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<p>Seeds are often treated with fungicides and antibiotics to eliminate pathogens during propagation. However, seeds harbour complex microbial communities, including beneficial endophytes that could also be affected by seed treatments. <i>Metrosideros excelsa</i> (Myrtaceae) is a New Zealand endemic tree widely planted within the country and overseas. Seedlings of <i>M. excelsa</i> display wide variation in susceptibility to a fungal pathogen <i>Austropuccinia psidii</i>, which causes myrtle rust disease suggesting that seed-borne microbial composition may play a role in seedling protection and growth. We investigated the effects of fungicides on the beneficial seed-borne bacterial isolates, the effects of antimicrobial treatment on seedling development, the plant growth-promoting properties of the seed microbiome, and the ability of bacterial isolates to suppress pathogenic fungi. Our results show that seed-borne bacteria <i>Bacillus</i> and <i>Priestia</i> suppressed seed-borne fungi, both pathogenic and endophytic, with average inhibition rates of 74%, and several bacterial isolates reduced <i>A. psidii</i> spore germination<i> in vitro</i>. In contrast, endophytic <i>Methylobacterium</i> and <i>Mycolicibacterium</i> facilitated fungal growth. Fungicide applications are considered the most effective method to control myrtle rust disease; however, we found that fungicides may adversely impact beneficial seed-borne bacteria. Antimicrobial seed treatment also suppressed the growth of corresponding seedlings. Our experiments demonstrate that treated seeds can be further inoculated with beneficial seed-borne endophytes, increasing seedling shoot biomass up to three times. Additionally, the bacterium <i>Kocuria</i> and the fungus <i>Penicillium</i> significantly enhanced root development. These results suggest that employing seed-borne microbial isolates with growth-promoting potential may improve outcomes in nursery conditions.</p>

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Effects of fungicides on the beneficial seed-borne microbiome and seedling development of a long-lived myrtaceae tree species

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年6月1日

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  • Vladislav Kholostiakov,
  • Bruce Burns,
  • Hayley Ridgway,
  • Mahajabeen Padamsee

摘要

Seeds are often treated with fungicides and antibiotics to eliminate pathogens during propagation. However, seeds harbour complex microbial communities, including beneficial endophytes that could also be affected by seed treatments. Metrosideros excelsa (Myrtaceae) is a New Zealand endemic tree widely planted within the country and overseas. Seedlings of M. excelsa display wide variation in susceptibility to a fungal pathogen Austropuccinia psidii, which causes myrtle rust disease suggesting that seed-borne microbial composition may play a role in seedling protection and growth. We investigated the effects of fungicides on the beneficial seed-borne bacterial isolates, the effects of antimicrobial treatment on seedling development, the plant growth-promoting properties of the seed microbiome, and the ability of bacterial isolates to suppress pathogenic fungi. Our results show that seed-borne bacteria Bacillus and Priestia suppressed seed-borne fungi, both pathogenic and endophytic, with average inhibition rates of 74%, and several bacterial isolates reduced A. psidii spore germination in vitro. In contrast, endophytic Methylobacterium and Mycolicibacterium facilitated fungal growth. Fungicide applications are considered the most effective method to control myrtle rust disease; however, we found that fungicides may adversely impact beneficial seed-borne bacteria. Antimicrobial seed treatment also suppressed the growth of corresponding seedlings. Our experiments demonstrate that treated seeds can be further inoculated with beneficial seed-borne endophytes, increasing seedling shoot biomass up to three times. Additionally, the bacterium Kocuria and the fungus Penicillium significantly enhanced root development. These results suggest that employing seed-borne microbial isolates with growth-promoting potential may improve outcomes in nursery conditions.