Host resistance mechanisms and cultural practices for control of gray leaf spot (cercospora zeae rnaydis) of maize in Tanzania
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Date
2011
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Publisher
Sokoine University of Agriculture
Abstract
Studies were carried out in selected villages of the Southern and Eastern Maize Agro-
ccological Zones to assess the potential variations in isolate aggressiveness, nature
and genetics of host resistance and explore cultural methods suitable for the
management of gray leaf spot. Southern Zone isolates (Mbcya and Iringa) grew 0.25
mm per day faster (9.3%), formed 1.1 cm longer lesions (25.9%), produced 1.1 x 104
more spores per cm2 of the lesion (13.6%), formed symptoms 1 day earlier, caused
21.2% more disease and produced more toxins than the Eastern Zone isolates.
Significantly (P<0.05) more germlings of C. zeae mayclis were established after
penetration on susceptible than on resistant and moderate resistant maize genotypes.
Histological studies suggest the possible involvement of inhibitory substances in host
cell, a possible resistance mechanisms against C. zeae maydis in maize. Heritability
and gene effect estimates for components of partial resistance to gray leaf revealed
significant differences between generations, crosses and generation x cross and
generation x location interactions. Results have shown that lesion size, lesion length,
lesion numbers and disease severity could be used for selection of partial resistance
to gray leaf spot based on field measurements. Composted cattle manure lowered
gray leaf spot compared to CAN by 29. 4% at 60 kg N ha'1 and by 32.2% at 90 kg N
ha’1 followed by composted poultry manure 24.5% and 22.9% and urea 17.6% and
18.2% at 60 kg N ha’1 and 90 kg N ha respectively. Grain yield in composted cattle
manure, composted poultry manure and urea fertilization was 1.41 ha’1, 0.91 ha’1, 0.6
t ha1 and 4.2 t ha’1, 3.7 t ha’1, 3.4 t ha’1 higher compared to CAN and none fertilized
(control) treatments respectively. There was an overall yield increase of about 41 %
in the intercropping compared to non-intercropping on susceptible maize cv ‘Pannar
(PAN 6549). It is recommended that breeders should consider the most aggressiveiii
isolates (MBY1, MBZI, IGAW1 and NJB1) and (DOMI, MKI1 and MGTl) when
screening and breeding for resistance cultivars to gray leaf spot in the Southern
highlands and Eastern agro-ecological Zone respectively.
Description
Keywords
Epidemiology, Gray leaf spot, Ercospora zeae rnaydis, Taxonomy, Tanzania, Maize production, Maize production systems