ASGSB 1998 Annual Meeting Abstracts

[49]
GROWTH IN MICROGRAVITY INCREASES SUSCEPTIBILITY OF SOYBEAN SEEDLINGS TO A FUNGAL PATHOGEN.    M. Ryba-White¹, O. Nedukha², E. Hilaire¹, J.A. Guikema³, E. Kordyum², J.E. Leach¹. ¹Dept of Plant Pathology, Kansas State University, Manhattan, KS ; ²Institute of Botany, Kiev, Ukraine, ³Division of Biology, KSU.

Extended life in microgravity will require adequate and continuous food production. Continuous crop production in contained systems and the negative effects of microgravity on plant growth will increase the potential for disease. The effects of microgravity on the susceptibility of soybean roots to disease caused by the fungal pathogen, Phytophthora sojae, were evaluated in Space Shuttle Mission STS-87 as part of the Collaborative US/Ukrainian Experiment (CUE). An experimental system was designed for use in the BRIC (Biological Research in Canisters) hardware. The design allowed soybean seed (cultivar Williams 82) to germinate in microgravity with growth directed toward the fungal inoculum. Seedlings were untreated or were inoculated with the pathogenic P. sojae isolate R25. Seedlings were fixed in microgravity at 4, 7 and 8 days after planting (DAP, flight days 3, 6 and 7). At all harvest times and in both gravity treatments, lengths of treated or untreated roots or numbers of lateral roots did not differ. No symptoms characteristic of infection by P. sojae were observed on fungal-treated seedlings at 4 DAP. At 8 DAP, however, the flight-grown roots infected with R25 showed significantly more disease (% brown and macerated areas) relative to the ground-grown roots infected with R25. Light and electron microscopy studies confirmed that soybean was more extensively colonized by R25 in flight than ground conditions. Although more fungal structures were present in the flight treatment, no morphological differences were observed in electron micrographs of fungal hyphae and haustoria. These data indicate that soybean grown in microgravity are more susceptible to colonization by a fungal pathogen relative to ground controls.

(Supported by NASA: NAG10-0142.)

Back to Meeting Program