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Revista mexicana de ciencias agrícolas

versión impresa ISSN 2007-0934

Rev. Mex. Cienc. Agríc vol.8 no.3 Texcoco abr./may. 2017

https://doi.org/10.29312/remexca.v8i3.43 

Investigation notes

Accelerated aging and vigor of Brachiaria brizantha cv Insurgente grass seeds

Edgar Hernández Flores1 

Bertín Maurilio Joaquín Torres2 

Adrián Raymundo Quero Carrillo1  §  

Alfonso Hernández Garay1 

Filogonio Jesús Hernández Guzmán1 

1Ganadería-Campus Montecillo, Colegio de Postgraduados en Ciencias Agrícolas. Carretera México-Texcoco, km 36.5. Montecillo, Texcoco, Estado de México. CP. 56230. Tel. (595) 9520200, ext. 75051, Fax. (595) 9520279. (edgar@colpos.mx; hernan@colpos.mx; fjesushg@hotmail.com).

2Universidad del Papaloapan. Av. Ferrocarril s/n, Cd. Universitaria, Loma Bonita, Oaxaca, México. CP. 68400. Tel. (281) 8729230, ext. 110. (bmaurilio@hotmail.com).


Abstract

With the objective of evaluating seed vigor tests of Brachiaria brizantha cv. Insurgente, two seeds lots with different initial physical and physiological quality, harvested on September 28th (lot 1, autumn) and December 21th (lot 2, winter) of the same year, were subjected to six temperatures (40, 41, 42, 43, 44 and 45 °C) and seven aging periods (24, 36, 48, 60, 72, 84 and 96 h) at 100% HR. A completely randomized design was used, with factorial arrangement and four replications. Seed vigor varied between temperatures (p< 0.001). The Autumn harvest (lot 1) showed a higher germination value (28.9%) at 40 ºC; similar value (p> 0.05), at 41 ºC (24.7%); but different and superior to the other levels (p< 0.05). For the seeds harvested in winter (lot 2), the highest germination value (50%) was obtained at 40 °C. The aging period had an effect on seeds vigor (p< 0.001). For the autumn seeds, the highest germination value (40.6%) was obtained at 48 h, similar value (p> 0.05) to that obtained at 36 h (34.7%), but different and superior to the other periods; while for lot 2 (winter harvest), the highest value (63%) was obtained at 60 h. The interaction was significant between lots (p< 0.001); in lot 1, the highest germination occurred at 40 ºC/48 h and 40 ºC/60 h, with values of 46 and 47%, respectively; while for lot 2 (winter harvest), the highest value (69.2%) was obtained at 40 °C/60 h. The accelerated aging test detected differences between seeds lots of B. brizantha cv Insurgente and the combination 40 ºC/48 h and 40 ºC/60 h were the most effective treatments to evaluate the vigor between seed lots. Seeds harvested in winter showed greater vigor and consistent germination.

Keywords: Brachiaria brizantha; accelerated aging test; germination; insurgent grass; vigor

Resumen

Con el objetivo de evaluar pruebas de vigor en semilla de Brachiaria brizantha cv. Insurgente, dos lotes de semilla, con diferente calidad física y fisiológica inicial, cosechados el 28 de septiembre (lote 1; otoño) y 21 de diciembre (lote 2; invierno) del mismo año, se sometieron a seis temperaturas (40, 41, 42, 43, 44 y 45 ºC) y siete periodos (24, 36, 48, 60, 72, 84 y 96 h) de envejecimiento, a 100% de HR. Se utilizó un diseño completamente al azar, con arreglo factorial y cuatro repeticiones. El vigor de semilla varió entre temperaturas (p< 0.001). La cosecha de Otoño (lote 1) mostró un mayor valor de germinación (28.9%) a 40 ºC; valor similar (p> 0.05), al de 41 ºC (24.7%); pero, diferente y superior a los demás niveles (p< 0.05). Para la semilla cosechada en invierno (lote 2), el mayor valor germinación (50%), se obtuvo a 40 ºC. El periodo de envejecimiento tuvo efecto en el vigor de semilla (p< 0.001). Para la semilla de otoño, el mayor valor de germinación (40.6%) se obtuvo a 48 h, valor similar (p> 0.05) al obtenido a 36 h (34.7%), pero diferente y superior a los demás periodos; mientras que, para el lote 2 (cosecha de invierno), el valor mayor (63%) se obtuvo a 60 h. La interacción fue significativa entre lotes (p< 0.001); en el lote 1, la mayor germinación se presentó a 40 ºC/48 h y 40 ºC/60 h, con valores de 46 y 47%, respectivamente; mientras que, para el lote 2 (cosecha de invierno), el mayor valor (69.2%) se obtuvo a 40 ºC/60 h. La prueba de envejecimiento acelerado detectó diferencias entre lotes de semilla de B. brizantha cv Insurgente y la combinación 40 ºC/48 h y 40 ºC /60 h fueron los tratamientos más efectivos para evaluar el vigor entre lotes de semillas. La semilla cosechada en invierno mostró mayor vigor y germinación de forma consistente.

Palabras clave: Brachiaria brizantha; germinación; pasto insurgente; prueba de envejecimiento acelerado; vigor

Introduction

Brachiaria brizantha (Hochst. Ex A. Rich.) Stapf, is a perennial plant native to tropical Africa belonging to the gramineae family, introduced to Mexico under the name of Insurgente, being widely used by farmers in tropical areas. The physiological quality of the seed is related to its ability to emerge under field conditions (Bhering et al., 2003). In this regard, the germination test is the most widely used and accepted procedure; however, it is not the most adequate to guarantee seed establishment in the field (Copeland and McDonald, 2001), because it is carried out under controlled conditions of humidity, temperature and substrate (Stanisavljevic et al., 2013).

In a test of vigor, the objective is to differentiate those lots that despite having a similar viability, show different capacity to germinate and to emerge. In this test, the seeds are exposed to high temperature conditions (41 to 45 ºC) and 100% relative humidity for a specific period (Carambula, 1984). Therefore, in the present paper, different levels of temperature and accelerated aging were used to evaluate the vigor of Insurgente grass seeds. The research was carried out in the Laboratory of Seed Analysis of the Institute of Genetic Resources and Productivity (IREGEP) of the Colegio de Postgraduados, Montecillo Campus, Estado de Mexico.

Two seed lots of B. brizantha cv. Insurgente, harvested on September 28th (lot 1, autumn) and December 21th (lot 2, winter) of 2007, in the Experimental Field of the University of Papaloapan, in Loma Bonita, Oaxaca. The obtained seeds were packed in Kraft paper bags and stored under laboratory ambient conditions for six months. At the beginning of the experiment, the values of physical purity, weight of 1 000 seeds, viability by the tetrazolium test and percentage of germination were obtained (Table 1).

Table 1 Initial physical and physiological quality of two seeds lots of Brachiaria brizantha cv Insurgente, used in accelerated aging treatments. 

In both seeds lots, six temperatures (40, 41, 42, 43, 44 and 45 °C) and seven exposure periods (24, 36, 48, 60, 72, 84 and 96 h) were evaluated. Accelerated aging was performed using the “Gerbox” method described by Perry (1980), placing 200 seeds per treatment on a stainless steel mesh inside a plastic box, to which 100 ml of distilled water were added, covered and placed inside a drying oven at the temperatures and aging periods previously indicated. After the aging period, the germination percentage was evaluated through a standard twinning test, where the seeds were placed in sandwich boxes of 14*14*5.5 cm, provided with a lid and absorbent paper inside a germinating chamber at constant temperature of 25 °C and relative humidity of 100%, counting the number of normal plants for 21 days (ISTA, 2005). A completely randomized experimental design was used in a 6*7 factorial arrangement (six temperatures and seven periods of aging). The comparison of means of the treatments was carried out by the Tukey test, with a level of significance of 5% (SAS, 1998).

Table 1 shows that the physical quality in terms of pure seed, weight of 1 000 seeds, viability and germination was higher in lot 2 (winter harvest) compared to lot 1 (fall harvest). The data in Table 1 were not analyzed statistically, serving only for the characterization of the seed lots quality.

In both lots, the germination percentage varied between the evaluated temperatures (p< 0.001; Table 2). Seeds harvested in autumn (lot 1) showed the highest germination value (28.9%) with a temperature of 40 ºC, similar (p> 0.05) to that obtained with 41 ºC (24.7%), being different and superior to the other temperature levels (p< 0.05). A similar behavior was observed for seeds harvested in winter (lot 2), where the highest germination values (50.1 and 46.9%) were obtained with the levels of 40 and 41 °C, respectively.

Table 2 Germination percentage of two seed lots of Brachiaria brizantha cv Insurgente, at different temperature levels. 

abcd= literales diferentes en cada columna, indican diferencia significativa (p< 0.05).

Temperatures of 40 and 41 ºC were the best estimates of seed vigor behavior. The decrease of germination as temperature increases is attributed to the acceleration and affect of the physiological processes of the seed, increasing its deterioration and reducing the processes of respiration and biosynthesis (Stanisavljevic et al., 2013). It is also observed that lot 2 showed, on average, 74% higher germination compared to that harvested in autumn (lot 1), due to the low percentage of pure seed, viability and germination of lot 1 because it was harvested at a lower physiological maturity. As regards the periods of accelerated aging, a significant effect (p< 0.001; Table 3) was found in germination percentages. In lot 1, it is observed that at 48 h, 40.6% of germination is obtained, a similar value (p> 0.05) at 36 h (34.7%), but different (p< 0.05) and higher than the values obtained in other periods. In lot 2, the highest germination was obtained at 60 h, with a value of 63%.

Table 3 Percentage of germination of two seed lots of Brachiaria brizantha cv Insurgente, to different periods of accelerated aging. 

abcde= literales diferentes en cada columna, indican diferencia significativa (p< 0.05).

The results indicate that the accelerated aging periods of 36 and 48 h are adequate to differentiate low quality seed lots; while for high quality lots, 60 h are enough to evaluate seed vigor. Lot 2 showed on average 58% higher germination compared to lot 1.

Finally, in terms of interactions between temperatures and aging periods, significant differences were found (p< 0.001, Table 4). In lot 1 (Autumn harvest), the highest germination values were at 40 ºC/48 h and 40 ºC/60 h, with accelerated aging, with values of 46 and 47%, respectively. In lot 2 (Winter harvest), it was found that at all temperature levels, the highest germination values were recorded at 60 h of aging; being the highest value (69.2%) at 40 ºC/60 h of accelerated aging. In lot 1 (Autumn harvest), the highest germination values were shown at 40 ºC/48 h and 40 ºC/60 h of accelerated aging exposure, with germination values of 46 and 47%, respectively.

Table 4 Percentage of germination of two seed lots of Brachiaria brizantha cv Insurgente at different temperature levels and periods of accelerated aging. 

Literales diferentes por columna, indican diferencia (p< 0.05).

In lot 2 (winter harvest), it was found that at all temperature levels, the highest germination values were recorded at 60 h of aging; however, the highest value (69.2%) was obtained at 40 °C/60 h of accelerated aging exposure.

The results indicate that in order to evaluate the vigor of seed lots of low quality, it is possible to use 40 ºC/48 h of aging; while for high quality batches 40 °C/60 h accelerated aging is required. Other studies have reported that temperature of 43 °C for 48 h, with 100% relative humidity is the best accelerated aging process to differentiate seed lots (Fernandes et al., 2004). Also in B. brizanthaMeschede et al. (2004), recommended 43 ºC/48 h of accelerated aging for medium high quality batches and 43 ºC/12 to 36 h of aging for low quality batches, concluding that the temperature and the period of seed exposure vary between species and lots of seeds.

Conclusions

The accelerated aging test detected differences between the seeds lots evaluated. The seeds harvested in winter were superior in physiological quality and vigor compared to Lot 1, harvested in autumn. The best combinations of temperature and the accelerated aging period to evaluate the seeds vigor of B. brizantha cv. Insurgent was 40-41 °C/48 h for low quality batches and 40-41 °C/60 h accelerated aging for superior quality batches.

Literatura citada

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Received: March 2017; Accepted: April 2017

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