The effects of seed size and maternal origin on the distribution of individual plant size in Ludwigia leptocarpa (Onagraceae)

Seed size is normally distributed for many annual species, while mature plant size is frequently positively skewed. A study was conducted to determine the influence of seed size and the role of genetic differences in determining relative seedling size for Ludwigia leptocarpa. Seed size had a significant effect on percentage germination and time of seed germination but no effect on dry weight or leaf area of seedlings. Seed size and spacing had a significant effect on seedling dry weight for plants grown under competition, while relative day of emergence had no effect. Familial (genetic) differences were found in average seed weight between maternal plants, but not in average number of days to germination, average weight of seeds which germinated, or shoot dry weight. It is concluded that neither seed size alone nor genetic differences between plants are directly responsible for the development of size hierarchies in Ludwigia leptocarpa populations. Large seed size does convey an advantage in growth when plants from seeds of differing initial size interact

Effect of seed age and soil texture on germination of some Ludwigia species (Onagraceae) in Nigeria.

Seed germination in Ludwigia was greatly influenced by seed age and soil type. In Ludwigia abyssinica germination was not influenced by seed age and soil texture. Freshly shed seeds and six month old seeds of Ludwigia decurrens variety B showed a very low percentage germination on all the germinationmedia, and six month old seeds germinated significantly earlier than freshly shed seeds. Some soil types could significantly reduce germination of freshly shed seeds of L. hyssopifolia, L. erecta, L. leptocarpa and L. octovalvis var linearis

Germination and seedling establishment in cashew (Anacardium occidentale L.): An interaction between seed size, relative growth rate and seedling biomass

Seeds of cashew were used to determine the effect of seed mass (5.2 to 7.8 g) on germination, seedling emergence and growthunder nursery conditions. Germination percentage and germination time showed significant correlation with seed mass. Largesized seeds had higher germination percentage (81.6%) and produced more vigorous seedlings. Per cent seedling emergence wasrelated to seed mass with large sized seeds exhibited faster emergence. Seed mass significantly affected seedling survival andsurvival rate was high in seedlings arising from large sized seeds (62.9%). Seedling vigor expressed in terms of shoot and rootlength, leaf number, leaf area and total dry matter was significantly affected by seed mass. Seedlings that emerged from large sizedseeds showed better growth and produced heavier seedlings as compared to medium sized seeds. RGR showed significant variation(0.152 to 0.240 g g-1day-1) among two seed size classes positively correlated with seed mass, leaf area (LA), unit leaf rate per unitleaf area (ULRM), root to shoot ratio (R/S) and root mass ratio (RMR) and negatively with stem mass ratio (SMR). The studyconcluded that the seed mass and RGR have influence on seedling growth and success of seedling establishment in cashew

Quality of seed produced by tropical forage legumes on low fertility soils

This study compared seed yields, seed and seedling characteristics of 8 forage legumes including Stylosanthes spp, Centrosema spp, Desmanthus spp, and Macroptilium spp grown on red and yellow kandosol soils of low fertility

Phenological patterns of terrestrial plants

The term phenology is derived from the Greek word phaino meaning to show or to appear. Hence, phenology is defined as the study of the seasonal timing of life cycle events. For plants the seasonal timing of such events can be critical to survival and reproduction. In agriculture the most common failure of introduced crops is the inability to adjust to the seasons imposed by the new, environment (68). In the past few years, interest in the ecology and evolution of timing of life cycle events has grown. Here we review the literature on phenological patterns of germination, flowering, and fruiting (including dispersal)

Exploring the Natural Variation for Seedling Traits and Their link with Seed Dimensions in Tomato

The success of germination, growth and final yield of every crop depends to a large extent on the quality of the seeds used to grow the crop. Seed quality is defined as the viability and vigor attribute of a seed that enables the emergence and establishment of normal seedlings under a wide range of environments. We attempt to dissect the mechanisms involved in the acquisition of seed quality, through a combined approach of physiology and genetics. To achieve this goal we explored the genetic variation found in a RIL population of Solanum lycopersicum (cv. Moneymaker) x Solanum pimpinellifolium through extensive phenotyping of seed and seedling traits under both normal and nutrient stress conditions and root system architecture (RSA) traits under optimal conditions. We have identified 62 major QTLs on 21 different positions for seed, seedling and RSA traits in this population. We identified QTLs that were common across both conditions, as well as specific to stress conditions. Most of the QTLs identified for seedling traits co-located with seed size and seed weight QTLs and the positive alleles were mostly contributed by the S. lycopersicum parent. Co-location of QTLs for different traits might suggest that the same locus has pleiotropic effects on multiple traits due to a common mechanistic basis. We show that seed weight has a strong effect on seedling vigor and these results are of great importance for the isolation of the corresponding genes and elucidation of the underlying mechanisms

Role of local climate and interspecific competition in the limitation of the invaded area of Ambrosia artemisiifolia L. in Western Europe

Le processus d’invasion est fondamentalement inscrit dans une dynamique temporelle et peut être décrit comme un phénomène durant lequel une espèce franchit différentes barrières. Une espèce doit en premier lieu franchir une « barrière géographique » pour être introduite dans un nouveau territoire. Une fois introduite, l’espèce doit survivre aux nouvelles conditions environnementales et être capable de se reproduire, afin de former des populations viables. Elle passe alors la « barrière environnementale » et peut être considérée comme naturalisée. Enfin, elle doit encore franchir la « barrière de la dispersion » et se répandre dans l’environnement pour être considérée comme une espèce invasive. En outre, sur un continent, une espèce peut être à différents stades de franchissement de ces barrières en fonction de la région considérée. On peut ainsi trouver, en fonction des zones géographiques, des populations non–naturalisées qui ne parviennent pas à se maintenir sans apport de propagules, des populations naturalisées, mais qui ne sont pas invasives, et des populations invasives. Cette variation géographique peut résulter, entre autres, d’une variation des conditions environnementales à l’échelle du continent. L’invasion de l’ambroisie à feuilles d’armoise (Ambrosia artemisiifolia L.) constitue une excellente opportunité d’étudier cet aspect de la biologie des invasions. En effet, l’historique d’invasion et la répartition actuelle de l’espèce sont bien documentés, et mettent en évidence des variations géographiques dans la dynamique d’invasion. En Europe de l’Ouest par exemple, il existe des régions fortement envahies (comme la vallée du Rhône, en France) et des régions où l’espèce n’est pas considérée comme naturalisée ou invasive, plus au nord (comme le Nord de la France, la Belgique et les Pays-Bas). Dans ce travail de thèse, nous avons testé l’hypothèse que l’aire d’invasion actuelle d’A. artemisiifolia était limitée vers le Nord, du fait d’un climat local défavorable ou d’une compétition interspécifique trop importante. Afin d’atteindre cet objectif général, quatre questions ont été posées. 1) Le climat local et/ou la compétition interspécifique causent-ils une variation des performances des individus dans différentes zones de l’aire d’introduction en Europe de l’Ouest ? ; 2) Au nord des zones actuellement envahies, le climat permet-il à de nouvelles populations introduites dans un habitat agricole de se maintenir et de s’accroître ? ; 3) Quelle est l’importance de la variabilité morphologique des graines dans l’invasion de zones à climat rigoureux ? ; et 4) Quelle est l’importance de l’effet de priorité lors de l’établissement de l’espèce au sein d’une communauté rudérale ? Nos recherches ont abouti aux conclusions suivantes : ni le climat local, ni la compétition interspécifique ne semblent empêcher la naturalisation et la future progression de l’espèce au nord de l’aire actuelle d’invasion, que ce soit dans les habitats rudéraux ou agricoles. En situation agricole au nord de l’aire d’invasion actuelle, l’espèce est capable de former des populations dont la production de descendants est importante. En moyenne au cours de notre expérimentation, chaque plant a produit un nombre de descendants égal à 273 ± 18.4 (moyenne ± erreur standard). Dans les habitats rudéraux, des populations existent déjà en Belgique et dans le sud des Pays-Bas, et sont capables de produire une grande quantité de graines : en moyenne, les plants mesurés portaient 222 ± 32.0 graines. Les performances des individus de ces populations sont d’ailleurs similaires à celles des individus au centre du foyer d’invasion. Aucune limite à la colonisation des zones au nord de l’aire d’invasion actuelle n’a été mise en évidence dans ce travail. Ceci est cohérent avec les observations d’autres auteurs mettant en doute le statut « non-naturalisé » de l’espèce en Belgique, et illustre l’aspect dynamique de l’invasion. L’importance de la temporalité dans la colonisation des milieux perturbés apparait critique. Lorsque la plante se développe quelques semaines avant le reste de la communauté, elle bénéficie d’une augmentation de performances bien supérieure à ce que d’autres astéracées rudérales sont capables d’atteindre dans la même situation. Dans notre expérience, l’effet de priorité induisait une biomasse aérienne 30.5 ± 1.94 fois plus élevée, et un nombre d’inflorescences 570 ± 160 fois plus important. Par ailleurs, la grande variabilité de l’espèce joue probablement un rôle important dans le succès de l’invasion. Ainsi, la grande variabilité des graines augmente la gamme de conditions environnementales où l’espèce peut se développer. Nos observations laissent présager un potentiel d’invasion au nord de l’aire d’invasion actuelle. Dans cette situation incertaine, il nous apparait important de mettre en place un système de détection précoce de l’ambroisie, afin de permettre son éradication et cela, avant que l’invasion ne soit aussi problématique qu’en France. Des campagnes de sensibilisation du secteur public et agricole devraient être envisagées en Belgique, afin que de nouvelles occurrences de la plante ne passent pas inaperçues et que la propagation de l’espèce puisse être endiguée.The invasion process is classically described from a temporal point of view, where a species overcomes a defined number of barriers. First, a species has to get through the geographical barrier, i.e., be introduced in the new area. Once introduced, the species has to survive new environmental conditions and reproduce successfully. When the environmental barrier is overcome, i.e. when the species is able to reproduce and its populations are self-sufficient, it is considered as naturalized. To finally be considered as invasive, the species has to overcome the dispersal barrier and spread across landscapes. Within a given continent, a species could have overcome a variable number of barriers depending on the considered area. At a given moment, depending on the geographical area, one can observe non-naturalized populations, naturalized populations that are not invasive, and invasive populations. This geographical variation may be the result of an environmental variation across the continent. The common ragweed (Ambrosia artemisiifolia L.) invasion in Western Europe is a good opportunity to study this aspect of invasion biology. The invasion history and the species distribution are well documented, and highlight a geographical variation of the invasion dynamics. This is particularly clear in Western Europe, where there is a contrast between the highly invaded zone of the Rhône valley in France, and more northern areas such as the North of France, Belgium, and the Netherlands. In this work, we tested the hypothesis that the current invasion area is limited northwards, because of an unfavorable local climate or a too strong interspecific competition. In order to answer this general objective, four different questions were asked: 1) Is the climate and/or the interspecific competition causing a variation in plant performances across Western Europe?; 2) In an agricultural context north to the current invaded range, is the local climate allowing the establishment and the reproduction of newly introduced populations?; 3) What is the role of seed morphological variability in the invasion of areas with rigorous climatic conditions?; and 4) What is the role of the priority effect in the species establishment within a ruderal community? No clear limit to the colonization of areas beyond the current invaded range was found in this study. The local climate and the interspecific competition did not appear to limit the naturalization or spread of the species north to the current invaded range, be it in agricultural or ruderal situations. Results showed that once introduced in an agricultural habitat outside the current invaded range, the species was able to establish self-sustaining populations. On average, each plant produced a number of descendants equal to 273 ± 18.4 (mean ± standard error). In ruderal habitats, populations already exist in Belgium and in Southern Netherlands, and are able to produce a high quantity of seeds: on average, the measured plants carried 222 ± 32.0 seeds. The measured plant performances were similar to those measured within the invaded area. The findings of this work are consistent with those of other authors that questioned the “non-naturalized” species status in Belgium, and illustrate how temporally dynamic invasions are. The results showed the importance of the timing in the colonization of disturbed habitats. When the species started its development a few weeks before the rest of the community, its performance gain was higher than that of other ruderal Asteraceae species: its above ground biomass was 30.5 ± 1.94 times higher, and the number of flower heads 570 ± 160 times more important. The high variability of the species observed all along this work is probably playing an important role in the invasion success. The high morphological variability of the seeds seems to widen the range of environmental conditions the species is able to colonize. This study suggests a great invasion potential north to the current invaded area in Western Europe. In this uncertain situation, it appears critical to create an early detection system of the species in Belgium. Early detection may allow the eradication of the species before the invasion becomes as problematic as in France. Awareness campaigns should be encouraged in Belgium in order to avoid that new occurrences of the species remain unnoticed

Understanding the genetic and morphological basis of bushy root and bifuricate, two mutations affecting plant architecture in Solanum lycopersicum L.

The classical ethyl methanesulfonate (EMS) tomato mutant bushy root (brt) was studied using a homozygous near isogenic line (brtNIL) in the Micro-Tom (MT) genetic background. The mutation has a pleiotropic phenotype comprising slow seedling development, which may be a consequence of a maternally-inherited small seed phenotype, and a more compact, smaller but not bushier, root phenotype. The number of lateral roots, total root length and taproot size are all smaller in brtNIL than the WT. The BRT locus was mapped to a 137 kbp region containing 9 candidate genes on chr 12; an InDel in the promoter region of Solyc12g014590 – containing two highly conserved pirin domains (Pirin_C and Pirin), was detected. Different expression patterns were confirmed by transcriptomic results, supporting Solyc12g014590 as the gene responsible for the brt phenotype. A naturally occurring recessive mutant named bifuricate (bif) shows an increase in inflorescence (truss) branching in comparison to the wild type (WT) control line, LAM183. In addition, the number of flowers per truss was 235% higher in bif plants than WT. Low temperature is known to increase truss branching, and so a four day low temperature treatment was applied and it was demonstrated that flowering increased significantly more in bif than in LAM183. The BIF locus was mapped to a 2.01 Mbp interval of chromosome 12 containing 53 genes. All coding region polymorphisms in the interval were surveyed, and two genes Solyc12g019420 (a BTB/TAZ transcription factor) and Solyc12g019460 (a MAP kinase) contained one stop codon predicted to disrupt gene function; both genes are excellent candidates for inflorescence branching control based on literature evidence. A newly developed introgression browser was used to demonstrate that the origin of the bif mutant haplotype is Solanum galapagense

Fisiología de plántulas procedentes de embriones cigóticos y nucelares de Mangifera indica L., identificados con marcadores moleculares

Polyembryonic seeds of mango (Mangifera indica L.) may contain or not one zygotic embryo and the remaining embryos are derived from the nucellus. Theoretically, nucellar embryos are more vigorous and are identical genetically to the mother plant, its allowing the propagation of clones that are used as rootstocks in commercial plantations to ensure uniformity in production and fruit quality and disease resistance and environmental factors such as salinity, for example. Identification of zygotic or nucellar origin can facilitate the rootstocks selection. Morphologically, the identify the seedling origin is not easy, but by means of isoenzyme analysis and DNA molecular markers some researchers have demonstrated that nucellar seedlings can be distinguished from the zygotic seedling. This study compare physical, chemical and morphological parameters of fruit and seed, and seed germination, seedling growth and survival of mango seedlings of varieties monoembryonics ‘Haden’ and polyembryonics ‘Manila’ and ‘Ataulfo’ in order to determine whether the allocation of resources that the mother plant provides to each embryo influences in the seedling vigor, or if vigorous seedlings come from nucellar or zygotic embryos, by means AFLP analysis. Seedlings of the variety monoembryonic were more vigorous than polyembryonics ones, the seed weight was significant on germination, growth and survival. Molecular AFLP analyzes were unclear to distinguished the zygotic seedling, due to high genetic variability in both polyembryonic varieties with a similarity index of 0.50 to 0.96. The genetic variability found in seedlings of the same seed and with respect to the mother plant, can represent advantages adaptive by response to different environmental stress factors in different ways.Las semillas de las variedades poliembriónicas de mango (Mangifera indica L.) pueden contener o no un embrión cigótico y el resto son derivados de la nucela. Teóricamente, los embriones nucelares son más vigorosos y genéticamente idénticos a la planta madre, lo que permite la propagación de clones que se usan como portainjertos en las plantaciones comerciales para garantizar la uniformidad en cuanto a producción y calidad de frutos y a la resistencia a enfermedades y factores ambientales como la salinidad, por ejemplo. La identificación del origen cigótico o nucelar puede facilitar la selección de portainjertos. Morfológicamente no es fácil identificar el origen de las plántulas, pero mediante análisis de isoenzimas y marcadores moleculares de ADN algunos investigadores han logrado la identificación. En este trabajo se compararon parámetros físico-químicos y morfológicos de frutos y semillas, así como de germinación de semillas, crecimiento y sobrevivencia de plántulas de variedades de mango monoembriónicas: ‘Haden’ y poliembriónicas ‘Manila’ y ‘Ataulfo’, con la finalidad de determinar si la asignación de recursos que la planta madre le proporciona a cada embrión influye en el vigor de las plántulas, o si las plántulas más vigorosas provienen de embriones nucelares o cigóticos, para lo cual se utilizaron marcadores moleculares AFLP. Las plántulas de la variedad monoembriónica resultaron más vigorosas que las poliembriónicas, el peso de las semillas fue importante en la germinación, crecimiento y sobrevivencia. Los análisis moleculares mediante AFLP no fueron claros para averiguar si sobrevive o no la plántula originada por el embrión cigótico, debido a que se evidenció amplia variabilidad genética en las dos variedades poliembriónicas con un índice de similitud de 0.50 a 0.96. La variabilidad genética encontrada en las plántulas de la misma semilla y con respecto a la planta madre puede representar ventajas adaptativas para responder a distintos factores ambientales de estrés de distintas maneras