Salinity is a major detrimental abiotic factor for plant growth. The main purpose of this study was to analyze the effects of different NaCl concentrations on growth and some physiological parameters related to gas exchanges and water relations in amaranth (Amaranthus cruentus) plants. Three weeks old amaranth plants from the cultivar ‘Locale’ were exposed in nutrient solution to 0, 30 or 90 mM NaCl (electrical conductivities of 1.915; 4.815 and 11.70 dS.m-1 respectively) in phytotron conditions. Shoot elongation as well as fresh and dry masses of shoot and root were determined after two weeks of stress exposure. Net photosynthesis (A), intercellular CO2 concentration (Ci), instantaneous transpiration (E), stomatal conductance (gs), osmotic potential (Ψs) as well as the efficiency of the instantaneous carboxylation (A/Ci), intrinsic (A/gs) and instantaneous (A/E) water use efficiency were estimated. Results reveal that salt stress induced a significant reduction in growth of aerial part as well as net photosynthesis, instantaneous transpiration, stomatal conductance and leaf and root osmotic potentials. In contrast, no significant reductions were recorded for root growth, shoot water content, intercellular CO2 concentration and instantaneous carboxylation efficiency. However, a significant increase was observed for intrinsic (A/gs) and instantaneous (A/E) water use efficiency. The plant growth reduction observed hinges upon a drop in photosynthetic activity due mainly to stomatal closure. These data suggest that photosynthetic activity may be used as a reliable criterion for physiological estimation of salt-tolerance in A. cruentus cultivars. Key words: Saline stress, net photosynthesis, stomatal conductance, osmotic potential, water use efficiency.

Dioscorea rotundata Poir. is mainly dioecious but it also produces monoecious individuals. Recently two genetic markers were proposed to determine the sex in this species. We tested them in 119 individuals from 101 different cultivars of the national collection of Benin to verify whether they can predict the sex observed in the field. Among the analyzed individuals, 72 were male, 37 were female, 7 were monoecious and 3 were non-flowering. Our results showed that the marker sp16, associated with the W allele (female allele), was present in all female individuals but also in more than 42% of male individuals. Thus, while the absence of sp16 confirmed the male sex of the individuals, its presence did not allow sex discrimination. The marker sp1 allowed the identification of four genotypes (AA, AB, BB and AC) in the analyzed individuals with AA and AB being the most represented. Although AA was observed in 62.16% of female individuals and AB in 83.33% of male individuals, we did not observe a clear correlation between sp1 genotypes and sex identity. We concluded that the tested markers did not allow a clear sex discrimination in Beninese Dioscorea rotundata cultivars. Our results also suggest that Beninese D. rotundata cultivars have adopted a male XX/XY heterogametic system that is undergoing reorganization.

Aims: In this study, salt resistance level of five amaranth (Amaranthus cruentus) cultivars: AA-04-028, AA-04-017, Locale, Rouge and Red-Sudan, was evaluated at young plants stage. Study Design: The experiment was laid out as a Randomized Complete Block Design (RCBD) with four replications. Place and Duration of Study: The experiment was carried out in a screen house at Center of Agricultural Research of Agonkanmey, Commune of Abomey-Calavi, Republic of Benin from July to September 2016. Methodology: Three weeks old plants of the five cultivars were submitted in pots containing a mixture of potting soil and sand to four NaCl concentrations: 0, 30, 60 and 90 mM NaCl corresponding respectively to an electric conductivity of 0, 1.915, 4.815 and 8.39 dS.m^-1 by irrigation every two days. Plant growth parameters were evaluated after two weeks. Results: Salt effect caused a reduction of young plant growth whatever the growth parameter considered with a significant difference among cultivars. The growth reduction due to NaCl is lower and non significant in cultivar Rouge for all growth parameters except root fresh mass, whereas this reduction is higher and significant (p=.05) in cultivars Locale and AA-04-028 for all growth parameters. For cultivars Red-Sudan and AA-04-017, the reduction due to NaCl was significant (p= .05) only for leaf number and plant height. The results indicated that cultivar Rouge was the less affected by NaCl, followed by AA-04-017, Red-Sudan and AA-04-028; cultivar Locale was the most affected. Conclusion: Plant height, leaf number and root length appeared as the most suitable growth parameters for studying salt stress effect in Amaranthus cruentus. For the first time, we demonstrated that there is a variability of relative salt-stress resistance among A. cruentus cultivars at young plant stage. Among the five cultivars, Rouge appeared as the most salt resistant whereas cultivar Locale was the most salt sensitive at young plants stage.

Cultivated yam (Dioscorea rotundata) is a staple tuber crop in West Africa which is mainly vegetatively propagated. Although the majority of yam cultivars flower, the control of their sexual reproduction remains largely unknown despite its importance for plant-breeding programs. While described as a dioecious species, yam has several monoecious (mix) cultivars that are often subject to spontaneous sex changes. This study aims to evaluate the impact of phytohormones on sex expression and flower development in cultivated yams D. rotundata. Exogenous applications of 1 mM 6-benzylaminopurine (BAP) and 1 mM methyl jasmonate (MeJa) were performed on seedlings of female (Gnidou, Anago), male (Flou) and mix (Katala and Laboko) cultivars. The mix cultivars produced monoecious, male and female plants while the female and male cultivars had rather stable sex. Our results showed that MeJa exhibited a significant masculinising effect in mix cultivars and induced inflorescence and flower malformations in female cultivars (56% in Gnidou and 37% in Anago). Most malformations were inflorescence branching and sterile flowers (non-differentiated ovary) with extra cycles of sepals. Moreover, MeJa reduced flowering time in the cultivars of all sexes and increased the number of inflorescences per plant as well as the number of flowers per plant. Our results showed that BAP reduced the flowering time, synchronized flowering in female plants and increased the number of inflorescences per plant in monoecious plants. However, our results did not allow for strong conclusions regarding the effect of BAP on sex expression due to the high proportion of female flowering in both the control and BAP-sprayed plants. Nevertheless, we did not observe any masculinising effect for BAP. Further research that would highlight hormone and homeotic gene interactions in flowering could be of key interest in understanding the hormonal control of sex in cultivated yams D. rotundata.

Aims: This study evaluated the role of sodium, potassium, proline and soluble sugars accumulation in the ameliorative effect of an exogenous application of calcium on the detrimental effect of salinity on tomato plants. Study Design: The experiment was implemented as a Completely Randomized Design (RCD) with four treatments and three replications. Place and Duration of Study: The experiment was realized in a green house of the Faculty of Agronomical Sciences, University of Abomey-Calavi, Benin Republic from June to July 2020. Methodology: Three weeks old plants of the tomato cultivar “Padma” was submitted in pots to four treatments comprising the control (without NaCl); salt stress (120 mM NaCl) and a combination of 120 mM NaCl and exogenous application of 40 mM CaSO₄ or Ca (NO₃)₂ by irrigation every two days. Plants growth, sodium (Na) and potassium (K) as well as proline and soluble sugars contents of leaves and roots were determined after two weeks. Results: Salt effect reduced significantly plant growth at P =.05, root K content at P =.05 and leaf K/Na ratio at P =.01 whereas it increased significantly leaf Na at P =.05 and root soluble sugars content at P =.05. The application of exogenous calcium (Ca) induced a significant amelioration of plant growth at P =.01 more marked with CaSO₄ than with Ca (NO₃)₂. This treatment induced a significant decrease at P =.01 in leaf and root Na content and a significant increase at P =.05 in root K content only for CaSO₄, a significant increase at P =.01 in leaf K/Na ratio and a significant increase at P =.01 in leaf and root proline content only for Ca(NO₃)₂. Conclusion: The ameliorative effect of both forms of calcium was due mainly to sodium (Na) exclusion from leaves and potassium (K) accumulation associated to a maintain of high K/Na ratio mainly in leaves. The importance of proline accumulation as an indicator of this ameliorative effect was associated only to Ca(NO₃)₂.