Yield evaluation of a wheat line with combined resistance to russian wheat aphid and stem rust race “Ug99” in Kenya

InKenya, Russian wheat aphid (RWA) and stem rust race TTKS (“Ug99”) are the most devastating pests of wheat. Severe infestations by RWA result in yield losses of up to 90% while epidemics of “Ug99”can cause up to 100% loss. The two pests combined have seriously affected farmer incomes forcing them to rely heavily on pesticides and increasing the cost of production. This study sought to evaluate a wheat line that has been developed to be resistant to both RWA and “Ug99”by pyramiding two major resistance genes. Three varieties were used in this study: “Kwale”, a Kenyan high yielding commercial variety but susceptible to both RWA and “Ug99”; “Cook”, an Australian variety carrying stem rust resistance gene Sr36 conferring immunity to “Ug99”; and “KRWA9”, a Kenyan line resistant to RWA but with poor agronomic attributes. The F1 of the double cross (DC F1) was obtained by crossing the F1 of “Kwale × Cook” and the F1 of “Kwale × KRWA9”. The DC F1 population was subjected to sequential screening for both RWA and “Ug99”resistance. The surviving DC F1 progenies were left to self pollinate in the field to obtain the DC F2. The DC F2 progenies were sequentially screened against RWA and “Ug99”to obtain a resistant population to both RWA and “Ug99”. The yield and yield components of the new resistant line were compared with the three parents. Results showed that the DC F2:3 had higher yields than the three parents based on 1000 kernel weight, weight of kernel per spike, and the actual yield in tons/ha, indicating that the genes were successfully introgressed. It is concluded that though races with virulence for Sr36 have been reported, the gene provides immunity to race “Ug99”and can be used as a component for “Ug99”resistance breeding together with other Sr genes

EVALUATION OF POPULAR CASSAVA VARIETIES FOR YIELD AND CYANIDE CONTENT UNDER ASAL CONDITIONS IN KENYA

Cassava ( Manihot esculenta Crantz) is a staple food crop grown by smallholder farmers in the marginal regions of western, coastal and eastern Kenya. The objective of this study was to evaluate popular cassava varieties for yield and cyanide content in the arid and semi-arid regions of Kenya. The study was carried out at five sites located in three sub-counties of Nakuru county in Kenya. Treatments included a collection of 27 sweet cassava varieties obtained from Western Kenya. Results revealed significant variations among varieties in all sites, for all parameters measured. The highest yields were obtained at Subukia, with the variety MM99/0067 yielding up to 200 t ha-1. Cyanide content varied significant among the varieties and sites; and was high in most of the cultivars, with highest levels recorded in variety Rao Onyoni (17.3 mg100 g-1) grown at the Lare site. The highest dry matter content was recorded in variety Selele rabuor (60.5%), at the Solai III site. Participating farmers ranked the materials based on yield, taste and order of general preference as follows: Subukia site (MM96/0067, NyaTanga, Adhiambo Lera, KME-1 and MH95/0183); Lare site (Nyar AICAD, Nyar Maseno, NyaTanga, and MM96/2480); and Solai site (KME-1, Nyar AICAD, Adhiambo Lera, Karembo, and Obaro dak).Le manioc ( Manihot esculenta Crantz) est une culture vivri\ue8re de base cultiv\ue9e par les petits agriculteurs dans les r\ue9gions marginales de l\u2019Ouest, de Littoral et de l\u2018Est du Kenya. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer les vari\ue9t\ue9s de manioc populaires pour le rendement et la teneur en cyanure dans les r\ue9gions arides et semi-arides du Kenya. L\u2019\ue9tude a \ue9t\ue9 r\ue9alis\ue9e sur cinq sites situ\ue9s dans trois sub-counties de Nakuru county in Kenya au Kenya. Les traitements comprenaient une collection de 27 vari\ue9t\ue9s de manioc sucr\ue9 obtenues dans l\u2019Ouest du Kenya. Les r\ue9sultats ont r\ue9v\ue9l\ue9 des variations importantes entre les vari\ue9t\ue9s dans tous les sites, pour tous les param\ue8tres mesur\ue9s. Les rendements les plus \ue9lev\ue9s ont \ue9t\ue9 obtenus \ue0 Subukia, la vari\ue9t\ue9 MM99 / 0067 produisant jusqu\u2019\ue0 200 t ha-1. La teneur en cyanure variait consid\ue9rablement selon les vari\ue9t\ue9s et les sites; et il \ue9tait \ue9lev\ue9 dans la plupart des cultivars, avec des niveaux plus \ue9lev\ue9s enregistr\ue9s dans la vari\ue9t\ue9 Rao Onyoni (17,3 mg 100 g-1) cultiv\ue9e sur le site de Lare. La teneur en mati\ue8re s\ue8che la plus \ue9lev\ue9e a \ue9t\ue9 enregistr\ue9e chez la vari\ue9t\ue9 Selele rabuor (60,5%), sur le site de Solai III. Les agriculteurs participants ont class\ue9 les mat\ue9riaux en fonction du rendement, du go\ufbt et de l\u2019ordre de pr\ue9f\ue9rence g\ue9n\ue9rale comme suit: Site de Subukia (MM96 / 0067, NyaTanga, Adhiambo Lera, KME-1 et MH95 / 0183); Site Lare (Nyar AICAD, Nyar Maseno, NyaTanga et MM96 / 2480); et le site de Solai (KME-1, Nyar AICAD, Adhiambo Lera, Karembo et Obaro dak)

Screening for host plant resistance to Helicoverpa armigera in selected chickpea (Cicer arietinum L) genotypes in Kenya

Hellicoverpa armigera (poad borer) is a major pest of chickpea (Cicer aurientinum) in many areas of the world, In Kenya, it causes up to 80% yield losses of the crop

Marker assisted backcross breeding to enhance drought tolerance in Kenyan chickpea (Cicer arietinum L.) germplasm

Drought is the number one constraint in chickpea production. In the past, breeding efforts to improve terminal drought tolerance have been hindered by its quantitative genetic basis and poor understanding of the physiological basis of yield in water-limited conditions

Development and characterization of wheat germplasm with combined resistance to Russian wheat aphid and stem rust (Race “Ug99”) in Kenya

Wheat is the second most important cereal in Kenya. However, production is severely constrained by both abiotic and biotic stresses. Of the biotic stresses a devastating pest (Russian wheat aphid (RWA)) and a serious disease (stem rust race TTKS (“Ug99”)) are currently the biggest problem for wheat producers in Kenya. Severe infestations by RWA may result in yield losses of up to 90% while “Ug99” infected fields may suffer 100% crop loss. The two pests combined are seriously affecting wheat farmers’ incomes because of the heavy reliance on pesticides that increase the cost of production. This study attempted to develop and characterize wheat lines that are resistant to both RWA and “Ug99” by pyramiding two major resistance genes. Three wheat varieties: “Kwale”, a Kenyan high yielding variety but susceptible to both RWA and “Ug99”; “Cook”, an Australian variety carrying stem rust resistance gene Sr36 conferring immunity to “Ug99”; and “KRWA9”, a Kenyan line with resistance to RWA but of poor agronomic attributes were used. A double cross F1 (DC F1) was obtained by crossing the F1 of “Kwale × Cook” and the F1 of “Kwale × KRWA9”. The DC F1 population was subjected to sequential screening for both RWA and “Ug99” resistance. Surviving DC F1 progenies were left to self pollinate to obtain the F2 of the double cross (DC F2). The DC F2 progenies were sequentially screened against RWA and “Ug99” to yield a population that was resistant to both RWA and “Ug99”. Genotyping of the DC F2:3 families were conducted to select homozygous resistant plants. Data indicated that the RWA and “Ug99” resistance genes were successfully pyramided. Though races with virulence for Sr36 have been reported, the gene provides immunity to race “Ug99” and can still be effectively used as a component for “Ug99” resistance breeding together with other Sr genes

Marker assisted backcross breeding to enhance drought tolerance in Kenyan chickpea (Cicer arietinum L.) germplasm

Drought is the number one constraint in chickpea production. In the past, breeding efforts to improve terminal drought tolerance have been hindered by its quantitative genetic basis and poor understanding of the physiological basis of yield in water-limited conditions