Okra yellow mosaic Bhubaneshwar virus

This virus is a single-stranded DNA virus with a bipartite genome, which allows it to efficiently replicate and manipulate the host's cellular machinery.

Transmission occurs primarily through the whitefly (Bemisia tabaci) in a semi-persistent manner, meaning the insect acquires the virus after feeding on infected plants and can transmit it for several days.

The viral particles exhibit the characteristic twin-headed (geminate) structure of the Geminiviridae group, which is highly adapted for survival and infection in tropical agricultural environments.

Genetic variability among isolates of this virus is significant, which presents challenges for breeding programs aimed at developing resistant okra cultivars.

The most distinctive symptom is the appearance of bright yellow or golden mosaic patterns on the leaves, resulting from the destruction of chlorophyll.

In severe infections, the entire leaf lamina may become chlorotic (white or pale yellow), severely limiting the plant's ability to perform photosynthesis.

Stunted growth is commonly observed in infected okra plants, with affected individuals failing to reach their normal height and biomass compared to healthy plants.

Fruit set is drastically reduced, and the pods that manage to develop are often small, malformed, and exhibit uneven skin texture, rendering them unmarketable.

As the disease progresses, premature shedding of flowers and flower buds occurs, leading to significant yield loss and early senescence of the plant foliage.

Disease outbreaks are closely linked to high population densities of the whitefly vector, which thrives in hot and dry climatic conditions.

Optimal temperatures for viral replication and insect vector activity typically range between 28°C and 35°C, making okra crops highly susceptible during peak summer months.

Poor field sanitation, such as the presence of weeds that act as alternate hosts, allows the virus to persist and migrate into the main crop during the season.

Close plant spacing and high humidity levels can create favorable microclimates that encourage faster spread of the whitefly population throughout the field.

Nutritional stress or improper irrigation practices can weaken the okra plant's natural defense systems, facilitating the establishment and rapid spread of the virus.

The primary economic impact is a massive reduction in marketable yield, which can reach up to 100% in highly susceptible okra varieties under heavy infection pressure.

Beyond quantity, the quality of the okra pods is significantly degraded, with fruits becoming hard, fibrous, and aesthetically unappealing to consumers.

The systemic nature of the infection means that once a plant is infected, the entire plant is compromised, leading to complete economic loss for that specific unit.

Infected fields serve as continuous reservoirs of the virus, posing a significant risk to neighboring fields and future cropping seasons in the region.

Farmers often incur high costs related to intensive insecticide applications aimed at suppressing whitefly populations to mitigate the disease risk.

The cornerstone of management is the rigorous control of the whitefly population using systemic insecticides and biological control agents where applicable.

Cultural practices, such as the removal of alternate weed hosts and maintaining clean field borders, are essential to break the virus disease cycle.

The use of reflective mulches or physical barriers like fine-mesh nets can be effective in preventing whiteflies from colonizing young, vulnerable seedlings.

• Regular monitoring of insect vector populations using yellow sticky traps.
• Prompt rogueing (removal and destruction) of symptomatic plants to minimize viral spread.
• Crop rotation with non-malvaceous plant species to disrupt the host-virus cycle.

Developing and planting resistant or tolerant okra varieties is the most sustainable long-term solution for managing this destructive viral disease.