Vernalization Days Research Articles

Temperature and duration of vernalization effect on the vegetative growth of garlic (Allium sativum L.) clones in Indonesia

Abstract Garlic is usually propagated asexually from the cloves. Clove as the propagation source for garlic has many weaknesses. Alternatively, bulbils could be used for the propagation. The aim of this study was to know the effect of temperature and time of vernalization from several clones of Indonesian garlic to bulbil production. This research was conducted at a farmer’s field at Banjarnegara, Central Java, Indonesia. The experiment was arranged in a Completely Randomized Block Design with three factors: temperature of vernalization, i.e., 0, 5, and 10°C, duration of vernalization, i.e., 20, 40, and 60 days, and on 12 garlic varieties/clones (V1–V12). Cloves of garlic were vernalized in cold storage according to the treatments and then planted in the field. The results revealed that a temperature of 5°C and duration of 20 days of vernalization independently single factor increased the number of bulbils of V3. Bulbil variables of V4 and V7 were enhanced with vernalization at 0°C for 20 days, although it did not significantly differ from the control. Therefore, these clones do not need particular vernalization treatment in order to produce bulbils.

Wheat Breeding Strategies under Climate Change based on CERES-Wheat Model

Climate change has inevitably had a negative impact on agricultural production and food security. Crop breeding improvement is an efficient option to adapt to future climate and increase grain production. To study the potential to provide valuable advice for breeding under climate change condition, the crop growth model was used as basis to investigate, the effects of the cultivar genotype parameters of the crop estimation through resource and environment synthesis-wheat (CERES-Wheat) model on yield under different climate scenarios. In this study, solar radiation had a positive effect on the yield of winter wheat, while the effects of daily temperature change conditions on yield were vague, particularly under a change in daily maximum temperature. For the seven cultivar genotype parameters in the CERES-Wheat model, the yield had an approximately linear increasing relationship with kernel number (G1) and kernel size (G2). Vernalization days (P1V) had a fluctuating effect on winter yield without an evident unidirectional tendency. The yield of winter wheat increased with an increase in photoperiodic response (P1D) when P1D values varied from 64.81 to 79.81. Phyllochron interval (PHINT) had a positive impact on the yield of winter wheat. This study presented the potential benefits of the crop growth model to provide directional suggestions for crop breeding.

Genetic dissection of flowering time in Brassica rapa responses to temperature and photoperiod

The Brassica rapa (B. rapa) species displays enormous phenotypic diversity, with leafy vegetables, storage root vegetables and oil crops. These different crops all have different flowering time, which determine their growing season and cultivation area. Little is known about the effects of diverse temperature and day-lengths on flowering time QTL associated with FLC paralogues. We phenotyped the flowering time of a doubled haploid population, established from a cross between Yellow sarson and Pak choi under diverse environmental conditions. We identified flowering-time QTL (fQTL) in different photoperiod and temperature regimes in the greenhouse, and studied their colocation with known flowering time genes. As several fQTL colocalized with FLC paralogues, we studied the expression patterns of four FLC paralogues during the course of vernalization in parental lines. Under all environmental conditions tested the major fQTL that mapped to the BrFLC2_A02 locus was detected, however its effect decreased when plants were grown at low temperatures. Another fQTL that mapped to the FLC paralogue, BrFLC5_A03 was also identified under all tested environments, while no fQTL colocated with BrFLC1_A10 or BrFLC3_A03. Furthermore, the vernalization treatment decreased expression of all BrFLC paralogues in the parental lines, and showed the lowest transcript level after 28 days of vernalization. Transcript abundance stayed low after returning the plants for seven days to normal growth temperature. Interestingly, transcript abundance of BrFLC3_A03 and BrFLC5_A03 was repressed much stronger and already reached lowest levels after 14d in the early-flowering type YS-143. This study improves understanding of the effects of daylength and vernalization on flowering time in B. rapa and the role of the different BrFLC paralogues therein.

Registration of Sugarbeet Doubled Haploid Line KDH13 with Resistance to Beet Curly Top

KDH13 is a sugar beet (Beta vulgaris L. ssp vulgaris) doubled haploid line (PI 663862) released as a genetic stock by USDA-ARS in cooperation with the Beet Sugar Development Foundation, Denver, CO. KDH13 is resistant to beet curly top (BCT) caused by Beet curly top virus which is transmitted by the beet leafhopper (Circulifer tenellus Baker). KDH13 was extracted from the BCT resistant C762-17 (PI 560130) parental line that segregates for BCT resistance and genetic male sterility. Intensive phenotypic screening was used for selecting plants from C762-17 that showed no symptoms under fully controlled infection conditions in the greenhouse. Seed from a single plant was used as a donor of floral buds for isolation of unfertilized ovaries to regenerate KDH13 via gynogenesis, and was confirmed a diploid by flow cytometry. The whole genome for this line was sequenced via next generation sequencing and its assembly was designated BvvSeq-1. The assembly was used to identify a large set of single nucleotide polymorphic markers (SNP) aligned to a BCT susceptible line (KWS2320) genome assembly. Homozygosity of KHD13 was confirmed using SNPs. It is a monogerm, self- fertile, and requires at least 90 days of vernalization for bolting. KDH13 outperformed BCT resistant commercial checks in greenhouse and field screening experiments. This line was used in crosses with susceptible parents and proved to be suitable as a donor parent for curly top resistance genes.

Research into the influence of contrasting trophic conditions of vernalization on the allelic state of Vrn genes and development rates of Triticum aestivum L.

The influence of contrasting trophic conditions of vernalization on the allelic state of the Vrn genes and development rates of two winter wheat varieties, Mironovskaya 808 and Olvia, was investigated. Vernalization was carried out during 45 days at the temperature 4 ± 1°С under different conditions of trophic support. Whole seeds with endosperm and isolated buds, with added water and 3% solution of sucrose, were vernalized. The allelic state of the Vrn genes was identified by PCR using allele-specific primers on the sprouts at different phases of vernalization – 15, 30, and 45 days. Phenological observations were carried out by determining of the transition to the generative development of wheat plants, cultivated from the vernalized sprouts. According to the results obtained, it was established that the recessive state of the genes Vrn-A1, Vrn-B1 and Vrn-D1 was unchanged in all variants of the two winter wheat varieties on the 15th and 30th days of vernalization. After 45 days of vernalization, the recessive and dominant alleles in sprouts, vernalized under normal trophic conditions and with added 3% solution of sucrose, were detected at the Vrn-B1. All variants of wheat plants grown from vernalized sprouts under contrasting trophic conditions were transferred to the generative phase, but at different times. It could indicate an epigenetic regulation vernalization process. It was established that different trophic conditions during vernalization affected the changes of the allelic state of the Vrn-B1 gene and determined the transition to the generative development of winter wheat.

Effect of trophic support on the dynamics of growth processes and carbohydrate content of winter wheat sprouts under vernalization

The influence of contrasting conditions of trophic support of vernalization on the growth reaction and dynamics of the content of various fractions of soluble carbohydrates of sprouts of two winter wheat varieties Statna and Doridna were studied. In experiments, the contrasting trophic conditions of vernalization were created by adding 3% sucrose solution, as well as isolation of endosperm, a natural reserve of carbohydrates and biologically active substances. It was shown that optimal conditions of trophic support (integral seeds + water) determined the maximum linear growth and accumulation of sprouts biomass during vernalization. The excess of exogenous sugars (integral seeds + 3% sucrose solution) inhibited growth processes. However, the deficit of trophic factors (isolated buds + 3% sucrose solution) also inhibited growth and the lack of trophic support (isolated buds + water) completely inhibited growth and accumulation of sprouts biomass during 45 days of vernalization. It was established that the dynamics of changes in soluble carbohydrates content in winter wheat sprouts also depended on the trophic support level of vernalization and correlated with changes of growth reaction. It was shown the oligosaccharide content was significantly higher than monosaccharide content of sprouts of all the variants of both varieties during the entire period of vernalization. In view of the fact that monosaccharides are the most metabolically active carbohydrates, they are probably spent as much as possible at the first stages of vernalization (15–30 days). It is discussed that different level of trophic support is able to be one of the important factors of genetic and/or epigenetic regulation of Triticum aestivum L. Thus, changes in metabolic processes, in particular carbohydrate metabolism, can effect on the reduction of VRN genes expression, which are the target of epigenetic regulation, and as a result, on the ability of soft wheat plants to flower. It is assumed that the regulatory role of carbohydrates in vernalization process can be realized only at the optimal level of trophic support.

Identification of Flowering-Related Genes Responsible for Differences in Bolting Time between Two Radish Inbred Lines.

Late bolting after cold exposure is an economically important characteristic of radish (Raphanus sativus L.), an important Brassicaceae root vegetable crop. However, little information is available regarding the genes and pathways that govern flowering time in this species. We performed high-throughput RNA sequencing analysis to elucidate the molecular mechanisms that determine the differences in flowering times between two radish lines, NH-JS1 (late bolting) and NH-JS2 (early bolting). In total, 71,188 unigenes were identified by reference-guided assembly, of which 309, 788, and 980 genes were differentially expressed between the two inbred lines after 0, 15, and 35 days of vernalization, respectively. Among these genes, 218 homologs of Arabidopsis flowering-time (Ft) genes were identified in the radish, and 49 of these genes were differentially expressed between the two radish lines in the presence or absence of vernalization treatment. Most of the Ft genes up-regulated in NH-JS1 vs. NH-JS2 were repressors of flowering, such as RsFLC, consistent with the late-bolting phenotype of NH-JS1. Although, the functions of genes down-regulated in NH-JS1 were less consistent with late-bolting characteristics than the up-regulated Ft genes, several Ft enhancer genes, including RsSOC1, a key floral integrator, showed an appropriate expression to the late-bolting phenotype. In addition, the patterns of gene expression related to the vernalization pathway closely corresponded with the different bolting times of the two inbred lines. These results suggest that the vernalization pathway is conserved between radish and Arabidopsis.

Produção de alho submetido a períodos de vernalização e épocas de plantio em região de clima semiárido

RESUMO Com o objetivo de avaliar a produção de alho nobre submetido a períodos de vernalização e épocas de plantio, realizou-se um experimento em Baraúna-RN, de maio a outubro de 2012. Os tratamentos foram dispostos no esquema de parcelas subdivididas, delineamento experimental de blocos casualizados completos, com três repetições. Nas parcelas foram alocadas as épocas de plantio (22 de maio, 5 de junho e 23 de junho), e nas subparcelas os períodos de vernalização pré-plantio do alho-semente (4±1°C durante 50, 55, 60, 65 e 70 dias). Foram avaliados comprimento de plantas, número de folhas, ciclo, estande final, massa média de bulbos, percentagem de plantas com bulbos, produtividade total de bulbos, classificação dos bulbos, número de bulbilhos por bulbo e classificação dos bulbilhos. O plantio em 22 de maio proporcionou maiores comprimento de plantas, número de folhas, estande final e massa média de bulbos; o ciclo decresceu com o tempo de vernalização; houve formação de bulbos com diferenciação de bulbilhos em todos os tratamentos sem, entretanto, haver ocorrência de plantas com superbrotamento; a produtividade total de bulbos aumentou com o tempo de vernalização de até 63 dias nos plantios em 22 de maio e 23 de junho, com médias de 5,20 e 3,85 t/ha; a combinação entre o plantio em 22 de maio e 65 dias de vernalização, foi a que proporcionou maior número de bulbilhos por bulbo e maior percentual de bulbos comerciais, distribuídos nas classes 3, 4 e 5. Esses resultados evidenciam ser possível o cultivo de alho nobre na região de Mossoró-RN utilizando o processo de frigorificação do alho-planta.

Impact of climate change on wheat flowering time in eastern Australia

The flowering time of wheat is strongly controlled by temperature and is potentially highly sensitive to climate change. In this study, we analysed the occurrence of last frost (days with minimum temperature under 2°C) and first heat (days with maximum temperatures exceeding 30°C) events of the year to determine the optimum flowering date in the wheat belt of New South Wales (NSW), eastern Australia. We used statistically downscaled daily maximum and minimum temperature data from 19 Global Climate Models (GCMs) with a vernalizing–photothermal model in order to simulate future flowering dates and the changes in frost and hot days occurrence at flowering date (± 7 days) for two future scenarios for atmospheric greenhouse gas concentrations (RCP4.5 and RCP8.5) in 2040s (2021–2060) and 2080s (2061–2100). Relative to the 1961–2000 period, the GCMs projected increased daily maximum and minimum temperatures for these future periods, accompanied by reduced frost occurrence and increased heat stress incidence. As a consequence, by the 2080s, simulations suggest a general advance in spring wheat flowering date by, on average, 10.2 days for RCP4.5 and 17.8 days for RCP8.5 across the NSW wheat belt. Winter wheat flowering dates were delayed by an average of 2.4 days for RCP4.5 and 14.3 days for RCP8.5 in the warmest parts of the region (the northwest) due to reduced cumulative vernalization days (requiring cool conditions). In the cooler regions (the northeast, southeast and southwest), flowering date occurred earlier by 6.2 days for RCP4.5 and 6.7 days for RCP8.5 on average. Moreover, in the western parts of the wheat belt the delay of winter wheat flowering date was about 9.5 days longer than that in the eastern parts. As a result of phenological responses to increasing temperatures, current wheat varieties may not be suitable for future climate conditions, despite reduced frost risk. In the future, it may be necessary to use longer-season wheat varieties and varieties with increased heat-stress resistance.

The role of BoFLC2 in cauliflower (Brassica oleracea var. botrytis L.) reproductive development.

In agricultural species that are sexually propagated or whose marketable organ is a reproductive structure, management of the flowering process is critical. Inflorescence development in cauliflower is particularly complex, presenting unique challenges for those seeking to predict and manage flowering time. In this study, an integrated physiological and molecular approach was used to clarify the environmental control of cauliflower reproductive development at the molecular level. A functional allele of BoFLC2 was identified for the first time in an annual brassica, along with an allele disrupted by a frameshift mutation (boflc2). In a segregating F₂ population derived from a cross between late-flowering (BoFLC2) and early-flowering (boflc2) lines, this gene behaved in a dosage-dependent manner and accounted for up to 65% of flowering time variation. Transcription of BoFLC genes was reduced by vernalization, with the floral integrator BoFT responding inversely. Overall expression of BoFT was significantly higher in early-flowering boflc2 lines, supporting the idea that BoFLC2 plays a key role in maintaining the vegetative state. A homologue of Arabidopsis VIN3 was isolated for the first time in a brassica crop species and was up-regulated by two days of vernalization, in contrast to findings in Arabidopsis where prolonged exposure to cold was required to elicit up-regulation. The correlations observed between gene expression and flowering time in controlled-environment experiments were validated with gene expression analyses of cauliflowers grown outdoors under 'natural' vernalizing conditions, indicating potential for transcript levels of flowering genes to form the basis of predictive assays for curd initiation and flowering time.

Role of endogenous growth regulators in vernalization of seeds of radish (Raphanus sativus L.)

In embryos and cotyledons of seeds of the radish cv. `Tetra Iłówiecka' (which needs 20 days of vernalization) and cv. 'Saxa' (which flowers without vernalization) germinating at a vernalizing temperature of 5°C, the levels of auxins, gibberellins, cytokinins and the aibscisic acid-like inhibitor were determined, The analyses were performed after 5, 10, 15, 20, 25 and 30 days of chilling. The levels of growth regulators were also determined in embryos and cotyledons of seeds germinated at 260C when in the same growth stage as the material taken from chilled seeds. Cold treatment significantly affected the level of all endogenous growth regulators in embryos and cotyledons of both varieties. However, changes in the levels of these substances were not directly connected with the vernalization process. It was found that the vernalization of seeds of 'the radish cv. `Tetra Iłówiecka' increased the level of GAs in leaves, this did not, however, coincide with flower initiation. It is concluded that the role of GAs in flowering of the studied plants is connected rather with photoinduction than with vernalization.

Influence of Vernalization and Photoperiod on the Duration of Stem Elongation and Spikelet Fertility in Wheat

A longer stem elongation phase (from the terminal spikelet-TS to the anthesis-ANT phases) increases grain production due to an increase in spikelet fertility. However, the mechanism behind the greater number of fertile flowers that occur when the duration of stem elongation is modified by photoperiod and vernalization is not fully understood. The goal of this study was to investigate the effect of combinations of photoperiod and vernalization on the duration of stem elongation and spikelet fertility in wheat. Thus, a greenhouse experiment was performed by subjecting 13 wheat genotypes to two vernalization regimes (V0—non-vernalized plants and V40—plants with 40 vernalization days) and to two photoperiod regimes (NP—natural and NP + 6—photoperiod extended by six hours), during the stem elongation phase. The natural photoperiod increased the spikelet fertility of eight cultivars without a corresponding increased duration of the TS-ANT phase, suggesting the existence of a direct effect of photoperiod on increased spikelet fertility. Vernalization increased the duration of the TS-ANT phase, without influencing spikelet fertility. There was genetic variability in the responses to photoperiod and vernalization.

Transcriptional Regulations on the Low-Temperature-Induced Floral Transition in anOrchidaceaeSpecies,Dendrobium nobile: An Expressed Sequence Tags Analysis

Vernalization-induced flowering is a cold-relevant adaptation in many species, but little is known about the genetic basis behind in Orchidaceae species. Here, we reported a collection of 15017 expressed sequence tags (ESTs) from the vernalized axillary buds of an Orchidaceae species, Dendrobium nobile, which were assembled for 9616 unique gene clusters. Functional enrichment analysis showed that genes in relation to the responses to stresses, especially in the form of low temperatures, and those involving in protein biosynthesis and chromatin assembly were significantly overrepresented during 40 days of vernalization. Additionally, a total of 59 putative flowering-relevant genes were recognized, including those homologous to known key players in vernalization pathways in temperate cereals or Arabidopsis, such as cereal VRN1, FT/VRN3, and Arabidopsis AGL19. Results from this study suggest that the networks regulating vernalization-induced floral transition are conserved, but just in a part, in D. nobile, temperate cereals, and Arabidopsis.

Response of spring type wheat (Triticum aestivum L.) cultivars to different chilling treatments

Late sowing of wheat in autumn due to environmental conditions or late harvesting of cotton crop results in substantial yield loss. It may be attributed to non-fulfillment of chilling requirements. The present study was conducted to identify the chilling requirement of autumn sown cultivars of wheat. Effect of chilling treatment (measured in vernalization days (VDs)) on seven wheat cultivars (five Pakistani and two American) was observed by exposing the seedlings to 6°C for 7, 14, 21, 28 and 35 days that is 6.72, 13.44, 20.16, 26.86 and 33.60 VDs. Seedlings which acted as control were not subjected to chilling treatment. All spring type wheat cultivars headed irrespective of their chilling treatment but increase in VDs, enhanced days to heading. Winter type wheat “Caldwell” did not show heading which indicated its high VDs requirement. Chilling treatment also affected grain yield of all cultivars. Sehar-06 and Marquillo demonstrated highest yields at 6.72 VDs while GA-02, Inqilab-91, Chakwal-50 and Freed-06 manifested highest yields at 13.44 VDs. The results of the experiment revealed that heading time and grain yield of all spring type wheat cultivars is affected by chilling treatments. Depending upon the response of the cultivars and available VDs calculated from temperature data of last 20 years. It is suggested that GA-02, Inqilab-91, Chakwal-50 and Fareed-06 must be sown in mid December while Sehar-06 can be sown in the start of January to meet their chilling requirement under field conditions without substantial yield reduction.

Photoperiod sensitivity in narrow-leafed lupin (Lupinus angustifolius L.)

The influence of photoperiod and vernalization on flower initiation in six genotypes of narrow-leafed lupin (Lupinus angustifolius L.) was investigated under growth chamber conditions to better understand the effect of these parameters in the crop's adaptation to northern European growing conditions. Time to flowering was decreased by long days in all six varieties when these were not subject to vernalization. The combined treatment of both vernalization and long days always resulted in the shortest time to flowering. The effect of daylength was most pronounced in the thermosensitive varieties. In the nonvernalized thermoneutral varieties time to flowering was reduced by 10 to 21 days. There was no flowering in the thermosensitive varieties without vernalization during the 132 days of the experiment. A reduced number of main-stem leaves in nonvernalized treatments in 24-h compared with 10-h days indicates that part of the hastening of flowering in long days was caused by a photoperiod-sensitive flower initiation, and not only caused by increased growth rate. A juvenile, photoperiod-insensitive pre-inductive phase was further established in another experiment where plants were transferred from short (11 h) to long day (18 h) and vice versa at set times. The results showed a well defined juvenile phase of about 35 days where the photoperiod had no effect. After this phase a clear daylength effect was evident both when expressed as time to flowering and as number of main stem leaves developed before flower initiation. Time to flowering was reduced from about 144 days to 65 days and the number of main-stem leaves from 78 to 45. Only a few diurnal cycles in the inductive phase were necessary to reach full photoperiod response.

Vernalization responses of field grown jointed goatgrass (Aegilops cylindrica), winter wheat, and spring wheat

Numerous studies have quantified the developmental responses of wheat to vernalization, but its response compared to a weedy relative, jointed goatgrass, remains relatively unknown. Six paired jointed goatgrass collections gathered from Washington and Oregon fields, and winter and spring wheat, were grown in field studies to quantify yield and germination in response to vernalization. Monthly planting dates initiated in October and concluded in March were used to vary the vernalization durations for plants sown at three Oregon locations (Corvallis, Moro, and Pendleton) over two growing seasons. Minimum vernalization requirements to produce reproductive spikes were similar among plants of six jointed goatgrass collections. Jointed goatgrass collections grown at Corvallis required a minimum of 89 and 78 vernalization days (January 17, 2003 and January 22, 2004 sowing, respectively) to produce reproductive spikes, and plants grown at Moro required 60 vernalization days (March 3 and February 23) in both years, and 48 and 44 vernalization days (March 3 and February 24) were required by plants to produce spikes at Pendleton. Jointed goatgrass spikelet and winter wheat seed yield were positively influenced by vernalization days, experiment location, and year. The strength of the interactions among these main effects differed among jointed goatgrass collections and winter wheat. The effects of vernalization on jointed goatgrass yields and seed quality were more pronounced at Pendleton, OR, a location where jointed goatgrass has adapted, compared to Corvallis, OR, where it has not adapted. The minimum vernalization days required to produce germinable seed differed among jointed goatgrass collections, winter and spring wheat. There was not a selection of spring-adapted jointed goatgrass populations in the populations tested. Yet if spring temperatures are cool, minimum conditions for vernalization may be satisfied, and the benefits of planting spring crops to control jointed goatgrass would be reduced.

Simulating the vernalization response of the "Snow Queen" lily (Lilium longiflorum Thunb.)

Vernalization is a process required by certain plant species, including lilies (Lilium spp.), to enter the reproductive phase, through an exposure to low, non-freezing temperatures. The objective of this study was to evaluate a nonlinear vernalization response function for the "Snow Queen" lily. An experiment was carried out in Santa Maria, RS, Brazil, to provide an independent data set to evaluate the performance of the model. Lily bulbs were vernalized at -0.5, 4.0, and 10ºC during two, four, six, and eight weeks. The daily vernalization rate (fvn) for each treatment was calculated with a beta function, and the effective vernalization days (VD) were calculated by accumulating fvn. The thermal time from plant emergence to visible buds at different VD treatments was used as the observed response to VD. Lily plants were not vernalized at values less than eight effective vernalization days and were fully vernalized at values greater than 40 days. The generalized nonlinear vernalization function described well the "Snow Queen" lily developmental response to VD, with a root mean square error of 0.178.

Vernalização do alho para cultivo in vitro

Com o objetivo de avaliar o período de vernalização sobre a incidência do índice de pseudoperfilhamento em plantas de alho (Allium sativum L.) cultivadas in vitro, visando maior multiplicação, foi conduzido este experimento em laboratório da UFLA (MG). Utilizou-se o delineamento inteiramente casualizado com seis períodos de vernalização (40; 50; 60; 70; 80 e 90 dias) em câmara frigorífica a 5±2°C, com quatro repetições, utilizando-se a cultivar Roxo Pérola de Caçador. O tratamento com 90 dias de vernalização foi o que apresentou os melhores resultados para as variáveis bulbo/meristema/tubo, massa fresca total das plantas e dos bulbos com 1,81 bulbo/meristema/tubo, 235,32 mg plantas-1 e 110,51 mg bulbo-1, respectivamente. A massa fresca media por bulbo obtida não evidenciou diferenças significativas entre os tratamentos, no entanto, o tratamento com 90 dias de vernalização (58,68 mg bulbo-1) apresentou-se com uma produção de bulbos 79,29% superior ao tratamento com 60 dias de vernalização, que demonstrou o pior resultado.

Vernalização afeta a mobilização de reservas de açúcares e nitrogênio e a emergência de plantas de lírio (Lilium longiflorum thunb.) ‘snow queen’

Com o objetivo de avaliar a resposta dos dias efetivos de vernalização do lírio sobre o conteúdo de açúcares solúveis e nitrogênio total e a emergência de plantas, bulbos de Lilium longiflorum, cv ‘Snow Queen’ foram submetidos a diferentes temperaturas de vernalização e períodos de exposição à temperaturas vernalizantes e cultivados em estufa plástica. O experimento foi conduzido na Universidade Federal de Santa Maria, Santa Maria (RS), em duas épocas de plantio dos bulbos: de 20/03/02 a 05/11/02 e 05/12/02 a 15/05/03. Os tratamentos foram 0, 9, 11, 14, 19, 23, 28, 29, 34, 38, 42, 45 e 56 dias efetivos de vernalização (DV), calculados a partir de uma função beta de resposta da vernalização à temperatura. Determinaram-se o conteúdo de açúcares solúveis e nitrogênio total e a duração do subperíodo de plantio dos bulbos-emergência das plantas (P-E). A vernalização promoveu a mobilização de reservas de açúcares e nitrogênio, o que é importante para nutrição da planta em emergência. O aumento do número de dias efetivos de vernalização reduziu a duração do subperíodo P-E. Bulbos tratados em temperaturas de 10ºC por 6 e 8 semanas de armazenamento (34 e 45DV), apresentaram uma menor duração do subperíodo P-E.

Vernalization Studies with Pacific Northwest Wheat

Lack of rain or excess soil moisture may create problems for fall sowing of winter cereals in the Pacific Northwest. Growers unable to plant in the fall question the potential for late winter sowings, which is determined to a large extent by cultivar vernalization requirement. This study was conducted to gain a better understanding of the vernalization requirement of winter wheat (Triticum aestivum L.) cultivars grown in the region and to determine if a tool could be developed for predicting latest winter sowing dates. A growth chamber–greenhouse procedure was developed to determine the relative vernalization requirement of new wheat cultivars. Twenty cultivars were sown in the field at intervals from early October through late March during the 1991–1993 cropping seasons. Accumulated heat units from sowing were used to determine vernalization days (VD). Heading date and yield were measured. Field results indicated that cultivars could be categorized in three groups—those with low, intermediate, and high vernalization requirements. Growth chamber–greenhouse results verified these groupings. Field data suggest that if 50% relative yield (late‐sown yield is 50% of that for the same cultivar when sown in fall or early winter) is acceptable, then cultivars with a low vernalization requirement can be sown with 60 VD expected after sowing while cultivars with a high vernalization requirement require 70 expected VD. If 70% relative yield is desired, all cultivars tested showed similar performance.