In Vitro Evaluation of Effect of Different Essential Oils in Management of Post-Harvest Fruit Rot of Banana (Musa Paradisiaca) Caused by Colletotrichum spp

A study was conducted to evaluate the in vitro efficacy of different essential oils in the management of post-harvest fruit rot of banana. It was carried out in completely randomized design (CRD) with three replications and six treatments at Nepal Plant Diseases and Agro Associates (NPDA). The each of six treatments: cinnamon oil (Cinnamomum verum), mustard oil (Brassica oleracea), castor oil (Ricinus communis), neem oil (Azadirachta indica), coconut oil (Cocos nucifera) and control were used at concentrations 200ppm, 500ppm and 1000ppm respectively. The radial growth of mycelium (mm) and percent growth inhibition (%) of Colletotrichum spp. was recorded. The decrease in the radial growth and increase in the percent growth inhibition was found in all the treatments except control as their concentration was increased, in which the lowest radial growth and the highest percent growth inhibition was found at 1000 ppm concentration. At 1000 ppm concentration, cinnamon oil shows the lowest radial growth and the highest percent growth inhibition (1.67mm and 98.15%) followed by mustard oil (54.00mm and 40.00%), neem oil (55.17mm and 38.70%), castor oil (55.83mm and 37.96%), coconut oil (61.17mm and 32.04%) and control (90mm and 0.00%) respectively.Thus, cinnamon oil is considered as a good essential oil in regards to a management of post-harvest disease of banana. Int. J. Appl. Sci. Biotechnol. Vol 9(3): 187-192.

In vitro screening of different Pseudomonas fluorescens isolates to study lytic enzyme production and growth inhibition during antagonism of Fusarium oxysporum f. sp. cumini, wilt causing pathogen of cumin

Land plants exist in close association with bacterial and fungal microbes, where some associations can be pathogenic and others can be mutualistic/beneficial. One such relation exists between host plant, Cuminum cyminum L. (Cumin) and Fusarium oxysporum f. sp. cumini (Foc), the causal pathogen of cumin wilt and Pseudomonas fluorescens (Pf), where Pf acts as a bio-agent for inhibiting Foc and promoting plant growth of cumin. In this study, antagonism by 10 different Pf isolates against Foc was studied under laboratory conditions through percent growth inhibition and biochemical mechanisms. Among these Pf isolates, Pf-5 exhibited the highest in vitro growth inhibition (82.51%). A positive correlation was observed between percent growth inhibition and specific activities of hydrolytic enzymes, chitinase, β-1, 3 glucanase, and protease, where a negative correlation was observed with cell wall degrading enzymes, cellulase and polygalacturonase. To conclude, isolate Pf-5 could be a potential biocontrol agent for Fusarium wilt disease of cumin.

In-vitro Studies of Plant Extracts against Alternaria brassicae (berk.) Sacc. of Indian Mustard (Brassica juncea (L.) Czern. and coss)

Six plant extract viz., Datura (Daturastramonium), Eucalyptus (Eucalyptus globulous), Karang (Pongamiaglabra),Neem (Azadirachtaindica), Madar (Calotropis gigantean) and Wild sage (Lantana camara) were evaluated in-vitro by poison food technique @ 3, 6, 9 and 12% concentrations against Alternariabrassicaecausing blight of mustard. The results revealed that all the plant extracts inhibited the percent growth inhibition against test fungus as compared to control. However A.indica was found most efficacious with growth inhibition of (38.7%) followed by E. globulus (36.7%). Some extract such as P. glabra and D. stramonium showed moderate inhibition over control (30.9 and 21.6 respectively). Among all plant extract, C. gigantean showed least (15.3%) inhibition over control against A. brassicae. These plant extracts can possibly be used as management of seedborne pathogenic fungi in an eco-friendly way.

Pythium Species and Isolate Diversity Influence Inhibition by the Biological Control Agent Streptomyces lydicus

Disease control of soilborne pathogens by biological control agents (BCAs) is often inconsistent under field conditions. This inconsistency may be partly influenced by pathogen diversity if there is a differential response among pathogen species and isolates to selected BCAs. The responses of 148 Pythium isolates obtained from soil at three forest nurseries and representative of 16 Pythium spp. were evaluated in the presence of Streptomyces lydicus strain WYEC108 in an in vitro assay. Percent growth inhibition, inhibition zone distance, mortality, and growth rate were recorded for each isolate, and data were analyzed for effects of species and isolate. Responses of three Pythium spp. (Pythium irregulare, P. sylvaticum, and P. ultimum) were further analyzed for a location (nursery) effect. Although S. lydicus inhibited all Pythium isolates, differences in percent growth inhibition, inhibition zone distance, and mortality were observed among Pythium spp. and isolates. Small but significant location effects were also noted. Growth rate also varied among Pythium spp. and isolates and was found to strongly bias percent growth inhibition and, to a lesser degree, inhibition zone distance; depending on which measure was used, slower-growing isolates appeared less sensitive (growth inhibition) or more sensitive (inhibition zone) to S. lydicus than faster-growing isolates. Results illustrate the importance of using multiple, representative pathogen isolates in preliminary BCA inhibition assays as well as accounting for the effect of pathogen growth rate on pathogen inhibition by BCAs. Future studies should take pathogen diversity into account when evaluating biological control efficacy.

Growth Response of Wheat (Triticum aestivum) Callus to Imazapyr and in Vitro Selection for Resistance

Intact wheat plants and wheat calli responded similarly to varying concentrations of imazapyr. Fifty percent growth inhibition of wheat callus occurred with 0.05 μM imazapyr after 70 d. As imazapyr concentration increased from 0 to 10 μM, the free isoleucine, leucine, and valine decreased from 160 to 35, 260 to 49, and 310 to 59 pmol mg−1, respectively. Resistant calli, which had relative growth rates exceeding a calculated upper prediction interval, were obtained by in vitro selection at 2 and 5 μM imazapyr. Resistant calli growing on 2 μM imazapyr had free isoleucine, leucine, and valine concentrations intermediate to the control and susceptible callus.

Effects of Fluometuron, Prometryne, Ametryne, and Diuron on Growth of Two Lemna Species

The effect of the herbicides Fluometuron, Prometryne, Ametryne and Diuron on the autotrophic growth of the aquatic species Lemna major L. and L. perpusilla Torr. was determined. Fluometuron was the least toxic chemical to both species. Diuron was the most toxic herbicide to L. major, Ametryne most toxic to L. perpusilla. Concentrations of herbicides causing 50 percent growth inhibition of L. major were as follows: a) Fluometuron, 2.6 X 10-6 M; b) Prometryne, 3.5 X 10-7 M; c) Ametryne, 2.30 X 10-7 M; and d) Diuron, 1.75 X 10-7 M. Concentrations of herbicides causing 50 percent growth inhibition of L. perpusilla were as follows: a) Fluometuron, 2.05 X 10-6 M; b) Diuron, 6.4 X 10-8 M; c) Prometryne, 5.4 X 10-8 M; and d) Ametryne, 4.6 X 10-8 M. These herbicides applied at micromolar concentrations proved to be phytotoxic to both Lemna species tested.