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University of Kassel (2018)

Etiology of Maize Root rot in Oman : Causal agents and effects of a compost based organic growing system

Al-Ansari, Mahmood Saleh Ali

Titre : Etiology of Maize Root rot in Oman : Causal agents and effects of a compost based organic growing system

Auteur : Al-Ansari, Mahmood Saleh Ali

Université de soutenance : University of Kassel

Grade : Doktorgrade 2018

Résumé p
In Oman, the main cereal crop Maize is facing serious problems due to high salinity, alkaline soils with low organic matter, high temperatures, and root rot diseases. Production peaked at 40,000 t in 2011 but dropped to less than 15,000 t in 2014. A survey on maize root rot in eight maize growing governorates in Oman yielded nine fungal and oomycetes species of which Pythium arrhenomanes and Fusarium fujikuroi were first reports on maize in Oman. Both are able to attack multiple hosts. Under controlled conditions, different pathogens caused varying degrees of severity but P. arrhenomanes was the most aggressive. Large differences were observed in root disease incidence between an organically managed field based on compost amendments and a conventionally managed field. Cropping histories and environmental conditions were similar and the maize seed originated from the same source. A comparison of the rhizosphere microbiome in the two fields showed enhanced microbial diversity in the organic field. Frequency of Trichoderma (Hypocrea) species was 17.5% compared to 0,01% in the conventional field. The organic field was also higher in organic matter (3.6 vs 1.2%) and N contents, and had lower Ca:Mg ratio, pH and EC. Nine local composts as affected by original materials and processing procedures were assessed. A detailed study of the dynamics of an aerobic (windrow) system showed that maturity was reached within 60 days which is considerably faster than what is typically reported under temperate climatic conditions. Storage for one year did not affect quality. Except for compost made of sewage sludge and the anaerobically processed compost composting results were acceptable with respect to physico-chemical properties, germination index and lack of human pathogens. An isolate of Trichoderma asperellum isolated from one of the organic composts was compared with a commercial T. harziamum biocontrol isolate. The local isolate was as active in biocontrol activity but more heat and salt tolerant than the commercial isolate making it an interesting candidate for developing a local biocontrol strain. In conclusion, compost based field management in Oman can be recommended to address as well biological as chemical soil related challenges to maize production

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Page publiée le 14 janvier 2019