Effect of maize intercrop plant densities on yield and beta-carotene contents of orange-fleshed sweetpotatoes

Despite efforts to demonstrate the value of orange-fleshed sweetpotato (OFSP) (Ipomoea batatas L.) and quality protein maize (Zea mays L.) in combating vitamin A and protein malnutrition, small land holdings by rural poor farmers still limit the crops’ overall production in Africa. As such, intercropping and optimum plant density in cropping systems will help farmers to improve productivity of the crop, and hence, improve household food and nutrition security. This study determined the effect of maize plant population, in a sweetpotato-maize intercrop, on yields and β-carotene content of two popular OFSP cultivars, Ejumula and NASPOT 9 O (Kabode). Each variety was intercropped with maize variety Longe 5, at three plant densities (i.e. 41,666, 55,555 and 88,888 plants ha-1), at Ngetta Zonal Agricultural Research and Development Institute in Uganda. While 55,555 plants of each OFSP cultivar were used for both sole and intercrops, the sole maize plot was 44,444 plants ha-1. Maize and sweetpotato were harvested at 120 and 135 days after planting, respectively. β-carotene content and yield in sweetpotato roots were significantly (P<0.05) reduced by high maize density. Irrespective of maize density, NASPOT 9 O produced more root yields than Ejumula. Land Equivalent Ratios of >1.2 were obtained at maize intercrop densities of 41,666 and 55,555 plants ha-1.Keywords: Ipomoea batatas, land equivalent ratio, Zea may

Virulence of Russian Wheat Aphid, Diuraphis Noxia (Kurdjumov) (Homoptera: Aphididae) Populations in Kenya

The Russian wheat aphid (RWA) Diuraphis noxia (Kurdjumov) is a serious pest of wheat in Kenya. Development and use of RWA resistant wheat (Triticum aestivum L.) varieties, has been constrained by RWA populations evolving with differential virulence to given resistant host plants. To fully exploit host plant resistance (HPR) in management of RWA, local populations of RWA have to be evaluated for differential virulence and biotypes in order to develop and deploy cultivars that exhibit cross biotype resistance. A study was conducted at KARI-Njoro to characterize virulence of RWA populations from the endemic areas (Eldoret, Mau Narok, Njoro and Egerton) in Kenya. A factorial experiment in randomized complete block design replicated three times was set up to evaluate seedling resistance to RWA with variety and aphid collection source as main factors in the screen house. Five adult RWA aphids from each of the four collection locations were used to infest four host genotypes; PI624933-1  containing Dn4 gene, 2414-11-2  containing Dn7 gene, KRWA9 which contains an unknown Dn gene and a susceptible check, K.KWALE, for 28 days to determine virulence of the RWA aphids  to seedlings of the four wheat genotypes in the greenhouse. Data was recorded on damage scores, plant height, plant height reduction, shoot biomass and biomass reduction of test plants 28 days after infestation. Results of an analysis of variance of these plant parameters show that Egerton population was more virulent than populations selected from other areas as it caused more damage on resistant lines. Keywords: Diuraphis noxia, biotype, virulence, RWA, Wheat.

EFFECT OF MAIZE INTERCROP PLANT DENSITIES ON YIELD AND \u3b2-CAROTENE CONTENTS OF ORANGE-FLESHED SWEETPOTATOES

Despite efforts to demonstrate the value of orange-fleshed sweetpotato (OFSP) ( Ipomoea batatas L.) and quality protein maize ( Zea mays L.) in combating vitamin A and protein malnutrition, small land holdings by rural poor farmers still limit the crops\u2019 overall production in Africa. As such, intercropping and optimum plant density in cropping systems will help farmers to improve productivity of the crop, and hence, improve household food and nutrition security. This study determined the effect of maize plant population, in a sweetpotato-maize intercrop, on yields and \u3b2-carotene content of two popular OFSP cultivars, Ejumula and NASPOT 9 O (Kabode). Each variety was intercropped with maize variety Longe 5, at three plant densities (i.e. 41,666, 55,555 and 88,888 plants ha-1), at Ngetta Zonal Agricultural Research and Development Institute in Uganda. While 55,555 plants of each OFSP cultivar were used for both sole and intercrops, the sole maize plot was 44,444 plants ha-1. Maize and sweetpotato were harvested at 120 and 135 days after planting, respectively. \u3b2-carotene content and yield in sweetpotato roots were significantly (P<0.05) reduced by high maize density. Irrespective of maize density, NASPOT 9 O produced more root yields than Ejumula. Land Equivalent Ratios of >1.2 were obtained at maize intercrop densities of 41,666 and 55,555 plants ha-1.Malgr\ue9 les efforts visant \ue0 d\ue9montrer la valeur nutritionnelle en combinaison de la patate douce \ue0 chaire orange (OFSP) ( Ipomoea batatas L.) et du ma\uefs \ue0 grande valeur proteique ( Zea mays L.) dans la lutte contre la malnutrition li\ue9e au manque de la vitamine A et de proteine, les petits producteurs Africains continuent de limiter les rendements de leur cultures. A cet effet, l\u2019association des cultures doubl\ue9e d\u2019une densit\ue9 optimale des plants dans les systems de cultures, aiderait les producteurs \ue0 am\ue9liorer les rendements de leurs cultures et par consequent am\ue9liorer la qualit\ue9 de vie dans les m\ue9nages et assurer la s\ue9curit\ue9 alimentaire. La pr\ue9sente \ue9tude a d\ue9t\ue9rmin\ue9 l\u2019effet de la densit\ue9 des plants de ma\uefs, dans une culture associ\ue9e avec la patate douce sur le rendements et la teneur en \u3b2-carotene de deux vari\ue9t\ue9s populaires de patate douce OFSP, Ejumula et NASPOT 9 O (Kabode). Chaque vari\ue9t\ue9 a \ue9t\ue9 plant\ue9e en association avec la vari\ue9t\ue9 de ma\uefs Longe 5, \ue0 trois diff\ue9rentes densit\ue9s (i.e. 41,666, 55,555 et 88,888 plants ha-1), et ceci \ue0 l\u2019Institut Zonale de Developpement et de Recherche en Agriculture de Ngetta en Ouganda. Pendant que la densit\ue9 55,555 plants de chaque vari\ue9t\ue9 de OFSP a \ue9t\ue9 utilis\ue9 dans la culture solitaire et en association, la culture solitaire de ma\uefs \ue9tait \ue0 44,444 plants ha-1. Ma\uefs et patate douce ont \ue9t\ue9 r\ue9colt\ue9s respectivement \ue0 120 et 135 jours apr\ue8s. La teneur en \u3b2-carotene et le rendement en tubercules de patate douce ont \ue9t\ue9 r\ue9duits de fa\ue7on significative (P<0.05) par une densit\ue9 forte de ma\uefs. Quelle que soit la densit\ue9 de ma\uefs, NASPOT 9 O a produit plus de tubercules qu\u2019Ejumula. Le ratio \ue9quivalent \ue9tait >1.2 pour une densit\ue9 de ma\uefs de 41,666 et 55,555 plants ha-1, en culture d\u2019association