Efficacy of chemotherapy and thermotherapy in elimination of East African cassava mosaic virus from Tanzanian cassava landrace

Cut, Root, and Grow: Simplifying Cassava Propagation to Scale

Cassava (Manihot esculenta Crantz) is an essential crop with increasing importance for food supply and as raw material for industrial processing. The crop is vegetatively propagated through stem cuttings taken at the end of the growing cycle and its low multiplication rate and the high cost of stem transportation are detrimental to the increasing demand for high-quality cassava planting materials. Rapid multiplication of vegetative propagules of crops comprises tissue culture (TC) and semi-autotroph hydroponics (SAH) that provide cost-effective propagation of plant materials; however, they contrast the need for specific infrastructure, special media and substrates, and trained personnel. Traditional methods such as TC and SAH have shown promise in efficient plant material propagation. Nonetheless, these techniques necessitate specific infrastructure, specialized media and substrates, as well as trained personnel. Moreover, losses during the intermediate nursery and adaptation stages limit the overall effectiveness of these methods. Building upon an earlier report from Embrapa Brazil, which utilized mature buds from cassava for rapid propagation, we present a modified protocol that simplifies the process for wider adoption. Our method involves excising single nodes with attached leaves from immature (green) cassava stems at 2 months after planting (MAP). These nodes are then germinated in pure water, eliminating the need for specific growth substrates and additional treatments. After the initial phase, the rooted sprouts are transferred into soil within 1-8 weeks. The protocol demonstrates a high turnover rate at minimal costs. Due to its simplicity, cost-effectiveness, and robustness, this method holds significant promise as an efficient means of producing cassava planting materials to meet diverse agricultural needs.

Somatic embryogenesis from flower tepals of Hippeastrum aiming regeneration of virus-free plants

Hippeastrum hybridum is an important bulbous flower plant in world floriculture, which are propagated conventionally by the technique known as double or twin scales to obtain plants with clonal origin. However, this technique promotes the propagation of systemic diseases, particularly mosaic-inducing viruses. The aim of this paper was to evaluate the somatic embryogenesis (SE) from tepals as an alternative to provide a technique for SE induction and to obtaining virus-free plantlets of Hippeastrum from infected plants. The concentrations of 2,4-Dichlorofenoxiacetic Acid (2,4-D) and thidiazuron (TDZ) was evaluated in SE induction pathway. The monitoring of viruses during the assays with tepals was performed by Reverse Transcription-Polymerase Chain Reaction. SE induction was obtained, for the first time, in tepal segments from flower buds of Hippeastrum. The 2,4-D was the main factor for embryogenic callus induction, and TDZ increased the SE induction rate. However, conversion of somatic embryos into plantlets were only developed in free-2,4-D media, replaced by 1.0 mg L^-1 6-Benziladenine. Out of five virus species monitored during the experiment, Cucumber mosaic virus was detected in tepals and Hippeastrum mosaic virus in leaves of donor plants. The SE-derived plantlets that germinated in vitro were acclimatized and tested negative for all viruses assayed.

Production of Virus-Free Chrysanthemum (Chrysanthemum morifolium Ramat) by Tissue Culture Techniques

Almost all plants in their natural environment are commonly infected by viruses. These viral infections can cause devastating diseases and result in severe yield and economic losses, making viral diseases an important limiting factor for agricultural production and sustainable development. However, these losses can be effectively reduced through the productions and applications of virus-free plantlets. In vitro culture techniques are the most successful approaches for efficient eradication of various viruses from almost all the most economically important crops. Techniques for producing virus-free plantlets include meristem tip culture, somatic embryogenesis, chemotherapy, thermotherapy, electrotherapy, shoot tip cryotherapy, and micrografting. Among them, meristem tip culture is currently the most widely used. Here, we describe a detailed protocol for producing virus-free plantlets of Chrysanthemum morifolium Ramat using tissue culture techniques.

Phytotoxicity and Other Adverse Effects on the In Vitro Shoot Cultures Caused by Virus Elimination Treatments: Reasons and Solutions

In general, in vitro virus elimination is based on the culture of isolated meristem, and in addition thermotherapy, chemotherapy, electrotherapy, and cryotherapy can also be applied. During these processes, plantlets suffer several stresses, which can result in low rate of survival, inhibited growth, incomplete development, or abnormal morphology. Even though the in vitro cultures survive the treatment, further development can be inhibited; thus, regeneration capacity of treated in vitro shoots or explants play also an important role in successful virus elimination. Sensitivity of genotypes to treatments is very different, and the rate of destruction largely depends on the physiological condition of plants as well. Exposure time of treatments affects the rate of damage in almost every therapy. Other factors such as temperature, illumination (thermotherapy), type and concentration of applied chemicals (chemo- and cryotherapy), and electric current intensity (electrotherapy) also may have a great impact on the rate of damage. However, there are several ways to decrease the harmful effect of treatments. This review summarizes the harmful effects of virus elimination treatments applied on tissue cultures reported in the literature. The aim of this review is to expound the solutions that can be used to mitigate phytotoxic and other adverse effects in practice.

Cryobiotechnology of Plants: A Hot Topic Not Only for Gene Banks

Agriculture has always been an important part of human evolution. Traditionally, farming is changing and developing with regard to challenges it faces. The major challenges of modern agriculture are food and nutrition safety for the growing world population. Promoting species and genetic diversity in agriculture appears to be an important approach to dealing with those challenges. Gene banks all around the world play a crucial role in preserving plant genetic resources for future crop improvements. The plant germplasm can be preserved in different ways, depending on the species or form of stored plant tissue. This review focuses on a special preservation method—cryopreservation. Cryopreservation is an effective technique for storing living systems at ultra-low temperatures, usually in liquid nitrogen or its vapor phase. This conservation method is crucial for plants that do not produce seeds or that produce non germinating seeds, as well as for plants that propagate vegetatively. Moreover, based on the cryopreservation method, a novel plant biotechnology tool for pathogen eradication called cryotherapy has been developed. The use of liquid nitrogen eliminates plant pathogens such as viruses, phytoplasmas, and bacteria. Our article reviews recent advances in cryo-biotechnologies such as cryopreservation and cryotherapy, with special focus on studies concerning fruit plants.

In vitro thermotherapy-based methods for plant virus eradication

Production of virus-free plants is necessary to control viral diseases, import novel cultivars from other countries, exchange breeding materials between countries or regions and preserve plant germplasm. In vitro techniques represent the most successful approaches for virus eradication. In vitro thermotherapy-based methods, including combining thermotherapy with shoot tip culture, chemotherapy, micrografting or shoot tip cryotherapy, have been successfully established for efficient eradication of various viruses from almost all of the most economically important crops. The present study reviewed recent advances in in vitro thermotherapy-based methods for virus eradication since the twenty-first century. Mechanisms as to why thermotherapy-based methods could efficiently eradicate viruses were discussed. Finally, future prospects were proposed to direct further studies.