Studies on Indigenous Plants of Karachi for the Control of Root Rot-Root Knot Disease Complex

Abstract

Several indigenous plants in Karachi region possessed various antimicrobial properties, among them some plants viz., Cyamopsis tetragonoloba (L.) Taub, Fagonia indica Burm f., Hibiscus rosa-sinensis L., Melia azedarach L., Prosopis juliflora (Sw.) DC., Rhynchosia minima (L.) DC., Solanum surattense Burm f., Terminalia catappa L., Thespesia populnea (L.) Sol. ex Corrêa, Withania somnifera (L.) Dunal were selected for present study. These plants were collected from different localities of Karachi and their grinded powders were used in vitro and in vivo against soil-borne plant pathogens like root-rot fungi and root-knot nematode. In vitro different parts of selected plants were extracted in five solvents such as water, methanol, n-hexane, chloroform and ethyl acetate. These extracts were tested against three root-rot fungi viz., Fusarium oxysporum Schltdl. emend. Snyd. & Hans., Macrophomina phaseolina (Tassi) Goid and Rhizoctonia solani (Kühn) by food-poisoned method on potato dextrose agar medium. Leaves, fruit and shoot extracts of selected plants significantly suppressed the growth of fungi as compared to stem extracts. However, H. rosa-sinensis (stem) extracts showed fungicidal activity than its leaves extracts. Among solvents, the water and methanol were found more effective against almost three fungi. Plants extracts were also tested against eggs hatching and mortality of second stage juveniles (J2) of root-knot nematode (Meloidogyne javanica (Treub) Chitwood) with varying concentrations (10, 5 and 2.5%). Significant reduction in the eggs hatching and increased in mortality was noticed in all plant extracts. Eggs hatching have been reduced and larval mortality has been increased when concentration of extracts increased therefore concentration 10% showed maximum nematicidal activity. Screen house trials were conducted in department of Botany, Federal Urdu University, to assess in vivo potential of plant species against targeted fungi and nematodes. Experiments carried out on okra (Abelmoschus esculentus (L.) Moench), mung bean (Vigna radiata (L.) R. Wilczek), cowpea (Vigna unguiculata (L.) Walp) and chickpea (Cicer arietinum L.). In soil amendment (organic amendment) experiment powder of plants were mixed in soil @ 0.5, 1 and 2% w/w fifteen days prior before sowing the seeds. T. populnea (leaves), M. azedarach (leaves), W. somnifera (leaves & stem), T. catappa xiii (leaves), P. juliflora (leaves), H. rosa-sinensis (stem), S. surattense (shoots) and C. tetragonoloba @ 1 and 2% showed more significant results than other plants. Amendment not only suppressed the incidence of root rot-root knot disease complex but it also enhanced the growth of test crops (okra & mung bean). Biochemical estimation of okra and mung bean also has been done after uprooting the crops. It was observed that T. populnea (leaves), M. azedarach (leaves) and W. somnifera (leaves) highly enhanced chlorophyll “a”, “b”, carotenoids and carbohydrate as compare to other treatments and control in okra. However, in mung bean S. surattense (shoots), H. rosa-sinensis (stem) and P. juliflora (leaves) highly enhanced the physiological parameters. Water extracts @ 1 and 2% w/v of selected plants has been used as soil drenching to check their efficacy. Both concentrations significantly promote growth of cowpea plant and also suppressed the infection caused by root-rot fungi and root-knot nematodes. However, W. somnifera (leaves) and S. surattense (shoots) extracts showed highly significant results as compared to others. The biochemical contents of cowpea showed increase in chlorophyll “a”, “b”, carotenoids, carbohydrate and decrease in phenol content. Combined application of microbial antagonists (Trichoderma harzianum & Pseudomonas aeruginosa), nematicide (Carbofuran) and fungicide (Aliette) in soil amended with plants dry powder @ 1 and 2% w/w showed remarkable suppression of root rot-root knot disease complex. While W. somnifera (leaves), S. surattense (shoots) and H. rosa-sinensis (stem) adequately affected on growth parameters of chickpea and reduced infection of targeted pathogens. On the other hand combination of plants powder (W. somnifera and S. surattense, H. rosa-sinensis and T. populnea) with P. aeruginosa, T. harzianum, Aliette and Carbofuran significantly enhanced biochemicals than other treatments.