Effect of cropping sequence on colonization and population of VA-mycorrhiza and root-knot nematode and yield of urdbean (Phaseolus mungo Roxb.)

摘要

Urdbean (Phaseolus mungo Roxb.) is one of the most important pulses in India. It is generally grown on marginal lands with low fertilizer inputs like other pulses. It is primarily a kharif crop but is grown now as a summer crop also where irrigationis possible. It is often infected by root-knot nematode (Meloidogyne spp.) which causes 23 percent-49 percent yield losses (Ali 1997). VA-mycorrhizae have long been known to enhance the growth/yield of various crops (Gerdemann 1968; Smith and Read 1997). Pulses are highly dependent on mycorrhizae due to their high P requirement (Bethlenfalvay 1993). The density of their spores in the field and/or the degree of root colonization are considered measures of plant performance (Fyson and Oaks 1990; Wani, McGill, and Tiwari 1991) as most of the plants are mycorrhizal in nature (Gerdemann 1968). Besides other factors, crop management practices such as fallowing, and rotations involving non-hosts to mycorrhizae (Bagyaraj 1994; Black and Tinker 1979; Thompson1987; Wani and Lee 1995) have been found to adversely affect the spore density and/or root colonization. These management practices influence the nematode population also (Johnson 1985; Swarup 1995). Besides these management practices, VAM fungi have also been reported to suppress various nematodes including root-knot (Meloidogyne spp.) in agricultural crops (Hussey and Roncadori 1982; Francl 1993).