Abstract:
Laboratory and greenhouse experiments were conducted, during the winter season 2019/2020, at the College of Agricultural Studies (CAS), Sudan University of Science and Technology (SUST) at Shambat, Khartoum North to study the effects of root exudates and plant residues of maize cultivars (Var113, Hudeiba2, Sennar1 and Sennar2) on early developmental stages of Striga and to evaluate the response of these cultivars to infestation by different levels of Striga seed bank size (8, 16 and 32mg/pot). The results of laboratory experiments showed that germination of Striga various with maize cultivars and root exudates level. Root exudates from Var113 displayed the highest Striga germination (59.2%), while root exudates from Sennar1 exhibited the lowest germination (16.5%). Striga germination was lowest at 10µl, however, increasing root exudates to 15µl or more increased germination significantly. Roots exudates from maize cultivars produced little haustorium (4-12.9%). Root exudates from Var113 significantly showed the highest radicle length (10.2 µm ×10-2). However, root exudates from cultivars Sennar1 and Sennar2 sustained the lowest. Maize root residues significantly stimulated highest Striga seeds germination (47.0%), while the shoot part sustained the lowest germination (30.4%). Var113 gave the highest Striga germination (46.5%). However, powder from cultivars Hudeiba2 and Sennar1 displayed the lowest germination percentage (34.1%). Maize roots powder induced poor haustorium initiation (4.9%), as compared to shoot powder (19.5%).
The results of greenhouse experiment showed that maize cultivars support fewer emerged Striga plants. Sennar2 cultivar displayed the highest Striga emergence, while cultivars Hudeiba2and Var113 revealed slight Striga number. On Sennar1, Striga showed no emergence. Striga dry weight progressively increased with seed bank size. The different cultivars displayed differential response to the parasite. Striga at all seed bank size reduce plant height on Var113 by 36.7-46.7 %, as compared to the control. In Sennar1, Striga at seed bank size of 8 and 16mg/pot decreased maize height by 19.8 and 29.9%, respectively. Striga at all seed bank size had no significant effect on number of leaves, as compared to Striga free control. In Var113, Striga reduced leaf area by 44.1- 73.6%. In Sennar1, at Striga seed bank size of 8 mg/pot leaf area was reduced by 52.0%. However, in Hudeiba2 at 32mg/pot the reduction in leaf area was 45.2%. Striga at seed bank size of 32 mg/pot reduced chlorophyll content significantly by 33.4%. Striga at seed bank size of 8, 16 and 32 mg/pot, decreased maize dry weight by 29.4, 28.8 and 41.8%, respectively but not significantly, as compared to the control.
