Production of Phytophthora infestans oospores in planta and inoculum potential of in vitro produced oospores under temperate highlands and subtropical plains of India

Summary High moisture content of the host tissue ( 88%) and low ambient r.h. (50-54%) favoured oospore formation under controlled environments. It took 14–16 days for oospores to develop; thereafter the number of oospores increased with time and decreased with moisture content of host tissue. High ambient r.h. (> 80%) did not favour oospore formation under field or controlled conditions. Oospore formation was detected in inoculated plants grown in the field when the ambient r.h. declined to 74% and moisture content of host tissue decreased to 83.7–85.6%. It took 8 days (cv. Kufri Chandramukhi) to 13 days (cv. Kufri Jyoti and Kufri Badshah) for oospores to develop. Cultivars also differed in their response to oospore production, cv. Kufri Chandramukhi being more responsive (4800 oospores g−1 f wt) than cv. Kufri Jyoti and Kufri Badshah (1320 and 390 oospores g−1 f wt respectively). Oospores produced in vitro remained viable when buried in soil in the temperate highlands of Himachal Pradesh and sub-tropical plains of Uttar Pradesh, India for more than 150 days, i.e. beginning of the next crop season. The oospores germinated and initiated late blight infection at the base of the stems after 21–30 days of incubation of the potato plants raised in oospore-infested soil. It took 2 days for newly formed oospores to germinate and this delay time increased to 75–77 days after 180-days burial. It took 15 days for their germination (47%) in soil extract as compared to 50 days in sterilised distilled water.

[1]  S. Roy,et al.  Occurrence of the A2 mating type ofPhytophthora infestans in India , 1994, Potato Research.

[2]  L. C. Davidse,et al.  Oospore formation by Phytophthora infestans in host tissue after inoculation with isolates of opposite mating type found in the Netherlands , 1987, Netherlands Journal of Plant Pathology.

[3]  N. Grünwald,et al.  Formation, production and viability of oospores of Phytophthora infestans from potato and Solanum demissum in the Toluca Valley, central Mexico , 2001 .

[4]  A. Mulder,et al.  Production, survival and infectivity of oospores of Phytophthora infestans , 2000 .

[5]  C. Smart,et al.  Oospore Survival and Pathogenicity of Single Oospore Recombinant Progeny from a Cross Involving US-17 and US-8 Genotypes of Phytophthora infestans. , 2000, Plant disease.

[6]  D. S. Shaw,et al.  Sprinkling irrigation enhances production of oospores of phytophthora infestans in field-grown crops of potato. , 2000, Phytopathology.

[7]  C. Smart,et al.  Implications of Sexual Reproduction for Phytophthora infestans in the United States: Generation of an Aggressive Lineage. , 2000, Plant disease.

[8]  M. Wikström,et al.  Infection of Potatoes by Oospores of Phytophthora infestans in Soil. , 1999, Plant disease.

[9]  H. W. Platt,et al.  Viability of oospores of Phytophthora infestans under field conditions in northeastern North America , 1999 .

[10]  Y. Cohen,et al.  Oospore Production of Phytophthora infestans in Potato and Tomato Leaves. , 1997, Phytopathology.

[11]  F. Govers,et al.  Formation and survival of oospores of Phytophthora infestans under natural conditions , 1995 .

[12]  R. Shattock,et al.  Viability, germination and infection potential of oospores of Phytophthora infestans , 1994 .

[13]  Barak A. Cohen,et al.  Historical and recent migrations of Phytophthora infestans: chronology, pathways and implications. , 1993 .

[14]  A. Ogoshi,et al.  Formation of Oospores by Phytophthora infestans in Inoculated Potato Tissues , 1991 .

[15]  J. Wilson,et al.  Identity and pathogenicity of two Marasmius species from the sterile white basidiomycete complex , 1991 .

[16]  D. Erwin,et al.  Morphology, Plasmolysis, and Tetrazolium Bromide Stain as Criteria for Determining Viability of Phytophthora Oospores , 1990 .

[17]  W. Fry,et al.  Genetics of Phytophthora infestans: determination of recombination, segregation, and selfing by isozyme analysis , 1986 .

[18]  H. Förster.  Factors Affecting Oospore Germination of Phytophthora megasperma f. sp. medicaginis , 1983 .

[19]  E. D. Sutherland,et al.  Evaluation of tetrazolium bromide as a vital stain for fungal oospores. , 1983 .

[20]  J. Mitchell,et al.  Factors affecting oospore germination in Phytophthora cactorum, the incitant of apple collar rot. , 1976 .