Kwaliteit van zaaizaad kool verbeteren

Kwalitatief goed biologisch zaaizaad voor koolsoorten is moeilijk te produceren. Oorzaken zijn de ongelijkmatige bloei en afrijping van het zaad. Daarnaast kunnen schimmels en bacteriën via het zaad de plant besmetten. In dit biokennis bericht informatie over onderzoek aan apparatuur die het optimale oogsttijdstip bepaalt of de zieke zaden eruit selecteert

Kwaliteit van biologisch zaaizaad en pootgoed

Bij een aantal gewassen is het nog problematisch om goed biologisch zaad te produceren zonder gewasbeschermingsmiddelen. Dat beperkt de beschikbaarheid en verhoogt de kosten van biologisch zaad. Onderzoek heeft kennis opgeleverd voor zaadbedrijven om de kwaliteit te verbetere

Trosontwikkeling bij tomaat

In opdracht van het Productschap Tuinbouw hebben onderzoekers van Plant Research International (onderdeel van Wageningen UR) een methode ontwikkeld om de trosaanleg bij jonge tomatenplanten eenduidig te meten. Dit onderzoek is uitgevoerd op verzoek van de plantenkwekers die behoefte hebben aan zo’n methode om de effecten van het kasklimaat op de trosvorming te kwantificeren. Bij de methode worden de planten van het toppen tot een paar weken daarna, onder de stereomicroscoop bekeken. Het aantal ontwikkelende bladeren en het stadium van de trosontwikkeling wordt genoteerd. Voor dat laatste zijn zes stadia van de bloemontwikkeling gedefinieerd. Met behulp van deze methode kunnen de plantenkwekers nauwkeurig bepalen wanneer in de groeipunt de omslag van vegetatieve naar generatieve groei plaats vindt. Juist in de dagen daarvoor zal de jonge plant gevoelig zijn voor omgevingsfactoren die de omslag beïnvloeden. Dit geeft de plantenkwekers de mogelijkheid om gericht experimenten uit te voeren om de plantontwikkeling zoveel als mogelijk te sturen in de richting van de wens van hun klanten, de tomatentelers. Uit het onderzoek is ook naar voren gekomen dat inductie van de trosontwikkeling eerder plaats vindt dan in het algemeen gedacht en dat er duidelijke effecten zijn van het klimaat

Determination of Temperature and Light Optima for Seed Germination and Seedling Development of Spiderplant (Cleome gynandra L.) Morphotypes from western Kenya

Spiderplant (Cleome gynandra) is an African indigenous vegetable (AIV) in many parts of sub-Saharan Africa, especially in most countries in eastern and southern Africa, where it is a semi-cultivated popular tropical species. In Kenya, it is among the most popular AIVs, particularly in the western and coastal regions. Seed supply systems for spiderplant is largely local and whatever material that is available is often of poor quality, mainly due to lack of development of seed quality testing protocols, thus hampering the correct assessment of the quality of seed used for sowing. The study aimed at determining temperature and light optima for seed germination and seedling development of spiderplant morphotypes from western Kenya. The original spiderplant seeds for the study were sourced from farmers in Kakamega District and from wildly growing plants within Chepkoilel Campus in Uasin Gishu District, both in western Kenya. Four morphotypes were identified and selected based on the presence or absence of anthocyanins on their stems and petioles, respectively. Tests on seed quality aspects were done at the Bioscience Business Unit at Plant Research International, Wageningen, The Netherlands. Determination of optimum temperature for seed germination was conducted by incubating three replicates of 100 seeds each of the four morphotypes at constant temperatures of 20, 25, 30, 35, 40 and 45OC, respectively. In order to determine the light regime for seed germination and optimum temperature for seedling development four replicates of 50 seeds each were incubated at constant temperatures of 30 and 35 OC at 8-hr light day-1 and 0-hr light day-1 (in 24-hr darkness), respectively. Data analysis (ANOVA, statistical descriptors and t-tests) were done using statistical package SeedCalculator 3.0. Germination was strongly influenced by temperature showing declines at both extremes of 20 and 45OC and optimum of 35 and 40OC. Light had no influence on germination since seeds germinated equally well under light and in the dark. Seedling development was strongly influenced by temperature with higher percentage of normal seedlings at 30OC than at 35OC. It is concluded that while temperature had an effect on seed germination performance and seedling development, light on the other hand showed no effect on seed germination for the spiderplant morphotypes studied. However, white light is required in order to aid in seedling evaluation

Betere test voor houdbaarheid zaad

Een nieuwe test maakt het mogelijk de houdbaarheid van zaaizaad nauwkeuriger vast te stellen. Dat geeft meer zekerheid bij bewaring en kan ook helpen bij de veredeling op houdbaarheid van zaad

A fast ethanol assay to detect seed deterioration

The most common way to test seed quality is to use a simple and reliable but time- and space-consuming germination test. In this paper we present a fast and simple method to analyse cabbage seed deterioration by measuring ethanol production from partially imbibed seeds. The method uses a modified breath analyser and is simple compared to gas chromatographic or enzymatic procedures. A modified method using elevated temperatures (40°C instead of 20°C) shortened the assay time and improved its sensitivity. The analysis showed an inverse correlation between ethanol production and seed quality (e.g. the final percentages or speed of germination and the number of normal seedlings). The increase in ethanol production was observed when cabbage seeds were deteriorated by storage under ambient conditions or hot water treatments, both of which reduced the number of normal seedlings. Premature seeds produced more ethanol upon imbibition than mature seeds. Ethanol production occurred simultaneously with oxygen consumption, indicating that lack of oxygen is not the major trigger for ethanol production

Hormonal regulation of seed development and germination in tomato : studies on abscisic acid- and gibberellin-deficient mutants

The role of endogenous gibberellins (GAs) and abscisic acid (ABA) in seed development and germination of tomato, was studied with the use of GA- and/or ABA-deficient mutants.GAs are indispensable for the development of fertile flowers. Fertility of GA-deficient flowers is restored by application of exogenous GAs. Fruits and seeds develop without GA, with a possible exception for the initial stage of seed growth. However, seed-produced GA delays maturation of the seeds and ripening of the fruit by one week and increases final seed and fruit weights.ABA levels in developing ABA-deficient mutant seeds are strongly reduced compared to wild-type seeds. Despite the strong reduction of endogenous ABA levels neither dry matter accumulation nor storage protein synthesis are affected.In wild-type seeds embryo-produced ABA is responsible for the development of dormancy during seed development. ABA-deficient seeds germinate viviparously in over-ripe fruits. Germination of wild-type seeds is also inhibited after harvest. Dormancy is relieved during a short period of dry storage. Stored wild-type seeds are much more sensitive to osmotic inhibition of radicle growth and germination than ABA-deficient seeds. Both types of seeds are equally sensitive to inhibition by exogenous ABA.GA is indispensable for tomato seed germination. GA produced by the embryo and excreted to the endosperm, induces hydrolysis of the galectomannan-rich endosperm cell walls. The hydrolysis causes weakening of the mechanical restraint of the endosperm layers that oppose the radicle tip. thereby permitting the radicle to protrude. The separation of ABA- and GA-action in time and in site is a strong argument against the existence of a hormone balance for the regulation of seed dormancy

Vroege scheutontwikkeling bij tomaat

In opdracht van het Productschap Tuinbouw hebben onderzoekers van Plant Research International (onderdeel van Wageningen UR) een methode ontwikkeld om de trosaanleg bij jonge tomatenplanten eenduidig te meten. De methode is door zes deelnemende bedrijven in de praktijk getest en de plantontwikkeling is onder begeleiding van de onderzoekers gedurende vier seizoenen gevolgd gedurende de opkweek van de planten

Production of organic seeds: Status, Challenges and Prospects

General article on the requirements of organic agriculture for seed production. Beside this the organic agricultural system has other demands for organic seed since it does not use chemical control measures and uses natural fertilizers instead of chemical fertilizers. Research can offer an important contribution in the production of seed without diseases