Witchweed’s Suicidal Germination: Can Slenderleaf Help?

• Main Authors: Fridah A. Mwakha, Nancy L.M. Budambula, Johnstone O. Neondo, Bernard M. Gichimu, Eddy O. Odari, Peter K. Kamau, Calvins Odero, Willy Kibet, Steven Runo
• Format: Article
• Language: English
• Published: MDPI AG 2020-06-01
• Series: Agronomy
• Subjects: <i>Crotalaria</i>; <i>Striga</i>; strigolactones; suicidal germination; trap crops
• Online Access: https://www.mdpi.com/2073-4395/10/6/873

The parasitic plant <i>Striga hermonthica</i> (Delile) Benth. is stimulated to germinate by biomolecules (strigolactones) produced in the roots of host and some non-host plants. Non-hosts induce <i>Striga</i>’s suicidal germination and are therefore used as trap crops. Among trap crops, the Slenderleaf legume in the genus <i>Crotalaria</i> (<i>Crotalaria brevidens</i> (L.) Benth.) and (<i>Crotalaria orchroleuca</i> (G.) Don.) has been popularized in African smallholder farms. However, the <i>Striga</i> germination efficiency of these locally grown <i>Crotalaria</i> varieties (landraces) is unknown. Also unclear is <i>Crotolaria</i>’s extent to inhibiting <i>Striga</i> growth, post germination. Extensive parasite penetration can expose the trap crop to secondary infections and possible phytotoxicity from <i>Striga</i>. We used <i>in vitro</i> germination assays to determine the <i>Striga</i> germination efficiency of 29 <i>Crotalaria</i> landraces. Furthermore, we determined <i>Crotalaria</i>’s ability to inhibit <i>Striga</i> attachment and growth using histological analysis. We found that: i) <i>Crotalaria</i> stimulated germination of <i>Striga</i> seeds at frequencies ranging between 15.5% and 54.5% compared to 74.2% stimulation by the synthetic strigolactone (GR24) used a positive control; ii) <i>Crotalaria</i> blocked <i>Striga</i> entry at multiple levels and did not allow growth beyond the pericycle, effectively blocking vascular connection with the non-host. Hence, <i>Crotalaria</i> is suitable as a trap crop in integrated <i>Striga</i> management.