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Population structure and epidemiology of Bipolaris sorokiniana in the rice-wheat cropping pattern of Nepal

By: Ruckstuhl, M | Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), Mexico DF (Mexico).
Contributor(s): Duveiller, E.|Dubin, H.J.|Reeves, J.|McNab, A [eds.].
Material type: materialTypeLabelBookAnalytics: Show analyticsPublisher: Mexico, DF (Mexico) CIMMYT|UCL|BADC : 1998ISBN: 970-648-001-3.Subject(s): Bipolaris | Crop management | Cropping patterns | Cropping systems | Epidemiology | Helminthosporium | Nepal | Oryza | Pathogens | CIMMYT | Triticum | Triticum aestivum AGROVOCDDC classification: 633.1194 Summary: Fungal species were isolated from foliar blight symptoms on spring wheat cultivars in the rice-wheat cropping pattern in the subtropical terai belt of Nepal. Bipolaris sorokiniana, Drechslera tritici-repentis, and several Curvularia spp. were identified from indistinguishable lesions typically associated with helminthosporium leaf blight (HLB) symptoms. HLB was successfully controlled with three to four foliar applications of propiconazole at a rate of 125 ml ai ha-1. Assessment of crop losses in 13 farmers' fields in 1990, 91 indicated significant wheat yield losses of 10.7% or 250 kg ha-1 on the most popular commercial variety UP262 due to HLB. To estimate crop losses of rice and wheat due to soilborne pathogens, solar heating through plastic mulching (soil solarization) was carried out in a series of split-plot experiments, combined with foliar fungicide applications to the wheat crop in farmers' fields in 1992/93. Soil solarization, before rice transplanting in May, increased the mean daily maximum temperature at the soil surface by more than 25 ºC and reached 65 ºC in the top-soil layer. Subsequent rice yields increased by 32%; yield of the succeeding wheat crop in fungicide protected plots increased by 25%, and in unprotected plots by 15%. Fungicide application enhanced grain yields by 15% in salaried and 6% in nonsolarized plots, mainly through an increase in 1000-grain weight. information on the population structure of B. sorokiniana was improved from a total of 799 fungal isolates divided into 17 populations, collected from five countries (Bolivia, Canada, Nepal, Mexico, and Switzerland). The isolates were characterized by means of randomly amplified polymorphic DNA (RAPD) obtained by polymerase chain reaction (PCR). Cluster analysis, using multidimensional scaling of Neil's genetic distance, clearly segregated populations into five groups according to region of origin. Gene flow, however, may be strong enough to prevent geographic isolation of populations both within and among regions. The percentage of total gene diversity that was allocated to differences among isolates within populations was 83%; of the remaining variance, 3% was attributed to differences among populations within regions, and 14% among regions.Collection: CIMMYT Publications Collection
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Conference proceedings CIMMYT Knowledge Center: John Woolston Library

Lic. Jose Juan Caballero Flores

 

CIMMYT Publications Collection 633.1194 DUV (Browse shelf) 1 Available M624337
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Fungal species were isolated from foliar blight symptoms on spring wheat cultivars in the rice-wheat cropping pattern in the subtropical terai belt of Nepal. Bipolaris sorokiniana, Drechslera tritici-repentis, and several Curvularia spp. were identified from indistinguishable lesions typically associated with helminthosporium leaf blight (HLB) symptoms. HLB was successfully controlled with three to four foliar applications of propiconazole at a rate of 125 ml ai ha-1. Assessment of crop losses in 13 farmers' fields in 1990, 91 indicated significant wheat yield losses of 10.7% or 250 kg ha-1 on the most popular commercial variety UP262 due to HLB. To estimate crop losses of rice and wheat due to soilborne pathogens, solar heating through plastic mulching (soil solarization) was carried out in a series of split-plot experiments, combined with foliar fungicide applications to the wheat crop in farmers' fields in 1992/93. Soil solarization, before rice transplanting in May, increased the mean daily maximum temperature at the soil surface by more than 25 ºC and reached 65 ºC in the top-soil layer. Subsequent rice yields increased by 32%; yield of the succeeding wheat crop in fungicide protected plots increased by 25%, and in unprotected plots by 15%. Fungicide application enhanced grain yields by 15% in salaried and 6% in nonsolarized plots, mainly through an increase in 1000-grain weight. information on the population structure of B. sorokiniana was improved from a total of 799 fungal isolates divided into 17 populations, collected from five countries (Bolivia, Canada, Nepal, Mexico, and Switzerland). The isolates were characterized by means of randomly amplified polymorphic DNA (RAPD) obtained by polymerase chain reaction (PCR). Cluster analysis, using multidimensional scaling of Neil's genetic distance, clearly segregated populations into five groups according to region of origin. Gene flow, however, may be strong enough to prevent geographic isolation of populations both within and among regions. The percentage of total gene diversity that was allocated to differences among isolates within populations was 83%; of the remaining variance, 3% was attributed to differences among populations within regions, and 14% among regions.

English

9806|AGRIS 9802

Jose Juan Caballero

CIMMYT Publications Collection

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