Colonization of Trichoderma harzianum strain SQR-T037 on tomato roots and its relationship to plant growth, nutrient availability and soil microflora

AIMS: This research was to study the capacity of Trichoderma harzianum strain SQR-T037 to colonize tomato roots and how this strain and its bio-organic fertilizer stimulate plant growth and increase yields under field conditions. METHODS: Field trials were conducted with a reduced application of chemical fertilizer (75 % of the recommended application) plus Trichoderma-enriched bio-organic fertilizer (BF) or organic fertilizer (OF) or Trichoderma spore suspension (SS), while 100 % of the recommended chemical fertilizer (CF) was used as control. RESULTS: Trichoderma SQR-T037 could efficiently colonize tomato roots and soils based on the reverse transcription-quantitative PCR analysis, and significantly stimulate biomass accumulation at an early stage. The 75 % rates of chemical fertilizer coupled with bio-organic fertilizer (BF) produced tomato yields equivalent to those obtained using the 100 % rates of chemical fertilizer (CF), while inoculation with the Trichoderma alone (SS) or supplement with organic fertilizer alone (OF) would cause 11 and 13 % decreases in yield over the control (CF). The efficacy of BF for maintaining a stable tomato yield may be due to the enhanced soil nutrients availability and the increased abundance of soil microflora, including bacteria, fungi, actinomycetes and Trichoderma communities, which had a positive linear correlation in most of the cases revealed by the Pearson correlation analysis. CONCLUSIONS: The results of this study imply that the reason by which the bio-organic fertilizer promotes plant growth and increases the tomato yields can be attributed to the enhancement of the rhizospheric microflora, which promotes nutrient activation. Therefore, T. harzianum could be employed in a combination with composts. In this way, the application rate of chemical fertilizers can be practically decreased by 25 % to obtain maximum benefits.