title: Do NERICA rice cultivars express resistance toStriga hermonthica(Del.) Benth. andStriga asiatica(L.) Kuntze under field conditions?
abstract: The parasitic weedsStriga asiaticaandStriga hermonthicacause high yield losses in rain-fed upland rice in Africa. Two resistance classes (pre- and post-attachment) and several resistant genotypes have been identified among NERICA (New Rice for Africa) cultivars under laboratory conditions (in vitro) previously. However, little is known about expression of this resistance under field conditions. Here we investigated (1) whether resistance exhibited under controlled conditions would express under representativeStriga-infested field conditions, and (2) whether NERICA cultivars would achieve relatively good grain yields underStriga-infested conditions. Twenty-five rice cultivars, including all 18 upland NERICA cultivars, were screened inS. asiatica-infested (in Tanzania) andS. hermonthica-infested (in Kenya) fields during two seasons. Additionally, a selection of cultivars was tested in vitro, in mini-rhizotron systems. For the first time, resistance observed under controlled conditions was confirmed in the field for NERICA-2, -5, -10 and -17 (againstS. asiatica) and NERICA-1 to -5, -10, -12, -13 and -17 (againstS. hermonthica). Despite highStriga-infestation levels, yields of around 1.8 t ha-1were obtained with NERICA-1, -9 and -10 (in theS. asiatica-infested field) and around 1.4 t ha-1with NERICA-3, -4, -8, -12 and -13 (in theS. hermonthica-infested field). In addition, potential levels of tolerance were identified in vitro, in NERICA-1, -17 and -9 (S. asiatica) and in NERICA-1, -17 and -10 (S. hermonthica). These findings are highly relevant to rice agronomists and breeders and molecular geneticists working onStrigaresistance. In addition, cultivars combining broad-spectrum resistance with good grain yields inStriga-infested fields can be recommended to rice farmers inStriga-prone areas.
authors.affiliation: Africa Rice Center (AfricaRice), East and Southern Africa, P.O. Box 33581, Dar es Salaam, Tanzania.
authors.forename: Jonne
authors.initials: J
authors.lastname: Rodenburg
authors.affiliation: Africa Rice Center (AfricaRice), East and Southern Africa, P.O. Box 33581, Dar es Salaam, Tanzania ; Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
authors.forename: Mamadou
authors.initials: M
authors.lastname: Cissoko
authors.affiliation: Mikocheni Agricultural Research Institute (MARI), Dar es Salaam, Tanzania.
authors.forename: Juma
authors.initials: J
authors.lastname: Kayeke
authors.affiliation: Africa Rice Center (AfricaRice), 01 BP2031, Cotonou, Benin.
authors.forename: Ibnou
authors.initials: I
authors.lastname: Dieng
authors.affiliation: International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772, Nairobi 00100, Kenya.
authors.forename: Zeyaur R
authors.initials: ZR
authors.lastname: Khan
authors.affiliation: International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772, Nairobi 00100, Kenya.
authors.forename: Charles A O
authors.initials: CA
authors.lastname: Midega
authors.affiliation: Africa Rice Center (AfricaRice), East and Southern Africa, P.O. Box 33581, Dar es Salaam, Tanzania ; International Crops Research Institute of the Semi-Arid Tropics (ICRISAT), Eastern and Southern Africa, P.O. Box 39063, Nairobi, Kenya.
authors.forename: Enos A
authors.initials: EA
authors.lastname: Onyuka
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
authors.forename: Julie D
authors.initials: JD
authors.lastname: Scholes
keywords: Africa; Oryza glaberrima; Oryza sativa; Parasitic weeds; Tolerance; Upland rice