The Effect of Pseudomonas putida on the Microbial Community in Casing Soil for the Cultivation of Morchella sextelata

<i>Morels</i> are a rare edible and medicinal fungus. A major factor contributing to difficulties with their continuous cropping is alteration in soil microbial communities. <i>Pseudomonas putida</i> is a key microorganism in morel cultivation soils; it has garnered significant attention due to its ability to degrade 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor of ethylene. However, the interaction between <i>Pseudomonas putida</i> and morels remains unclear. This study evaluated the growth-promoting potential of <i>P. putida</i> KT2440 by measuring the casing soil ACC content and assessing its ACC utilization capacity. Metagenomic sequencing was performed to assess the changes in soil microbial composition and function. The results indicated that ACC accumulated in the soil following morel cultivation and that <i>P</i>. <i>putida</i> KT2440 was capable of utilizing ACC as its sole nitrogen source for growth on plates. Inoculation enhanced the depletion of available nitrogen, phosphorus, and potassium; increased bacterial diversity; improved the stability of the soil microbial community; and caused the mycelium of morels to grow earlier. These processes occurred along with a decline in the abundance of the <i>Streptomyces</i> genus. Furthermore, a positive correlation was identified between the abundance of <i>P. putida</i> and ACC deaminase activity in the soil. Overall, this study examined the role of <i>Pseudomonas putida</i> inoculation in modulating the soil microbial community and metabolic processes within casing soil during <i>Morchella sextelata</i> cultivation. The findings indicate that <i>P. putida</i> inoculation promotes <i>Morchella</i> growth through ACC decomposition and microbial restructuring, offering a potential strategy for mitigating ethylene-related suppression in continuous cropping systems.