Molecular and cytological characterization of the global Musa germplasm collection provides insights into the treasure of banana diversity

© 2016, The Author(s). Bananas (Musa spp.) are one of the main fruit crops grown worldwide. With the annual production reaching 144 million tons, their production represents an important contribution to the economies of many countries in Asia, Africa, Latin-America and Pacific Islands. Most importantly, bananas are a staple food for millions of people living in the tropics. Unfortunately, sustainable banana production is endangered by various diseases and pests, and the breeding for resistant cultivars relies on a far too small base of genetic variation. Greater diversity needs to be incorporated in breeding, especially of wild species. Such work requires a large and thoroughly characterized germplasm collection, which also is a safe depository of genetic diversity. The largest ex situ Musa germplasm collection is kept at the International Transit Centre (ITC) in Leuven (Belgium) and currently comprises over 1500 accessions. This report summarizes the results of systematic cytological and molecular characterization of the Musa ITC collection. By December 2015, 630 accessions have been genotyped. The SSR markers confirmed the previous morphological based classification for 84% of ITC accessions analyzed. The remaining 16% of the genotyped entries may need field verification by taxonomist to decide if the unexpected classification by SSR genotyping was correct. The ploidy level estimation complements the molecular data. The genotyping continues for the entire ITC collection, including newly introduced accessions, to assure that the genotype of each accession is known in the largest global Musa gene bank. Open Access ispartof: Biodiversity and Conservation vol:26 issue:4 pages:801-824 status: publishe

Somatic Embryogenesis in Peach Palm Using the Thin Cell Layer Technique: Induction, Morpho-histological Aspects and AFLP Analysis of Somaclonal Variation

• Background and Aims: The thin cell layer (TCL) technique is based on the use of very small explants and has allowed enhanced in vitro morphogenesis in several plant species. The present study evaluated the TCL technique as a procedure for somatic embryo production and plantlet regeneration of peach palm. • Methods: TCL explants from different positions in the shoot apex and leaf sheath of peach palm were cultivated in MS culture medium supplemented with 0-600 μm Picloram in the presence of activated charcoal. The production of primary calli and embryogenic calli was evaluated in these different conditions. Histological and amplified fragment length polymorphism (AFLP) analyses were conducted to study in vitro morphogenetic responses and genetic stability, respectively, of the regenerated plantlets. • Key Results: Abundant primary callus induction was observed from TCLs of the shoot meristem in culture media supplemented with 150-600 μm Picloram (83-97 %, respectively). The production of embryogenic calli depends on Picloram concentration and explant position. The best response observed was 43 % embryogenic callus production from shoot meristem TCL on 300 μm Picloram. In maturation conditions, 34 ± 4 somatic embryos per embryogenic callus were obtained, and 45.0 ± 3.4 % of these fully developed somatic embryos were converted, resulting in plantlets ready for acclimatization, of which 80 % survived. Histological studies revealed that the first cellular division events occurred in cells adjacent to vascular tissue, resulting in primary calli, whose growth was ensured by a meristematic zone. A multicellular origin of the resulting somatic embryos arising from the meristematic zone is suggested. During maturation, histological analyses revealed bipolarization of the somatic embryos, as well as the development of new somatic embryos. AFLP analyses revealed that 92 % of the regenerated plantlets were true to type. The use of TCL explants considerably improves the number of calli and somatic embryos produced in comparison with previously described protocols for in vitro regeneration of peach palm. • Conclusions: The present study suggests that the TCL somatic embryogenesis protocol developed is feasible, although it still requires further optimization for in vitro multiplication of peach palm, especially the use of similar explants obtained from adult palm trees. © The Author 2007. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved