TY  - PRO
AU  - Van Dyk,K.
AU  - Du Toit Meiring,J.J.
AU  - Kuwite,C.A.
AU  - Meyer L.
ED  - Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), Addis Ababa (Ethiopia)
TI  - Patchy stunting of wheat and barley in Tanzania -- preliminary results
SN  - 92-9146-058-3
PY  - 1999///
CY  - Addis Ababa (Ethiopia)
PB  - CIMMYT
KW  - Barley
KW  - Disease resistance
KW  - AGROVOC
KW  - Pathogens
KW  - Plant diseases
KW  - Rhizoctonia solani
KW  - Tanzania
KW  - Triticum
KW  - CIMMYT
N1  - Abstract only
N2  - Patchy stunting (PS) of cereals has been observed on wheat farms of the Hanang Wheat Complex, Tanzania, since the early 1970s and recently also on farms at West Kilimanjaro and Karatu. Estimated yield losses amount to approximately 5-30%, but could be as high as 40-50% during drier years on newly-broken land. A survey was conducted to determine the incidence of the PS pathogen (Rhizoctonia solani AG-6) and other pathogenic fungi in the main production areas and in different soil types. Potentially pathogenic fungal species comrnonly isolated from roots and crowns of wheat and barley included: Bipolaris sorokiniana, Fusarium equiseti, F. nygamai, F. oxysporum, F. solani, Periconia macrospinosa and Rhizoctonia spp. Roots yielded mainly Fusarium spp., whereas B. sorokiniana was predominantly and almost exclusively isolated from crowns. The incidence of fungi in the various soil types and production areas did not differ significantly. Contrary to crater disease of wheat in South Africa, PS occurs not only in black montmorillonitic clay soils, but also in clay, clay loam and sandy clay soils. However, the disease is more pronounced in the predominating black clay soils. Chemical analysis of the different soil types revealed significantly higher levels of Ca, Mg and Na and a lower K content in the black soil compared to the other soil types. Accordingly, in vitro growth of R. solani AG-6 was stimulated by increasing levels of Ca, Mg and Na, whereas high concentrations of K inhibited the organism
ER  -