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Abstract
SUMMARY
Faba bean (Vicia faba L.) is one of the important crops in Egypt. It is important source of human consumption as well as for animal feed. However, faba bean seedlings are subjected to the attack by numerous pathogens causing root-rot diseases which reduce the quantity and quality of the crop. The present investigation was planned to isolate and study the pathogenicity of soil-borne fungi associated with faba bean (Vicia faba L.) roots of many cultivars. The investigation includes also the study of the effect of some biological agents, plant oils and extracts, biofertilizers and fungicide were tested for controlling root-rot and determine activity of the enzymes involved in phenolic compounds. The following results were obtained:
Pathogenicity experiment
1- Causal agents were isolated from faba bean seedlings collected from different location in Egypt, purified and identified as: one isolate of Sclerotium rolfsii, six isolates of Rhizoctonia solani, six isolates of Fusarium solani, one isolate of F. moniliforme and one isolate of Macrophomina phaseolina.
2- The pathogenicity tests proved that all the tested fungi were pathogenic and able to reduce pre-emergence (PRD), and post-emergence (PTD) and incited root-rot on faba bean cultivars, namely; Giza 2, Giza 3, Giza 40, Giza 716, Sakha 2 and Mass 1.
3. The highest PRD values were obtained on Masser 1, Giza 3 and G 716, inoculated with S. rolfsii (43.85%, 41.54% and 41.54% respectively) and G 716 cv inoculated with M. phaseolina was (34.16%), moreover inoculated with R. solani and F. solani on G 2 cv (36.7% and 34.16%, respectively). Whereas, S 2 cv was the least (21.25%) compared to control.
4. The highest PTD incidence ratios were obtained by S. rolfsii on G 2, G 3, G 40, G 716 (39.23%, 34.16%, 34.16% and 34.16% respectively, whereas, G 2 and G 40 inoculated with F. solani (34.16%) compared with control. In addition, high PTD value was realized by M. phaseolina on G 2 cv (31.63%).
5. Inoculation experiments using S. rolfsii led to significant reduction in SS values (26.56%) on G 2 and Masser 1 cvs. On the other hand, the highest SS (seedlings survival) values obtained from S 2, G 3, G 40 and M 1 cultivars inoculated with M. phaseolina (55.84%, 46.38%, 43.85% and 43.85% respectively and G 716, S 2 inoculated with F. solani (43.85%, 50.99% respectively).
Disease control
Biological control
6- Significant reduction in PRD and PTD values were recorded due to treatment with the tested biofungicides, the tested pathogen and the cultivated cultivar was as follows:
a. Seed treatment with Bio-zeid (T. album) significantly decreased percentage of the PRD values produced by S. rolfsii isolate by 59.3% less than control, whereas seed treatment with bio-arc realized 32.27% reduction less than control. and seed treated with vitavax-captan 72.9%.
b. The highest reduction % in PRD values 45.83% was obtained in Giza 2 cv seeds treated with Bio-zeid and with Bio-arc but in Sakha 2 cv inoculated with R. solani was (83.21% with Bio-zeid T. album and 66.39% with Bio-arc B. megaterium) reduction less than control. While reduction was 83.21% S 2 seeds treated by vitavax-captan.
c. PRD produced by F. solani was reduced 27% less than control with bio-zeid (T. album) in G 2 cv whereas the ratio was 37% less than control in S 2 cv.
d. The percentage of PRD values produced by M. phaseolina significantly decreased when seeds were treated with the tested (Bio-zeid or Bio-arc) 49.6% and 72.9% respectively.
7. Seed treatment with the two biofungicides significantly decreased PTD values, depending upon the bioagent, pathogen and cultivar as shown below:
a- In spite of the significant decrease in PTD values developed by S. rolfsii (27.6% - 56.5% than control), however, differences in PTD values between treatments was insignificantly. Reduction percentage were 32.27% and 56.5% respectively in Giza 2 and Sakha 2 cultivars with seed treated with Bio-zeid. Treatment by Bio-arc was 32.27% and 48.99% in G 2 and S 2 cvs respectively.
b. Seed treatment of Giza 2 and Sakha 2 cvs with bio-zeid (T. album) significantly reduced PTD (59.3% and 53.3%, respectively less than control) caused by R. solani, and treated with bio-arc the reduced PTD (32.27% and 37.79,% respectively) and vitavax-captan reduced (86.46% and 84.45%) in the two cvs.
c. Seed treatment with bio-zeid (T. album) significantly decrease the percentage value of PTD on Giza 2 and Sakha 2 cvs 56.5% and 66.39 caused by F. solani, while, 48.9% and 49.6% treated with Bio-arc (B. megaterium) in G 2 and S 2 cultivars respectively.
d. PTD values produced by M. phaseolina were significantly decrease by (53.3% - 84%) less than control when seeds of Giza 2 and Sakha 2 cvs were treated with Bio-zeid and to 37.7% - 53.3% with Bio-arc and 84% with vitavax-captan.
8. The tested biofungicides and vitavax-captan considerably increased the seedling survival rates escaping infection with root-rot disease. Increasing percentage of SS values in case of S. rolfsii (114.6%, 96.4% and 147%), R. solani were (93.1%, 73.5% and 125%) and F. solani were (59.38%, 45.87% and 94.6) and M. phaseolina (94%, 68.9% and 124% respectively) compared the control.
Plant oils
I. Effect of crude oils in vitro
The antagonistic effect of some crude plant oils, i.e. spearmint, cinnamon, clove, castor beans, onion, and garlic oils were tested against root rot pathogens in vitro.