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INTRODUCTION
The seed is the effective vehicle through which plant breeding achievements are transferred from the research field to the farmer's field. Varieties become important agricultural inputs when the corresponding seed is genetically genuine, physiologically viable and mechanically pure (Ortiz-Aragón & Larios-González, 2020).
Modern agriculture demands high quality seed, this being the main input that must be met, among these are: genetic, physiological, physical and sanitary quality (Rojas et al., 2010). All of this refers to intrinsic mechanisms of the fruit that determine its ability to emerge and the development of those structures essential to produce a normal seedling under favorable conditions.
The result of the germination test is expressed as a percentage per number of normal and abnormal seedlings (Estrada-Zúniga, 2013; Flores de la Cruz et al., 2018; Acuña et al., 2019).
Seeds that germinate quickly and uniformly, generating healthy plants and reaching levels greater than 90% of total germination, can be considered high quality seeds, both for domestic consumption and for marketing according to Garay-Ayala et al. (2008); Romero-Pintor et al. (2020); Santana-Baños et al. (2021).
MATERIALS AND METHODS
The black bean (Phaseolus vulgaris L.) grains, variety BAT 304, used in this study were obtained from the "El Guayabal" University Farm, belonging to the Agrarian University of Havana (UNAH), which is located at 23 °00'12.5" North latitude, and 82°09'57.9" West longitude in the municipality of San José de Las Lajas, Mayabeque province, Cuba. The existing soil is classified as Typical Red Ferralitic according to Hernández et al. (2015) in its entirety. It has a flat relief, height above sea level of 120 m and annual sunshine of 1825kWh/m2. The meteorological variables recorded during the period 2015-2022 at the Tapaste Meteorological Station showed that the maximum temperatures reached in the region exceeded 26 ºC between the months of June to September and the coldest temperatures fell on average to 20.76 ºC in January. . Precipitation showed increases starting in May, and indicated the highest average values in June and August with 255.50 and 245.16 mm, respectively. The relative humidity varied between 72.8% (minimum, in March) and 84.6% (maximum, in December), while the wind speed expressed its maximum limit of 5.46 km/h during the month of February. (Figure 1).
The germination potential was carried out in the Quality laboratory at the “Agrarian University of Havana” for this, 100 black bean seeds (Phaseolus Vulgaris L.) variety BAT 304 were selected, taken at random, and placed on a cardboard base with substrate ( in this case cotton) moistened with water. (Figure 2)
The experiment was carried out under controlled conditions of temperature and humidity, protected from the sun, rain and strong winds, and periodic irrigation of the seeds was carried out according to the need. Among the seedlings that emerged, the normal ones are differentiated from the abnormal ones to know the germination percentage. This procedure is repeated from the 2nd to the fourth day after setting up the experiment.
The germination process can be divided into several events:
(1) Imbibition: The physical process of water absorption.
(2) Activation: The start-up of the synthesis and degradation machinery.
(3) Cell division and elongation.
(4) Rupture of the seed coat by the embryo.
(5) Establishment of the seedling as an autonomous entity.
It is necessary to carry out a final germination count at 7, 8 or 10 days, depending on the species, to determine the percentage, counting normal (PN), abnormal (PA) seedlings and ungerminated seeds (SSG) (Figure 3).
Those that met the following requirements were considered normal seedlings:
Well developed root system, primary root and seminal roots.
Hypocotyl with good development without tissue damage.
Plumule with good growth, with well-developed leaves.
One cotyledon in monocotyledons and two cotyledons in dicotyledons.
Seedlings with the following defects are classified as abnormal:
Damaged primary root, without development and/or emergence, with little vigor without passing through the seed coat, with negative geotropism, without secondary roots.
Bud (hypocotyl, epicotyl, mesocotyl) without development, widened, twisted or without emergence.
Cotyledons and leaves deformed, necrotic or damaged by infections.
Ungerminated seeds: they did not germinate at the end of the test period. The classification is as follows:
Hard: seeds that remain hard at the end of the analysis period, because they did not absorb water. Seed hardness is a form of dormancy. It is common in many species of Fabaceae, but can also occur in other families.
Fresh: seeds (other than hard seeds) that have failed to germinate under the conditions of the germination test due to dormancy, but remain clean and firm and can develop into a normal seedling. They can absorb water under the conditions established in the ISTA standards, but the germination process is obstructed.
Dead: seeds that are not hard or fresh and have not produced any part of a seedling at the end of the testing period. Dead seeds absorb water, are usually soft or discolored, and often have molds. They give no signs of seedling formation.
To analyze the growth of the seedlings on each day mentioned above, their elongation is obtained using those less than 5 mm as a classification scale; between 5 and 9.9 mm; between 10 and 14.9 mm; between 15 and 19.9; between 20 and 24.9 mm; and between 25 and 29.9 mm, measurements are made using a conventional, flexible 1-150 mm measuring tape, three times on each seedling to obtain the average seed stem length.
The germination percentage is expressed as follows:
Those that germinate quickly and uniformly, generating healthy seedlings and reaching levels greater than 90% of total germination, can be considered high quality seeds, according to Garay-Ayala et al. (2008); Rojas et al. (2010); Ramírez y Suris, (2015); Romero-Pintor et al. (2020).
To determine germination in the field, the experiment was carried out on a farm of the Tapaste Popular Council located in the municipality of San José de las Lajas. The crop to be investigated was the black bean (Phaseolus vulgaris L.) variety BAT 304; in non-optimal sowing period. The preparation of the experimental area was done using animal traction. On a sialitic brown soil, the furrow was drawn with 4 furrows of 25 seeds. (Figure 4).
The distance between furrows was 50 cm with a depth of no more than 2 cm. They are watered daily with 20 to 25 ml of drinking water for each plant and on the fourth day the germination process should begin. Two experimental samplings were carried out to collect the information, the first four days after sowing, the second at 9 and fourteen days according to the Technical Manual “Seeds in Emergency” of the (FAO (2011) and Minagri-Cuba (2000).
RESULTS AND DISCUSSION
Germinative index of black bean (Phaseolus vulgaris L., var. BAT 304) in the laboratory.
Table 1 and Figure 5 show the values corresponding to the growth of the seedlings per day for those that underwent the germination test in the laboratory. These values show the growth of the bean per day, which shows that on the second day, of the 100 seeds that underwent the germination experiment, 8 of them were the most vigorous, which measured between the values of 20 and 24.9 mm. On the third day, the most vigorous were 8 seedlings with values between 25 and 29.9 mm. On the fourth day, 6 seedlings were the most vigorous with values less than 30 mm.
TABLE 1 Growth of seedlings for days in the laboratory
| STEM ELONGATION | |||
|---|---|---|---|
| 2nd day | 3rd day | 4th day | |
| < 5 mm | 18 | 14 | 8 |
| 5 -9,9 mm | 21 | 14 | 10 |
| 10 - 14,9 mm | 16 | 13 | 16 |
| 15 - 19,9 mm | 10 | 8 | 19 |
| 20 - 24,9 mm | 8 | 7 | 20 |
| 25 -29,9 mm | 8 | 15 | |
| > 30 mm | 6 | ||
In (Figures 6 A, B and C) the germination index is evident in percentage per day, in Figure 6 A only 1% of the plants showed a change in color, 45% of the beans were born and 54% represent the born beans , there was no sample of shelled beans.
In Figure 6 B, 3% changed color and were beans without shells, 14% represent those that were not born and 80% of them were born with good vitality.
In Figure 6 C, 2% of the beans change color, 3% are unshelled, 6% are unborn, and 89% of the beans are born. All this shows that the biological natures of seeds are good for giving rise to healthy and vigorous plants.
The result of the germination index of the seeds is shown in (Figure 7) the values obtained per day demonstrate that the seeds selected for the germination test in the laboratory, the fourth day was 94%, it can be demonstrated that the selected seed for the germination test in the laboratory it is of high quality since it reaches levels greater than 90% according Garay-Ayala et al. (2008); Peña-Calzada et al. (2017); Kangue y Boicet-Fabre (2020).
Germinative index of black bean (Phaseolus vulgaris L., var. BAT 304) in the field
Table 2 shows the values per day of the growth of the bean seedlings, the sampling was carried out on the fourth day, where 100 seeds that were subjected to the germination experiment, only 3 of them were the most vigorous, which measured between the values of 20 and 24.9 mm. On the ninth day, the most vigorous were 10 seedlings with values between 25 and 29.9 mm. On the fourteenth day, 9 seedlings were the most vigorous with values less than 30 mm.
TABLE 2 Growth of seedlings per day in the field
| STEM ELONGATION | |||
|---|---|---|---|
| 4th day | 9th day | 14 day | |
| < 5 mm | 16 | 15 | 11 |
| 5 -9,9 mm | 18 | 14 | 12 |
| 10 - 14,9 mm | 14 | 13 | 10 |
| 15 - 19,9 mm | 12 | 10 | 14 |
| 20 - 24,9 mm | 3 | 23 | 25 |
| 25 -29,9 mm | 10 | 13 | |
| > 30 mm | 9 | ||
The result of the germination index of the seeds is shown in (figure 8) the values obtained per day demonstrate that the seeds selected for the germination test in the field, the fourteenth day was 95%, it can be demonstrated that the seeds selected are of high quality. According Garay-Ayala et al. (2008); González-Torres et al. (2008), due to its rapid and uniform form of germination, it reaches levels greater than 90%.
