Cucumber root colonization by T. virens wild type and tmkA mutant. (A) Roots were detached 48 h postinoculation and washed. After sterilization in 1% NaOCl for 2 min, the roots were homogenized in water and serial dilutions were plated on Trichoderma selective medium at 30°C. Bars: 1, WT; 2, ΔMAPK-72; 3, ΔMAPK-95; 4, ΔMAPK-7. (B) Expression of Trichoderma tmkA and the β-tubulin gene (βtub) was assessed 48 h after inoculation in cucumber roots by RT-PCR with specific primers. Actin of C. sativus was used as a reference for RNA equal loading. Noninoculated roots (R) were used as controls for primer specificity.