PATHOGENIC FUNGI AND NEMATODES AFFECTING ROOTS OF CUCUMBER PLANTS GROWN IN COMPACTED RICE STRAW BALES COMPARED WITH NATURAL SOILS.

The cultivations of cucumber seedlings , Hesham cv ., on compacted rice straw bales were carried out in unheated plastic greenhouses in EL – Nuberia / Beheira Governorate and Abo – Khalifa / Ismailia Governorate during the winter season  of 2007 . The occurrence of basal stem rot, root rot, wilt and root knot nematodes in cucumber plants grown in rice straw bales (mean of the two locations) reached 1.05, 0.62, 0.35 and 0.27 %, respectively. However, the corresponding figures for cucumber plants grown in natural infested soil under the same conditions were 12.37, 11.52, 23.3 and 16.62 %, respectively. Fusarium oxysporum and Pythium ultimum were the most common microorganisms invading cucumber roots as they recorded the highest rates during isolation reached  about 48 and 36 %, respectively. Rhizoctonia solani and Fusarium solani occurred in less frequency recorded 24 and12 %, respectively of total count of fungal colonies developed from 25 tested samples. Pathogenicity test proved that all pathogens are pathogenic to cucumber causing pre and post emergence damping off, root rot and wilt of adult plants. Determination of pathogenic nematodes in natural soil and rice straw bales recorded the presence of 360 juvenile (J2) of Meloidogyne spp. and 70 juvenile (J2) of Tylenchorhynchus sp. per 250 g natural soil (average of two locations). However, the pathogenic nematodes were absent in rice straw . The temperature degrees around roots in rice straw bales increased by about 3 to 5 C^o compared to those cultivated in the natural soil during the winter season. This favored the plant growth, increasing fresh weight,plant height and the development of leaves. It influenced the number of fruits and finally the yield that was considerably higher in rice straw bales than that in natural soil. Due to the higher temperature in rice straw bales the phenomenon of fruit abortion was completely absent. Cucumber plants grown in rice straw bales recorded lower E.C. (ppm) value around the roots compared with natural soil during different stages of cucumber development. In the natural soil, EC value increased with increasing the plant age .Accumulation of excessive amounts of nutrients takes place in natural soil ( 3.63 EC equal to 2320 ppm) more than in rice straw bales (2.19 EC. equal to1400 ppm). The pH value around the roots of cucumber plants grown in straw bales ranged from 6.3 to 6.6 (slightly acidic substrate). However, the pH around the roots of cucumber plants grown in natural soil ranged from 7.4 to 8.4 (alkaline soil).