Planococcus citri (citrus mealybug).

Planococcus citri is a highly polyphagous, adaptable mealybug that can feed on many host plants in a variety of conditions, and can reproduce rapidly. It has been reported on over 200 host-plant species belonging to 191 genera and 82 families, and can seriously damage many crops, particularly citrus and glasshouse tomatoes. It is known to transmit some plant virus diseases like Cacao swollen shoot virus. The mealybug is of Old World origin, but its polyphagy has facilitated its spread about the world by human transport of infested plants over many years, and it is now established in in all the temperate and tropical zoogeographic regions, and lives under glass in higher latitudes. Its small size and cryptic habits makes it difficult to detect and identify at plant quarantine inspection. The increase in international trade in fresh plant material in recent years is facilitating its continued spread.

Identification and distribution of novel badnaviral sequences integrated in the genome of cacao (Theobroma cacao)

Theobroma cacao is one of the most economically important tropical trees, being the source of chocolate. As part of an ongoing study to understand the diversity of the badnavirus complex, responsible for the cacao swollen shoot virus disease in West Africa, evidence was found recently of virus-like sequences in asymptomatic cacao plants. The present study exploited the wealth of genomic resources in this crop, and combined bioinformatic, molecular, and genetic approaches to report for the first time the presence of integrated badnaviral sequences in most of the cacao genetic groups. These sequences, which we propose to name eTcBV for endogenous T. cacao bacilliform virus, varied in type with each predominating in a specific genetic group. A diagnostic multiplex PCR method was developed to identify the homozygous or hemizygous condition of one specific insert, which was inherited as a single Mendelian trait. These data suggest that these integration events occurred before or during the species diversification in Central and South America, and prior to its cultivation in other regions. Such evidence of integrated sequences is relevant to the management of cacao quarantine facilities and may also aid novel methods to reduce the impact of such viruses in this crop.

Swollen Shoots

This chapter deals with cacao swollen shoot disease, which has wreaked havoc in cacao-growing areas of West Africa since its first report in the early part of the twentieth century. First thought to be caused by drought, it was subsequently found to be caused by a virus—the cacao swollen shoot virus—and to be transmitted between cacao trees by several species of mealybug, including Formicococcus njalensis. Today, we know that ten viruses are involved in causing the disease, which is restricted to West Africa. The chapter examines the transmission of the virus and the efforts made to restrict its spread and reduce its impact. Attempts to tackle the disease have resulted in the destruction of some 300 million trees so far, which gives an indication of the considerable efforts that have been made to contain this devastating disease.

Spatiotemporal Spread of Cacao Swollen Shoot Virus Severe Strain 1A in Mixed Hybrid Cacao Pre-inoculated With Mild Strain N1

The spatiotemporal spread of cocoa swollen shoot virus disease (CSSVD), which is caused by cacao swollen shoot virus (CSSV) severe strain 1A in mixed hybrid cacao pre-inoculated with CSSV mild strain N1 (CSSV-N1), was investigated during a field experiment from 2006 to 2017, at the Cocoa Research Institute of Ghana. The development of disease epidemics has been described by the use of statistical modeling. Protecting all cacao plants with CSSV-N1 reduced the rate of CSSV-1A symptom appearance by 43% (P = 0.05) compared with the nonprotected control and by 33% compared with plots where cacao plants in the outer three or five rows were protected with CSSV-N1. Similarly, creating the protective outer rings three or five rows deep reduced the rate of CSSV-1A symptoms by 14% (P = 0.05) compared with the nonprotected control. CSSV-1A epidemics increased approximately 18% faster (P = 0.05) in transects oriented from the north and east compared with those oriented from the south and west. During the last 2 years of the study, CSSVD spread decreased significantly (P = 0.05) faster in plots where all test cacao plants were inoculated with CSSV-N1 compared with other treatments. The growth of cacao did not differ significantly among the treatments over the 9-year assessment period. Similarly, differences in the cumulative yield among the treatments over the 8-year assessment period were not significant.

Molecular characterization of Mosaic Virus from the cocoa trees showing mosaic symptoms in Yogyakarta, Indonesia

Abstact. Probowati W, Somowiyarjo S, Hartono S. 2019. Molecular characterization of Mosaic Virus From the cocoa trees showing mosaic symptoms in Yogyakarta, Indonesia. Biodiversitas 20: 3698-3704. Indonesia is the world's second-biggest producer of cacao after Ivory Coast with its cacao plantations spreads over 1,652 million hectares and mostly managed by smallholders. Cacao as a beneficial commodity can provide job opportunities for over 1.64 million people, with its contribution of more than US-$ 1.6 billion/year to national income. However, pest and disease infections are inevitably common constraints for the cacao cultivators. One current disease is caused by Cacao Swollen Shoot Virus (CSSV). Despite its noticeable symptoms on the cacao trees suffering from the disease, the knowledge on both the virus existence and the prevention steps in dealing with it is lacking. The information on the diversity of mosaic virus will help us to comprehend its epidemiologic development and the needed countermeasures, as well as its evolution. This research is intended to study the mosaic disease virus molecularly, the virus was obtained from DR1 clones from Kalibawang cacao plantation in Kulon Progo, Yogyakarta. The virus morphology was observed using a transmission electron microscope applying quick dipping method. The PCR analysis with conserved region ORF1 primers was conducted to detect the viral existence in the infected trees. The identification of CSSV molecular characters was undertaken using PCR sequencing analysis which was then examined using BioEdit and Mega5 programs to initiate a relationship dendrogram. The result showed that the DR1 cacao tree clones from Kalibawang were infected by mosaic virus with mild visual severity of leaf typical symptom. From the electronic microscope observation, a ±100 nm rod-shaped viral particle with a diameter of 15.3 mm was found. On the molecular level, the cause of mosaic symptom has CSSV amplified at conserved regions with size 375 bp. The results are the first report confirming that the molecular cause of cacao mosaic disease in Indonesia is CSSV. The molecular characters of CSSV in Yogyakarta are very different from those found abroad.