Desert truffle mycorrhizosphere harbors organic acid releasing plant growth–promoting rhizobacteria, essentially during the truffle fruiting season

Abstract

Desert truffle is becoming a new crop in semiarid areas. Climatic parameters and the presence of microorganisms influence the host plant physiology and alter desert truffle production. Desert truffle plants present a typical summer deciduous plant phenology divided into four stages: summer dormancy, autumn bud break, winter photosynthetic activity, and spring fruiting. We hypothesize that the bacterial community associated with desert truffle plants will show a seasonal trend linked to their plant growth–promoting rhizobacteria (PGPR) traits. This information will provide us with a better understanding about its potential role in this symbiosis and possible management implementations. Bacteria were isolated from root-adhering soil at the four described seasons. A total of 417 isolated bacteria were phenotypically and biochemically characterized and gathered by molecular analysis into 68 operational taxonomic units (OTUs). They were further characterized for PGPR traits such as indole acetic acid production, siderophore production, calcium phosphate solubilization, and ACCD (1-amino-cyclopropane-1-carboxilatedeaminase) activity. These PGPR traits were used to infer functional PGPR diversity and cultivable bacterial OTU composition at different phenological moments. The different seasons induced shifts in the OTU composition linked to their PGPR traits. Summer was the phenological stage with the lowest microbial diversity and PGPR functions, whereas spring was the most active one. Among the PGPR traits analyzed, P-solubilizing rhizobacteria were harbored in the mycorrhizosphere during desert truffle fruiting in spring.

Phosphate-Solubilizing Bacteria Isolated from Phosphate Solid Sludge and Their Ability to Solubilize Three Inorganic Phosphate Forms: Calcium, Iron, and Aluminum Phosphates

“…Many PSB strains have been observed secreting a variety of organic acids, including acetic, citric, formic, oxalic, and formic acid, amongst many others. Organic acids [ 1 , 25 , 37 , 38 , 39 , 40 , 41 ] convert tricalcium phosphate to mono and dicalcium phosphate, allowing plants to receive phosphorus minerals. According to Nahas [ 42 ] and Anand et al [ 43 ], organic acids generated by bacteria dissolve insoluble phosphate with a decrease in pH, chelation of cations, and interaction with phosphate on sorption sites in the soil.…”

Design and Validation of qPCR-Specific Primers for Quantification of the Marketed Terfezia claveryi and Terfezia crassiverrucosa in Soil

“…In accordance with the desert truffle life cycle [ 82 , 83 ], the first rainfalls of late summer and early autumn promote primordia formation, which is associated with the high production of ascocarps in the next spring [ 14 , 15 ]. As well as in the genus Tuber [ 84 , 85 ], T. claveryi exhibited a heterothallic lifestyle, which requires the combination of mycelia with different mating type genes in order to form fruiting bodies [ 82 ].…”

Draft Genome Sequence of Pseudomonas mandelii Strain 29, Isolated from the Desert Truffle Terfezia claveryi

“… Pseudomonas mandelii strain 29 (phosphorus solubilizing) was isolated from the peridium of ascocarps of the ectendomycorrhizal fungus Terfezia claveryi Chatin, and it is characterized by its ability to increase mycorrhizal colonization of Helianthemum almeriense host plants under nursery conditions ( 2 ). Since mycorrhizal helper bacteria (MHB) appear to have specificity for certain strains of mycorrhizal fungi ( 3 ), understanding the mechanisms of action of MHB could be useful to employ P. mandelii as a promising option for sustainable use in agriculture ( 2 , 4 ).…”