Overexpression of Arabidopsis FLOWERING LOCUS T (FT) gene improves floral development in cassava (Manihot esculenta, Crantz)

Cassava is a tropical storage-root crop that serves as a worldwide source of staple food for over 800 million people. Flowering is one of the most important breeding challenges in cassava because in most lines flowering is late and non-synchronized, and flower production is sparse. The FLOWERING LOCUS T (FT) gene is pivotal for floral induction in all examined angiosperms. The objective of the current work was to determine the potential roles of the FT signaling system in cassava. The Arabidopsis thaliana FT gene (atFT) was transformed into the cassava cultivar 60444 through Agrobacterium-mediated transformation and was found to be overexpressed constitutively. FT overexpression hastened flower initiation and associated fork-type branching, indicating that cassava has the necessary signaling factors to interact with and respond to the atFT gene product. In addition, overexpression stimulated lateral branching, increased the prolificacy of flower production and extended the longevity of flower development. While FT homologs in some plant species stimulate development of vegetative storage organs, atFT inhibited storage-root development and decreased root harvest index in cassava. These findings collectively contribute to our understanding of flower development in cassava and have the potential for applications in breeding

A milestone in the doubled haploid pathway of cassava

This study was aimed at inducing androgenesis in cultured anthers of cassava (Manihot esculenta Crantz) to develop a protocol for the production of doubled haploids. Microspore reprogramming was induced in cassava by cold or heat stress of anthers. Since the anthers contain both haploid microspores and diploid somatic cells, it was essential to verify the origin of anther-derived calli. The origin of anther-derived calli was assessed by morphological screening followed by histological analysis and flow cytometry (FCM). Additionally, simple sequence repeat (SSR) and amplified fragmented length polymorphism (AFLP) assays were used for the molecular identification of the microspore-derived calli. The study clearly demonstrated the feasibility of producing microspore-derived calli using heat- or cold-pretreated anthers. Histological studies revealed reprogramming of the developmental pathway of microspores by symmetrical division of the nucleus. Flow cytometry analysis revealed different ploidy level cell types including haploids, which confirmed their origin from the microspores. The SSR and AFLP marker assays independently confirmed the histological and FCM results of a haploid origin of the calli at the DNA level. The presence of multicellular microspores in the in vitro system indicated a switch of developmental program, which constitutes a crucial step in the design of protocols for the regeneration of microspore-derived embryos and plants. This is the first detailed report of calli, embryos, and abnormal shoots originated from the haploid cells in cassava, leading to the development of a protocol for the production of doubled haploid plants in cassava

Coconut micropropagation for worldwide replanting needs

Coconut (Cocos nucifera L.) is an oil-bearing crop contributing to the income of more than ten million farmers and their dependents. However, coconut farmers commonly encounter many challenges since productivity is influenced by the senility of the palms, the reduction of soil fertility, and natural calamities. In addition, an important reduction in the cultivated area has resulted from outbreaks of lethal pests and diseases. In this context, micropropagation via somatic embryogenesis (SE) holds a great hope of producing many palms, of a desired genotype in a relatively short period. SE in coconut was first attempted over 40 years ago. Over time, it was discovered that plumular tissue isolated from mature embryo was the optimal explant type to form embryogenic callus. However, this type of explant may not be ideal to produce true-to-type clones due to the outcrossing of some coconut varieties. More recent attention has shifted back to the development of protocols using floral tissue explants such as immature inflorescences. Different compounds have been applied to improve the success rate of somatic embryogenesis, including abscisic acid, brassinosteroids, polyamines, etc. Furthermore, morpho-histological, biochemical, and physiological studies have been undertaken to better understand the coconut somatic embryogenesis. These studies have been helpful in scaling up the plumule-based process which has successfully produced palms in field trials. The protocols developed would be very valuable for the renewal of coconut plantations with appropriate genotypes and the creation of individuals with the desirable agronomic characteristics. Although coconut micropropagation has already progressed to a commercial level, further improvements are still of great demand. This will require active collaboration between the most advanced institutions on this field. It could be achieved through a virtual international institute for coconut research and development, with coordination of internationally recognized organizations, such as the International Coconut Community and COGENT