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Comparison of four inoculation methods and three Fusarium species for phenotyping stalk rot resistance among 22 maize hybrids (Zea mays)

Posted on 4 February 2024 by

Needle injection of Fusarium graminearum and assessment of internode proportion are the most promising methods in phenotyping maize genotypes for Fusarium stalk rot resistance in central Europe.

Abstract

Fusarium stalk rot (FSR) is among the most destructive maize diseases causing significant global yield losses. Resistance of 22 maize hybrids to FSR was tested using four inoculation methods in each of two locations in 2021 and 2022. The inoculation methods included needle injection (NI), toothpick method (TM), stick method (SM) and mycelium method (MM), and the inoculated fungi were Fusarium culmorum, F. graminearum and F. temperatum. NI displayed the highest FSR infection among maize hybrids followed by TM and SM. MM showed the least infection. From five stalk rot-related traits, full-length infection and internode proportion, that is, the percentage of visible infection summed up over internodes, captured most of the genetic variation. The latter was the trait with the highest heritability (0.90). No significant (p > 0.05) genotype × method and genotype × fungus interaction variances were observed for any traits. For F. graminearum inoculation, NI showed the highest internode proportion followed by TM and SM, with F. culmorum responding in a similar way. For F. temperatum, TM outranked all other methods. F. graminearum was the most aggressive fungal pathogen compared to F. culmorum and F. temperatum. For phenotyping maize lines with varying degrees of resistance to FSR, we recommend needle injection and internode proportion.

Fine mapping of sterile genes in soybean (Glycine max [L.] Merril.) based on cross populations between multi‐elite parent and sterile lines ms1 and ms6

Posted on 4 February 2024 by

Abstract

The male sterile line of soybean is crucial for hybrid seed production, and has allowed significant advancements in soybean germplasm innovation and yield increase in China. In this study, we created two bulks of sterile plants and collected a natural population consisting of 100 elite soybean germplasms. There were significant phenotypic differences between the sterile and natural populations resulting from flowers and pods. The sterile plants exhibited fleshy spherical pods and large black-green leaves in the maturity stage, while the leaves of the fertile plants fell off. After I₂-KI staining, the pollen of the sterile line turned light brown and yellow, while the pollen of the fertile line turned black. On the basis of the SNP sequencing results, the sterility genes were located on eight chromosomes. Additionally, they were fine-mapped to 13 regions on six chromosomes using 72 pairs of SSR markers. Five genes involved in auxin response and pollen development were predicted as candidate genes underlying soybean sterility. These candidate genes for soybean sterility will help with gene cloning and functional analysis and accelerate the widespread use of hybrid seed production and yield increase in soybean grown in cool regions.

Comparative analysis of Argentinian and European populations of Ramularia collo‐cygni on barley

Posted on 1 February 2024 by

Argentinian Ramularia collo-cygni population shows lower diversity and higher structuring than European populations, suggesting the occurrence of a founder effect and an ongoing establishment phase.

Abstract

Ramularia collo-cygni (Rcc) is a major barley pathogen that causes yield and grain quality losses worldwide. The main sources of Rcc inoculum are the seed and asexual airborne spores. In Argentina, Rcc is considered to be an emerging threat to barley crops, especially as most varieties are susceptible to Rcc and have a European genetic background. Here, we describe the population genetic diversity and structure of the Argentinian Rcc population, based on 10 simple-sequence repeat (SSR) markers, in order to compare it with Rcc populations from the Czech Republic and Scotland. The Argentinian Rcc population showed lower genetic diversity, higher level of structuring and higher number of clonal isolates than European populations. Significant differentiation at population origin (country) and region (Europe and South America) level suggests the occurrence of a genetic bottleneck and/or a founder effect on Rcc entry to Argentina and that this population could still be in a state of establishment and emergence. Further research on Rcc genetic structure at local and global scale will be crucial for the understanding of Rcc population dynamics for disease management.

Species diversity of fusarioid genera associated with sweet potato in Brazil, including the description of a new species

Posted on 30 January 2024 by

This is the first report of Fusarium agrestense, Fusarium annulatum, Fusarium caatingaense, Fusarium elaeidis, Fusarium pernambucanum, Fusarium pseudocircinatum, Neocosmospora falciformis and Neocosmospora suttoniana associated with root and stem rot of sweet potato.

Abstract

The sweet potato is of great socioeconomic importance in Brazil and throughout the world. Among the fungal pathogens associated with root diseases of this crop, Fusarium is of particular importance due to the diversity of species, the pathogenic potential in their various hosts and their ability to survive inside plants as endophytes without apparently causing damage. The objective of this work was to identify fusarioid genera from stems and roots of symptomatic and asymptomatic plants. The identification of fungal species was based on multilocus phylogenetic analysis and morphology. A total of 51 isolates, distributed in the Fusarium incarnatum-equiseti species complex (FIESC), Fusarium fujikuroi species complex (FFSC), Fusarium oxysporum species complex (FOSC)—with a taxonomic novelty—and Neocosmospora were identified. The pathogenicity test on roots showed that 13 of the 14 tested isolates obtained from symptomatic roots and stems and from asymptomatic stems were capable of reproducing the rot symptoms observed in the field. The confirmation of the pathogenicity of isolates from asymptomatic stems corroborates the hypothesis that these fungi can live endophytically in asymptomatic tissue and are capable of causing damage to their hosts in stress situations. This is the first report of Fusarium agrestense, Fusarium annulatum, Fusarium caatingaense, Fusarium elaeidis, Fusarium pernambucanum, Fusarium pseudocircinatum, Neocosmospora falciformis and Neocosmospora suttoniana associated with root and stem rot of sweet potato.

Genetic analysis and molecular mapping of fruit‐bearing habit locus (Bh1) in eggplant (Solanum melongena L.)

Posted on 30 January 2024 by

Abstract

In eggplant, two kinds of fruit-bearing habits can be observed, that is, cluster and solitary. The fruits grown in cluster are small in size but contribute towards yield and productivity. In this investigation, we have studied the genetics of fruit-bearing habit and identified the SSR markers linked to this trait. Pusa Safed Baingan 1 (cluster bearer) and Pusa Hara Baingan 1 (solitary bearer) having contrasting traits were crossed to generate F₁ (20 plants), F₂ (215 plants), B₁ (73 plants) and B₂ (64 plants). Genetic analysis of the trait was carried out using Chi-square test. The segregation of plants in F₂ suggested recessive epistasis with ratio of 9:3:4 (solitary: mixed: cluster) indicating involvement of two genes for controlling the fruit-bearing habit. The parental polymorphic 6 SSR markers were used for genotyping F₂ plants and co-segregated with the fruit-bearing habit (Bh ¹ ) locus in 1:2:1. A linkage map covering 63.86 cm distance was developed, the SSR marker emf11A03 was closest with a distance of 4.37 cm, emk03O04 at 12.5 cm distance, and emf21O06 at 14.5 cm. The physical positions of the SSR markers emb01J19 and emf11A03 flanking Bh ¹ gene were located at 4.77 mb position of contig Sme2.5_05721.1 and 5.18 Mb position of contig Sme2.5_00994.1, respectively. The findings in the present study will be helpful in marker-assisted breeding to enhance yield in eggplant.

Overexpression of an NLP protein family member increases virulence of Verticillium dahliae

Posted on 30 January 2024 by

The role of VdNEP, an NLP protein gene, in virulence was investigated by overexpressing the gene in multiple pathotypes and monitoring its cellular localization during infection.

Abstract

Verticillium dahliae is a xylem-invading fungal pathogen that causes vascular wilt in a wide range of angiosperms. The pathogen uses a variety of virulence factors to invade and colonize its hosts. Here, we report that VdNEP, an NLP (Necrosis and ethylene inducing peptide 1-Like Protein), functions as one such factor in multiple hosts. Eggplant leaves treated with VdNEP developed necrotic symptoms. Overexpression of VdNEP by incorporating extra copies of the VdNEP gene increased virulence to cotton, eggplant and tomato plants, suggesting its role as a virulence factor in diverse plants. Increased expression of VdNEP among the transformants did not correlate with the number of VdNEP inserts, suggesting that its expression was affected by the genomic context of the insertion sites. Interestingly, a transformant derived from a defoliating strain with high VdNEP transcript levels caused disease symptoms in tomato plants, whereas the corresponding wild-type strain did not cause visible symptoms. The amount of V. dahliae DNA in plants infected with this VdNEP-overexpressing transformant was 22 times higher than that in plants infected with the wild-type isolate, further supporting the critical role of VdNEP in infection. A VdNEP-EGFP fusion was constructed to follow its localization in fungal cells and during infection.

Unravelling the aetiology of Dickeya zeae using polyphasic approaches for bacterial stalk rot in maize

Posted on 30 January 2024 by

This study identifies and molecularly characterizes Dickeya zeae isolates from bacterial stalk rot of maize, using six genomic regions (16S rRNA, recN, gyrB, dnaX, recA and dnaJ) using multiple phylogenetic analyses.

Abstract

Bacterial stalk rot (BSR), caused by Dickeya zeae (syn. Erwinia chrysanthemi pv. zeae), has emerged as a significant disease affecting maize crops worldwide. In this study, symptomatic maize plants were collected from diverse agroclimatic zones in India over the period of kharif 2019–2021. Various approaches, including pathogenicity tests, cultural characteristics, biochemical profiling and molecular analysis, were employed to accurately identify the collected bacterial isolates as Dickeya. Pathogenicity assessments were conducted on 40-day-old maize plants, following Koch's postulates, as well as through potato maceration assays. Furthermore, cross-infectivity studies were conducted on rice, potato, tomato and banana plants. Phenotypic and biochemical characterization confirmed that all the isolates belonged to the Dickeya genus. Additionally, PCR amplification of a pel gene fragment, specific to the genus Dickeya, further verified the pathogenic isolates as Dickeya. Molecular characterization studies were performed on four isolates (UKMDZ-3, PBMDZ-7, TSMDZ-11 and HPMDZ-16), selected to represent distinct maize agroclimatic zones and four states of India, and which caused severe infections on susceptible maize cv. Early Composite. Amplification of six characteristic genome regions (16S rRNA, recN, gyrB, dnaX, recA and dnaJ) from these isolates facilitated individual and concatenated gene phylogenetic analyses, confirming their resemblance to Dickeya zeae. This study represents the first comprehensive molecular analysis of D. zeae isolates from India, providing valuable insights for future crop improvement strategies. The findings contribute to our understanding of the genetic basis of BSR in maize and offer potential avenues for genetic enhancement to mitigate the disease's impact on maize cultivation.

Rice leaf disease detection based on enhanced feature fusion and target adaptation

Posted on 28 January 2024 by

The proposed EFFTAN model was validated for robustness and generalization of four rice leaf spot data plus maize data samples, and the experimental data demonstrated the significance and validity of the research work.

Abstract

Intelligent rice disease recognition methods based on deep neural networks can predict the degree of disease on the basis of, for example, the number of disease spots on an image, so that preventive measures can be taken. Currently, intelligent recognition methods for rice diseases suffer from the disadvantages of poor versatility and low accuracy. This paper uses eight common image classification networks to classify and identify four rice diseases. ResNet50 was selected as the feature extraction network and an enhanced feature fusion and target adaptive network (EFFTAN), referred to as EFFTAN, is proposed. The EFFTAN was used to detect four rice spot diseases in the rice leaf disease image samples dataset; the mean average precision of the final detection was 95.3%, and effective detection was also achieved for the dense spot features.

Special Issue on Breeding and breeding research for resistance to Fusarium diseases in cereals

Posted on 25 January 2024 by

Plant Breeding, Volume 143, Issue 1, Page 1-1, February 2024.

Differential expression of antimicrobial metabolites, phenylpropanoid and phytohormone metabolic pathway genes determines resistance or susceptibility to Ascochyta rabiei in chickpea

Posted on 25 January 2024 by

Defence to Ascochyta rabiei in chickpea is composed of a two-tier system separated by time wherein jasmonic acid, phenylpropanoids, antimicrobial peptides and defence genes govern resistance and abscisic acid susceptibility.

Abstract

Blight caused by Ascochyta rabiei is a major constraint in the productivity of chickpea (Cicer arietinum). The mechanisms governing resistance/susceptibility to blight in chickpea are poorly understood. We used a blight-resistant (HC1) and a blight-susceptible (GPF2) genotype of chickpea and genes of pathogenesis-related proteins (PRPs), phenylpropanoid pathway metabolites, abscisic acid (ABA), gibberellic acid (GA) and jasmonic acid (JA) to understand the role of these in A. rabiei resistance/susceptibility. The JA, ABA and GA biosynthesis genes of chickpea were retrieved, characterized and gene-specific primers were used for transcriptional studies. Gene expression revealed that chickpea activated its defences rather quickly and well before initiation of spore germination. In resistant HC1, the majority of the JA, GA and phenylpropanoid pathway genes had peak maxima at 2 h post-inoculation (hpi) whereas PRPs/defence genes had peak maxima at 24/36 hpi implying that defence to A. rabiei in chickpea is composed of a two-tier system separated by time: immediately after spore attachment and at or just prior to host penetration. Unlike HC1, susceptible GPF2 was late in activation of defence responses or did not activate them. Another striking difference between HC1 and GPF2 was up-regulation of ABA biosynthesis genes in inoculated GPF2 and down-regulation in HC1. This study revealed that phenylpropanoids, PRPs, JA, 8-(1R,2R)-3-oxo-2-(Z)-pent-2-enyl cyclopentyl octanoate, (15Z)-12-oxophyto-10,15-dienoic acid and methyl-jasmonate govern resistance to A. rabiei in chickpea whereas ABA governs susceptibility.