Efficacy of Two New Fungicides Against Colletotrichum Kahawae Infecting Coffee in Kenya

Coffee Berry Disease(CBD) caused by Colletotrichum kahawae is a destructive fungal disease of coffee in Kenya, leading to a loss of about 75%. This study aimed to assess the In Vitro efficacy of two fungicides:- CRI 1 (Pyraclostrobin 150 g/L + Fluxapyroxad 75 g/L) and CRI 2 (Pyraclostrobin 128 g/Kg + Boscalid 252 g/Kg) against C. kahawae using poisoned food technique on Potato Dextrose Agar. A total of 170 coffee berries with C. kahawae symptoms were purposively collected from both sprayed and unsprayed plots. Ten rates of each of the two fungicides were assessed ranging from 0.01% to 0.1% at an interval of 0.01%. Two commercial standard fungicides Pyraclostrobin 250 g/L at 0.04% and Tebuconazole 200 g/L + Trifloxystrobin 100 g/L at 0.1% were used as positive controls. Fungal inoculum in PDA media devoid of the fungicide acted as the negative control. Data on colony diameter was collected after every 24 hours for 13 days. Analysis of Variance (ANOVA) of the data on colony diameter was done using CoStat software version 6.400. The results revealed that all the rates of CRI 1 and CRI 2 fungicides controlled the colony diameter of C. kahawae compared to the control treatment. CRI 1 fungicide suppressed the growth of C. kahawae even at the lowest concentration of 0.01% with a percentage control of 64.74 %. The highest concentration of 0.1% had a percentage control of 66.15% . CRI 1 is more effective in controlling C. kahawae since it controls the fungus at a rate even lower than Pyraclostrobin 250 g/L which had a percentage control of 66.10 at a recommended rate of 0.04% and Tebuconazole 200 g/L + Trifloxystrobin 100 g/L fungicides which had a percentage control of 65.76 at a recommended rate of 0.1%. CRI 1 also hade a better percentage control as compared to CRI 2. CRI 2 had a percentage control of 54.63% at the highest rate of 0.1% and a percentage control of 35.60% at the lowest rate of 0.01% . Further studies on CRI 1 and CRI 2 fungicides should be carried out for yield assessment in the field.

In-vitro Efficacy of Fungicides against Rhizoctonia solani Causing Banded Leaf and Sheath Blight of Maize

An experiment was carried out to find out the in-vitro efficacy of systemic and contact fungicides against the pathogen of maize banded leaf and sheath blight (Rhizoctonia solani f. sp. sasakii) by using poisoned food technique. The present experiment was conducted in College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University, Umiam, Meghalaya for the evaluation of different fungicides against the pathogen R. solani f. sp. sasakii. Eight systemic (Carbendazim, Tebuconazole, Propiconazole, Myclobutanil, Azoxystrobin, Metalaxyl, Tricyclazole, Pyraclostrobin), three contact (Mancozeb, Captan and Chlorothalonil) and combination of systemic and contact fungicide (Carbendazim + Mancozeb) were used for the experiment with different concentrations. Among twelve fungicides, Carbendazim was found to be the most effective at concentration of 0.1 % with 95.96 % growth inhibition. Suimilarly, Metalaxyl at concentration of 0.28 % was found to be the least effective with growth inhibition of 55.55 %. The results showed significant differences between different fungicides to inhibit the growth of R. solani.

Chemical composition and in vitroantifungal activity of turmeric oilfrom Curcuma longa L. rhizomeagainst Colletotrichum spp.

The production of curcumin produces large quantities of the spent turmeric oleoresin as a by-product, which often pollutes the environment. This study was conducted to obtain turmeric oil from this by-product and evaluate its antifungal activity. Turmeric oil afforded by partitioning the turmeric oleoresin from the production of curcumin (Curcuma longa L.) with n-hexane showed a strong inhibition for Colletotrichum species. The volatile components of turmeric oil were determined by GC-MS. Then, 23 volatile compounds were identified from this oil, of which four main compounds were α-zingiberene, α-turmerone, ar-turmerone, and β-sesquiphellandrene. Besides, the authors also isolated Colletotrichum gloeosporioides from lychee fruits, which were harvested in Luc Ngan district, Bac Giang province. By poisoned food technique, the antifungal activity of turmeric oil against C. gloeosporioides, C. orbiculare, C. acutatum, Phytophthora infestans, and Fusarium oxysporum was demonstrated. The results showed that at a concentration of 1 mg/ml, turmeric oil showed the highest inhibitory effect on C. gloeosporioides (67.9%). As for other fungi, in vitro growth inhibition varied in the range of 41-62%.

Antifungal Activity of Morinda citrifolia leaf extracts against Colletotrichum acutatum

Anthracnose is a plant disease that can infect a variety of plants worldwide. Fungal pathogen groups are the cause of anthracnose, one of which is Colletotrichum acutatum. Morinda citrifolia is famous for having antimicrobial activity. This study aims to determine the antifungal activity of M. citrifolia leaves extract against the growth of the fungus C. acutatum. The extract solvent used was 96% ethanol. The experiment consisted of five treatments (0%, 20%, 40%, 60% and propineb 0.1% as positive control). The method used in this study was the poisoned food technique. In this technique, C. acutatum was grown on PDA media mixed with M. citrifolia leaves extract. Antifungal activity was observed based on reduced mycelium growth compared to control. Observations were made every day by measuring the diameter of the fungus mycelium for eleven days. The analysis showed that 60% M. citrifolia leaves extract effectively inhibited the growth of the mycelium C. acutatum on the eleventh day of observation.

Antifungal Activity in Urginea indica Kunth. (Asparagaceae)

Aqueous extract of Urginea indica kunth. (Udupi acccession) was screened for antifungal activity against Fusarium oxysporum, Sclerotium rolfsii, Magnaporthe orzae, Aspergillus flavus, Alternaria alternata, Aspergillus niger and Fusarium moniliformae by poisoned food technique. The results confirmed Urginea indica extracts showed very significant antifungal activity against Fusarium oxysporum and showed significant inhibition for Sclerotium rolfsii and Magnapothea orzaea it showed no activity against Aspergillus niger and Aspergillus flavus. All the activity was evaluated to determine the lowest concentration required to inhibit visible mycelial growth of the pathogen at minmum concentration. Fusarium oxysporum showed very significant inhibition in 10% concentration (Reconfirmed) while Sclerotium showed significant inhibition in 25% concentration followed by Magnoporthe oryzae. The number of sclerotia spores formed was also reduced drastically. These results show that a potential and safe antifungal agent can be obtained from Urginea.

Inhibition of Mycelial Growth of Rhizoctonia Solani by Chitosan in vitro and in vivo

Objective: Evaluate the antifungal effect of chitosan against Rhizoctonia solani in vitro and the possible mechanisms of its induced activity in potato tubers to control black scurf disease. Methods: The in vitro influence of chitosan at different concentrations on mycelial growth of R. solani was tested by using the poisoned food technique in PDA medium. The effect of these concentrations on the development of lesion diameters in tubers inoculated with R. solani mycelium was assayed for 30 days. The concentration that showed the greatest inhibitory effect on lesion diameters was tested to assess the induced activity of defense-related enzymes in the infected tubers. Results: In the poisoned food technique, chitosan at 1% completely inhibited the growth of R. solani mycelium. In vivo tests showed that chitosan treatment at 0.5% effectively controlled the black scurf in tubers inoculated with R. solani mycelium. Chitosan increased the activities of defense-related enzymes such as Peroxidase (POD), Polyphenol Oxidase (PPO) and Phenylalanine Ammonia-lyase (PAL) in treated tubers of tested cultivars. Conclusion: This work demonstrated that chitosan directly inhibited the growth of R. solani, and potentially elicited defense reaction in potato tubers.

Antifungal Activity of Semecarpus anacardium Linn. Oil against Four Phytopathogenic Fungi

The present study was undertaken to evaluate in-vitro antifungal activity of Semecarpus anacardium Linn. oil against four fungal pathogens, viz. Curvularia penniseti, Curvularia lunata, Fusarium oxysporum f. sp. ciceris and Helminthosporium maydis using poisoned food technique. The DMSO extract of S.anacardium oil was found to be more or less active against almost all tested pathogenic fungi with a varied spectrum of reduced growth. C.lunata has shown 93.3% inhibition and F.oxysporum and H.maydis have shown 94.4% inhibition and 100% mycelial inhibitions at 15% and 18% concentrations of the extract respectively. Whereas, C.penniseti was found to be quite sensitive that showed 88.9 inhibitions at 10% concentration but it showed 100% inhibition at 18% concentration.

ANTIFUNGAL ACTIVITY OF DIFFERENT SYSTEMIC FUNGICIDES AGAINST FUSARIUM OXYSPORUM F. SP. LYCOPERSICI ASSOCIATED WITH TOMATO WILT AND EMERGENCE OF RESISTANCE IN THE PATHOGEN

Fusarium wilt in tomato (Lycopersicon esculentum L.) caused by Fusarium oxysporum f. sp. lycopersici. Pathogen is notorious because of its adverse effect on plant growth with causing significant yields losses. Further complication is developing by raising issue of resistance in F. oxysporum f. sp. lycopersici particularly in developing countries due to injudicious fungicides applications in the field of tomato plant infected by this pathogen. F. oxysporum f. sp. lycopersici was isolated from collected infected samples from tomato field in Multan, southern Punjab on Potato dextrose medium by adopting poisoned food technique. Antifungal activity of different systemic fungicides viz. Pyrimethanil, Fludioxonil, Benlate, Bromuconazole, Fosetyl-Al, Flumorph, Prochloraz, Myclobutanil, Epoxiconazole, Strobilurin, carbendazim, Fentin hydroxide, Streptomycin, Tebuconazole, Iprobenfos and azoxystrobin were tested against F. oxysporum f. sp. lycopersici in vitro by using poisoned food technique. All tested fungicides suppressed fungal mycelial growth with significantly high or low percent inhibition ranging from 1.48 to 85.92%. Among 16 tested fungicides, different concentrations of Bloom, Prochloraz and Bromuconazole significantly inhibited fungal growth ranging from 75 to 85.92 %. Carbendazim and epic reside in the bottom with reference to their efficacy in suppression of F. oxysporum f. sp. lycopersici. The results of present research expressed that isolates of Fusarium oxysporum f. sp. lycopersici develops resistance with time which causes reduced efficacy of fungicides as compared to previously published data. The results provided information about fungicides application and selection for the management of holistic disease in tomato crop in Pakistan.

In-vitro antimicrobial and antioxidant activity of Argyreia cuneata (Willd.) Ker Gawl. (Convolvulaceae)

Objectives: Argyreia cuneata (Willd.) Ker Gawl. belongs to the family Convolvulaceae. The present study was performed to screen the potential of crude extract of various parts of A. cuneata to exhibit antimicrobial activity. Methods: Extraction of shade dried and powdered leaf, stem and flower of A. cuneata was carried out by maceration technique. Antibacterial and antifungal activity of extracts was evaluated by Agar well diffusion and Poisoned food technique respectively. Antioxidant activity was determined by DPPH radical scavenging, ABTS radical scavenging and ferric reducing assays. Results: All extracts were effective in inhibiting test bacteria and the susceptibility of bacteria to extracts was in the order: Bacillus cereus > Shigella flexneri > Escherichia coli > Salmonella typhimurium. Leaf extract and stem extract exhibited highest and least antibacterial activity, respectively. Extracts were effective in causing inhibition of seed-borne fungi viz. Aspergillus niger and Bipolaris sp to >50%. Leaf extract exhibited marked antifungal activity followed by flower extract and stem extract. All extracts were shown to exhibit concentration dependent scavenging and reducing activity. Antioxidant activity of extracts observed was in the order: leaf extract > flower extract > stem extract. Conclusion: Among various parts of A. cuneata, leaf extract exhibited marked antimicrobial and antioxidant activity. The plant can be employed as an effective antimicrobial and antioxidant agent in suitable form. Further studies may be undertaken to recover phytochemicals from the plant and to investigate the antimicrobial and antioxidant activity of isolated components. Keywords: Argyreia cuneata, Maceration, Antimicrobial, Agar well diffusion, Poisoned food technique, Antioxidant

Antibacterial, antifungal and antioxidant activity of Dichapetalum gelonioides (Roxb.) Engl. (Dichapetalaceae)

Objectives: Dichapetalum gelonioides (Roxb.) Engl. belongs to the family Dichapetalaceae. In the present study, we investigated antibacterial, antifungal and antioxidant activity of methanolic extract of leaf and fruit of D. gelonioides. Methods: Maceration process was carried out for extraction of leaf and fruit of D. gelonioides. Agar well diffusion method was employed to evaluate antibacterial activity of extracts against gram positive and gram negative bacteria. Poisoned food technique was performed to investigate antifungal activity of extracts against two seed-borne fungi. Antioxidant activity was evaluated by DPPH radical scavenging and ferric reducing assays. Results: Both leaf and fruit extracts were effective in causing inhibition of all test bacteria. Highest and least inhibitory activity was observed against Bacillus cereus and Escherichia coli respectively. Both Aspergillus niger and Bipolaris sp. were inhibited to >50% by leaf and fruit extracts. Extent of inhibition of Bipolaris sp. was slightly higher when compared to A. niger. Both leaf and fruit extracts showed a dose dependent scavenging of DPPH radicals with high activity being showed by leaf extract. Leaf extract was shown to exhibit marked reducing potential than fruit extract. Conclusions: Overall, leaf extract was shown to be more effective in displaying antioxidant activity and causing inhibition of bacteria and fungi when compared to fruit extract. The results indicate that the plant possess active principles which are to be purified, characterized and subjected for antimicrobial and antioxidant assays in further studies. Keywords: Dichapetalum gelonioides, Maceration, Agar well diffusion, Poisoned food technique, DPPH, Ferric reducing