University of Khartoum

Epidemiology of Potato Viruses Affecting Potato Crop Grown Under Semi-Arid Conditions of the Sudan

Epidemiology of Potato Viruses Affecting Potato Crop Grown Under Semi-Arid Conditions of the Sudan

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Title: Epidemiology of Potato Viruses Affecting Potato Crop Grown Under Semi-Arid Conditions of the Sudan
Author: Mohammed, Nafisa Hussein Baldo
Abstract: Field surveys and experiments were conducted at different locations in Khartoum and River Nile states to study the epidemiology of viruses affecting potato crop grown under the semi-arid conditions of the Sudan. Field surveys were carried out for three consecutive seasons (1999/2000, 2000/2001 and 2001/2002) at three locations in Khartoum state (Elnayia, Elshehinab and Shambat) plus one main seed growing area in River Nile state (i.e. Elmisiektab) to detect and estimate the occurrence of viruses spreading in commercial seed and ware potato field and to compare virus incidence in different seed grades. In 1999/2000 and 2000/2001, significant differences were obtained between locations and seed grades as well as significant interactions between locations and seed grades in total virus incidence. The total virus incidence (%) in the basic seed stock increased from zero percent to 3.3 % and 40 % in the once-grown in 1999/2000 and 2000/2001, respectively. While the incidence in the certified stocks increased in season 2000/2001 to 4 % and 98.1% in once and twice-grown locally multiplied seed. Four important viruses were recorded in commercial potato fields and were identified as potato leaf roll virus (PLRV), potato virus Y (PVY), beet curly top virus (BCTV), alfalfa mosaic virus (AMV) depending on visual diagnostic symptoms and/or sero-diagnosis using dot-Immuno-blotting assay (DIBA). The incidence of these viruses were in the range of: PLRV, 0-13.3 %, PVY, 0-44.67 %, BCTV, 0-100 % and AMV, 0-100 %. Significant differences were noticed between seed grades and locations in incidence of individual viruses but not in all seasons. The interaction between locations and seed grades was significant in 1999/2000. Significant interactions between locations and seed grades were also observed in almost all seasons under test. The individual viruses were least in certified (G0). The present thesis reports for the first time the occurrence of AMV and potato virus M (PVM) in potatoes grown in the Sudan. Replicated experimental plots were conducted at two locations, Elnayia and Shambat for 2 consecutive seasons (1999/2000 and 2000/2001) to evaluate the virus status of different seed grades and to assess the role of aphid populations in the virus spread and its impact on potato yield. The differences between seed grades were significant in all parameters assessed (i.e. emergence (%), number of stems/hill, total virus incidence and total yield). The emergence % varied between 53.6% and 97.2 % at Elnayia and 91.2 to 100 % at Shambat. The lowest emergence % was noticed in G0. The number of stems/hill in the different seed grades ranged between 1.79-3.31 at Elnayia and 2.13-4.63 at Shambat. In 1999/2000 the final tuber yield in the different seed grades varied between 6.32-18.89 (tons ha-1) at Elnayia and 7-12.5 (tons ha-1) at Shambat. In 2000/2001 the final tuber yield was 10.4-29 (tons ha-1) at Shambat. The once-grown seed (G1) produced significantly the highest yield followed by once-grown of basic seed (B1) and certified seed (G0). Total virus incidence in the different seed grades grown at Elnayia was estimated at 0.30% to 87.6 %. At Shambat, the total virus incidence was found to vary between 56 % to 100 %. The certified seed (var. Alpha) consistently scored the smallest number of stems/hill. But the degenerative conditions at the two locations seems to influence the levels of infection in the different seed grades. Aphid populations in both locations were not detected during December and January, but they were appeared in February. The aphid count / 100 leaves was appreciably high at Shambat (i.e. 6558, 5000) in the 1st and 2nd seasons, respectively while it was very low in both seasons at Elnayia (0,50).
Description: December 2003151page
URI: http://khartoumspace.uofk.edu/handle/123456789/10529
Date: 2015-05-11


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