DETERMINATION OF PROPERTIES OF A STRAIN OF TOBAMOVIRUS FROM MUCUNA PRURIENS

A virus-infected leaf of Mucuna pruriens was collected and tested for an incidence of a virus through biological properties using various plant host range inoculation tests, longevity-in-vitro, dilution-end-point, thermal-inactivation point and electron microscopy. Results of host range inoculation tests showed the following plant species to be susceptible to the virus; Nicotiana tabacum, N. rustica, N. benthamiana, N. glutinosa, N. occidentalis, N. Sylvesris (Speg and Comes) and others. No plant in the family Convolvulacaee, Cucurbitaceae was found to be infected with the virus. However Chenopodium quinoa and C. murale in the family Chenopodiaceae were infected with symptoms of mottling and necrotic lesions. In the family Fabaceae, hybrid cowpea line TVu 76, IT84S – 2114 were infected with mosaic, leaf crinkling and severe leaf curl respectively. The virus had a dilution-end-point of 10-6-10-7, thermal-inactivation-point of 95°C in crude sap of TVu 76. The virus is of agricultural importance because of its incidence on seed coats of legumes which are freely exchanged between agricultural stakeholders.

Biological and Physico-chemical Properties of Causal Agent of Virus Disease of Coccinia barteri (Hook. f.) Keay in Calabar, Cross River State

The physico-chemical properties of the causal agent of virus disease of Coccinia barteri (Hook. f.) Keay were studied. The virus causing the disease was characterized using diagnostic tools such as host range, longevity in vitro, thermal inactivation point, dilution endpoint and aphid transmission. The virus was mechanically transmitted from the natural host (C. barteri) to the healthy test plants in the green house. In the biological properties, the virus was successfully transmitted by Aphis spiraecola (obtained from Chromolaena odorata (L.) R. M. King & H. Rob.) from infected Cucumeropsis mannii Naudin to a healthy C. mannii in a non-persistent manner and had a narrow host range limited to the family Cucurbitaceae. In the physico-chemical properties based on crude sap with an unknown virus concentration, beyond which infectivity was lost. It was readily inactivated by heating to 35 – 65°C for 10 minutes in determination of thermal inactivation point. The virus had a longevity in vitro of between 4 – 5 days beyond which it was non-infectious. Symptoms induced by the virus were leaf cupping, mottle chlorosis, blisters, stunted growth, rugosity, leaf malformation and mosaic patterns.

Lavandula angustifolia Mill. as a natural host of Cucumber mosaic virus (CMV)

A virus was isolated from Lavandula angustifolia Mill. plants exhibiting yellow mottling and distortion of leaves. After mechanical inoculation it induced in the major part of used test plants symptoms characteristic for Cucumber mosaic virus (CMV). Its standard properties regarding the stability in crude plant sap were as follows: longevity in vitro 1-2 days, thermal inactivation point 55-60°C, dilution end point log10minus 3 - 4. The virus reacted positive with diagnostic antiserum against CMV in DAS-ELISA test. RT-PCR reaction revealed similarity between the investigated isolate and the isolate of CMV from the Netherlands belonging to subgroup II. In the light of the foregoing facts the isolated pathogen can be identified as the Cucumber mosaic virus and Lavandula angustifolia may be regarded as its natural host.

Occurrence, Distribution and Properties of Alfalfa Mosaic Virus

Alfalfa Mosaic Virus (AlflMV) was recorded on 21 hosts comprising of four field crops, 14 vegetables, one ornamental plant and two new weed species (Heliotropium europaeum and Ammi majus) belonging to nine families. The virus was identified and confirmed on the basis of its biological, serological (ELISA) and physical properties. The leaves, stem and crown from systemically infected alfalfa plant contained high concentration of the virus. It was nonpersistently transmitted by cotton aphids (Aphis gossypii). The wide host range, including virus reservoirs, seed-borne infection and insect transmission account for high incidence and distribution of AlfMV in the country. The virus isolate had a dilution end point between 1 x 10-3 to l x 10-4, 65-67 °C thermal inactivation point and a few days in-vitro longevity and appears to be similar to the AlfMV-S strain.

Host range and properties of tobacco stunt virus

Tobacco stunt virus (TSV) was mechanically transmitted to 41 species in 9 families: i.e., Aizoaceae, Amaranthaceae, Apocynaceae, Caryophyllaceae, Chenopodiaceae, Cucurbitaceae, Leguminosae, Pedaliaceae, and Solanaceae. TSV remained infective for 60 h in 0.001 M 1-phenylthiosemicarbazide (1-PTC) in 0.01 M phosphate buffer, pH 6.8, but was infective only immediately after extraction in phosphate buffer. TSV in 1-PTC-phosphate buffer had a thermal inactivation point between 75 and 80 °C and a dilution end point between 10−2 and 10−3. Comparative studies made on reaction of host plants, serological reaction, and cross protection indicate that TSV is unrelated to a California isolate of tobacco necrosis virus.

The occurrence of Peanut Mottle virus in Queensland

A disease causing a mottle in the leaves of peanuts (Arachis hypogaea L.) in the Mingaroy district of Queensland has been shown to be caused by a virus which appears to be indistinguishable from peanut mottle virus. This virus has not previously been reported in Australia. The virus was sap-transmissible to a range of plants, all but one of which were in the Leguminosae, but the only hosts in the field were peanut and garden pea (Pisum sativum L.). It was shown to be transmitted in a stylet-borne manner by five aphid species including Aphis craccirora Koch, which is the most common species found infesting peanuts. The virus was also seed-transmitted and probably spread to Australia in infected seed. The virus had a thermal inactivation point between 55 and 60�C and a dilution end-point between 10-3 and 10-4, and infectivity was lost within 48 hr of storage at 25�C. Partially purified virus preparations were obtained by clarification of sap by freezing and thawing and :he addition of activated charcoal followed by differential centrifugation An antiserum with an homologous> title of 1 : 64 was prepared but no serological relationships could be demonstrated between this virus and common bean mosaic or bean yellow mosaic viruses Flexuous rod-shaped particles with a normal length of 704 nm were seen in electron micrographs of virus preparations.

Summer Cosmos – A Host of Cucumber mosaic virus

In order to identify the cause of virus disease-like symptoms developed naturally in Summer cosmos (Cosmos sulphureus) plants at Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur campus, a study was conducted during March 2004 to August 2005. The natural symptoms in Summer cosmos were consisted of mosaic, yellowing, shoe-string and leaf curling along with severe stunting of the infected plants. The ailments were found to be sap transmissible. Gomphrena globosa and Chenopodium amaranticolor were found to be good local lesion hosts producing chlorotic local lesion in the inoculated plants. The virus isolates obtained from the infected G. globosa plant had wide host range including Amaranthaceae, Chenopodiaceae, Compositae, Cucurbitaceae, Ligominosae and Solanaceae. The dilution end point, thermal inactivation point and longevity in vitro were determined as 10-6, 65°C and 10 days, respectively. The host range test, dilution end point, thermal inactivation point and longevity in vitro suggested that the virus was identical to Cucumber mosaic virus (CMV). Double Antibody Sandwich Enzyme-Linked Immuno-Sorbent Assay (DAS-ELISA) detected the virus as CMV. The results of the study revealed that the virus disease-like symptoms naturally manifested in summer cosmos plants was identified as CMV. Key words: Summer cosmos, CMV, virus identification. DOI = 10.3329/jard.v5i1.1463 J Agric Rural Dev 5(1&2), 84-93, June 2007