*2.3. Extracellular Hydrolytic Enzymes*

The results showed that all studied isolates were able to produce some extracellular hydrolytic enzymes (Table 2). In particular, the highest significant hydrolytic activity of chitinase (chitin azure), glucanase, and protease was observed in the case of *A. humicola*, where the diameter of the hydrolysis zones was 31.5, 36.0, and 21.5 mm, respectively. On the other hand, *Streptomyces* sp. and *S. atratus* showed the highest significant activity of amylase with a diameter of hydrolysis area of 37.5 and 42.0 mm, respectively, whereas the same two isolates showed moderate activity for pectinase with a diameter of hydrolysis area of 14.0 and 10.5 mm, respectively. However, *S. atratus* and *A. humicola* did not show either glucanase or pectinase activity, respectively. None of the three tested isolates showed hydrolytic activity for chitinase (chitin from crab shells) and polygalacturanase.

**Table 2.** Extracellular hydrolytic enzymes produced by the tested *Actinomycetes* isolates.


(a) Lugol solution was prepared as follows: 0.35 g iodide + 0.66 g potassium iodide KI in 100 mL dis. H2O; (b) CTAB: hexadecyltrimethylammonium bromide; values followed by different letters in each row for each tested enzyme were significantly different according to *Tukey's* B multiple comparison test post hoc test at *p* < 0.05.

*2.4. In Vivo Growth Promoting and Disease Control*

2.4.1. Eco-Physiological Parameters

The results revealed that all studied *Actinomycetes* isolates were able to stimulate the growth of bacterized tomato seedlings, which showed higher values of eco-physiological parameters in comparison with the negative control (non-bacterized plants), as represented in Table 3. In particular, seedlings inoculated with *Streptomyces* sp. and *A. humicola* showed the highest significant values (*p* < 0.05) of number of leaves, shoot length, shoot fresh weight, and shoot dry weight. The eco-physiological parameters of bacterized tomato seedlings artificially infected with *S. sclerotiorum* are reported in Table 4. In particular, seedlings inoculated with *Streptomyces* sp. and *A. humicola* demonstrated high values (*p* < 0.05) of number of leaves, twigs, shoot fresh weight, and shoot dry weight. However, *S. atratus* showed a moderate growth-promoting effect on tomato seedlings, especially in terms of the number of twigs, shoot length, and total shoot dry weight.


**Table 3.** Effect of *Actinomycetes* isolates on eco-physiological parameters of tomatoes (health control).

Note: TN: twig number; SL: shoot length; LN: leaf number: SFW and SDW: fresh and dry weight of shoot systems, respectively. Values followed by different letters in each vertical column for each measured parameter were significantly different according to *Tukey's* B multiple comparison test post hoc test at *p* < 0.05.

**Table 4.** Effect of *Actinomycetes* isolates on eco-physiological parameters of tomatoes (artificially infected with *S. sclerotiorum*).


Note: TN: twig number; SL: shoot length; LN: leaf number: SFW and SDW: fresh and dry weight of shoot systems, respectively. Values followed by different letters in each vertical column for each measured parameter were significantly different according to *Tukey's* B multiple comparison test post hoc test at *p* < 0.05.
