Selecting the most appropriate vigor test for rice to predict seedling emergence remains a challenge. This is mainly attributed to the diversity of available tests that evaluate vigor; however, there is a critical need for tests that can show a high correlation with field emergence. Thus, this study aimed to determine which vigor tests are the most efficient in predicting the emergence of rice seedlings, to facilitate correct selection for quality control analyses and pre-sowing for rice seed commercialization. Across two growing seasons, 2016/17 and 2017/18, different seed lots of ‘SCS122 Miura’ rice were subjected to vigor evaluations including germination test, electrical conductivity, cold test, low temperature germination, accelerated aging, root and shoot length, seedling dry weight, emergence speed, and emergence speed index, and greenhouse and field emergence tests. A completely randomized design with four replicates was used for the experiments. All statistical analyses were performed using R software. The germination rate for ‘SCS122 Miura’ seed lots in both growing seasons was greater than 80%. In both growing seasons, unlike the similar results obtained for field emergence, in the laboratory tests, differences were observed between these same seed lots. Electrical conductivity and emergence speed showed a negative correlation with greenhouse and field emergence. The vigor tests for accelerated aging, emergence speed, and dry weight are more efficient in predicting the emergence of rice seedlings. Among the tested methods, accelerated aging (41 °C for 120 h) is one of the most efficient for predicting the emergence of rice seedlings and the best option for laboratory analysis of quality control and pre-sowing owing to its practicality and time required for execution.
After physiological maturity, the seed is physiologically independent of the plant, and responds to climatic variations that can decrease its vigor, which is dependent on the cultivar. The objective of this work was to evaluate the vigor of soybean cultivars and identify the biochemical components that have the greatest contribution to the maintenance of the physiological quality of the seeds after physiological maturity. The experiment was conducted in Fraiburgo, SC, Brazil, during the 2015/2016 crop season, using four soybean cultivars NA 5909 RG, BMX Ativa RR, BMX VanguardaIPRO, and NS 5959 IPRO. The seed physiological quality and the biochemical composition were evaluated at the phenological stages R7, R7+5 days, R7+10 days (R8), and R7+20 days. The data were subjected to analysis of variance (F test) and the means were compared by the Tukey's test (p<0.01). The seed biochemical composition and physiological quality were correlated using multivariate statistics. The germination of the seeds decreased 6% after physiological maturity up to R7+20 days. This decrease in vigor was dependent on the cultivar; NA 5909 RG decreased 3%, and BMX Ativa RR and NS 5959 IPRO decreased 7%. The biochemical components soluble protein, phytate, soluble sugar, and lipids decreased as a function of the harvest times, indicating the beginning of the process of seed quality loss. The maintenance of seed vigor after physiological maturity was dependent on the cultivar. The soluble protein content can be used as an indicator of the maintenance of physiological quality of soybean seeds after R7.
O arroz é uma das espécies que apresenta dormência após a colheita, podendo esta ser prolongada durante o armazenamento das sementes. Este trabalho teve por objetivo determinar se o ácido giberélico (GA3) é um promotor eficiente da superação de dormência em sementes de arroz e avaliar mudanças nas estruturas biológicas via histoquímica. A cultivar utilizada foi a SCS122 Miura submetida a 0 mg L-1, 500 mg L-1 e 1000 mg L-1 de GA3. Foram realizadas análises de germinação, viabilidade, comprimento de raiz, parte aérea e plântula, microscopia óptica do amido e quantificação dos açúcares solúveis totais. A utilização de 500 mg L-1 e 1000 mg L-1 de GA3 foi eficiente para a superação da dormência de sementes de arroz, reduzindo o percentual de sementes dormentes para 4% e 1% respectivamente. Apesar de reduzir o percentual dormência, a presença de GA3 provoca aumento do percentual de plântulas anormais, e por isso, nas concentrações utilizadas, não pode ser recomendado como método de superação em sementes de arroz. A microscopia óptica é eficiente para verificar que com a superação de dormência, ocorre a degradação dos grânulos de amido, aumentando a disponibilidade de açúcares solúveis totais para o crescimento e desenvolvimento de plântulas.
The fungus Microdochium albescens is one of the main pathogens associated with irrigated rice seeds in southern Brazil. The objective of the present study was to quantify the transmission of M. albescens from naturally infected seeds to the crown, coleoptile, and first true leaf of the seedlings of six cultivars growing in pre-germinated cultivation system of irrigated rice. Seeding was carried out on a water-saturated substrate, using four untreated seed lots for each of the six cultivars. At 14 days after sowing, the crown, coleoptile, and first true leaf of the seedlings were carefully highlighted, and the samples were disinfected and plated onto potato-sucrose-agar culture medium. M. albescens was transmitted asymptomatically to crown, coleoptile, and first true leaf, at rates of 39.3%, 25.8%, and 5.4%, respectively (these values represent the average incidence of the six cultivars). This is the first report that proves that M. albescens is transmitted from infected seeds to irrigated rice seedlings in a pre-germinated seed system.
O GRAU DE UMIDADE NA COLHEITA E O SISTEMA DE SECAGEM SÃO DETERMINANTES PARA O VIGOR DE SEMENTES DE ARROZ JAQUELINI GARCIA1, CILEIDE MARIA MEDEIROS COELHO1 1Programa de Pós-graduação em Produção vegetal, Universidade do Estado de Santa Catarina, Avenida Luiz de Camões, 2090, Conta Dinheiro, 88520-000, Lages, SC, Brasil, jaquelini.garcia@hotmail.com, cileide.souza@udesc.br RESUMO: O grau de umidade na colheita e o sistema de secagem podem ser determinantes na qualidade das sementes produzidas. Neste trabalho foi avaliado se o sistema de secagem e o grau de umidade na colheita interferem na qualidade fisiológica das sementes de arroz. Foi realizado em delineamento inteiramente casualizado em esquema fatorial triplo. Foi utilizada seis cultivares produzidas no Alto Vale do Itajaí/SC na safra 2016/17 com grau de umidade na colheita igual ou superior a 17% (19,30 - 17,30%) e inferior a 17% (16,40 - 15,03%) (base úmida). As sementes foram submetidas aos sistemas de secagem estacionário e intermitente. Realizou-se testes de germinação, viabilidade, vigor pelo envelhecimento acelerado e frio. Sementes colhidas com grau de umidade ≥ 17% apresentaram maior vigor. A cultivar foi um fator de grande relevância na sensibilidade ao dano térmico e mecânico. O sistema de secagem não afetou a viabilidade das sementes, com exceção da cultivar SCS122 Miura que foi sensível a dano térmico e mecânico. A secagem estacionária comprometeu a qualidade fisiológica. Conclui-se que a secagem intermitente e a colheita com grau de umidade igual ou superior a 17%, mantém a qualidade fisiológica das cultivares SCSBRS Tio Taka, SCS122 Miura, SCS116 Satoru e SCS121 CL. Palavras-chaves: Secagem estacionária, secagem intermitente, qualidade fisiológica. THE DEGREE OF MOISTURE IN THE HARVEST AND THE DRYING SYSTEM ARE DETERMINANT FOR THE RICE SEED VIGOR ABSTRACT: The degree of moisture at harvest and the drying system can determine the quality of the seeds produced. In this work, it was evaluated whether the drying system and the degree of moisture at harvest affect the physiological quality of rice seeds. It was conducted in a completely randomized design in a triple factorial scheme. Six cultivars produced in Alto Vale do Itajaí/SC in the 2016/17 crop were used, with moisture content at harvest equal or greater than 17% (19.30 – 17.30%) and less than 17% (16,40 - 15,03%) (wet basis). Seeds were submitted to stationary and intermittent drying systems. Tests of germination, viability, vigor by accelerated aging and cold were performed. Seeds harvested with moisture content ≥ 17% showed greater vigor. The cultivar was a factor of great relevance in the sensitivity to thermal and mechanical damage. The drying system did not affect seed viability, except for the cultivar SCS122 Miura, which was sensitive to thermal and mechanical damage. Stationary drying compromised physiological quality. It was concluded that intermittent drying and harvesting with moisture content equal or greater than 17% maintain the physiological quality of the SCSBRS Tio Taka, SCS122 Miura, SCS116 Satoru and SCS121 CL cultivars. Keywords: Stationary drying, intermittent drying, physiological quality.
Knowledge of the effect of the seedborne inoculum is important for knowing the level of tolerance of the pathogen by the seed. This research evaluated the effect of the incidence of the fungus Microdochium albescens on the physiological quality of the seeds of different cultivars of irrigated rice. The study was carried out in the seed testing laboratory (STL), phytopathology laboratory and in greenhouse, located at the Center of Agroveterinary Sciences of the Santa Catarina State University, Lages, SC, Brazil. Seeds from six irrigated rice cultivars produced in the Alto Vale do Itajaí Region in the 2016/17 harvest, were used. The lots were submitted to the seed health test, identifying four lots per cultivar with a natural incidence of M. albescens, with two lots of each cultivar with an incidence greater than 40% and two lots equal or less than 40%, totaling 24 seed lots. The following evaluations were carried out on the lots: germination, accelerated aging test, emergence in a greenhouse at 14 days, emergence speed index (ESI), emergence speed (ES), shoot length, root length and fresh and dry mass. There was a significant interaction between cultivar and level of incidence only in the variables germination, vigor and root length. Fresh mass, shoot length and ESI were not affected, regardless of cultivar and incidence of fungus in the seed. The irrigated rice cultivars SCS118 Marquês and SCSBRS Tio Taka are susceptible to a high incidence (> 40%) of the fungus M. allbescens.
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