Effects of Desmodium uncinatum and D. intortum on parasitism by Phelipanche ramosa, Orobanche crenata and Striga Hermonthica

• Main Author: Shrif, Mohamed
• Published: University of Reading 2014
• Subjects: 632
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.658876

Root parasitic plants such as Striga, Phelipanche and Orobanche species cause severe loss of crop production worldwide. In some areas of East Africa, intercropping with Desmodium species has given good control of Striga hermonlhica. The root exudates of Desmodium contain compounds that affect germination, early development and attachment of S. hermonthica to the host plants. Laboratory and glasshouse experiments were carried out at the Seed Science and the Plant Environment Laboratories at the University of Reading, UK to investigate whether these known effects of Desmodium on Striga also apply to Phelipanche ramosa and Orobanche crenata. The results of this study indicated that Desmodium uncinatum and D. intortum both provided a high level of control of Ph. ramosa and O. crenata while confirming the effect on S. hermonthica. Significant reductions in infestations by these parasites were obtained when hosts (tomato, pea, maize / millet, respectively) were planted in soil with high densities of parasitic seeds and were irrigated by the water draining from the pots where D. uncinatum and D. intortum plants were being grown. Exposing to Desmodium root exudates for twelve rather than four weeks was more effective in controlling the parasites. Likewise, applications of Desmodium root exudates at different concentrations were also effective. Experiments were also conducted to investigate the effects of environmental factors on the activity of Desmodium root exudates as germination stimulants and attachment inhibitors. Desmodium root exudates from plants grown at different temperatures had no effect on S. hermonthica and Ph. ramosa Dl germination, but they did affect the germination of 0. crenata. In contrast, drought significantly decreased the germination Ph. ramosa D6 compared to non-drought treatments. D. uncinatum proved more effective in controlling attachments of Ph. ramosa D6 compared to D. in/orlum. Root exudates were collected at several different times and all samples were effective at reducing attachment of Ph. ramosa Dl, Ph. ramosa D6 and O. crenata compared to control treatments. However, no significant effects were found for different temperatures on the production of attachment inhibitors.