Wide Range Of Pathogenicity Research Articles

Pathogenic diversity of Sclerotium rolfsii isolates, a potential biocontrol agent against Parthenium hysterophorus L.

Parthenium hysterophorus L. is a wide-spread weed creating problems for agriculture and public health. Microbes and their by products is now proved to be a worthy alternative to toxic chemicals used for weed management. We determined the relative pathogenicity of ten Sclerotium rolfsii isolates recovered from diseased parts of Parthenium collected during a survey of various habitats in Central India. There was a considerable diversity amongst various isolates. The isolate designated Par # 02 from Jabalpur showed the maximum disease incidence (80%) whereas isolate Par#10 also from Jabalpur showed the lowest infection rate against targeted hosts (30%). The wide range of pathogenicity among S. rolfsii support the view that strain breeding for biological control of P. hysterophorus L. is warranted. Key words : Parthenium hysterophorus , variability, pathogenicity, Sclerotium rolfsii

Comparative analysis of pathogenicity of Cryptococcus neoformans serotypes A, D and AD in murine cryptococcosis

ObjectivesTo characterize the pathogenicity of 15 strains of Cryptococcus neoformans belonging to several serotype/mating type allele patterns (Dα, Da, Aα, Aa, Aα/Da and Dα/Aa) in experimental models of murine cryptococcosis. MethodsCD1-infected mice were examined for survival and fungal loads in either brain or lung during the course of infection. ResultsAll strains, with the exception of one Da strain, produced melanin in vitro. Similarly, all strains were encapsulated and produced phospholipase. When CD1 mice were challenged intravenously (i.v.) with 5×105CFU/mouse and observed for 60 days post-infection, a significant variation of mortality rate was observed among mice infected with different strains. Aα and Aα/Da strains all produced 100% mortality within the study period with mean survivals significantly shorter than those of mice infected with strains belonging to any other allele type (P<0.0001). A wide range of pathogenicity was shown by haploid and diploid strains presenting Dα allele. This finding was confirmed by an intranasal model of challenge. To investigate the progression of infection, the mice were challenged i.v. with 5×104CFU/mouse and tissue burden experiments (brain and lung) were performed on days 6 and 12 post-infection. Only the mice infected with Aα and Aα/Da strains showed a >1log10 increase of CFU/g in both tissues throughout the study period. ConclusionsOur results suggest that the presence of the Aα mating type allele in either haploid or diploid strains is correlated with virulence, while the presence of the Aa or Da allele in haploid strains is associated with moderate or no virulence. Finally, either haploid or diploid strains presenting Dα allele vary in virulence.

Pathogenicity of Meloidogyne spp. (Tylenchida: Meloidogynidae) isolates from Central America and Brazil on four genotypes of Coffea arabica

Abstract Fifteen isolates of Meloidogyne spp. collected from coffee plantations in every country in Central America, with one isolate from Brazil, were inoculated on two common cultivars (Catuai and Sarchimor) and two wild genotypes from Ethiopia (ET15 and ET28) of coffee (Coffea arabica) under controlled conditions. These isolates displayed a wide range of pathogenicity on the different varieties. Meloidogyne sp. 2 isolate esterase 'VS1S1' from Guatemala, was unable to multiply on any cultivar. All other isolates multiplied on cv. Catuai. The Meloidogyne incognita isolate from Brazil did not multiply on cv. Sarchimor or genotype ET28. Four Meloidogyne sp. 1 (esterase 'F1') isolates from Guatemala multiplied at relatively low rates on cv. Sarchimor, but did not multiply on genotypes ET15 and ET28. Meloidogyne arenaria and Meloidogyne sp. 3 (displaying the new esterase phenotype 'M1F1a'), both from El Salvador, multiplied at a high rate on cv. Sarchimor; M. arenaria multiplied at a low rate on genotype ET15, but did not multiply on genotype ET28. Meloidogyne sp. 3 multiplied at a low rate on genotype ET28. Meloidogyne sp. 4 from El Salvador (esterase 'Sa4') multiplied at a high rate on genotype ET15. The M. arabicida isolate from Costa Rica did not multiply at all on genotype ET15. All isolates of Meloidogyne exigua multiplied on cv. Sarchimor as well as on both Ethiopian genotypes. This new information highlights the great parasitic diversity of root-knot nematodes parasitising coffee in Central America, a diversity which must be taken into account when developing integrated pest management strategies and breeding for resistance to nematodes.

Assessment of pathogenicity ofRhizoctonia solani Kühn to some potato tissues and to cereals

Isolates ofRhizoctonia solani Kuhn were tested for their pathogenicity to potato sprouts growing from seed tubers. Those originating from sclerotia on tubers showed a wide range of pathogenicity but those from sprout tissue were only moderately pathogenic. Similar results were not obtained with detached potato sprouts, leaflets, or stem tips. Isolates from sclerotia which were very pathogenic to tubers, also caused considerable damage to sprouts, but isolates from potato caused little damage to wheat and barley seedlings compared to that caused by wheat isolates.

The Influence of Calcium on the Susceptibility of Peanut Pods to Pythium Myriotylum and Rhizoctonia Solani1

Abstract No correlation was found between calcium applied at an equivalent rate of either 897 or 1,793 kg/ha in an artificial medium and the amount of pod breakdown incited by either Pythium myriotylum or Rhizoctonia solani. R. solani appeared to be the dominant organism although the isolates tested exhibited a wide range of pathogenicity to peanut pods.