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Currently, seed priming is reported as an efficient and low-cost approach to increase crop yield, which could not only promote seed germination and improve plant growth state but also increase abiotic stress tolerance. Salinity represents one of the most significant abiotic stresses that alters multiple processes in plants. The accumulation of polyamines (PAs) in response to salt stress is one of the most remarkable plant metabolic responses. This paper examined the effect of osmopriming on endogenous polyamine metabolism at the germination and early seedling development of Brassica napus in relation to salinity tolerance. Free, conjugated and bound polyamines were analyzed, and changes in their accumulation were discussed with literature data. The most remarkable differences between the corresponding osmoprimed and unprimed seeds were visible in the free (spermine) and conjugated (putrescine, spermidine) fractions. The arginine decarboxylase pathway seems to be responsible for the accumulation of PAs in primed seeds. The obvious impact of seed priming on tyramine accumulation was also demonstrated. Moreover, the level of ethylene increased considerably in seedlings issued from primed seeds exposed to salt stress. It can be concluded that the polyamines are involved in creating the beneficial effect of osmopriming on germination and early growth of Brassica napus seedlings under saline conditions through moderate changes in their biosynthesis and accumulation.

Salinity is a growing global concern that affects the yield of crop species, including tomato (Solanum lycopersicum). Its wild relative Solanum chilense was reported to have halophyte properties. We compared salt resistance of both species during the reproductive phase, with a special focus on sodium localization in the flowers. Plants were exposed to NaCl from the seedling stage. Salinity decreased the number of inflorescences in both species but the number of flowers per inflorescence and sepal length only in S. lycopersicum. External salt supply decreased the stamen length in S. chilense, and it was associated with a decrease in pollen production and an increase in pollen viability. Although the fruit set was not affected by salinity, fruit weight and size decreased in S. lycopersicum. Concentrations and localization of Na, K, Mg, and Ca differed in reproductive structures of both species. Inflorescences and fruits of S. chilense accumulated more Na than S. lycopersicum. Sodium was mainly located in male floral organs of S. chilense but in non-reproductive floral organs in S. lycopersicum. The expression of Na transporter genes differed in flowers of both species. Overall, our results indicated that S. chilense was more salt-resistant than S. lycopersicum during the reproductive phase and that differences could be partly related to dissimilarities in element distribution and transport in flowers.

Cultivated yam (D. rotundata) is a staple tuber crop in West Africa whose sexual reproduction control remains largely unknown despite its importance for plant breeding programs. In this paper, we compared self-pollination, intracultivar cross-pollination and intercultivar cross-pollination in three monoecious cultivars (Amoula, Heapala and Yassi). Results showed that pollen viability (49%) and stigma receptivity (40%) were similar in monoecious and dioecious plants, suggesting that autogamy could occur in monoecious plants. However, fruit and seed sets were significantly lower after self-pollination compared to cross-pollination. Overall, autogamy reached 11% and pollen lability was almost zero (<1%). The low percentage of pollen grains germinating on the stigma (37%) and pollen tubes reaching the ovules (25%) after self-pollination partly explained the low seed set. Strong inbreeding depression was observed after self-pollination and almost all fruits and about 75% of the seeds resulting from self-pollination showed malformations. Seed germination was also 20 times lower after self-pollination compared to cross-pollination. Sexual reproduction remained low in D. rotundata even after cross-pollination as fruit and seed set did not exceed 18% and 13% respectively. Moreover, comparison between intracultivar cross-pollination and self-pollination revealed intravarietal genetic diversity inside the analyzed yam cultivars. Overall, our results showed that D. rotundata has a very low tolerance to autogamy in monoecious cultivars and has developed pre- and postzygotic mechanisms to limit selfing.

Salinity is a growing global concern that affects the yield of crop species, including tomato (Solanum lycopersicum). In contrast to S. lycopersicum, its wild relative Solanum chilense was reported to have halophyte properties. We compared salt resistance of both species during vegetative and reproductive phases and investigated Na and Cl accumulation in the different organs. Plants were exposed to NaCl (0, 60, 120 mM) from the seedling stage up to flowering (85 days after stress). Overall, S. chilense accumulated more Na than S. lycopersicum while Cl concentration was similar in both species under salt stress. Sodium accumulated mainly in roots in S. lycopersicum and in stems in S. chilense, showing that S. lycopersicum had an excluder behavior and S. chilense an includer behavior regarding Na accumulation while such a difference was not observed regarding Cl accumulation. Both species limited the accumulation of Na and Cl in the inflorescences. The concentration of Na and Cl in the inflorescences were respectively lower and higher in S. lycopersicum compared to S. chilense under salt stress. Na localization in the flowers was analyzed by laser ablation ICP-MS. Na was mainly located in male floral organs of S. chilense but in non-reproductive floral organs of S. lycopersicum under salinity. Na and Cl accumulation and repartition could be partly explained by gene expression of transporters involved in Na and Cl distribution. Overall, our results indicated that S. chilense was more salt-resistant than S. lycopersicum and that both species differed towards strategies of Na and Cl accumulation.

The use of orphan crops could mitigate the effects of climate change and improve the quality of food security. We compared the effects of drought, high temperature, and their combination in 12 varieties of Tartary buckwheat (Fagopyrum tataricum). Plants were grown at 21/19 °C or 28/26 °C under well-watered and water-stressed conditions. Plants were more discriminated according to environmental conditions than variety, with the exception of Islek that was smaller and produced fewer leaves, inflorescences, and seeds than the other varieties. The combination of high temperature and water stress had a stronger negative impact than each stress applied separately. The temperature increase stimulated leaf and flower production while water stress decreased plant height. Leaf area decreased with both temperature and water stress. High temperature hastened the seed initiation but negatively affected seed development such that almost all seeds aborted at 28 °C. At 21 °C, water stress significantly decreased the seed production per plant. At the physiological level, water stress increased the chlorophyll content and temperature increased the transpiration rate under well-watered conditions. High temperature also increased the polyphenol and flavonoid concentrations, mainly in the inflorescences. Altogether, our results showed that water stress and temperature increase in particular negatively affected seed production in F. tataricum.

Pear (Pyrus communis) is the main fruit crop in Belgium and ‘Conférence’ accounts for 90% of the pear production. ‘Conférence’ is self-incompatible and thus requires cross-pollination to produce fruits by fertilization. Hives could be settled in the orchards to facilitate pollination and to allow a better fruit size production. However, blooming occurs early in the spring and climatically unfavorable conditions (frost, low temperatures, rain, etc.) could prevent the pollination by insects. To overcome this inconvenience, parthenocarpy induction by spraying gibberellins is a common practice in ‘Conférence’ orchards. However, whether gibberellin treatment affects fruit set and quality of fruits produced by fertilization has not been investigated. We therefore compared the impact of gibberellin spraying on the development of parthenocarpic fruits and fruits obtained by fertilization. Un-pollinated, open-pollinated and hand-pollinated flowers were sprayed or not with 10 mg L-1 GA4/7 at the balloon, full bloom and petal fall stages and the resulting fruit production and quality were assessed. Compatible hand-pollination increased fruit size and fruit weight by respectively 9 and 8% and decreased fruit length by 10% compared to parthenocarpic fruits whatever the gibberellin treatment. Treatment with GA4/7 increased the fruit set at harvest compared to untreated fruits. The time of GA4/7 spraying significantly affected fruit parameters and treatment was more efficient when applied at the balloon stage. Regarding fruits produced by fertilization, GA4/7 treatment decreased seed development by respectively 12, 13 and 36% when applied at the balloon, full bloom and petal fall stages compared to untreated fruits. Consequently, fruit size decreased by 2 and 5% and fruit weight by 8 and 13% when GA4/7 was sprayed at full bloom and petal fall stages compared to untreated fruits. However, treatment at the balloon stage did not affect fruit size and weight. Thus, our results showed

Salinity is a growing global concern that affects the yield of crop species, including tomato (Solanum lycopersicum). In contrast to S. lycopersicum, its wild relative Solanum chilense was reported to have halophyte properties. We compared salt resistance of both species during reproductive phase and investigated minerals accumulation and sugar metabolism to identify the main causes of the decrease of flower production and fertility. Plants were exposed to NaCl (0, 60, 120 mM) from the seedling stage for 91 days. Inflorescence production decreased in both species under salinity while inflorescences and flowers abortion increased in S. lycopersicum only. Regarding flower fertility, the number of pollen grains per flower decreased in S. chilense. Pollen viability increased with salt in S. chilense. Both species limited the accumulation of Na and Cl in the inflorescences without affecting K concentration. The concentration of Na and K in the inflorescences was lower in S. lycopersicum than in S. chilense under salt stress while the concentration of Cl was higher in the inflorescences of S. lycopersicum. In flowers, Na was mainly located in male floral organs of S. chilense but in non-reproductive floral organs of S. lycopersicum under salinity. Sugar analysis showed that S. lycopersicum and S. chilense did not present the same composition of sugars in the inflorescences and that S. lycopersicum presented more sugars in inflorescences than S. chilense. Overall, our results indicated that both species differed towards strategies of minerals and sugars accumulation in reproductive organs.

The Old Limachino Tomato is a valuable fruit with exceptional nutritional values and organoleptic sensory properties. However, it suffers from a short shelf-life, compromising post-harvest behavior. As an attempt to improve the fruit’s qualities, Limachino (L) scion was grafted onto rootstock from the rustic landrace Poncho Negro (R). Fruits produced in this graft combination were compared with fruits produced by self-grafted plants (L/L) and from a long-shelf-life cultivar Seminis (LSL). The trials were carried out for 146 days during summer of two consecutive years. Poncho Negro rootstock increased the total number of fruits produced by Limachino scion (L/R). It did not affect the fresh weight of individual fruits but reduced their water content. It has no impact on the Limachino fruit form (quality), a typical characteristic well appreciated by consumers. Fruits produced by LSL exhibited a higher firmness but a lower titratable acidity and antioxidant capacity than L/R and L/L fruits. Panels of 104 untrained final consumers and a trained panel of 13 experts attributed the highest value to L/R fruits and the lowest one to LSL. It was concluded that Poncho Negro rootstock contributes to increasing preferences and the level of acceptability towards Limachino fruits. Further research is needed to develop local technologies in order to expand the production of local tomatoes that are highly valued by consumers.

Cultivated yam (Dioscorea rotundata) is a staple tuber crop in West Africa that is mainly propagated vegetatively. Although the majority of yam cultivars flower, the control of its sexual reproduction - in particular sexual expression - remains largely unknown despite its importance for breeding programs. Our objectives were to: 1) characterize the flowering phenology and identify the causes of sex variation in this species; 2) analyze the genetic and hormonal controls of sex determinism; and 3) study the performance of sexual reproduction in monoecious cultivars. Our histological study showed that during floral morphogenesis, stamen and carpel primordia are initiated in all flowers irrespective of sex, but while only primordia corresponding to the sex of the flower continue to develop in sex-stable plants, male and female flowers of sub-dioic populations retain remnants of organs of the opposite sex. Our results also showed that the sex variation of the offspring was more related to the sex of the parents (monoecious in this case) than to the tuber sections used as seed tubers. Our genetic study did not identify a clear genetic marker for early determination of sex identity in D. rotundata yams from Benin but supported the involvement of a genetic locus (Z-) in sex expression with a possible transition from a ZZ/ZW female heterogamous system to an XX/XY male heterogamous system. Our hormonal analyses showed that jasmonates (MeJa) had a masculinizing effect in monoecious plants and that application of MeJA and cytokinins (BAP) accelerated flowering and increased inflorescence production. Furthermore, our crossing results showed that flowers of monoecious plants were fertile and showed a reproductive performance comparable to that of dioecious plants, so that they can partially compensate for the scarcity of female flowers in breeding programs. Altogether, our study has improved our understanding of the control of sex in cultivated yam (Dioscorea rotundata)., (AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 2022

Drought and high temperature significantly limit plant growth and productivity in tomato (Solanum lycopersicum). The elucidation of tolerance strategies in wild relatives is a powerful approach to understand local adaptations for potential crop improvement. Solanum chilense is able to cope with harsh environment in its area of origin and could represent an abundance of genetic diversity for tomato improvement. However, physiological basis of drought and heat tolerance in Solanum chilense has received only minor attention until now. In this study, we compared the effects of drought, high temperature, and their combination in two cultivars of S. lycopersicum and six populations of S. chilense. Plants were grown at 21/19°C or 28/26°C under well-watered and water-stressed conditions. Plant growth, physiological responses, and expression of stress-responsive genes were investigated. The effects of water stress, high temperature, and their combination differed according to the accession, suggesting differences in stress resistance between species and populations. Water stress affected plants more negatively than temperature from a morpho-physiological point of view, while the expression of stress-responsive genes was more affected by temperature. Accessions clustered in two groups regarding resistance to water stress and high temperature. The expression of stress-responsive genes was more stable in resistant accessions than in sensitive ones in response to water stress and high temperature. Altogether, our results suggest that water stress and high temperature resistance in S. chilense did not depend on single traits but on a combination of morphological, physiological, and genetic traits.

The germination of pollen is a key factor in the fertilization success of selfincompatible flowering trees such as apple (Malus domestica Borkh.). Breeding programs have a particular interest in evaluating the germinability of pollens from the male parents before performing controlled crosses. In vitro pollen germination is often considered a simple reliable method to determine the exact amount of viable pollen but the composition of the artificial medium has important implications. In this study, we evaluated the optimal concentration of sucrose (5, 10, 15 and 20%) in the agar-plate medium by testing the germination capacity of 8 apple cultivars. Over the concentrations tested, 15% sucrose solution gave the best results followed by 20%. The percentage of germination significantly varied among cultivars. In the 15% sucrose concentration, the highest percentage was found in ‘Perurico’ (95%) and the lowest in ‘Raxina Dulce’ (66%). These levels are sufficient for an effective fertilisation. Furthermore, the germination of pollen was not affected by the flowering date of the cultivars.