|Keywords (Extracted from title, table of contents and abstract of thesis)
fungi, root rot, root knot disease, macrophomina phaseolina, rhizoctonia solani, fusarium moniliforme, f. oxysporum, f. semitectum, f. solani, selerotium rolfsii, pythium aphanidermatum, botryodiplodia theobromae, curvularia lunata, c. oryzae, c. tuberculata, drechslera australiensis, d. halodes, d. huwaiiensis, d. papendorfii, d. rostrata, cochliobolus spicifer, melanospora sp., cephalosporium sp., trichometasphaeria holmii, pythium periplocum, benomyl, captan, kasumin, mancozeb, oxadixyl, thiram, tolclofos-methyl, vitavax, fungicides, antagonists
During a survey of cultivated fields of different parts of Pakistan, several new hosts of root infecting fungi viz., Macrophomina phaseolina (48 hosts), Rhizoctonia solani (60), Fusarium moniliforme (6), F. oxysporum (9), F. semitectum (1), F. solani (16), Selerotium rolfsii (2), Pythium aphanidermatum (4), Botryodiplodia theobromae (8), Curvularia lunata (22), C. oryzae (1), C. tuberculata (15), Drechslera australiensis (50), D. halodes (14), D. huwaiiensis (1), D. papendorfii (2), D. rostrata (2), D. state of Cochliobolus spicifer (12), Melanospora sp., (4) and Cephalosporium sp., (3) were recorded. Drechslera state of Trichometasphaeria holmii on 4 hosts and Pythium periplocum on 5 hosts have been recorded for the first time in Pakistan.
Use of fungicides viz., Benomyl, Captan, Kasumin, Mancozeb, Oxadixyl, Thiram, Tolclofos-methyl and Vitavax as seed treatment or soil drench provided significant suppression in colonization of mung bean root by M. phaseolina, R. solani and Fusarium spp. The efficacy of fungicides, however, varied with the host, the pathogen and the method of application. Soil drench with a mixture of Cap tan and Benomyl was found more effective in the control of M. phaseolina, R. solani and Fusarium spp., on sunflower.
In vitro tests, Trichoderma hamatum and T. harzianum produced coiling around the hyphae of R. solani but not on M. phaseolina and F oxysporum. Use of microbial antagonists viz., Aspergillus candidus, Gliocladium virens, Paecilomyces lilacinus, T. harzianmun, Streptomyces sp., Bacillus subtilis and Rhizobium spp., as seed dressing, soil drench or after growing on organic substrates showed promising results in the control of M. phaseolina, R. solani and Fusarium spp., on different crop plants. Like fungicides, the efficacy of biocontrol agents varied with the host, the pathogen and the soil type.
Seed dressing with different doses of microbial antagonists viz., G. virens, P. lilacinus, T. harzianum and R. meliloti effectively reduced root colonization by root infecting fungi on mung bean. There was a correlation between the population of the pathogen in soil and the amount of antagonist inoculum required for the control of the disease. Soil drench or soil amendment ,with P. lilacinus multiplied on rice grain was found effective against low populations of M. phaseolina (5-10 scl. g-l soil) but not at high population levels (50 scl. g-l soil).
A 15 day mulching treatment with transparent polyethylene sheets reduced the population of M. phaseolina, R. solani and Fusarium spp., to zero in soil upto 1520 cm depth. Significantly less colonization of roots by root infecting fungi was observed in mulched plots as compared to non-mulched plots. Soil amendment with lucerne @ 10% w/w either alone fir with microbial antagonists viz., A. candidus, Cladosporium cladosporioides and Trichothecium roseum showed 87-97% reduction in sclerotial population of M. phaseolina after 15 days of amendment but the population of M. phaseolina increased thereafter. Organic fertilizers viz., cow dung, sewage sludge and Zarkhez suppressed root colonization by R. solani whereas no significant suppression in colonization of roots by M. phaseolina and Fusarium spp., was observed. Seed treated with P. lilacinus and sown in soil amended with inorganic fertilizers viz., urea, NPK, DAP and Superphos significantly suppressed the colonization of mung bean root by R. solani. Colonization of roots by M. phaseolina was suppressed in some treatments but not in others whereas none of the treatments provided any suppression in Fusarium colonization. Water stress conditions resulted in greater colonization of sunflower roots by soilborne root infecting fungi.
Frequency of colonization of mung bean roots by M. phasealina increased with an increase in population of M. phasealina and Meloidogyne incognita. Infection by root-knot nematode was not affected by the presence of M. phaseolina. Fungicides showed effective suppression in root colonization by M. phaseolina, R. solani and Fusarium spp., with no significant effect on root-knot nematode. Furadan which effectively suppressed root-knot nematode was found ineffective in the control of root infecting fungi. Use of P. lilacinue, however, showed effective suppression of root-knot nematode and root infecting fungi on mung bean, okra, gram and tomato. Combined use of P. lilacinus, Pasteuria penetrans and Talaromyces flavus was more effective in the control of root rot and root-knot disease complex on mung bean as compared to their separate use. Use or P. lilacinus in soil amended with organic fertilizers viz., cow dung, sewage sludge, Zarkhez and Ravi Pak resulted in greater control of root-knot nematode, R. solani and Fusarium spp., but not M. phaseolina.