The Use of Fungal Pathogens as Mycoherbicides for The Biocontrol Of Striga Hermonthica (Del.) Benth

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Ali, Somia Basheir Mohammed
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Twenty fungal isolates were collected from diseased Striga plants at the Faculty of Agriculture Demonstration Farm, University of Khartoum Farm, at Shambat, and from the Gezira Scheme. The isolates were identified using Potato Dextrose Agar (PDA), Czapek Dox Agar (CZ), Spezieller Nahrstffarmer Agar (SNA) and Potato Sucrose Agar (PSA). Eighteen of the isolates were identified as Aspergillus. niger, while only two were identified as Asp. flavus. Pathogenicity tests of these fungi on Striga hermonthica, in vitro and in the glasshouse, using spores of these fungi, revealed the potential to utilize Aspergillus species in Striga biocontrol. Investigations conducted on the stimulants produced by sorghum plants that induce Striga hermonthica germination showed that certain stimulatory chemical cues are produced at a specific stage in sorghum germination, and that the major portion of these chemicals was more water-soluble than diethyl ether-soluble. Water-soluble sorghum seedling extracts resulted in high stimulation of Striga hermonthica germination than ether-soluble extracts. However stimulation in the presence of sorghum seedling was even higher than both extracts, indicating inability of the extractants used to extract all the cues implicated in the stimulation process. Moreover, these chemicals don’t seem to be produced at the very early stages of sorghum germination, but need at least five days to be produced in effective concentrations. Pesta formulations were found to be most suitable for Asp. niger spore fermentation. In the present investigations the Pesta formulated from sorghum straw (70%), alfalfa hay (25%) and sucrose (5%) was the best for spore multiplication. Application of the Pesta inoculum as a dressing for sorghum seeds resulted in high suppression of Striga seed germination as compared to soil inoculation or after-emergence application on Striga hermonthica plants.
University of khartoum