Assessment of the Effectiveness of Ectomycorrhizal Inocula to Promote Growth and Root Ectomycorrhizal Colonization inPinus patulaSeedlings Using the Most Probable Number Technique

Abstract

The aim of this study was to evaluate the response ofPinus patulaseedlings to two inocula types: soil from aPinusplantation (ES) and anin vitroproduced inoculum (EM). The most probable number method (MPN) was used to quantify ectomycorrhizal propagule density (EPD) in both inocula in a 7-order dilution series ranging from 100(undiluted inoculum) to 10−6(the most diluted inoculum). The MPN method allowed establishing differences in the number of infective ectomycorrhizal propagules’ density (EPD) (ES=34per g;EM=156per g). The results suggest that the EPD of an inoculum may be a key factor that influences the successfulness of the inoculation. The low EPD of the ES inoculum suggests that soil extracted from forest plantations had very low effectiveness for promoting root colonization and plant growth. In contrast, the high EPD found in the formulated inoculum (EM) reinforced the idea that it is better to use proven high quality inocula for forest nurseries than using soil from a forestry plantation.

Plant Growth Response ofPinus patulaandP. maximinoiSeedlings at Nursery to Three Types of Ectomycorrhizal Inocula

“…Seedling growth promotion was significantly higher with the increase of the inocula dose in both species. is trend agrees with the results for growth promotion of P. patula seedlings reported by Restrepo-Llano et al [8]. us, as the inoculum dose increases, the density of ectomycorrhizal propagules also increases and favors more REC in the seedlings [26,27,31].…”

“…is likely occurred as a result of a higher density of infective propagules in IV inoculum (156 per g), which was four times higher than that in PS inoculum (39 per g) as measured by Restrepo-Llano et al [8].…”

“…(iii) e third inoculum was a mixture of two ectomycorrhizal fungi (A. muscaria and S. luteus) multiplied under in vitro conditions in the autoclaved (120°C, 0.1 MPa, 20 min) potatodextrose-agar medium for 10 days at 25°C; 5 mL of this broth was mixed with 1 kg of disinfected soil and was named In Vitro inoculum (IV). is inoculum contained 156 infective propagules per g (MPN technique) [8].…”

“…ese plants form a symbiotic association with ectomycorrhizal fungi, which promotes seedling growth and nutrient uptake in P-deficient soils [5,6]. is strategy is considered a key factor at nursery in ensuring the growth and subsequent establishment of seedlings in the field [7,8]. e effectiveness to promote plant nutrient uptake and growth depends on ectomycorrhizal propagule-density (EPD) of the inoculum [8][9][10].…”