EFFICIENCY OF SOME ECHO FRIENDLY MICROELEMENTS IN CONTROLLING SOYBEAN DAMPING-OFF

Abstract

Soybean plants doubted to be infcted with damping-off were collected from different naturaly infected districts of Dakahlia Governorate. Frequency of the isolated pathogens revealed that Fusarium solani, Fusarium oxysporum, Rizoctonia solani, Pythium ultimum and Macrophomina Phaseolina. were the most aggressive pathogenic fungi causing the highest percentage of preemergence damping-off in Giza 35and Giza 111soybean cultivars. Among the five isolated fungi, only F. solani, R. solani and P. ultimum were the most pathogenic ones. F. solani exhibit the highest percentage of post-emergence damping-off in both cultivars followed by R. solani. Moreover,the highest percentage of haelthy survived soybean plants were obtained when Pythium ultimum, was investigated. In vitro study boron, cobalt and molybdenum proved microelemnts that Fusarium solani was the most affected pathogen when evaluated at any of microelements compared with R. solani and P. ultimumthe. Cobalt at 5ppm reveal the highest growth reduction percentage against the 3 fungi where it valued 74%. However, the least inhibitory effect was recorded when molybdenum used at 2ppm being 34.77% for the three pathogenic fungi. Whereas, boron at 2 ppm was apparently equal with molybdenum at 5 ppm. In vivo experiments of two consecutive growing seasons 2016 and 2017, revealed that molybdenum(5 ppm) proved to be the most effective where the least percentages of both pre and post emergence (5.66) were obtained followed by cobalt (2 ppm) resulting 8%, meanwhile, boron (2 ppm) was the least effective revealed 9% .Plant morphological parameters in treated soybean showed that plant height ranged from 89 cm for boron (5 ppm) and 111.6 cm for molybdenum cultivar 35 (5 ppm) in growing season 2016 and ranged from 96.0 cm for boron (5 ppm) and 118.6 cm for molybdenum (5 ppm) in 2017 season. The highest chlorophyll a and b values were affected by the application of molybdenum followed by cobalt then boron. Carotenoids and total phenols revealed the highest values when Cobalt (2 ppm), was used. Oil and protein percentages in soybean seeds reported the highest values when molybdenum was applied followed with cobalt.