Biological Control of Pythium Damping-off of Bush Okra Using Rhizosphere Strains of Pseudomonas fluorescens

A severe damping-off disease of bush okra caused by Pythium aphanidermatum, was diagnosed in plastic houses in Der Attia village, 15 km southwest of El-Minia city, Egypt, during the winter of 2001. Bush okra seedlings showed low emergence with bare patches inside the plastic houses. Seedlings that escaped pre-emergence damping-off showed poor growth, stunting and eventually collapsed. Examination of the infected tissues confirmed only Pythium aphanidermatum, showing its typical intercalary antheridia, and lobulate zoosporangia. P. aphanidermatum was shown to be pathogenic on bush okra under pot and field experiments. Bacteria making inhibition zones against the damping-off fungus P. aphanidermatum were selected. Agar discs from rhizosphere soil of bush okra containing colonies were transferred onto agar plate culture of P. aphanidermatum. After 2 days of incubation, colonies producing clear zones of non-Pythium growth were readily detected. The two bacteria with the largest inhibition zones were identified as Pseudomonas fluorescens. Bush okra emergence(%) in both pot and plastic houses experiments indicated that disease control could be obtained by applying P. fluorescens to the soil or coating the bacteria to the bush okra seeds before sowing. In the plastic houses, application of the bacteria onto Pythium-infested soil and sowing bush okra seeds dressed with bacteria gave 100% emergence. In addition, This was the first reported disease of bush okra by this oomycete in Egypt.

Kinds, Abundance and Pathogenicity of Pythium Species Isolated from Maize Rhizosphere of Various Habitats in El-Minia Governorate, Egypt

A total of 374 Pythium isolates were isolated and identified from the rhizosphere soils of maize plants grown in 100 different agricultural fields in nine provinces at El-Minia Governorate, Egypt. Five Pythium spp. of P. deliense, P. graminicola, P. irregulare, P. oligandrum and P. splendens were obtained P. deliense and P. oligandrum were predominant in all of the locations with 48.1% and 41.4% of total counts, respectively. P. graminicola, P. irregulare and P. splendens were not isolated in 4, 2 and 4 provinces out of 9 provinces with 5.3%, 3.5%, and 1.6% of isolation percentage from total counts, respectively. Number of Pythium isolates in each were 34, 31, 34, 33, 34, 96, 37, 37 and 38 out of 374, for locations of El-Edwa, Maghagha, Beni-Mazar, Matai, Samalout, El-Minia city, Abou-Querquas, Mallawi and Der Mawas, respectively. Pre- and post-emergence pathogenicity tests indicated that only P. deliense was highly pathogenic to germinating grains and seedlings of maize whereas P. oligandrum was non-pathogenic.

Dynamics of phytoplankton succession in the river Nile at Minia [upper Egypt]; as influenced by agricultural runoff

The influence of agricultural wastewater effluents dumped to the Nile water at Minia [Upper Egypt] on phytoplankton distribution, diversity, succession and standing crop was monthly evaluated in a comprehensive study for one year. Autumn harboured the highest standing crop at all sites. Bacillariophyta contributed the highest percentage composition. Chlorophyta and Cyanophyta rated second and third in the order of dominance, Euglenophyta was poorly represented however, some members of the three groups tended to form blooms at certain times. The agricultural runoff induced gross changes in physico chemical characteristics of the Nile water and community structure of phytoplankton populations. Species of high occurrence being densely encountered at all sites were excelled by: Tabellaria fenestrata. Cyclotella bandanica, Cocconeis caespidata and Microcystis aeruginosa