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<p>Similar to <i>Salicornia europaea</i>, <i>S. brachiata</i> is a highly resilient halophytic crop with agronomic and commercial importance owing to its wide range of applications in food, pharmaceutical, and industrial biotechnology<i>.</i> Due to its high adaptability to marginal environments, the plant is considered less affected by diseases and information on diseases affecting <i>Salicornia</i> spp. remains limited. As part of an agronomic optimization field experiment, S<i>. brachiata</i> cultivated in a coastal area of Sri Lanka showed unexpectedly sever disease outbreaks consecutively in the 2023 and 2024 growing seasons. Disease incidence ranged from 45–50% in mid- to late-vegetative stages. Affected individuals exhibited wilting, chlorosis, crown rot, and root necrosis, prompting a systematic investigation to identify the causal agent and evaluate potential control strategies. Pathogen isolations from symptomatic tissues consistently yielded a melanized fungus, identified as <i>Macrophomina phaseolina</i> along with a less frequently isolated species identified as <i>Fusarium falciforme</i>, based on morphological characteristics and molecular analyses. Pathogenicity assays confirmed <i>M. phaseolina</i> as the primary causal agent, causing 73% disease incidence 28&#xa0;days after inoculation, whereas <i>F. falciforme</i> resulted in 7% disease incidence, and mixed inoculations significantly increased disease incidence to 100%<i>. In vitro</i> salinity tolerance assays revealed that <i>M. phaseolina</i> could tolerate up to 10% w/v NaCl concentration and seawater concentration up to 100% v/v, whereas <i>F</i>. <i>falciforme</i> showed reduced growth and suppressed macroconidia production under both conditions. Among the tested fungicides, Captan® and Ridomil® showed a 100% inhibitory effect against <i>M. phaseolina</i>, consistently across all tested concentrations (500–2500&#xa0;ppm), regardless of the prescence of NaCl in the PDA (0–5% NaCl). These findings challenge the assumption that halophytic crops are inherently protected from soilborne pathogens and underscore the emerging risk of salt-tolerant pathogens in saline agriculture systems. The identification of <i>M. phaseolina</i> as the primary causal agent of crown and root rot, alongside <i>F. falciforme</i> acting as a secondary synergist, fills a critical knowledge gap on disease threats to this resilient crop and saline agriculture.</p>

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Halotolerant Macrophomina phaseolina causing severe root and crown rot of Salicornia brachiata: Field outbreaks in Sri Lanka and implications for halophyte cultivation

  • 期刊论文

  • 发表日期：

    2026年7月3日

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  • Lakshani Thilakarathna,
  • Kalmi Siridewa,
  • Chamara L. Mendis,
  • Ambalikka Kulakalaharan,
  • Priyangi Edirisinghe,
  • Chaminda Egodawatta,
  • Dinum Perera,
  • Renuka N. Attanayake

摘要

Similar to Salicornia europaea, S. brachiata is a highly resilient halophytic crop with agronomic and commercial importance owing to its wide range of applications in food, pharmaceutical, and industrial biotechnology. Due to its high adaptability to marginal environments, the plant is considered less affected by diseases and information on diseases affecting Salicornia spp. remains limited. As part of an agronomic optimization field experiment, S. brachiata cultivated in a coastal area of Sri Lanka showed unexpectedly sever disease outbreaks consecutively in the 2023 and 2024 growing seasons. Disease incidence ranged from 45–50% in mid- to late-vegetative stages. Affected individuals exhibited wilting, chlorosis, crown rot, and root necrosis, prompting a systematic investigation to identify the causal agent and evaluate potential control strategies. Pathogen isolations from symptomatic tissues consistently yielded a melanized fungus, identified as Macrophomina phaseolina along with a less frequently isolated species identified as Fusarium falciforme, based on morphological characteristics and molecular analyses. Pathogenicity assays confirmed M. phaseolina as the primary causal agent, causing 73% disease incidence 28 days after inoculation, whereas F. falciforme resulted in 7% disease incidence, and mixed inoculations significantly increased disease incidence to 100%. In vitro salinity tolerance assays revealed that M. phaseolina could tolerate up to 10% w/v NaCl concentration and seawater concentration up to 100% v/v, whereas F. falciforme showed reduced growth and suppressed macroconidia production under both conditions. Among the tested fungicides, Captan® and Ridomil® showed a 100% inhibitory effect against M. phaseolina, consistently across all tested concentrations (500–2500 ppm), regardless of the prescence of NaCl in the PDA (0–5% NaCl). These findings challenge the assumption that halophytic crops are inherently protected from soilborne pathogens and underscore the emerging risk of salt-tolerant pathogens in saline agriculture systems. The identification of M. phaseolina as the primary causal agent of crown and root rot, alongside F. falciforme acting as a secondary synergist, fills a critical knowledge gap on disease threats to this resilient crop and saline agriculture.