Soybean growth promoting autochthonous Trichoderma spp. for biocontrol

SANTONE, A.; CAMPOS BERMUDEZ, V.A.; SPAMPINATO, C.

Congreso; XXXIV Reunión de la Sociedad Argentina de Fisiología Vegetal (RAFV); 2023

Soybean yield and grain quality usually decrease due to phytopathogens, such as Diaporthe caulivora which cause stem canker. The use of growth-promoting microorganisms as biological control agents present a sustainable alternative to agrochemicals. Trichoderma, a genus of filamentous fungi inhabiting the rhizosphere and beneficially interacting with plant roots, shows promise in this regard. We identified and selected autochthonous strains of Trichoderma with the ability to promote soybean growth and control D. caulivora. Three strains of Trichoderma (T4, T10 and T12) were isolated from the local soil biota. The ITS, Rpb2, and Tef1 genes were amplified and sequenced to identify the strains as members of the Trichoderma harzianum complex. First, in vitro tests were carried out. We observed that all the strains inhibited the growth of D. caulivora. T10 and T12 showed carboxymethyl cellulase activity producing 0.66 and 1.64 nmol/mL of glucose, respectively. T4 and T10 with the addition of Trp produced 16 and 10 μg/mL of indoleacetic acid, respectively. Also, all the strains were able to solubilize phosphate. Then, in vivo tests were conducted on hydroponically and soil-grown soybean. Stem cuttings from two-week-old plants were exposed to 1:500 V/V diluted cell-free liquid from T4, T10, T12 and T. harzianum cultures, with and without TRP. Moreover, soybean seeds were inoculated with supernatants from each strain, with and without conidia. After 21 days of sowing, plants were infected with D. caulivora. Results indicate that the T10 strain showed the most promising results. It promoted robust root development and displayed the lowest water consumption in hydroponic conditions. In the soil trial, it exhibited the lowest number of dead plants after infection, thus concluding that this strain has a significant potential to promote soybean growth and control the pathogen. Further studies are being conducted to determine secondary metabolites released by the T10 strain.