Imaging genetics of seed performance
Joosen, R.V.L. - \ 2013
Wageningen University. Promotor(en): Linus van der Plas, co-promotor(en): Henk Hilhorst; Wilco Ligterink. - S.l. : s.n. - ISBN 9789461734976 - 196
zaden - zaadkieming - kiemkracht - genetica - kiemrust - genomica - arabidopsis thaliana - moleculaire genetica - moleculaire biologie - loci voor kwantitatief kenmerk - seeds - seed germination - germinability - genetics - seed dormancy - genomics - arabidopsis thaliana - molecular genetics - molecular biology - quantitative trait loci
The Netherlands has a long history of plant breeding which has resulted in a leading position in the world with respect to the sales of vegetable seeds. Nowadays high-tech methods are used for crop-production which demands high standards for the quality of the starting materials. While breeding has mainly focused on crop yield and disease resistance in the past, it now becomes equally important to create seeds that rapidly and uniformly germinate under a wide range of production environments. A better understanding of the molecular processes that are underlying seed quality is a crucial first step to enable targeted breeding. In this thesis we describe the results of new methods that were used to map the genetics of seed germination.
For this research we have used the leading plant science model species Arabidopsis thaliana which has a short generation time and a fully sequenced genome. Further, the large scientific community working on this model species is providing a wealth of resources ranging from large collections of worldwide accessions, genetic mapping populations, mutants and knowledge about gene, protein and metabolite action. A disadvantage of using Arabidopsis is the small size of the seeds, which requires evaluation of the germination of individual seeds with the use of magnifying glasses. This problem has been solved by using image analysis to create an automated procedure to obtain detailed information for parameters such as rate, uniformity and maximum germination. This procedure, called ‘the Germinator’, is described in Chapter 2 and has been enthusiastically adopted by the seed community.
Plants cannot walk away from the environment at which the seed is dispersed. To survive and to enable reproduction, plants adapt to the prevailing environment which results in considerable genetic variation. This ‘natural variation’ is a great resource to study the mechanisms of adaptation. In Chapter 3 we have used two distinct Arabidopsis accessions, one originating from Germany (Bayreuth) and the other from high altitude in the Pamiro-Alay Mountains in Tadjikistan (Shahdara). In contrast to the Bayreuth accession, the Shahdara accession is well adapted to survive harsh conditions and is known to be stress tolerant to a range of environments. A genetic mapping (recombinant inbred line; RIL) population, consisting of 165 lines, that was derived from these two accessions is therefore particularly suitable to locate the genomic regions with genetic differences that influence seed germination. Such genomic regions are commonly referred to as quantitative trait loci (QTL). With help of the Germinator system we were able to evaluate germination of this RIL population under many different conditions. This resulted in a description of the ‘genetic landscape of seed performance’ in which we identified many QTLs for Arabidopsis seed germination.
QTL regions are often large and identification of the causal gene requires intensive follow up research. We therefore aimed for a high throughput analysis using modern ‘omics’ techniques to analyze differences in metabolite levels and gene expression between the lines. A method to classify and visualize the vast amount of data derived from such an approach is described in Chapter 4. The so called genetical ‘omics’ experiments are expensive and therefore often force researchers to limit their study to a single developmental stage or environment only. A novel generalized setup overcomes this limitation and was tested for metabolite level changes in Chapter 5. This setup offers a unique reduction of experimental load with minimal effect on statistical power and is of great potential in the field of system genetics. Four different developmental stages of seed germination were tested in the RIL population. This approach resulted in a large dataset for which efficient analytical procedures were lacking. Thus, Chapter 5 also includes a description of a newly developed statistical procedure to analyze this type of data. The same approach and material were used in Chapter 6 to evaluate the genetics of genome wide gene expression.
Another approach to zoom in on the molecular mechanisms underlying seed performance is described in Chapter 7. Here, the genetic diversity was maximized by using 360 different Arabidopsis accessions which had been subjected to ultra-high density genotyping. In potential, such a genome wide association (GWA) study can provide high resolution mapping of genetic variation resulting in only a few candidate genes per association for the phenotype under study. Although we were able to replicate experiments over two years with a high level of heritability, no significant associations were found. This emphasizes the need to critically review the power of such an approach for traits that are expected to be determined by many small effect loci.
Finally, closing in on the molecular mechanisms underlying the seed traits that we studied might be possible by a full integration of the datasets that were described in the different chapters. Two examples that show the potential and the complexity of such integration are described in the General Discussion (Chapter 8). Research focused on seed quality does not end here but has gained an impulse by the described new methods and hypotheses to continue on both the fundamental and applied level in the coming years.
Het onderzoek in 2010
Groot, S.P.C. ; Scholten, O.E. ; Raaijmakers, M. - \ 2010
Wageningen [etc.] : Wageningen UR etc. (BioKennis bericht. Uitgangsmateriaal en veredeling 1 (aug. 2010)) - 4
akkerbouw - zaadproductie - koolsoorten - penen - pompoenen - aardappelen - uien - preien - lupinen - biologische plantenveredeling - vollegrondsgroenten - kiemkracht - arable farming - seed production - cabbages - carrots - pumpkins - potatoes - onions - leeks - lupins - organic plant breeding - field vegetables - germinability
Biologische telers zijn verplicht biologisch uitgangsmateriaal te gebruiken, maar daarvan is niet altijd voldoende beschikbaar. Onderzoek op het gebied van uitgangsmateriaal, gerichte veredeling en samenwerking in de keten moeten het aanbod en het gebruik van biologisch uitgangsmateriaal stimuleren. Dit bioKennisbericht geeft een tussenstand van de lopende onderzoeksprojecten.
Een alcoholtest voor zwakke zaden
Groot, S.P.C. ; Kodde, J. - \ 2009
biologische landbouw - zaadbehandeling - groeikracht - gewasbescherming - analytische methoden - vermeerderingsmateriaal - kiemkracht - organic farming - seed treatment - vigour - plant protection - analytical methods - propagation materials - germinability
Deze poster bevat resultaten uit onderzoek naar een snellere bepaling van de vigour van biologische zaden: alcoholproductie van de zaden
Conservation of tree seeds from tropical dry-lands
Neya, O. - \ 2006
Wageningen University. Promotor(en): Linus van der Plas, co-promotor(en): Folkert Hoekstra. - [S.l.] : S.n. - ISBN 9789085045311 - 159
zaden - bomen - plantenfysiologie - azadirachta indica - lannea - sclerocarya birrea - khaya senegalensis - zaadkieming - opslag - burkina faso - kiemkracht - seeds - trees - plant physiology - azadirachta indica - lannea - sclerocarya birrea - khaya senegalensis - seed germination - storage - burkina faso - germinability
The tropical trees, Azadirachta indica (neem), Lannea microcarpa, Sclerocarya birrea and Khaya senegalensis, are important multipurpose species. Unfortunately, difficult seed storage behaviour limits the utilization of these species in reforestation programs and agroforestry systems. This thesis presents the results of investigations aimed at a better understanding of the seed biology, particularly focussed on the improvement of seed survival after drying and subsequent dry storage. Seeds collected from several stands in Burkina Faso were studied in an attempt to elucidate the causes of viability loss and improve life span. Initially it was thought that the difficulty in storing seeds of these species is due to intolerance of desiccation and sensitivity to low (subzero 0C) storage temperatures. However, the results of the current study indicated that other factors are responsible for the difficult storage behaviour of these seeds. When the moisture content (MC) was reduced from 27 to 5%, neem seeds became sensitive to rehydration temperatures below 25°C, resulting in a noticeable decrease in germination percentage. Rehydration of these dried seeds at elevated temperatures (25-400C) for one hour prior to further incubation at 300C substantially improved germination to a level comparable to that of fresh seeds (27% MC). We concluded that neem seed is desiccation tolerant, but that during drying its germination requirements change, which is the main cause of its difficult storage behaviour.
Germination capability of S. birrea seeds was low in all seed lots at harvest, but improved substantially during drying and/or dry storage. Improvement of germination with drying is completely in contrast with what would happen in a desiccation-sensitive seed. We interpreted the observed increase in germination during drying and dry storage as resulting from the slow disappearance of an initially present physiological dormancy. Seeds of S. birrea thus behave as orthodox seeds, but the irregularity in their germination behaviour has obviously contributed to discrepancies between reports on the species seed biology.
Seeds of L microcarpa harvested in three successive years were extremely variable as to their germinability and storability. Some seed accessions had a generally low germination, while others had an initially high germination. Drying did not affect germination capability of the poorly germinating seed accessions, but did so in the well germinating accessions. These observations would suggest that seeds can be either tolerant or sensitive to desiccation. However, when mechanically scarified prior to germination tests, seeds from all accessions germinated at high percentage (>80%), regardless of MC and age. This indicates that seeds experienced germination constraints upon drying rather than being sensitive to desiccation. Imbibed, intact seeds that failed to germinate displayed a moderate rate of respiration with RQ values< 1, which indicates that the seed coat is permeable to water and respiratory gases. On scarification, water uptake and respiration steeply rose in narrow association with radicle emergence. Non-scarified seeds lost germination ability and cellular viability after approx 15d of moist incubation at 300C. Apparently, coat-imposed inhibition of germination does not prolong viability of seeds in the hydrated state. These results suggest that radicle emergence is inhibited mechanically and not by germination inhibitors or physiological dormancy. We conclude that L microcarpa seeds display orthodox storage behaviour, but that physical dormancy explains the difficult seed storage behaviour reported for this species.
In the case of K. senegalensis, the MC of seeds at harvest was low (<0.1g H2O g DM"1) and further drying did not affect the initially high germinability (90-100%). During storage a relative!y fast viability loss was observed for seeds stored at 4°C in comparison with seeds stored at -20, 15, and 200C. The sensitivity to low above-zero (0C) temperatures might be the cause of the erratic loss of viability often observed in these seeds.
We concluded that seeds of all the species investigated in this thesis display orthodox storage behaviour, but that various factors including sensitivity to imbibitional stress, physiological and physical dormancy, and sensitivity to low above-zero (0C) storage temperatures cause the reported difficulties in storing these seeds. Tropical tree seeds are thought to be particularly sensitive to low imbibition temperatures because of the relatively high gel-to-liquid crystalline phase transition temperature (Tm) of their membranes as compared to the relatively low T177 of membranes of temperate zone seeds. In relation with this, the sensitivity of the four seed species to rehydration at low temperatures was investigated. The results indicated that dried neem seeds are particularly sensitive to imbibitional stress, whereas the seeds of the other species appeared to be less (K. senegalensis) or not (L microcarpa and 5. birrea) sensitive to low imbibition temperatures. This difference in sensitivity to imbibitional stress was observed despite comparable T177 of membranes in the roots of seedlings of K. senegalensis, L microcarpa and neem (11.5, 14.5 and 9.60C, respectively). The hypothesis of tropical tree seeds being particularly sensitive to imbibitional stress because of their high membrane Tm therefore does not have general validity. LTSEM images of cryo-pianed K. senegalensis seed embryos revealed the presence of a dense peripheral cell layer, which might have slowed water uptake and reduced sensitivity to imbibitional stress. On the other hand, for the sensitive neem seeds, it was observed that the loss of germinability of imbibitional damaged seeds did not involve death of all the cells. An assessment of membrane integrity by ESR and cryo-SEM indicated that seed germination is not supported when approx. 30% or more of axis cells have died. This supposes that there are still on average 70% or less of live cells in a non-germinating seed. From this observation, we argue that up to this lethal threshold, seeds are able to repair the damage caused by imbibitional stress or survive with a number of damaged cells. We suggest that differences in tolerated number of damaged cells, in intrinsic repair capabilities, or in morphology of the outer cell layers determine the level of sensitivity of seeds to imbibitional stress.
Low temperatures are expected to better maintain viability of seeds in dry storage than do high temperatures. However, we noticed that storage conditions at 4°C were more detrimental for K. senega/ensis seeds than at -200C or 15°C, and this was, to a lesser extent, true for L microcarpa seeds. Because viability loss associated with ageing is often attributed to the loss of membrane barrier function, membrane polar lipids (PLs) were analysed in several K. senegalensis seed lots differing in age and viability. The data indicated that the content of membrane PLs steadily decreased with ageing. However, it appeared that seeds can withstand the loss of a certain amount of PLs without losing germinability. Based on data of seeds stored dry at 15°C and at 4°C, it was observed that the loss of germinability coincided with a loss of between 15% and 25% of the PLs. With the decrease in PL content, the free fatty acid content rose. Because the free fatty acid also can arise from degradation of triacylglycerols, it was difficult to establish a critical content of accumulated free fatty acids associated with viability loss.
Chemical analysis of membranes in 20 year-old dry-stored K. senegalensis seeds, which were already non-germinable for a long period of time, indicated a loss of 80% of the PLs. However, this did not lead to changes in the structure of the plasma membranes in the dried axis as could be observed by high resolution SEM after freeze fracturing. This was interpreted to mean that the deesterified acyl chains were still at the position, at which they originally occurred in the membranes of the fresh seed. This was also the case for the 4°C-stored dried specimens that had just become non-viable. The IMPs (transmembrane proteins) were regularly distributed in the plane of the membrane, indicating the absence of a phase separation in the dry state. The data of the current study suggest that membrane phase separation, thought to occur during viability loss, is unlikely to happen in the dry state. However, at rehydration the plasma membranes suffered considerable damage or ceased existing.
The question as to how the deesterification takes place - via free radical activity or by phospholipase activity - was addressed. With free radicals being involved one would not expect a greater amount of acyl chains to be split off at 4°C than at 15°C. However, since the physical state of the membrane determines the activity of phospholipases, we focussed on the membrane phase issue. The mismatch between gel phase domains and the liquid crystalline matrix at mid-melting temperature gives better access to the site of action, thus increasing the activity of phospholipases. At either the gel or liquid crystalline phase, accessibility to the site of action is more difficult. An ESR spin labe! study indicated that membranes in dried and rehydrated axes of K. senegalensis seeds were rigid at -200C, while at 7°C they appeared to be in a mixed liquid crystalline - gel phase condition. The liquid crystalline phase prevailed at 15°C. Thus, it can be expected that during dry storage at 4°C the mixed phase can occur for extended periods of time. Therefore, we suggest that the deesterification of acyl chains leading to the loss of viability of seeds at low above zero (0C) temperatures occurs, at least part!y, via phospholipase activity. Because of their high Tm, membranes of tropical seeds are likely to reach mid me!ting condition at low above zero (0C) temperatures that are high enough to support enzyme activity. By contrast, it is expected that the lower mid-me!ting temperatures of seeds from the temperate climate zones are too low to effectively support phospholipase activity at sub-zero (0C) temperatures. This special feature of tropical seeds dismisses the use of cold rooms for short and medium term (1-3 years) storage purposes.
The results obtained in this study will increase and facilitate the use of these species in reforestation and agroforestry programs in Burkina Faso and other Sahelian countries.
|Effect van de fysiologische ouderdom van het pootgoed op de opbrengst van poot- en zetmeelaardappelen
Wijnholds, K.H. ; Wustman, R. - \ 2003
Kennisakker.nl 2003 (2003)1 juli.
vermeerderingsmateriaal - pootknollen - pootaardappelen - aardappelen - verouderen - koelcellen - aardappelopslagplaatsen - gewasopbrengst - kiemkracht - fabrieksaardappelen - propagation materials - seed tubers - seed potatoes - potatoes - aging - cold stores - potato stores - crop yield - germinability - starch potatoes
In zijn algemeenheid heeft voorkiemen van pootgoed voordelen. Ten opzichte van het "witte puntjesstadium" betekent voorkiemen echter wel, dat het pootgoed fysiologisch iets ouder wordt. Naarmate knollen fysiologisch ouder zijn, worden er minder kiemen en stengels en dus ook minder knollen aangelegd per plant.
|Zaadvoorraad en herintroductie: achtergronden, spectra van plantengemeenschappen en voorbeelden uit de praktijk
Bekker, R.M. ; Strykstra, R.J. ; Schaminée, J.H.J. ; Hennekens, S.M. - \ 2002
Stratiotes (2002)24. - ISSN 0928-2297 - p. 27 - 48.
plantengemeenschappen - rassen (planten) - zaden - herstel - geïntroduceerde soorten - kiemkracht - blauwgrasland - ecologie - natuurherstel - plantensociologie - vegetatie - Friesland - Brabant - plant communities - varieties - seeds - rehabilitation - introduced species - germinability
Het effect van toediening van calcium en borium aan de grond op de opbrengst, kwaliteit en minerale samenstelling van pootaardappelen
Velema, R. ; Griend, P. van de - \ 2001
Wageningen : Plant Research International (Nota / Plant Research International 101) - 10
aardappelen - solanum tuberosum - calcium - vermeerderingsmateriaal - veldproeven - akkerbouw - pootaardappelen - kiemkracht - potatoes - solanum tuberosum - calcium - propagation materials - field tests - arable farming - seed potatoes - germinability
In het kader van het deelproject 'Nutriëntenvoorziening' van het deelcluster 'Innovatie Aardappelteelt' van Agrobiokon is onderzoek uitgevoerd naar de calciumvoorziening van pootgoed. Calcium speelt een belangrijke rol bij de kieming van pootgoed. Lage calciumgehaltes kunnen leiden tot een verminderde kiemkracht en afsterving van kiemen. Het doel van het onderzoek is na te gaan op welke wijze het calciumgehalte in pootaardappelen kan worden verhoogd. Hiertoe zijn in 1998 twee veldproeven aangelegd. Van deze veldproeven wordt in dit rapport verslag gedaan. De proef is aangelegd op twee locaties, namelijk Valthermond en Rolde
Het effect van het calciumgehalte van pootgoed opm de groei en opbrengst van zetmeelaardappelen
Velema, R. ; Griend, P. van de; Velvis, H. - \ 2001
Wageningen : Plant Research International (Nota / Plant Research International 104) - 14
pootaardappelen - solanum tuberosum - aardappelen - veldproeven - calcium - vermeerderingsmateriaal - gewasopbrengst - akkerbouw - borium - kiemkracht - seed potatoes - solanum tuberosum - potatoes - field tests - calcium - propagation materials - crop yield - arable farming - boron - germinability
In het kader van het deelproject ‘Nutriëntenvoorziening’ van de deelcluster ‘Innovatie Aardappelteelt’ van Agrobiokon is door HLB onderzoek uitgevoerd naar de calciumvoorziening in pootaardappelen. In het onderzoek dat in dit rapport wordt beschreven, is gekeken naar het effect van het calciumgehalte in de knollen op de kieming. Daarnaast wordt verslag gedaan van twee veldproeven uit 1999 en 2000. In deze veldproeven is pootgoed gebruikt met verschillen in calciumgehalte. Gekeken is naar de effecten op de opbrengst
Calcium in aardappel
Velvis, H. - \ 2001
Wageningen : Plant Research International - 22
aardappelen - solanum tuberosum - calcium - ziekteresistentie - kiemkracht - potatoes - solanum tuberosum - calcium - disease resistance - germinability
Een overzicht wordt gegeven van de literatuur m.b.t. het element calcium in aardappel. Daarbij wordt gekeken naar de functie in de plant, de opname en het interne transport, en de gevolgen van tekorten voor de opbrengst en de vatbaarheid voor pathogenen
Verspreiding van onkruiden en planteziekten met dierlijke mestDissemination of weeds and plant diseases by cattle slurry
Elema, A.G. - \ 1991
In: Jaarboek 1987-1992 : verslagen van in 1987-1992 afgesloten onderzoekprojecten op Regionale Onderzoek Centra en het PAGV Lelystad : Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond (Publikatie / Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond, Regionale Onderzoekcentra no. 38-64) - p. 226 - 228.
dierlijke meststoffen - distributie - epidemiologie - plantenziekten - plantenplagen - zaadkieming - drijfmest - onkruiden - kiemkracht - animal manures - distribution - epidemiology - plant diseases - plant pests - seed germination - slurries - weeds - germinability
Door mest gedurende vier weken in een afgesloten ruimte te bewaren verliezen onkruiden hun kiemkracht. Ook de meeste planteziektenverwekkers overleven een lang verblijf in dunne mest niet
De overleving van onkruidzaden en -knolletjes in rundermengmest en in een snijmaiskuil
Schokker, A.H. - \ 1988
Wageningen : CABO (CABO-verslag 90) - 34
dierlijke meststoffen - distributie - epidemiologie - kieming - plantenziekten - plantenplagen - kiemrust - zaadkieming - kuilvoer - drijfmest - onkruiden - kiemkracht - animal manures - distribution - epidemiology - germination - plant diseases - plant pests - seed dormancy - seed germination - silage - slurries - weeds - germinability
Het beschreven onderzoek naar de verspreiding van onkruiden door mengmest had tot doel na te gaan hoe lang zaden van onkruiden een verblijf in drijfmest kunnen overleven en wat het effect is van het ensilageproces op de vitaliteit van onkruidzaden. Op basis van de verkregen resultaten kan geconcludeerd worden dat door opslag van mest gedurende ca. 4 maanden (met name tijdens de zomermaanden) en door maiskuilen ca. 4 weken gesloten te houden een risico voor verspreiding van onkruiden met mest flink gereduceerd wordt
|Use temperature and short wave radiation to predict the rate of seedling emergence and the harvest date
Bierhuizen, J.F. ; Feddes, R.A. - \ 1973
Wageningen : I.C.W. (Verspreide overdrukken / Instituut voor Cultuurtechniek en Waterhuishouding no. 144) - 9
zaadkieming - oogsttijdstip - luchttemperatuur - kiemkracht - seed germination - harvesting date - air temperature - germinability
|De invloed van IPC/CIPC - houdende middelen op de kiemkracht van graszaad : verslag van het onderzoek in 1969/1970
Buitelaar, N. - \ 1970
Wageningen : [s.n.] (Mededelingen / Instituut voor bewaring en verwerking van landbouwproducten no. 373) - 8
plantenvermeerdering - lolium - plantenvoeding - kunstmeststoffen - mest - profam - chloorprofam - voedergrassen - kiemkracht - propagation - plant nutrition - fertilizers - manures - propham - chlorpropham - fodder grasses - germinability
|De invloed van IPC/CIPC - houdende middelen op de kiemkracht van graszaad : verslag van het onderzoek in 1968
Buitelaar, N. - \ 1969
Wageningen : [s.n.] (Mededelingen / Instituut voor bewaring en verwerking van landbouwproducten no. 341) - 11
kunstmeststoffen - lolium - mest - plantenvoeding - plantenvermeerdering - profam - chloorprofam - voedergrassen - kiemkracht - fertilizers - manures - plant nutrition - propagation - propham - chlorpropham - fodder grasses - germinability