Walnut Blight and Apical Necrosis

Garcin, A.; Duchesne, D.

doi:10.17660/actahortic.2001.544.50

Cited by 8 publications

(6 citation statements)

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“…During the last 15-20 years, an additional severe syndrome, the so-called "apical necrosis" of fruit, has been more frequently observed on J. regia cultivars for which Xaj plays a fundamental role in causing such a symptom [1]. So far, this syndrome has been reported in Mediterranean countries and California [2,3] (Figure 2). …”

Section: Introductionmentioning

confidence: 99%

Multilocus Sequence Typing Reveals Relevant Genetic Variation and Different Evolutionary Dynamics among Strains of Xanthomonas arboricola pv. juglandis

Marcelletti¹,

Ferrante²,

Scortichini³

2010

Diversity

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Forty-five Xanthomonas arboricola pv. juglandis (Xaj) strains originating from Juglans regia cultivation in different countries were molecularly typed by means of MultiLocus Sequence Typing (MLST), using acnB, gapA, gyrB and rpoD gene fragments. A total of 2.5 kilobases was used to infer the phylogenetic relationship among the strains and possible recombination events. Haplotype diversity, linkage disequilibrium analysis, selection tests, gene flow estimates and codon adaptation index were also assessed. The dendrograms built by maximum likelihood with concatenated nucleotide and amino acid sequences revealed two major and two minor phylotypes. The same haplotype was found in strains originating from different continents, and different haplotypes were found in strains isolated in the same year from the same location. A recombination breakpoint was detected within the rpoD gene fragment. At the pathovar level, the Xaj populations studied here are clonal and under neutral selection. However, four Xaj strains isolated from walnut fruits with apical necrosis are under diversifying selection, suggesting a possible new adaptation. Gene flow estimates do not support the hypothesis of geographic isolation of the strains, even though the genetic diversity between the strains increases as the geographic distance between them increases. A triplet deletion, causing the absence of valine, was found in the rpoD fragment of all 45 Xaj strains when compared with X. axonopodis pv. citri strain 306. The codon adaptation index was high in all four genes studied, indicating a relevant metabolic activity

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Section: Introductionmentioning

confidence: 99%

Multilocus Sequence Typing Reveals Relevant Genetic Variation and Different Evolutionary Dynamics among Strains of Xanthomonas arboricola pv. juglandis

Marcelletti¹,

Ferrante²,

Scortichini³

2010

Diversity

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“…Walnut blight, caused by Xaj, is one of the most important diseases of walnut and can cause severe economic loss (Garcin and Duchesne, 2001). Yet, the mechanisms of walnut response to this infection are poorly understood.…”

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confidence: 99%

Induction of Polyphenol Oxidase in Walnut and Its Relationship to the Pathogenic Response to Bacterial Blight

Khodadadi

Tohidfar

Mohayeji

et al. 2016

J. Amer. Soc. Hort. Sci.

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Plants respond to pathogens with both active and passive defense mechanisms. These defense responses include the induction of defense or defense-related genes such as polyphenol oxidase (PPO) and pathogenesis-related (PR) proteins. The role of PPO in the interaction between bacterial blight [Xanthomonas arboricola pv. juglandis (Xaj)] and walnut (Juglans regia) was studied. JrPPO-1 and P14a genes were identified in two walnut cultivars, Chandler and Serr, using standard polymerase chain reaction (PCR) to understand their inducible ability in response to Xaj. ‘Serr’ and ‘Chandler’ were inoculated with Xaj strain 417. PPO activity in leaves was assayed at 0, 24, 72, 96, 120, and 144 hours after inoculation. Results showed a steady increase in activity commencing within 24 hours of inoculation. Increase in PPO activity was close to 2-fold greater in ‘Chandler’ than in ‘Serr’ at all time points examined. Real-time PCR analysis showed differences between cultivars in PPO gene expression. The JrPPO-1 gene was highly expressed in both cultivars 24 hours after inoculation but expression in ‘Serr’ was much greater than in ‘Chandler’. Significant expression of P14a gene was observed in both cultivars within 24 hours. Expression in ‘Serr’ was strong and maximized with a significant increase at 96 hours. Expression in ‘Chandler’ was far weaker than ‘Serr’ at 24 hours and did not increase further. Our results imply that the walnut–bacterial blight interaction induces the expression of JrPPO-1 and P14a as well as the activity of PPO.

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“…It has been noted that nutrient deficiency and soil properties (acidity, light texture, low manganese and magnesium content, and phosphorus and calcium deficiency) in addition to microbial infection could predispose trees to be infected and increase the severity of apical necrosis [1]. This pathology could also be related to climatic factors such as rainfall or temperature.…”

Section: Molecular Methodsmentioning

confidence: 99%

“…Xanthomonas campestris pv. juglandis) is an important pathology affecting up to 50% of a walnut cultivar (Juglans regia L.) yield, as reported in France [1]. At a global scale, this disease occurs practically in all the countries where walnut trees are grown.…”

Section: Introductionmentioning

confidence: 99%

First Report of Apical Necrosis in Walnut Cultivars from Northern Argentinean Patagonia

Temperini¹,

Pardo²,

Pose³

2017

J Plant Pathol Microbiol

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Walnut blight caused by Xanthomonas arborícola pv. juglandis and apical necrosis are severe diseases that cause premature drop of walnuts all around the world. Evidence from previous studies proposes Xanthomonas arborícola pv. juglandis together with Fusarium spp. and Alternaria spp. as causal agents of apical necrosis. While walnut blight is a well-known pathology in Argentina, apical necrosis has not been reported yet in this country. However, during 2013 and 2014 seasons, serious damages were registered in the nut producing region of Río Negro Middle Valley in northern Argentinean Patagonia. Diseased fruits exhibited symptoms that matched those described for walnut blight and apical necrosis. Therefore, the aim of this study was to determine the incidence of these pathologies and the microorganisms involved in their etiology. As a result, it was possible to identify morphologically and molecularly the bacteria isolated from damaged fruits, confirming their identity as Xanthomonas arborícola pv. juglandis. Moreover, A. tenuissima was found in a high prevalence in damaged as well as in healthy fruits, whereas Fusarium spp. was isolated with a low frequency in both. When pathogenicity tests were performed, it was demonstrated the ability of the three microorganisms to produce typical lesions in healthy nuts. Thus, we can presume that both diseases occurred during this couple of years in this region. This is the first report of apical necrosis in Argentina

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Walnut Blight and Apical Necrosis

Cited by 8 publications

References 0 publications

Multilocus Sequence Typing Reveals Relevant Genetic Variation and Different Evolutionary Dynamics among Strains of Xanthomonas arboricola pv. juglandis

Multilocus Sequence Typing Reveals Relevant Genetic Variation and Different Evolutionary Dynamics among Strains of Xanthomonas arboricola pv. juglandis

Induction of Polyphenol Oxidase in Walnut and Its Relationship to the Pathogenic Response to Bacterial Blight

First Report of Apical Necrosis in Walnut Cultivars from Northern Argentinean Patagonia

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