG, 2.38 M NaCl, and 0 h incubation time.


Abstract

Bacteriophages have emerged as effective antimicrobial agents in combating pathogenic bacteria. To successfully apply phages in real-life scenarios, it is crucial to optimize their large-scale production, concentration and purification processes. In this study, our objective was to optimize the phage concentration parameters with a high recovery rate within a shorter time and minimum chemical consumption. We isolated and characterized a specific Erwinia amylovora phage. Subsequently, we employed response surface methodology (RSM) combined with a three-factor central composite design to optimize the phage recovery. The factors considered were polyethylene glycol (PEG) concentration, NaCl concentration and incubation time. The optimized values for PEG, NaCl and incubation time, which resulted in a maximum recovery rate of 85.37%, were determined as 18%, 2.38 M and 0 h, respectively. This finding indicates that the concentration step, which traditionally took up to 18 h with a recovery rate of 65%, can now be accomplished in a significantly shorter time with an improved recovery rate. Our study demonstrates the effectiveness of RSM to identify the optimum conditions for phage precipitation. This approach allows for the rapid and efficient design of precipitation protocols tailored to specific bacteriophages, resulting in shorter processing times and higher recovery rates.

Approaches and progress in breeding drought‐tolerant maize hybrids for tropical lowlands in west and central Africa

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Abstract

Drought represents a significant production challenge to maize farmers in West and Central Africa, causing substantial economic losses. Breeders at the International Institute of Tropical Agriculture have therefore been developing drought-tolerant maize varieties to attain high grain yields in rainfed maize production zones. The present review provides a historical overview of the approaches used and progress made in developing drought-tolerant hybrids over the years. Breeders made a shift from a wide area testing approach, to the use of managed screening sites, to precisely control the intensity, and timing of drought stress for developing drought-tolerant maize varieties. These sites coupled with the use of molecular markers allowed choosing suitable donors with drought-adaptive alleles for integration into existing elite maize lines to generate new drought-tolerant inbred lines. These elite maize inbred lines have then been used to develop hybrids with enhanced tolerance to drought. Genetic gains estimates were made using performance data of drought-tolerant maize hybrids evaluated in regional trials for 11 years under managed drought stress, well-watered conditions, and across diverse rainfed environments. The results found significant linear annual yield gains of 32.72 kg ha−1 under managed drought stress, 38.29 kg ha−1 under well-watered conditions, and 66.57 kg ha−1 across multiple rainfed field environments. Promising hybrids that deliver high grain yields were also identified for areas affected by drought and variable rainfed growing conditions. The significant genetic correlations found among the three growing conditions highlight the potential to exploit the available genetic resources and modern tools to further enhance tolerance to drought in hybrids.