Abstract: Use of biocontrol fungi viz., Verticillium chlamydosporium, Paecilomyces lilacinus and Talaromyces flavus alone or mixed with carbofuran significantly (P<0.05) reduced root knot indices on okra plants as compared to control. Maximum reduction in glass formation was observed in the treatments where carbofuran was used either with V. chlamydosporium or P. lilacinus. Greater increase in fresh weight of shoot was observed where P. lilacinus was used with carbofuran followed by the use of P. lilacinus alone.
Introduction
Carbofuran being one product available in the local market is generally recommended for nematode control in Pakistan (Zaki and Maqbool, 1995). Various biocontrol agents viz., Verticillium chlamydosporium, authority and Paecilomyces lilacinus authority which are parasites of eggs of root knot and cyst nematodes (Jatala et al., 1979; Zaki and Maqbool, 1993) have also been found to effectively control root knot nematodes on crop plants. Talaromyces flavus authority a biocontrol agent of root infecting fungi (Fahima and Henis, 1990; Ehteshamul-Haque et al., 1994a) has been reported to reduce root knot infestation on crop plants (Zaki and Maqbool, 1991a; Ehteshamul-Haque et al., 1994b). It was therefore considered useful to study the efficacy of V. chlamydosporium Goddard, P. lilacinus (Thom) Samson and T. flavus (Klocker) Stolk & Samson with carbofuran in the control of the root knot nematode, Meloidogyne favanica (Treub) Chitwood in okra.
Materials and Methods
Pure cultures of V. chlamydosporium, P. lilacinus and T. flavus were obtained from the Culture Collection of the Department of Botany, University of Karachi, Karachi, Pakistan. Fungi were multiplied on wheat bran in 250 ml flasks. One month old cultures of V. chlamydosporium, P. lilacinus and T. flavus respectively containing 1×106 and 2×106 cuf/g were used. Sandy loam soil, pH 8.0, supplemented with farm yard manure (2:1, soil: manure) was inoculated with wheat bran culture of biocontrol agents 1% w/w. In a separate set, soil treated with carbofuran at 11 mg a.i./kg soil mixed with inoculums of biocontrol agents. Five seeds of okra were sown in each pot, 250 g soil/pot. After sowing the seeds, soil was artificially infested with eggs and larval suspension of root knot nematode, M. javanica at 3000 eggs+J2/pot. Non inoculated and nonamended soil served as control. There were 3 replicates of each treatment and pots were randomized in green house bench at the National Nematological Research Centre, University of Karachi. The pots were watered daily and after 2 months the plants were removed and washed with running tap water. Weight and length of roots and shoots of okra plants were measured and root knot index determined on 0-5 scale as described by Taylor and Sasser (1978). Data were analysed statistically.
Results and Discussion
Use if biocontrol fungi such as V. chlamydosporium, P. lilacinus and T. flavus individually or in combination with carbofuran significantly (P<0.05) reduced root knot indices on okra plants as compared to control (Table 1). Maximum reduction in root knot indices was observed in the treatment where carbofuran was used with V. chlamydosporium or P. lilacinus followed by combined used of carbofuran with T. flavus. V. chlamydosporium or P. lilacinus used alone showed similar results as the nematicide in the control of root knot infestation on okra plants.
Use of biocontrol fungi alone or in combination with carbofuran showed significant (P<0.05) increase in shoot weight of okra as compared to control (Table 1). Maximum increase in shoot weight was observed in treatment where carbofuran was used with P. lilacinus (110%) followed by P. lilacinus (102%) used alone and where V. chlamydosporium was used with the nematicide (84%). Weight of roots of plants was less in all the treatments as compared to untreated control which may presumably be due to infestation of root knot nematodes. Plant height also increased significantly (P<0.05) in all the treatments as compared to untreated control. Maximum plant height was observed in treatment where P. lilacinus (27%) was used alone followed by carbofuran (22%) and where carbofuran was used with T. flavus (17%).
| Table 1: | Effect of biocontrol fungi with carbofuran in the control of root knot nematodes in okra |
Means followed by the same letters in each column are not significantly different at 5% level according to Duncan’s multiple range test. | |
In the present study V. chlamydosporium and P. lilacinus significantly (P<0.05) controlled infection of root knot nematode. Use of V. chlamydosporium on tomato (De Leij, 1992), chickpea (Ehteshamul-Haque et al., 1994b) and on mungbean (Abid et al., 1992) has been reported to reduce gall formation. T. flavus which is known to parasitize the microselerotia of Verticillium dahliae (Fahima and Henis, 1990) also reduced gall formation on chickpea (Ehteshamul-Haque et al., 1994b) and okra (Zaki and Maqbool, 1991b). Since greater fresh weight and reduced root knot index was observed in treatments where carbofuran was used either with P. lilacinus or V. chlamydosporium would suggest that both the antagonists are compatible with carbofuran and could thus be sued for the control of root knot nematodes as also suggested by Crump and Kerry (1986).