Somaclonal variation induced in vitro during tissue culture can be a problem in clonal micropropagation of elite plants. This study investigated the extent of morphological and genetic similarity or dissimilarity between Melia volkensii in vitro plants (somatic seedlings) obtained via somatic embryogenesis and normal seedlings. Comparisons were made between in vitro plants regenerated directly from cotyledon explants, indirectly from zygotic embryos and normal seedlings of the same parent trees. Regeneration was achieved using half MS medium supplemented with 0.05 mg/l thidiazuron. Shoots were elongated in half MS with 0.1 mg/l BAP plus 0.01 mg/l IAA then rooted in half MS with 0.1 mg/l IBA and 0.1 mg/l NAA. Six morphometric and five meristic characters were used for the morphological characterization. PCR-RAPD markers were used for assessment of genetic similarity or distance. Multivariate analysis using principal coordinates, cluster analysis, analysis of similarities (Anosim) and similarity percentages analysis (SIMPER) revealed significant dissimilarities (p< 0.0001) in morphometric and meristic characters between the in vitro plants and normal seedlings. However, significant similarity (p<0.01) was observed in the RAPD-genic characters of the in vitro plants and normal seedlings. Out of six morphometric traits, taproot length, internode length and shoot height were the most important sources of dissimilarity, cumulatively accounting for 72.37% of overall morphometric dissimilarity. Number of lateral roots was the single most important source of meristic dissimilarity, with 77.02% contribution. Plants regenerated directly from cotyledons were more similar to the normal seedlings in morphological and RAPD-marker characters than those regenerated indirectly from zygotic embryos. This study paves the way for identification of trait-specific RAPD markers for further characterization through sequence-characterized amplified regions (SCARs).

Melia volkensii Gurke is a drought-tolerant tree native to East Africa's arid and semiarid lands (ASALs), with vast but underutilized potential for agroforestry and sustainable livelihoods in the ASALs. Its cultivation is limited by difficulties in propagation via conventional means. Full exploitation of the ability of thidiazuron (TDZ) to elicit regeneration in plant tissue cultures, as sole plant growth regulator (PGR), is hampered by high costs. This study tested the effectiveness of a low-cost agrochemical TDZ for in vitro propagation of M. volkensii. Zygotic embryos from mature seeds were cultured on Gamborg's B5 medium containing 0 to 4 mg/L of agrochemical TDZ from Kingtai Chemicals Co.,Ltd., China. Callus induction frequency was 96.67 to 100%. Significantly large callus fresh mass was produced at 0.05 mg/L TDZ concentration (ANOVA, P < 0.001). The effect of TDZ on embryogenicity was significant over certain ranges of concentrations (Anova, P < 0.001). Multiple somatic embryos developed within 14 days of subculture to hormone-free B5 medium. Somatic embryos developed into microshoots which elongated when transferred to 1/2 MS medium supplemented with 0.1 mg/L 6-benzylaminopurine plus 10% coconut water. The Kingtai-TDZ showed a high potency and suitability for use in M. volkensii tissue culture.

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The cultivation of bananas and plantains (Musa spp.) holds significant global economic importance, but faces numerous challenges, which may include diverse abiotic and biotic factors such as drought and various diseases caused by fungi, viruses, and bacteria. The genetic and asexual nature of cultivated banana cultivars makes them unattractive for improvement via traditional breeding. To overcome these constraints, modern biotechnological approaches like genetic modification and genome editing have become essential for banana improvement. However, these techniques rely on somatic embryogenesis, which has only been successfully achieved in a limited number of banana cultivars. Therefore, developing new strategies for improving somatic embryogenesis in banana is crucial. This review article focuses on advancements in banana somatic embryogenesis, highlighting the progress, the various stages of regeneration, cryopreservation techniques, and the molecular mechanisms underlying the process. Furthermore, this article discusses the factors that could influence somatic embryogenesis and explores the prospects for improving the process, especially in recalcitrant banana cultivars. By addressing these challenges and exploring potential solutions, researchers aim to unlock the full potential of somatic embryogenesis as a tool for banana improvement, ultimately benefiting the global banana industry.

The study reports the first DNA-barcode and molecular phylogeny of the East African endemic tree species Melia volkensii using the standard two-locus plant barcoding genes (rbcL and matK). The two genes were amplified and the PCR products sequenced. Complete coding sequences were obtained for both genes. The edited and aligned sequences had lengths of 1371 bp for rbcL and 1524 bp for matK. These DNA sequences were deposited into the DNA Data Bank of Japan (DDBJ) with cross-listing in the European Molecular Biology Labaratory (EMBL) and GenBank databases. The deposited gene sequences were then subjected to separate nucleotide BLASTs in NCBI's GenBank database. Out of 100 Blast results in which the query (M. volkensii) had 96-100 percentage similarity in nucleotide sequence for the rbcL gene and 90-100% similarity for the matK gene, only 16 taxa had data for both rbcL and matK genes. These 16 taxa were used for the phylogenetic analysis and comprised of 6, 9 and 1 taxa respectively from the families Meliaceae, Simaroubaceae and Rutaceae. The barcode allowed adequate discrimination of the taxa into their respective generic and species clades. Availability of a barcode for M. volkensii will ease identification of the species, provide more robust phylogenetic reconstructions and allow for better tracking of its exotic dispersal.

Banana (Musa spp) is among the top ten most important food crops worldwide in terms of production and consumption. However, banana production is threatened by several bacterial diseases, including Banana Xanthomonas wilt (BXW) caused by Xanthomonas campestris pathovar (pv). musacearum, Moko disease caused by Ralstonia solanacearum, and Blood disease caused by Ralstonia syzygii sub-species (subsp). Celebesensis. Banana Xanthomonas wilt (BXW), caused by Xanthomonas campestris pv. musacearum (Xcm) is the most economically important bacterial disease affecting banana production, particularly in the African Great Lakes region. Banana breeding through conventional approach is key to overcoming yield losses to bacterial phytopathogens. However, conventional breeding of bananas is limited by low male and female fertility and the lack of diversity and important traits in the gene pool. At present, only Musa balbisiana (banana progenitor species) is resistant to BXW, but breeders do not prefer it for breeding because it harbors banana streak virus (BSV) sequences in its B genome, which get activated during abiotic stress, such as drought, leading Banana Streak Disease (BSD). Thus, genetic engineering serves as a viable alternative and complement to conventional breeding for banana improvement. This review highlights the strategies, challenges, status, and prospects of genetic engineering of bananas against bacterial diseases.

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