Identification of a distinct strain of Cotton leaf curl Gezira virus infecting tomato in Oman

Tomato (Solanum lycopersicum) plants exhibiting yellowing, curling and stunting symptoms were identified in fields of the Tawoos Agricultural Systems, in Al‐Batinah in Oman. Cloning and sequencing of restriction endonuclease digested rolling circle amplified viral DNA identified a cotton begomovirus (family Geminiviridae) associated with the symptomatic tomato plants. Detailed analysis of complete sequences showed the virus to be a previously unknown strain of Cotton leaf curl Gezira virus (CLCuGeV) in association with the betasatellite Tomato leaf curl betasatellite (ToLCB). The new CLCuGeV strain, for which the name “Al Batinah” strain is suggested, has the greatest levels of sequence identity (91.9%) to an isolate of CLCuGeV recently reported from the neighbouring United Arab Emirates. Additionally, CLCuGeV‐Al Batinah was shown to have a recombinant origin with sequences donated by an African cassava mosaic virus‐like parent. This is the first identification of this Malvaceae‐adapted begomovirus in tomato. Although ToLCB is common in Oman, being one of only two betasatellites identified there so far, this is the first identification of this betasatellite with CLCuGeV. The significance of these findings is discussed.     

Entomopathogenic fungus Clonostachys rosea as a biocontrol agent against whitefly (Bemisia tabaci)

Whitefly (Bemisia tabaci) is a notorious insect pest of many economic important crop plants including cotton, tomato, etc. The main objective of the study was to evaluate the efficacy of new biological control agent to replace toxic chemical pesticides from agro-ecosystem. Clonostachys rosea associated with whitefly and aphid (Aphis gossypii) on cotton plants was isolated and characterised on a morphological and molecular basis. Phylogenetic analysis was also performed based on the internal transcribed spacer (ITS) region. Pathogenicity of C. rosea was evaluated in two concentrations against fourth instar nymphal and adult stages of B. tabaci. The study revealed that C. rosea was highly parasitic against fourth instar nymphs than adults at different spore concentrations. Two isolates of C. rosea were identified in this study, and both were morphologically similar. However, differences were observed in the ITS region of the C. rosea isolates. Our results showed that C. rosea has the prospects to serve as a potential biocontrol agent against economically important insect pests.     

Population Structure and Management of Podosphaera pannosa Associated with Peach Powdery Mildew in Oman

In 2004, severe powdery mildew infection on peach occurred in Al‐Jabal Al‐Akdhar, Oman, and resulted in substantial yield losses to growers. This study was conducted to investigate occurrence, causal agents, genetic diversity and efficacy of azoxystrobin in management of this disease. Powdery mildew was observed on all farms and peach trees in Al‐Jabal Al‐Akdhar. Disease symptoms were first observed on shoots in April, followed by appearance on fruits. Disease severity reached its peak between May and June. Morphological and molecular identification of 22 powdery mildew isolates indicated that all belong to Podosphaera pannosa. Podosphaera pannosa reproduced the same symptoms upon inoculation on peach leaves. Amplified fragment length polymorphisms analysis of 35 isolates of P. pannosa from five different villages using four primer pair combinations produced 688 polymorphic loci and 35 different genotypes. Populations of P. pannosa were found to have low levels of gene diversity (H = 0.1858), which suggests that P. pannosa has been recently introduced into Al‐Jabal Al‐Akdhar. Analysis of molecular variance showed low levels of genetic differentiation among populations from the different villages, implying the introduction of P. pannosa into the different villages via common sources as well as frequent movement of pathogen inoculum among the different villages. Evaluating the efficacy of azoxystrobin showed that azoxystrobin is as efficacious as thiophanate‐methyl in managing the disease, with sulphur being the least efficacious. The study is the first to report the presence of P. pannosa in Oman. Also reported are its genetic diversity and its management under commercial conditions.     

Serological evidence of bovine herpesvirus 1-related virus infection in the white-tailed deer population on Anticosti Island, Quebec

High white-tailed deer (Odocoileus virginianus) population densities and the occurrence of harsh environmental conditions are present on Anticosti Island, located in the Gulf of Saint-Lawrence (Quebec, Canada). This island is the northernmost region of white-tailed deer distribution in northeastern North America. The aim of this work was to determine whether a herpesvirus serologically related to bovine herpesvirus 1 (BHV1) may occur in a stressed white-tailed deer population. One hundred one deer sera were collected from apparently healthy animals during the hunting season from September to late November 1985. Fifty-three percent of tested deer were positive to the seroneutralization test using Colorado strain of BHV1 virus. Higher percentages of seropositivity were observed in animals of both sexes greater than 4-yr-old. Analysis of antibody titers in seropositive animals according to age suggests that BHV1-related viral infection is endemic in the Anticosti Island deer population. It is postulated that environmental stress may induce immunosuppression of certain infected and/or carrier animals in their population that shed virus for long periods of time.