Susceptibility of Selected Wheat Cultivars and Sorghum bicolor (cv.Abusabeen) to Striga hermonthica (Del.) Benth

Abstract

Striga hermonthica, (Del.) Benth an obligate root parasitic plant, causes serious yield losses in cereals in Sub-Sahara Africa, threat to agriculture and food security. Maize, sorghum, millet, rice and sugar cane are the traditional hosts, however, recently wheat was reported susceptible to the parasite. Green house and Laboratory experiments were undertaken at the College of Agricultural Studies (CAS), Sudan University of Science and Technology (SUST) at Shambat in 2012 - 2013 to determine i) reactions of local wheat cultivars to the parasite and their ability to sustain successful parasitism and ii) ability of air dried of the wheat residues to induce germination of the parasite. Laboratory experiments showed that wheat residues, irrespective of cultivars, plant parts and amount of powder, induced both germination and haustorium initiation (8.7-75.5%) and (22.9-100%), respectively in S. hermonthica. Germination varied with the amount of powder and the cultivar used. Elnelien cultivar displayed the highest germination, followed in descending order by Wadi-Elniel, Emam and Napta. Germilings from seeds induced to germinate by wheat residues showed pre-mature haustoria and shorter radicle length than those stimulated by GR24. Wheat residues, irrespective of cultivars, plant parts and amount of powder induced haustorium initiation (22.9 – 100%), and reduced radicle length by 67- 82%, as compared to the control. Seeds placed in vicinity of Abusabeen roots for 6, 9 and 12 days displayed 21.0, 37.0 and 37.7% germination, respectively. Of the resulting Striga germilings 30.0- 61.9% were attached to sorghum (Abusabeen). Of the Striga germilings 2.2- 42.9 % died prior to attachment and 0.7- 1.6% died after attachment. At 9 days seeds placed in proximity of Elnelien, Napta, Wadi-Elnile and Emam roots displayed 22.8, 12.4, 7.8 and 5.5% germination, respectively. Of the resulting germilings 63.8, 25.0, 32.0 and 38.8% achieved attachment to Elnelien, Emam, Napta and Wadi-Elnile roots and 63.2, 75.0, 68.0 and 61.2. % germilings failed to attach, respectively. About 6.3 and 2.1% of the germilings attached to Elnelien and Napta died. Seeds placed for 12 days in vicinity of Elnelien, Napta, Wadi-Elnile and Emam roots showed 79.4, 32.4, 22.7and 15.0% germination, respectively. Attachment was 25.3, 39.4, 35.3 and 49.0% on Elnelien, Emam, Napta and Wadi-Elnile roots, respectively and about 74.7, 60.6, 46.7 and 51.0% of the germilings was failed to attachment. S. hermonthica emergence, irrespective of seed bank size was influenced by host species and cultivar. Striga emergence on sorghum (cv. Abusabeen) displayed a progressive increase with seed bank size. Striga emergence on wheat was lower than on sorghum and showed dependence on time and cultivar. On sorghum Striga emergence was evident 45 DAS. However, on wheat Striga emergence was noticed 60 DAS on Emam, Elnelien and Wadi-Elnile, while emergence was delayed to 75 DAS on Napta. S. hermonthica, irrespective of seed bank size on wheat cultivar reduced tillering and biomass producing in wheat. However, the magnitude of the reduction varied with cultivars and Striga seed bank size. In general, the observed reduction, with few exceptions, increased with increasing Striga seed bank size and was highest (61.8%) on Napta and lowest (4.2%) on Emam. The experiment showed that wheat is susceptible to S. hermonthica and was able to support germination, attachment, and subsequent development of Striga.