2.4.2. Disease Control

The bacterized plants with *Streptomyces* sp. and *A. humicola* did not show any symptoms on their leaves and roots after the infection with *S. sclerotiorum*. The disease indexes of the plants bacterized with *Streptomyces* sp. and *A. humicola* were 0.3% and 0.2% (Figure 1), whereas the control effects were 99.2% and 99.5%, respectively (Figure 2). The seedlings bacterized with *S. atratus* showed a moderate disease index of 7.6% (Figure 1) and a control effect of 79.5% (Figure 2). Regarding the positive control (plants inoculated only with *S. sclerotiorum*), the results showed the development of leaf yellowing and chlorosis at 20 DAI, where the leaf chlorotic zone of infected tomato plants became necrotic. Moreover, complete leaf wilting and root necrosis was also observed at 35 DAI. In particular, a significantly higher symptomatic leaves percentage (*p* < 0.05) was observed in the positive control, where the disease index was 36.8% compared with the negative control and bacterized plants with *Actinomycetes* isolates (Figure 1). *S. sclerotiorum* was always re-isolated from the inoculated plants.

**Figure 1.** Disease index of tomato inoculated with *S. sclerotiorum*. Bars with different letters indicate mean values significantly different at *p* < 0.05 according to *Tukey's* B test. Data are expressed as mean of 3 replicates ± SDs. DI (%) = [Σ (Scale × No. of SL)/(HS × TL)] × 100 (Equation (1)). AC1, OL2, and RS3 are *Streptomyces* sp., *Arthrobacter humicola*, and *Streptomyces atratus*, respectively.

**Figure 2.** Control effect of the tomato inoculated with *S. sclerotiorum*. Bars with different letters indicate mean values significantly different at *p* < 0.05 according to Tukey's test. Data are expressed as mean of 3 replicates ± SDs. CE (%) = 100 × (DI-P-DI-B)/DI-P (Equation (2)).
