Emerging Topic in Current Issue
Biological management of Orobanche with Fusarium oxysporum - a new record from India During extensive surveys of rapeseed mustard fields, in Churu and Jhunjhunu districts of Rajasthan and Mahendragarh district of Haryana in Rabi crop season (2004- 06), Rapeseed mustard crop was found to be heavily infested with an angiospermic root parasite Orobanche ramosa, ranging from 10-90 % infection.
The genus Orobanche is known to possess more than 100 different species but only seven are considered to be economically important viz., Orobanche crenata, O. minor, O. cumana, O. aegiptaca, O. cernua and O. foetida are the other devastating species infesting leguminous, asteracious and solanaceous crops. The parasitic weed was found in different stages of its growth from budding to flowering stage in rapeseed mustard field. This weed was found to cause very heavy level of crop damage in terms of both quality and yield. Orobanche is difficult to be controlled in rapeseed mustard fields with the help of conventional methods of control using herbicides as they can cause injury to host plant (3) and also because of the biological nature of the weed parasite. This weed plant produces very large amount of small seeds approximately 5 lakhs per fully grown Orobanche plant. These seeds remain viable for decades even in the absence of the host. Orobanche seeds germinate only after receiving stimulation by the host root exudates by means of germ tube. This germ tube when near enough to the root of the host plant attaches itself with the help of haustorium and start drawing nutrition from the host plant. However, in absence of near vicinity of host root the germ tube dries up. Other reason being that Orobanche plants have long underground phase and by the time of their emergence they have already completed final damage to the host (5).Therefore biological management of this weed is considered to be the only suitable alternative (1,2).   The article is featured in Vol. 60(2):2007 by Dr. R.K. Sharma et al., Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi 110012, India Full Text