Rikhab Raj Bhansali
Central Arid Zone Research Institute, Jodhpur, 342 003 Rajasthan, India. Mexico
Scanty tree vegetation of Indian arid region is affected by a variety of biotic and abiotic factors. Basal rot diseases, caused by a wide variety of wound colonizing fungi, cause decay of the trunk, large branches, and roots of many woody plants of arid and semiarid zones. The root and butt rot fungi include Ganoderma lucidum, Inonotus hispidus, Phellinus pachyphloeus and P. badius are most frequently encountered in natural agroforestry stands in Western India. The rate of decay development within hardwoods varies with the specific wood decay fungus present and the host species involved. Decay usually develops slowly over a period of many years and may not noticeably shorten the life of an affected tree or shrub. But in recent years it causes huge mortality of Prosopis and Acacia trees. Discoloration and decay of wood are much more common and serious in over mature trees and poorly managed agroforestry stands. In living trees, most of the decay is confined to the older, wood (soft and heartwood) of roots, trunks. Once the tree is wounded, however, the outer wood or sapwood is quickly colonized by the wood-decay Ganoderma fungi. Most affected parts of the trees are root and butt regions. The lower bole has always been of most concern due to the injury during various farm machines operations in cropping period. Management of basal rot disease is difficult due the natural growth of agroforestry trees in farmer’s field and soil borne nature of pathogens. Cultural practices for disease control are cumbersome as well as non-practical because of mixed culture of trees and crops. However, biocontrol by using antagonistic fungi such as Trichoderma and Gliocladium can minimize the attack of G. lucidum. Thus management of basal rot in tree replanting areas should be based upon the following strategy: (i) use of G. lucidum uninfected soil having biocontrol fungi in polybags to grow seedlings; (ii) prevention of wounds and infection in young growing tree; (iii) eradication of all sources of Ganoderma in the field; and (iv) application of native strains of biofungicides (Trichoderma spp.) for the management of basal rots.