ABSTRACT To determine the distribution of Stagonospora nodorum and Pyrenophora tritici-repentis o... more ABSTRACT To determine the distribution of Stagonospora nodorum and Pyrenophora tritici-repentis on wheat in Ohio, flag leaves with lesions were collected from wheat-producing counties in 2002 and 2003. Counties were arbitrarily grouped into seven regions. Log-linear analysis of pathogen presence within regions indicated that the presence of S. nodorum was independent of the presence of P. tritici-repentis. A logistic analysis revealed that the occurrence of both pathogens varied by region in one or both years. The aggressiveness of S. nodorum isolates was determined by inoculating two susceptible genotypes with a subsample of isolates from each region from both years. S. nodorum isolates obtained from northeast Ohio, with fewer wheat fields, were less aggressive than those from other regions. Isolates obtained from west-central Ohio, surrounded by regions with high wheat production annually, were significantly more aggressive than those obtained in the remaining five regions. Isolates from the five other regions did not differ significantly (P > 0.05) in aggressiveness. Races 1 and 2, and a few race 3 isolates, of P. tritici-repentis were detected in Ohio. The distribution of P. tritici-repentis races 1 and 2 was not associated with any region, although the prevalence of race 1 was three times greater than race 2. The rarer race 3 was associated with three dispersed regions. Results indicate that S. nodorum was the major wheat leaf-blotching pathogen. There were no positive or negative associations of S. nodorum and P. tritici-repentis or individual races of P. tritici-repentis in any of the tested regions, which indicates that neither pathogen can be used to predict the presence of the other. The isolated northeastern corner of Ohio appeared to contain isolates of S. nodorum with unique characteristics and potentially only one race of P. tritici-repentis, indicating that this area may be genetically isolated from the remaining tested areas of the state.
In western Kenya, groundnuts (Arachis hypogaea L.) is one of the major legumes where it is not on... more In western Kenya, groundnuts (Arachis hypogaea L.) is one of the major legumes where it is not only the principal source of protein but also a major source of small-holder cash income. However, groundnut production has continued to decline with farmers realizing less than 50% of the yield potential. Viral diseases play a great role in yield reduction. Cowpea mild mottle virus (CPMMV) has been reported to be one of the viruses infecting groundnuts but its status in western Kenya was not known. Therefore this study sought to establish whether the virus was already infecting groundnuts in this region. Two surveys were conducted in seven major groundnut growing Counties of western Kenya; Bungoma, Busia, Vihiga, Siaya, Migori, Nandi and Homabay, basing on various Agro-ecological zones (AEZs). Leafy samples were collected and tested by DAS-ELISA. Indicator plants were mechanically inoculated with CPMMV from positive samples and symptoms observed. The disease was found to be widespread in all the AEZs surveyed with high incidence at farm levels. Most farmers were found to use uncertified seed. ELISA tests confirmed the presence of CPMMV in the leafy samples collected from the farms. The virus induced varied symptoms on indicator plants tested. All the indicator plant used were major legumes grown in western Kenya and were found to be susceptible to CPMMV. This implies that CPMMV is a serious threat to legume production in western Kenya
ABSTRACT To determine the distribution of Stagonospora nodorum and Pyrenophora tritici-repentis o... more ABSTRACT To determine the distribution of Stagonospora nodorum and Pyrenophora tritici-repentis on wheat in Ohio, flag leaves with lesions were collected from wheat-producing counties in 2002 and 2003. Counties were arbitrarily grouped into seven regions. Log-linear analysis of pathogen presence within regions indicated that the presence of S. nodorum was independent of the presence of P. tritici-repentis. A logistic analysis revealed that the occurrence of both pathogens varied by region in one or both years. The aggressiveness of S. nodorum isolates was determined by inoculating two susceptible genotypes with a subsample of isolates from each region from both years. S. nodorum isolates obtained from northeast Ohio, with fewer wheat fields, were less aggressive than those from other regions. Isolates obtained from west-central Ohio, surrounded by regions with high wheat production annually, were significantly more aggressive than those obtained in the remaining five regions. Isolates from the five other regions did not differ significantly (P > 0.05) in aggressiveness. Races 1 and 2, and a few race 3 isolates, of P. tritici-repentis were detected in Ohio. The distribution of P. tritici-repentis races 1 and 2 was not associated with any region, although the prevalence of race 1 was three times greater than race 2. The rarer race 3 was associated with three dispersed regions. Results indicate that S. nodorum was the major wheat leaf-blotching pathogen. There were no positive or negative associations of S. nodorum and P. tritici-repentis or individual races of P. tritici-repentis in any of the tested regions, which indicates that neither pathogen can be used to predict the presence of the other. The isolated northeastern corner of Ohio appeared to contain isolates of S. nodorum with unique characteristics and potentially only one race of P. tritici-repentis, indicating that this area may be genetically isolated from the remaining tested areas of the state.
In western Kenya, groundnuts (Arachis hypogaea L.) is one of the major legumes where it is not on... more In western Kenya, groundnuts (Arachis hypogaea L.) is one of the major legumes where it is not only the principal source of protein but also a major source of small-holder cash income. However, groundnut production has continued to decline with farmers realizing less than 50% of the yield potential. Viral diseases play a great role in yield reduction. Cowpea mild mottle virus (CPMMV) has been reported to be one of the viruses infecting groundnuts but its status in western Kenya was not known. Therefore this study sought to establish whether the virus was already infecting groundnuts in this region. Two surveys were conducted in seven major groundnut growing Counties of western Kenya; Bungoma, Busia, Vihiga, Siaya, Migori, Nandi and Homabay, basing on various Agro-ecological zones (AEZs). Leafy samples were collected and tested by DAS-ELISA. Indicator plants were mechanically inoculated with CPMMV from positive samples and symptoms observed. The disease was found to be widespread in all the AEZs surveyed with high incidence at farm levels. Most farmers were found to use uncertified seed. ELISA tests confirmed the presence of CPMMV in the leafy samples collected from the farms. The virus induced varied symptoms on indicator plants tested. All the indicator plant used were major legumes grown in western Kenya and were found to be susceptible to CPMMV. This implies that CPMMV is a serious threat to legume production in western Kenya
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