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vol.32 número1COMPONENTES DE PRODUÇÃO DA VIDEIRA ‘ISABEL PRECOCE’ SUBMETIDA À ADUBAÇÃO NITROGENADA E ORGÂNICA NO SEMIÁRIDO POTIGUARGERMINAÇÃO E VIGOR DE SEMENTES DE FEIJÃO-CAUPI EM RESPOSTA AOS ESTRESSES SALINO E TÉRMICO índice de autoresíndice de assuntospesquisa de artigos
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Revista Caatinga

versão impressa ISSN 0100-316Xversão On-line ISSN 1983-2125

Rev. Caatinga vol.32 no.1 Mossoró jan./mar. 2019  Epub 09-Maio-2019

http://dx.doi.org/10.1590/1983-21252019v32n114rc 

Agronomia

PHYSIOLOGICAL AND SANITARY QUALITY AND OIL CONTENT OF CASTOR BEAN SEEDS UNDER DIFFERENT STORAGE CONDITIONS?1

A CONDIÇÃO DE ARMAZENAMENTO INTERFERE NO POTENCIAL FISIOLÓGICO E SANITÁRIO E NO TEOR DE ÓLEO DE SEMENTES DE MAMONA?

Heloisa Oliveira dos Santos2 
http://orcid.org/0000-0003-1384-4969

Maria Laene Moreira de Carvalho2 
http://orcid.org/0000-0001-9121-3404

Camila Aparecida Lopes2  * 
http://orcid.org/0000-0002-4913-9607

Édila Vilela de Resende Von Pinho2 
http://orcid.org/0000-0002-0757-0095

Stefânia Vilas Boas Coelho2 
http://orcid.org/0000-0002-6408-9601

2Department of Agriculture, Universidade Federal de Lavras, Lavras, MG, Brazil; heloisa.osantos@ufla.br, mlaene@gmail.com, camilalopes_sjc@hotmail.com, edila@reitoria.ufla.br, stefaniavbc@gmail.com.


ABSTRACT

The objective of this work was to evaluate the effects of different storage conditions on the physiological and sanitary quality and oil content of castor bean (Ricinus communis) seeds. Seeds of castor bean plants of the Guarani, and IAC-80 cultivars were stored in two environments (cold room, and room conditions), using three package types (multifoliate Kraft paper bag, and polyethylene bag, and polyethylene bag with vacuum at 1 atm). In addition, another storage condition was evaluated: cryopreservation (-196 °C) in foil paper bags. Seed quality was evaluated before storage and at 4, 8, and 12 months after storage by testing their 7-day and 14-day germination, emergence, health, water content, and oil content. The experiment was conducted in a completely randomized design, with 7×4 factorial arrangement consisting of seven storage conditions and four evaluation times. Cryopreservation is the ideal condition for maintaining the seed physiological quality of the Ricinus communis cultivars used throughout storage. The oil content of the R. communis seeds decreases, and the incidence of Aspergillus spp. and Fusarium spp. fungi increases throughout storage, regardless of the storage conditions.

Keywords: Room conditions; Cold room; Cryopreservation; Packaging; Ricinus communis

RESUMO

Para investigar se diferentes condições de armazenamento interferem no potencial fisiológico, sanitário e no teor de óleo de sementes de mamona (Ricinus communis) foram utilizadas sementes de duas cultivares, Guarani e IAC-80, armazenadas em dois ambientes (câmara fria e armazém convencional) em duas embalagens (saco de papel Kraft multifoliado e saco plástico - com e sem acondicionamento a vácuo a 1 atm). Testou-se ainda outro tipo de acondicionamento, utilizando-se papel aluminizado para criopreservação das sementes (-196 °C). A qualidade das sementes foi avaliada antes do armazenamento e após 4, 8 e 12 meses por meio dos testes de geminação (contagem aos 7 e 14 dias), emergência, sanidade, teor de água e teor de óleo. O delineamento experimental utilizado foi o inteiramente casualizado, em esquema fatorial 7x4, sendo sete condições de armazenamento e quatro épocas. A criopreservação (-196 °C) é a condição ideal para manutenção do potencial fisiológico de sementes de Ricinus communis, cultivares IAC-80 e Guarani, ao longo do armazenamento. Independente das condições de armazenamento de sementes de R. communis, o teor de óleo decresce e a incidência dos fungos Aspergillus spp. e Fusarium spp. aumenta ao longo do armazenamento.

Palavras-chave: Armazém; Câmara fria; Criopreservação; Embalagem; Ricinus communis

INTRODUCTION

Castor bean (Ricinus communis L.) is a plant of the Euphorbiaceae family. The oil extracted from its seeds is a promising alternative to produce biodiesel, an ecological biodegradable fuel (MENDES et al., 2009).

Brazil is one of the largest producing countries of R. communis (CONAB, 2016); however, the Brazilian average crop yield of this species is low (551 kg ha-1) compared to other oilseeds, such as soybean, sunflower, and peanuts (FANAN et al., 2009; SANTOS et al., 2016). The use of low-quality seeds that are produced by the farmers themselves (FANAN et al., 2009), and storage problems due to the high oil content of these seeds (35% to 55% depending on the cultivar) are factors that contribute to this low yield (SANTOS et al., 2016).

Oil seeds, including R. communis, is more affected by storage than starch seeds because lipids have lower chemical stability than starch; a moderate increase in temperature due to the respiratory process is sufficient to increase lipid decomposition and seed deterioration rates (FANAN et al., 2009). Therefore, the storage condition is important for the physiological quality of these seeds; and although it cannot be improved, seeds with good physiological quality are viable for longer periods by delaying the deterioration process (ALMEIDA et al., 2010). Several factors affect the quality of stored seeds, such as seed water content at storage, package use for their conservation, temperature and relative humidity of the storage environment, and seed chemical composition (CALDEIRA et al., 2016). However, few studies on these factors affecting R. communis conservation are found (QUEIROGA; BELTRÃO, 2004; FANAN et al., 2009; ALMEIDA et al., 2010; REED et al., 2011; SANTOS et al., 2016).

According to Queiroga and Beltrão (2004), commercial seeds of R. communis should be stored with water content of 8% to 10% in multilayer paper bags for a maximum of eight months. However, to maintain their quality for a longer period for trade, or conservation of genetic material, other techniques should be used, such as cryopreservation.

Cryopreservation can preserve seeds for unlimited time by reducing their metabolism to low levels, reducing significantly all biochemical processes, and almost stopping deterioration (SANTOS et al., 2016). Traditional conservation methods only postpone deterioration for a specific period, depending on the material and species (COSTA et al., 2012).

In this context, the objective of this work was to evaluate the effects of different storage conditions on the physiological and sanitary quality and oil content of Ricinus communis seeds.

MATERIAL AND METHODS

The experiment was conducted with Ricinus communis seeds of the Guarani, and IAC-80 cultivars. The seed lot of each cultivar was evaluated by germination tests. The seeds were homogenized, packed in multilayer Kraft paper bags (KPB), polyethylene bags (PEB), and polyethylene bags with vacuum at 0.1 atm (PEBV), and stored in two different environments: room conditions (RC) (25 °C), and cold room (CR) (10 °C and relative humidity of 50%); in addition, they were stored in liquid nitrogen (cryopreservation at -196 ºC) in foil paper bags (CP), resulting in seven storage conditions for each cultivar (RC-KPB; RC-PEB, RC-PEBV, CR-KPB, CR-PEB, CR-PEBV, and CP).

Packed seeds were immersed directly in liquid nitrogen for cryopreservation. The packages containing the seeds were withdrawn from the liquid nitrogen and thawed at room temperature (25± 2 °C) for 24 hours at each evaluation time (0, 4, 8 and 12 months).

The physiological and sanitary quality and oil content of the R. communis seeds of each cultivar were evaluated by determining their water content by the oven method at 105±2 °C for 24 hours (BRASIL, 2009).

Germination test and first germination count was performed with eight replicates of 25 seeds per treatment, using germination test papers (Germitest®), moistened with distilled water at a ratio of 1:2.5 (w/w). The germination test papers with seeds were kept in a germinator with a constant temperature of 25 ºC, and germination counts were performed at 7 and 14 days of incubation, with results expressed as percentage of normal seedlings (BRASIL, 2009).

Seedling emergence was evaluated with four replicates of 50 seeds per treatment. The seeds were placed in plastic trays (60×40×10 cm) containing 4 kg of a substrate (sand and soil 2:1), with water retention set to 60%. These trays were transferred to a growth chamber at 25 °C. Seedling emergence was evaluated at 21 days after sowing, considering the number of seedlings emerged, with results expressed as percentages.

Emergence speed index was evaluated through daily readings of the number of seedlings with cotyledon leaves above ground (MAGUIRE, 1962).

The oil was extracted from the seeds and its content was determined with three replicates of 25 g of ground R. communis seeds per treatment. The ground material was placed in a volumetric flask (500 mL) with 200 mL of the hexane solvent (H3C(CH2)CH3), refluxed for 24 hours, and the solution was then vacuum filtered using a Buchner's funnel. The filtrate was concentrated on a rotary evaporator (Buchi R-114) under reduced pressure. The oil obtained was taken to an oven at 35 °C for 24 hours for complete evaporation of the solvent. The oil content was determined by gravimetric percentage-ratio between the weights of the oil obtained and seeds subjected to extraction (KOUTROUBAS; PAPAKOSTA; DOITSINIS, 2000).

The sanitary test consisted of incubation of seeds in filter paper without freezing (MOURA et al., 2012). The seeds were incubated in Petri dishes (15 cm in diameter) containing two sheets of filter paper moistened with water plus 2,4-dichlorophenoxyacetic acid, using 200 seeds of each treatment divided into eight replicates. The plates were incubated at 20 ºC with photoperiod of 12 hours for seven days, and then evaluated for presence of pathogens.

The experiment was conducted in a completely randomized design, with 7×4 factorial arrangement consisting of seven storage conditions and four evaluation times. Statistical analysis consisted of analysis of variance, comparison of qualitative data through the Scott-Knott test at 5% probability, and comparison of quantitative data through regression analysis, using the SISVAR program (FERREIRA, 2011).

RESULTS AND DISCUSSION

The R. communis seeds showed a germination of 80% (IAC-80) and 75% (Guarani) before storage, in the initial characterization.

The effect of the storage condition on IAC-80 seeds varied depending on the evaluation time for four of the five analyzed variables (first germination count, germination percentage, emergency speed index, and emergency percentage). The oil content of these seeds was similar in all storage conditions and evaluation times. The seed germination, and seedling emergence percentages in the different storage conditions were dependent on the evaluation time for Guarani seeds.

The initial water content of seeds packed in paper bags (KPB), polyethylene bags (PEB) polyethylene bags with vacuum (PEBv) and stored at room conditions decreased after four, and eight months of storage (Table 1). These seeds are hygroscopic, their water content vary according to environmental conditions (SILVA et al., 2015). The equilibrium water content is dependent on the chemical composition of the seed. Proteins are the most hygroscopic organic compounds, celluloses and starch the lesser, and lipids are essentially hydrophobic (GOLDFARB; QUEIROGA, 2013). These changes in water content were not found for seeds stored in cold room, and cryopreserved seeds.

Table 1 Water content of Ricinus communis seeds of the IAC-80 and Guarani cultivars evaluated at 0, 4, 8 and 12 months in different storage conditions. 

Cultivar Evaluation time Water contents (%)
RC-KPB RC-PEB RC-PEBV CR-KPB CR-PEB CR-PEBV CP
IAC-80 0 7.8 7.7 7.7 7.8 7.6 7.8 7.4
4 6.2 6.6 6.4 7.6 7.7 7.6 7.3
8 5.5 5.7 5.9 7.7 7.6 7.8 7.2
12 7.3 7.1 7.1 7.8 7.5 7.6 7.5
Guarani 0 8.0 8.1 8.0 8.2 8.1 8.0 8.2
4 7.9 8.0 8.1 8.0 8.3 8.2 8.3
8 7.0 7.2 7.1 8.1 8.2 8.1 8.2
12 7.8 7.7 7.9 8.3 8.3 8.0 8.1

KPB = packed in multilayer Kraft paper bags; PEB = packed in polyethylene bags; PEBV = packed in polyethylene bags with vacuum at 0.1 atm; RC = room conditions (25 °C); CR = cold room (10 °C and relative humidity of 50%); CP = stored in liquid nitrogen (cryopreservation at -196 ºC) in foil paper bags.

The percentage of normal seedlings of the IAC-80 cultivar at seven days of germination varied with the storage condition (Table 2). The germination speed of seeds stored in liquid nitrogen was higher than those of seeds stored under other conditions after twelve months of storage. The cryopreservation was beneficial to the preservation of castor bean seeds from the fourth month of storage. According to Kaviani (2011), all biochemical activities decrease during cryopreservation, and biochemical deterioration is interrupted; this preserves the seeds and increases their longevity throughout storage. Almeida et al. (2010) found similar results for five oilseeds, including R. communis, denoting the superior physiological quality of seeds stored in liquid nitrogen when compare to conventional environments.

Table 2 Percentage of normal seedlings at seven days of germination of Ricinus communis seeds of the IAC-80 cultivar evaluated at 0, 4, 8 and 12 months in different storage conditions. 

Cultivar Evaluation time Storage conditions
RC-KPB RC-PEB RC-PEBV CR-KPB CR-PEB CR-PEBV CP
IAC-80 0 30.0Bb 39.5Aa 35.5Aa 31.0Bb 38.0Aa 35.0Aa 24.0Cb
4 39.0Ab 31.0Ac 25.5Ac 41.5Bb 27.0Ac 40.0Ab 57.0Ba
8 47.5Ab 27.0Ac 34.0Ac 61.5Aa 32.5Ac 31.5Ac 55.0Ba
12 12.0Cc 29.0Ab 28.0Ab 39.5Bb 29.0Ab 35.0Ab 68.0Aa
CV (%) 19.81

KPB = packed in multilayer Kraft paper bags; PEB = packed in polyethylene bags; PEBV = packed in polyethylene bags with vacuum at 0.1 atm; RC = room conditions (25 °C); CR = cold room (10 °C and relative humidity of 50%); CP = stored in liquid nitrogen (cryopreservation at -196 ºC) in foil paper bags. Means followed by the same uppercase letter in the columns and lowercase letter in the rows do not differ by Scott-Knott's test at 5% probability.

The germination speed of seeds stored in liquid nitrogen, and cold room using paper package increased after four months of storage. The germination speed of seeds packaged in paper bags and stored in cold room increase up to eight months of storage, and up to twelve months for cryopreserved seeds (Figure 1A). Therefore, the cryopreservation of R. communis seeds enabled a long-term conservation. Similarly, Santos et al. (2016) evaluated the cryopreservation of R. communis seeds of the IAC-226 cultivar and found positive results for this treatment; and Almeida et al. (2010) evaluated cryopreserved seeds of R. communis and found a positive effect on the preservation of the quality of these seeds.

Figure 1 First germination count of Ricinus communis seeds of the IAC-80 cultivar evaluated at 0, 4, 8 and 12 months in different storage conditions (KPB = packed in multilayer Kraft paper bags; PEB = packed in polyethylene bags; PEBV = packed in polyethylene bags with vacuum at 0.1 atm; RC = room conditions at 25 °C; CR = cold room at 10 °C and relative humidity of 50%; CP = stored in liquid nitrogen - cryopreservation at -196 ºC in foil paper bags) (A); and first germination count of Ricinus communis seeds of the Guarani cultivar evaluated at 0, 4, 8 and 12 months of storage. 

The first germination count of Guarani seeds showed significant differences within the storage periods (Table 3). The seed germination percentage in the first count increased up to four months and remained constant up to eight months of storage. Decreases in the number of seedlings in the first germination count was only found at twelve months of storage, but with similar percentages to those found at the beginning of storage (Figure 1B).

Table 3 First germination count of Ricinus communis seeds of the Guarani cultivar at 0, 4, 8 and 12 months of storage. 

Evaluation time (months) Normal seedlings (%)
0 29.5 b
4 34.0 a
8 38.0 a
12 26.0 b
CV(%) 26.8

Means followed by the same letter do not differ by Scott-Knott's test at 5% probability.

The highest germination percentage was found for IAC-80 seeds stored in liquid nitrogen, and in cold room (Table 4). However, after eight months of storage, a lower germination percentage was found for seeds packaged in polyethylene bags, or polyethylene bags with vacuum and stored in the cold room, when compared to that of seeds in the other storage conditions. These results were similar at twelve months, with a decrease of up to 47 percentage points in the germination of seeds stored in the cold room when compared to the others. Cryopreservation was efficient in maintaining the physiological quality of IAC-80 seeds throughout the storage. Even after twelve months of storage, seeds preserved in liquid nitrogen presented germination rates higher than the minimum described by the Brazilian Ministry of Agriculture (Normative Instruction 45 of September 13, 2013) for commercial seeds-80% germination for R. communis seeds (BRASIL, 2013).

Table 4 Normal seedlings in the germination of Ricinus communis seeds of the IAC-80 and Guarani cultivars evaluated at 0, 4, 8 and 12 months in different storage conditions. 

Cultivar Evaluation time Storage conditions
RC-KPB RC-PEB RC-PEBV CR-KPB CR-PEB CR-PEBV CP
IAC-80 0 71.0Ab 74.5Ab 76.5Ab 82.0Aa 80.0Aa 80.0Aa 84.0Aa
4 75.0Ab 72.0Ab 75.0Ab 78.0Aa 66.0Bb 70.0Bb 85.0Aa
8 78.0Ab 66.0Bb 72.0Ab 73.5Ab 57.0Cc 63.0Bc 85.0Aa
12 51.5Bc 63.5Bc 69.5Ab 64.5Bb 44.0Dd 42.0Cd 85.0Aa
CV (%) 7.53
Guarani 0 68.5Ac 77.0Ab 66.0Ac 64.5Ac 75.5Ab 74.0Ab 89.0Aa
4 54.0Bb 50.0Bb 54.0Bb 51.5Bb 52.0Bb 52.5Bb 86.0Aa
8 49.0Bb 36.0Cc 47.0Cb 43.0Cb 35.0Cc 43.0Cb 87.0Aa
12 27.0Cc 31.0Cc 39.5Cb 36.5Cb 29.0Cc 23.0Dc 66.0Ba
CV (%) 11.79

Means followed by the same uppercase letter in the columns and lowercase letter in the rows do not differ by Scott-Knott's test at 5% probability.

The germination percentage of Guarani seeds stored in liquid nitrogen remained constant up to the eighth month of storage, but decreased after this period. The germination percentage of seeds stored in the other conditions decreased after the fourth month. Therefore, the cryopreservation provided better conditions for the conservation of R. communis seeds when compared to room, or cold room storage conditions.

The germination percentage of cryopreserved IAC-80 seeds remained constant throughout the storage period (Figure 2A). However, the germination percentage of IAC-80 seeds stored in the other conditions decreased with storage time. These results denote the effect of the storage condition on the preservation of viability of R. communis seeds, as reported by Santos et al. (2016), who evaluated the conservation of R. communis seeds in conventional, and cold room conditions for twelve months.

Figure 2 Normal seedlings in the germination of Ricinus communis seeds of the IAC-80 (A) and Guarani (B) cultivars evaluated at 0, 4, 8 and 12 months in different storage conditions (KPB = packed in multilayer Kraft paper bags; PEB = packed in polyethylene bags; PEBV = packed in polyethylene bags with vacuum at 0.1 atm; RC = room conditions at 25 °C; CR = cold room at 10 °C and relative humidity of 50%; CP = stored in liquid nitrogen - cryopreservation at -196 ºC in foil paper bags). 

The germination percentage of Guarani seeds decreased from the fourth month, regardless of the storage condition (Figure 2B). Despite this decrease, the highest percentage of normal seedlings were found for cryopreserved seeds when compared to that of seeds stored in the other conditions. The germination percentage of cryopreserved seeds increased at four months of storage when compared to the initial evaluation due to overcoming of dormancy. According to Rocha et al. (2009), cryogenic conservation increases the seed germination percentages and vigor because the low temperature promotes overcoming of dormancy. Despite the efficient of cryopreservation as a method to overcome tegument dormancy, there is no indication in the literature of using subzero temperatures as a method for overcoming dormancy of R. communis seeds.

Cryopreservation was more efficient in maintaining the physiological quality of IAC-80 seeds throughout the storage than the other conditions, confirming the results found in the germination test.

After twelve months of storage, the seeds stored in cold room in polyethylene bags with vacuum resulted in seedlings with lower emergence percentages when compared to those of seeds in the other storage conditions (Table 5). This confirms the action of oxygen restrictions and low temperatures in accelerating the deterioration process of R. communis seeds, reducing their longevity (SANTOS et al., 2016).

Table 5 Emergence of Ricinus communis seedlings of the IAC-80 and Guarani cultivars evaluated at 0, 4, 8 and 12 months in different storage conditions. 

Cultivar Evaluation time Storage conditions
RC-KPB RC-PEB RC-PEBV CR-KPB CR-PEB CR-PEBV CP
IAC-80 0 69.0Ac 74.0Ab 65.0Ac 67.0Ac 60.5Ad 67.0Ac 92.0Aa
4 63.0Bb 62.0Bb 58.5Bc 54.0Bc 58.5Ac 61.0Bb 91.0Aa
8 55.5Cb 52.0Cb 57.5Bb 45.0Cc 56.0Ab 53.5Cb 90.0Aa
12 49.0Dc 41.0Dd 54.0Bb 40.5Cd 56.0Ab 33.0De 85.0Ba
CV (%) 6.09
Guarani 0 49.5Ab 40.5Ac 41.0Ac 45.5Ab 45.5Ab 41.0Ac 86.0Aa
4 46.5Ab 33.5Bd 39.5Ac 40.5Ac 30.0Bd 31.0Bd 84.0Aa
8 43.5Ab 29.5Bd 37.0Ac 34.1Bc 22.0Cd 25.0Bd 80.5Aa
12 28.5Bb 29.5Bb 34.5Ab 23.5Cc 17.0Cd 11.0Cd 67.0Ba
CV (%) 10.61

KPB = packed in multilayer Kraft paper bags; PEB = packed in polyethylene bags; PEBV = packed in polyethylene bags with vacuum at 0.1 atm; RC = room conditions (25 °C); CR = cold room (10 °C and relative humidity of 50%); CP = stored in liquid nitrogen (cryopreservation at -196 ºC) in foil paper bags. Means followed by the same uppercase letter in the columns and lowercase letter in the rows do not differ by Scott-Knott's test at 5% probability.

The storage condition had a significant effect on the seedling emergence of Guarani seeds, with higher percentages for cryopreserved seeds throughout the twelve months of storage, confirming the results found in the germination test. The emergence percentage of cryopreserved seedlings was higher than those of seeds stored in the other conditions, confirming the effect of storage condition on the maintenance of R. communis seed quality. The emergence of seedlings from seeds packaged in polyethylene bags, and polyethylene bags with vacuum and stored in cold room was lower than those of seeds stored in the other conditions after twelve months of storage.

The emergence percentage of seedlings from IAC-80 seeds decreased with storage time. These decreases in emergence of seedlings from seeds stored in liquid nitrogen only occurred from the eighth month of storage, differing from the other treatments (Figure 3A). Seeds packaged in polyethylene bags with vacuum and stored in cold room had the greatest decrease in seedling emergence percentage after twelve months of storage.

Figure 3 Emergence of Ricinus communis seedlings of the IAC-80 (A) and Guarani (B) cultivars evaluated at 0, 4, 8 and 12 months in different storage conditions (KPB = packed in multilayer Kraft paper bags; PEB = packed in polyethylene bags; PEBV = packed in polyethylene bags with vacuum at 0.1 atm; RC = room conditions at 25 °C; CR = cold room at 10 °C and relative humidity of 50%; CP = stored in liquid nitrogen - cryopreservation at -196 ºC in foil paper bags). 

The emergence percentage of seedlings from the Guarani seeds decreased, regardless of the seed storage condition from the fourth month of storage, confirming the germination test (Figure 3B). The highest seedling emergence percentage was found for cryopreserved seeds.

IAC-80 seeds stored in liquid nitrogen presented higher emergency speed than those in the other storage conditions in all evaluations. The seeds stored in cold room in polyethylene bags with vacuum presented the worst performance after twelve months of storage (Table 6).

Table 6 Emergence speed index of Ricinus communis seeds of the IAC-80 cultivar evaluated at 0, 4, 8 and 12 months in different storage conditions. 

Cultivar Evaluation time Storage conditions
RC-KPB RC-PEB RC-PEBV CR-KPB CR-PEB CR-PEBV CP
IAC-80 0 2.61Ac 2.71Ac 3.23Ab 2.91Ac 3.33Ab 2.75Ac 4.95Aa
4 2.44Ad 2.46Ad 2.79Bc 2.83Ac 3.23Ab 2.57Ad 4.43Ba
8 2.31Bc 2.29Bc 2.52Bc 2.46Bc 3.08Ab 2.35Bc 4.07Ca
12 2.09Bb 1.95Cb 1.92Cb 1.90Cb 1.82Bb 0.96Cc 3.11Da
CV (%) 7.59

KPB = packed in multilayer Kraft paper bags; PEB = packed in polyethylene bags; PEBV = packed in polyethylene bags with vacuum at 0.1 atm; RC = room conditions (25 °C); CR = cold room (10 °C and relative humidity of 50%); CP = stored in liquid nitrogen (cryopreservation at -196 ºC) in foil paper bags. Means followed by the same uppercase letter in the columns and lowercase letter in the rows do not differ by Scott-Knott's test at 5% probability.

IAC-80 seeds stored in liquid nitrogen had the highest emergence speed (Figure 4A), but the overall emergence speed decreased with time of storage, even for cryopreserved seeds. These decreases are related to natural deterioration, which is an irreversible process that increases the time needed to obtain an adequate plant stand (ANTONELLO et al., 2009).

Figure 4 Emergency speed index of Ricinus communis seeds of the IAC-80 cultivar evaluated at 0, 4, 8 and 12 months in different storage conditions (KPB = packed in multilayer Kraft paper bags; PEB = packed in polyethylene bags; PEBV = packed in polyethylene bags with vacuum at 0.1 atm; RC = room conditions at 25 °C; CR = cold room at 10 °C and relative humidity of 50%; CP = stored in liquid nitrogen - cryopreservation at -196 ºC in foil paper bags) (A); and Emergency speed index of Ricinus communis seeds of the Guarani cultivar evaluated at 0, 4, 8 and 12 months of storage. 

The emergence speed index of Guarani seeds did not change due to the storage condition and time of storage, but there were isolated effects of these two variables. The emergence speed of Guarani seeds decreased with increasing storage time (Figure 4B), but it was due to natural deterioration.

The emergence speed index of Guarani seeds stored in liquid nitrogen was higher than those of seeds stored in the other conditions (Table 7). According to Antonello et al. (2009), although seed deterioration is an irreversible process, delaying its speed is possible by a correct and efficient management of environmental conditions during storage, which can increase the time that the seeds remain viable during the storage period.

Table 7 Emergence speed index of Ricinus communis seeds of the Guarani cultivar in different storage conditions. 

Storage conditions Emergence speed index
RC-KPB 1.88c
RC-PEB 1.63d
RC-PEBV 2.08b
CR-KPB 2.17b
CR-PEB 2.07b
CR-PEBV 1.55d
CP 2.85a
CV (%) 12.86

KPB = packed in multilayer Kraft paper bags; PEB = packed in polyethylene bags; PEBV = packed in polyethylene bags with vacuum at 0.1 atm; RC = room conditions at 25 °C; CR = cold room at 10 °C and relative humidity of 50%; CP = stored in liquid nitrogen - cryopreservation at -196 ºC in foil paper bags. Means followed by the same letter do not differ by Scott-Knott's test at 5% probability.

The oil content of the IAC-80, and Guarani seeds did not vary with storage times and storage conditions used, these two variables had only isolated effects. The seeds stored in liquid nitrogen presented lower oil content than those in the other storage conditions (Table 8). Since this difference was not dependent on the storage time, it is assumed that the cryopreservation conditions affected the oil extraction or contents in some way. Decreases in oil content of R. communis seeds with increasing storage time was found for both cultivars. The oil content of IAC-80 seeds decreased from the fourth month of storage, however, the oil content of Guarani seeds decreased in the first few months of storage (Figure 5). According to Koutroubas, Papakosta and Doitsinis (2000), the storage conditions of castor bean seeds affect significantly their oil content, especially temperature and relative humidity; and variations in the storage conditions cause degradation of the oil.

Table 8 Oil content of Ricinus communis seeds of the IAC-80 and Guarani cultivars in different storage conditions. 

Cultivar Storage conditions Oil content (%)
RC-KPB 38.08 b
RC-PEB 38.54 b
RC-PEBV 37.55 b
IAC-80 CR-KPB 39.24 b
CR-PEB 41.63 a
CR-PEBV 38.23 b
CP 31.33 c
CV (%) 5.41
RC-KPB 39.01 a
RC-PEB 38.34 a
RC-PEBV 38.64 a
Guarani CR-KPB 39.10 a
CR-PEB 38.53 a
CR-PEBV 38.86 a
CP 30.00 b
CV (%) 4.01

KPB = packed in multilayer Kraft paper bags; PEB = packed in polyethylene bags; PEBV = packed in polyethylene bags with vacuum at 0.1 atm; RC = room conditions at 25 °C; CR = cold room at 10 °C and relative humidity of 50%; CP = stored in liquid nitrogen - cryopreservation at -196 ºC in foil paper bags. Means followed by the same letter do not differ by Scott-Knott's test at 5% probability.

Figure 5 Oil content of Ricinus communis seeds of the IAC-80 (A) and Guarani (B) cultivars evaluated at 0, 4, 8 and 12 months of storage. 

Aspergilus spp. and Fusarium spp. were the fungi with the highest occurrence in the sanitary test of IAC-80 and Guarani seeds, regardless of the storage conditions.

Seeds of the IAC-80 cultivar had higher incidence of Aspergillus flavus (Table 9). A similar result was found by David et al. (2014) in R. communis seeds of the IAC-226 cultivar, which had high incidence of this fungus. According to Lima et al. (1997), Aspergillus flavus causes seed rot and affects the germination of castor bean seeds. The occurrence of these microorganisms is associated with the seed storage conditions (DAVID et al., 2014).

Table 9 Incidence of fungi found in Ricinus communis seeds of the IAC-80 cultivar evaluated at 0, 4, 8 and 12 months in different storage conditions. 

Evaluation time Storage conditions Fungi (%)
AF AO AN AC PE FU PH
0 RC-KPB 42 37 5 0 15 36 0
RC-PEB 58 38 8 0 13 37 0
RC-PEBV 54 38 5 0 14 26 0
CR-KPB 57 37 4 0 10 36 1
CR-PEB 56 52 9 0 18 35 0
CR-PEBV 58 36 8 0 11 33 0
CP 49 10 6 0 14 48 0
4 RC-KPB 51 41 8 0 17 29 0
RC-PEB 52 37 10 0 15 31 0
RC-PEBV 58 35 9 0 16 34 2
CR-KPB 61 35 7 0 14 30 0
CR-PEB 53 39 11 0 18 26 1
CR-PEBV 63 41 13 0 19 29 0
CP 51 29 12 0 14 35 0
8 RC-KPB 48 42 20 0 16 31 0
RC-PEB 53 41 18 0 18 30 0
RC-PEBV 61 38 18 0 17 24 2
CR-KPB 62 34 15 0 15 29 0
CR-PEB 60 37 14 1 14 24 0
CR-PEBV 64 45 17 0 19 21 1
CP 53 34 17 0 15 32 0
12 RC-KPB 58 45 22 0 16 26 0
RC-PEB 62 49 19 1 14 24 0
RC-PEBV 61 44 23 3 17 27 0
CR-KPB 59 42 18 2 18 22 0
CR-PEB 54 46 16 0 12 20 0
CR-PEBV 53 44 17 1 16 23 0
CP 52 41 19 2 15 25 0

KPB = packed in multilayer Kraft paper bags; PEB = packed in polyethylene bags; PEBV = packed in polyethylene bags with vacuum at 0.1 atm; RC = room conditions at 25 °C; CR = cold room at 10 °C and relative humidity of 50%; CP = stored in liquid nitrogen - cryopreservation at -196 ºC in foil paper bags. AF = Aspergillus flavus; AO = Aspergillus ochraceus; AN = Aspergillus niger; AC = Aspergillus candidus; PE = Penicillium spp.; FU = Fusarium spp; PH = Phoma spp.

Guarani seeds (Table 10) had increases in storage fungi with storage time, and a high incidence of Fusarium oxysporum f. sp. ricini in all seeds, regardless of storage conditions. The high incidence of this fungus in the Guarani seeds is associated with decreases in germination percentage throughout storage.

Table 10 Incidence of fungi found in Ricinus communis seeds of the Guarani cultivar evaluated at 0, 4, 8 and 12 months in different storage conditions. 

Evaluation time Storage conditions Fungi (%)
AF AO AN AC PE FU PH
0 RC-KPB 36 45 5 0 16 65 0
RC-PEB 37 49 8 0 18 63 6
RC-PEBV 26 44 5 0 17 62 0
CR-KPB 36 42 4 0 15 68 4
CR-PEB 35 46 9 0 14 65 0
CR-PEBV 33 44 8 0 19 62 3
CP 48 41 6 0 15 63 0
4 RC-KPB 29 43 5 0 20 71 0
RC-PEB 31 42 8 0 19 74 3
RC-PEBV 34 40 5 0 21 73 1
CR-KPB 30 47 4 1 17 76 0
CR-PEB 26 46 9 0 18 71 0
CR-PEBV 29 45 8 1 20 78 3
CP 35 42 6 0 17 72 0
8 RC-KPB 31 51 11 0 22 78 0
RC-PEB 30 50 10 7 21 76 0
RC-PEBV 24 49 15 3 24 82 5
CR-KPB 29 47 14 0 27 90 0
CR-PEB 24 45 11 4 25 83 4
CR-PEBV 21 46 9 2 29 75 0
CP 32 44 8 0 22 74 0
12 RC-KPB 26 53 15 0 27 92 0
RC-PEB 24 50 19 6 28 89 0
RC-PEBV 27 58 14 3 31 86 0
CR-KPB 22 61 16 8 29 91 0
CR-PEB 20 54 14 0 30 90 0
CR-PEBV 23 51 12 5 26 85 0
CP 25 46 14 3 28 87 0

KPB = packed in multilayer Kraft paper bags; PEB = packed in polyethylene bags; PEBV = packed in polyethylene bags with vacuum at 0.1 atm; RC = room conditions at 25 °C; CR = cold room at 10 °C and relative humidity of 50%; CP = stored in liquid nitrogen - cryopreservation at -196 ºC in foil paper bags. AF = Aspergillus flavus; AO = Aspergillus ochraceus; AN = Aspergillus niger; AC = Aspergillus candidus; PE = Penicillium spp.; FU = Fusarium spp; PH = Phoma spp.

CONCLUSIONS

The storage conditions affect the physiological quality of R. communis seeds of the IAC-80 and Guarani cultivars. Cryopreservation (-196 °C) is the ideal condition for maintaining the physiological quality of R. communis seeds of the IAC-80 cultivar for twelve months, and seeds of the Guarani cultivar for eight months of storage.

The oil content of R. communis seeds decreases and the incidence of Aspergillus spp. and Fusarium spp. fungi increases throughout storage, regardless of the seed storage condition.

ACKNOWLEDGEMENTS

The authors thank the Brazilian Coordination for the Improvement of Higher Education Personnel (Capes) and the Brazilian Council for Scientific and Technological Development (CNPq) for granting scholarships and for the financial support for the development of this research.

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1Paper extracted from masters dissertation of the first author.

Received: March 16, 2018; Accepted: August 23, 2018

*Corresponding author: camilalopes_sjc@hotmail.com.

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