Being sessile, plants must regulate energy balance, potentially via source-sink relations, to compromise growth with survival in stressful conditions. Crops are sensitive, possibly because they allocate their energy resources toward growth and yield rather than stress tolerance. In contrast, resurrection plants tightly regulate sugar metabolism and use a series of physiological adaptations to suppress cell death in their vegetative tissue to regain full metabolic capacity from a desiccated state within 72 h of watering. Previously, we showed that shoots of the resurrection plant Tripogon loliiformis , initiate autophagy upon dehydration as one strategy to reinstate homeostasis and suppress cell death. Here, we describe the relationship between energy status, sugar metabolism, trehalose-mediated activation of autophagy pathways and investigate whether shoots and roots utilize similar desiccation tolerance strategies. We show that despite containing high levels of trehalose, dehydrated Tripogon roots do not display elevated activation of autophagy pathways. Using targeted and non-targeted metabolomics, transmission electron microscopy (TEM) and transcriptomics we show that T. loliiformis engages a strategy similar to the long-term drought responses of sensitive plants and continues to use the roots as a sink even during sustained stress. Dehydrating T. loliiformis roots contained more sucrose and trehalose-6-phosphate compared to shoots at an equivalent water content. The increased resources in the roots provides sufficient energy to cope with stress and thus autophagy is not required. These results were confirmed by the absence of autophagosomes in roots by TEM. Upregulation of sweet genes in both shoots and roots show transcriptional regulation of sucrose translocation from leaves to roots and within roots during dehydration. Differences in the cell’s metabolic status caused starkly different cell death responses between shoots and roots. These findings show how shoots and roots utilize different stress response strategies and may provide candidate targets that can be used as tools for the improvement of stress tolerance in crops.

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Sorghum (Sorghum bicolour (L.) Moench), the second most important staple crop in Sub-Saharan Africa (SSA) after maize, is well adapted to marginal environments of drought stress and high temperatures. But besides drought stress, the obligate root-parasitic flowering plant Striga hermonthica is an equally economically important biotic stress in agro-ecological zones where soils are marginal. Notwithstanding widespread and intense Striga infestation, genetic variations in defence mechanisms against the parasite have been reported. Sorghum variants, producing low levels of chemical stimulants such as sorgolactones that deter the advance of Striga seed germination and are therefore deemed resistant to the parasite, have been also reported in a few studies. But the existence of sorghum genetic variation for this resistance especially among farmers' landraces is yet to be demonstrated. The objective of this study was therefore to determine the levels of Striga germination stimulants in response to each of the 111 collected sorghum landraces and their progenies from Eritrea. The ability of a sorghum genotype to cause germination of a Striga seed as a measure of the amount of the germination stimulant produced was used to assess the resistance of these accessions. The data were recorded as Striga germination percentage by counting the number of germinated Striga seeds. Landraces EG47, EG1261, EG830, EG1076, EG54 and EG746 with 14.68%, 15.32%, 11.85%, 13.05%, 15.74% and 16.5% germination percentages respectively were found to stimulate low levels of Striga germination percentage compared to commercial checks, IS9830, SRN39, Framida, with 22.46%, 22.67%, 23.27% germination respectively. While these variants did not show complete resistance against Striga seed germination, the low level How to cite this paper: Yohannes, T., Ngugi, K., Ariga, E., Abraha, T., Yao, N., Asami, P. and Ahonsi, M. 2471production of stimulant indicated their high level of resistance to Striga. These results implied that these accessions are likely potential sources of resistance against Striga infestation in SSA sorghum breeding programs.

Garlic is one of the most crucial Allium vegetables used as seasoning of foods. It has a lot of benefits from the medicinal and nutritional point of view; however, its production is highly constrained by both biotic and abiotic challenges. Among these, viral infections are the most prevalent factors affecting crop productivity around the globe. This experiment was conducted on eleven selected garlic accessions and three improved varieties collected from different garlic growing agro-climatic regions of Ethiopia. This study aimed to identify and characterize the isolated garlic virus using the coat protein (CP) gene and further determine their phylogenetic relatedness. RNA was extracted from fresh young leaves, thirteen days old seedlings, which showed yellowing, mosaic, and stunting symptoms. Pairwise molecular diversity for CP nucleotide and amino acid sequences were calculated using MEGA5. Maximum Likelihood tree of CP nucleotide sequence data of Allexivirus and Potyvirus were conducted using PhyML, while a neighbor-joining tree was constructed for the amino acid sequence data using MEGA5. From the result, five garlic viruses were identified viz. Garlic virus C (78.6 %), Garlic virus D (64.3 %), Garlic virus X (78.6 %), Onion yellow dwarf virus (OYDV) (100%), and Leek yellow stripe virus (LYSV) (78.6 %). The study revealed the presence of complex mixtures of viruses with 42.9 % of the samples had co-infected with a species complex of Garlic virus C, Garlic virus D, Garlic virus X, OYDV, and LYSV. Pairwise comparisons of the isolated Potyviruses and Allexiviruses species revealed high identity with that of the known members of their respected species. As an exception, less within species identity was observed among Garlic virus C isolates as compared with that of the known members of the species. Finally, our results highlighted the need for stepping up a working framework to establish virus-free garlic planting material exchange in the country which could result in the reduction of viral gene flow across the country.Author SummaryGarlic viruses are the most devastating disease since garlic is the most vulnerable crop due to their vegetative nature of propagation. Currently, the garlic viruses are the aforementioned production constraint in Ethiopia. However, so far very little is known on the identification, diversity, and dissemination of garlic infecting viruses in the country. Here we explore the prevalence, genetic diversity, and the presence of mixed infection of garlic viruses in Ethiopia using next generation sequencing platform. Analysis of nucleotide and amino acid sequences of coat protein genes from infected samples revealed the association of three species from Allexivirus and two species from Potyvirus in a complex mixture. Ultimately the article concludes there is high time to set up a working framework to establish garlic free planting material exchange platform which could result in a reduction of viral gene flow across the country.

Cowpeas (Vigna unguiculata) are important grain legumes grown by resource poor farmers across Sub-Saharan Africa. In Kenya, cowpeas continue to produce low yields due to erratic rainfall caused by the current climate change. This study sought to enhance drought tolerance in Kenyan cowpeas through transformation by Agrobacterium tumefaciens using L-Pyrroline-5-carboxylate synthase (P5CS) gene. Cowpea variety K80 was inoculated with Agrobacterium tumefaciens strains EHA105 and LBA4404 harbouring recombinant plasmids pCAMBIA1301:VuP5CS or pCIP100:VuP5CS through vacuum infiltration of pre-germinated seeds at 60 kpa for 25 min. The presence of the transgene in the transformed cowpea plants and its transfer to progeny was confirmed by PCR analysis of T 0 and T 1 plants. The highest transformation efficiency of 20.5% was achieved with strain EHA105 harbouring plasmid pCAMBIA1301:VuP5CS. A segregation analysis of the transgenes gave a 1:4 ratio for the VuP5CS transformed: non-transformed plants and did not follow the 3:1 Mendelian inheritance pattern for dominant genes. There was no difference in proline content in the transformed and non-transformed T 1 plants. However, the roots of the transformed plants were significantly longer than those of the nontransformed plants. The numbers of harvested seeds were also significantly higher in the transformed plants with 10 to 11 seeds per pod in comparison to the non-transformed plants with an average of 5.58 seeds per pod, indicating drought tolerance potential of the transformed plants. The T 2 and T 3 plants need to be screened further to evaluate the stable integration of the transgene and physiological characterization under water stress.

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Background and Objective: Several factors affect the optimization of tissue culture protocols of cereals including hormones and media composition. This the first study in East and Central Africa to assess the effect of the hormone 2,4-D on callus initiation and regeneration of sweet sorghum via mature embryos. Materials and Methods: Callus induction and regeneration of 5 sweet sorghum varieties IESV92008DL, IESV92001DL, IESV92021DL, ICSV700 and ICSV93048 were evaluated using mature embryos as a source of explants and MS medium supplemented with five levels of the hormone 2,4-D (0, 1, 2, 4 and 6 mg LG 1 ). Results: The highest callus induction frequency was observed in 6 mg LG 1 of 2,4-D level for all the genotypes while the lowest callus induction frequency was observed in 0 and 1mg LG 1 of 2,4-D level. The highest embryogenic callus induction frequency was observed in 4 and 6 mg LG 1 of 2,4-D for all the genotypes while the lowest embryogenic callus induction frequency was observed in 0 and 1 mg LG 1 of 2,4-D. Regeneration efficiency was observed higher for the 2 genotypes ICSV93046 and ICSV700. Conclusion: This study revealed that the auxin 2,4-D level 4 and 4 mg LG 1 are very important for callus initiation and regeneration of sweet sorghum and helpful for researcher to set up other protocols for improvement of sweet sorghum crop through tissue culture and transformation techniques.