Testing of rapid vigor method for sorghum (Sorghum bicolor L. Moench) by using radicle emergence

Sorghum has a higher protein nutrient content (11%) than rice (6.8%) per 100 grams of ingredients. However the development and yield of sorghum is still low. One of the causes of low sorghum production yields is because seed deteriorate rapidly. The deterioration of sorghum seeds during storage signals a low seed vigor. So it is necessary to improve seed vigor tests efficiency in order to shorten test time. The objective of this research are determining observation time of Radicle emergence test and determining correlation between Radicle emergence test results with vigor test and seed viability. The results showed that radicula observations using Radicle emergence method can be carried out after the seeds are germinated for 96 hours at 25 + 2 0C temperature. The second result show there is positive correlation between Radicle emergence value to the vigor test and viability seed such as Vigor Index, Speed of Germination, Germination Seed, Maximum Growth Potential. It means the higher value of Vigor Index, Speed of Germination, Germination Seed, Maximum Growth Potential, the higher Radicle emergence value. The correlation between Radicle emergence and Mean Germination Time and Sprout Growth Rate changes shows a negative correlation.


Introduction
Sorghum (Sorghum bicolor (L.) Moench) is an important cereal crop after wheat, rice, corn, and barley.Sorghum as a multifunctional plant because all parts of the plant can be used for food sources, animal feed and industrial raw materials ethanol [1].The soaring world oil prices were accompanied by continued the increasing need for food and feed has encouraged various groups to develop sorghum as an energy renewable, for example the Phillippines and India have launched the development of sorghum sweet for bioethanol and feed.Bioethanol from sweet sorghum is expected can substitute partly for other countries fuel completely depending on imports [2].The development and yield of sorghum is still low compared to other food crops.One of the causes of low sorghum production is that sorghum seeds quickly deterioration (deterioration) or are easily damaged during storage [3].The deterioration of sorghum seeds during storage indicates that the seed vigor is low.High grade seeds are seeds that have a high vigor, in the sense of seeds that are able to grow under sub-optimum conditions.Seed vigor testing aims to obtain information about the value of growing power under broad environmental conditions or storage potential of seed lots [4].
Seed vigor testing that has been validated by the International Seed Testing Association (ISTA) to obtain results in a relatively short time, namely the radicle emergence test.RE test is characterized by the level of radicula emergence at the beginning of germination which is an indication of the vigor of a seed [5].The advantage of radicle emergence test is that it is a fast, inexpensive vigor testing method and has been validated by ISTA for corn seeds.Evaluation of the test results is carried out earlier, namely when the radicula has appeared at least 2 mm long, so the RE test is said to be faster than other vigor tests.The principle of the RE test method is that slow-germinating seeds is an early sign of the physiological deterioration of the seed and indicates that the seed lot is low germinated.
The results of the Radicle Emergence test were correlated with the results of tests of several other vigor benchmarks, germination and seed vigor in the field.In previous studies, RE test on soybean seeds of ten varieties with different levels of vigor (sorted based on vigor index value) using the test method on paper at 25 ± 2 0 C and observed at 42 hours ± 15 minutes after germination, showed a strong correlation and could predict germination, vigor index, growth speed, average germination time, field germination, and average seedling emergence time, so that Radicle Emergence can be used as a quick test of soybean seed vigor [6].
The objectives of research are determining observation time of Radicle emergence test and determining correlation between Radicle emergence test results with vigor test and seed viability.

Place and time of research
This research was carried out in Juli -September 2022 at the Laboratory of the Center for Supervision and Certification of Horticultural Food Plant Seeds in Central Java Province.

Material
The Radicle emergence test uses 4 varieties of sorghum (Numbu, Kawali, Suri 3 and Suri 4).Seeds germinated 50 grains of sorghum seeds x 8 repetitions per each variety through the test substrate between papers rolled by wetting the planting medium of 3 sheets then the seeds to be tested were arranged on moistened paper then rolled and put in plastic before being put in the standard germinator at temperature of 25 + 2 0 C [7].The calculation of seeds that appear radicula is carried out every 24 hours, then the percentage of the number of seeds that have appeared radicula is calculated with the minimum length of radicula that grows, which is 2 mm.

Methods
The study used a completely randomized design with 1 factors varieties of sorghum consist of Numbu (V1), Kawali (V2), Suri 3 (V3) and Suri 4 (V4).In the study using media papers, the pH media increased 6.5

Treatment application and observation 2.4.1. Radicle Emergence Test.
The calculation of the radicula emergence test is carried out every 24 hours, then the percentage of the number of seeds that have appeared radicula is calculated with the minimum length criteria of radicula that grows, which is 2 mm.
The calculated of RE is as follows : 3

Mean Germination Test (MGT).
Testing was carried out to determine the average seed germination time ranging from imbibition to radicula emergence of at least 2 mm [8].MGT testing is carried out to determine the average time of seed germination.The average germination time is calculated by the formula: Note : n = the number of newly germinated seeds at time t t = hours after germination

Data analysis
The data obtained were analyzed using variance analysis (α = 5%) and continued with Duncan Multiple Range Test) if there is a significant effect.

Results and discussion
Based on table 1 show that the variety of sorghum seed varieties, it has a significantly different influence on the radicula emergence test variable.The Suri 4 variety has the highest radicula emergence value of 95.25% followed by the Kawali variety (95.00%), the Numbu variety (88.00%) and the Suri 3 variety (83.50%).On the observation of the radicula emergence test, the Suri 4 variety had the highest radicula emergence value, but had the lowest average germination time value (Mean Germination Time).The radicula emergence value is used to estimate the normal number of sprouts in determining seed quality [9].The high and low value of radicle emergence is a marker of seed vigor.Seeds that have a low RE value illustrate the slow germination caused by seed aging [10].The average radicula emergence in each observation period showed that radicula appeared the most in the first 24 hours followed by the next 48 hours.The average germination time (Mean Germination Time) is the basis for the radicula emergence test.According to [11], that the average germination time (MGT), is closely related to the Radicle emergence (RE) value, the lower the MGT value, the faster the time it takes for seeds to germinate.Based on Table 2 show that the mean germination time (MGT) differed markedly among the sorghum varieties tested.The Suri 4 variety has the smallest mean germination time value of 28.87 hours, while the mean germination time value in the Numbu variety is 33.57hours.
The MGT value for the Suri 4 variety of 28.87 hours has the highest germination value of 97.50%.This is consistent with [9] that Lot seeds with low MGT germinate faster and have a high percentage of final germination.Observations of Radicle emergence (RE) were carried out at a temperature of 25 + 2 0 C with germination times ranging from 24 hours to 120 hours.The determination of the observation time was carried out to see the difference in radicle emergence values for each observation period in each sorghum variety.
There was a difference in the average radicula emergence in each sorghum variety during the observation period.The table above shows that radicula appears the most in the first 24 hours followed by the next 48 hours.Based on table 3 from this research showed that radicula observations using Radicle emergence method can be carried out after the seeds are germinated for 96 hours at 25 + 2 0 C temperature.This is in accordance with the results of previous studies that have been conducted by [12] that the determination of the final time of the radicle emergence test on coffee seeds by making observations every day, namely by counting the number of seeds that have emerged roots along 2 millimeters until the condition of the radicle emergence accretion rate decreases.The Suri 4 variety sorghum has the highest average radicula output of 98% while the Suri 3 variety has the lowest average radicula output of 83.5%.Seed lots with low MGT germinate faster and have a high final percentage of germination.The lower the average value of germination time, the faster the seeds will germinate and have a high percentage of germination [13].The highest correlation coefficient value on the Vigor Index variable is 0.505 and has a significant effect on the Radicle emergence value.This can be interpreted that the variable x is 50.5%, that the level of the relationship between the two variables is quite strong.The Vigor Index variable has a positive correlation with the Radicle emergence value, which shows a significant value of P <0.05, which means that the Radicle emergence value has a significant relationship with the Vigor Index variable.Based on Table 5 and Figure 1 show that there is positive correlation between Radicle emergence value to the vigor test and viability seed such as Vigor Index, Speed of Germination, Germination Seed, Maximum Growth Potential.The Mean Germination Test and Sprout Growth Rate showed a negative correlation with the Radicle emergence (RE) value, the negative correlation indicates that the higher the Radicle emergence value, the lower the Mean Germination Time and Sprout Growth Rate values.

Conclusion
Radicle emergence Method can be used as a vigor test method because it has advantages, including the test being fast, inexpensive, and the procedure is simple.Radicle emergence testing in this research takes 96 hours.Based on the research results Suri 4 variety of sorghum had the smallest mean germination time 28.87 hours but had the highest radicle emergence average of 95.25%.The result show there is positive correlation between Radicle emergence value to the vigor test and viability seed such as Vigor Index, Speed of Germination, Germination Seed, Maximum Growth Potential.It means the higher value of Vigor Index, Speed of Germination, Germination Seed, Maximum Growth Potential the higher Radicle emergence value, while Mean Germination Time and Sprout Growth Rate changes shows a negative correlation with the Radicula emergence value.

Table 1 .
Radicula Emergence test results on sorghum seeds.

Table 2 .
Mean germination time between sorghum seed varieties

Table 3 .
Average Radicula emergence in each observation period.

Table 4 .
Correlation and regression analysis results between radicle emergence (RE) values and parameters of vigor index, speed of germination, mean germination time, germination seed, maximum growth potential and sprout growth rate.Based on Table4shows that the variables and vigor index, speed of germination, germination seed and maximum growth potential have a positive correlation with the Radicle emergence value, while the Mean Germination Time and sprout growth rate variables show a negative correlation with the Radicle emergence value.The positive correlation indicates that the higher the Radicle Average Germination Test Results, Vigor Index, Speed, of germination Radicle emergence, Mean Germination Time, Maximum Growth Potential and Sprout Growth Rate of 4 sorghum varieties Numbu Kawali Suri 3 Suri 4 emergence value, the higher the vigor index, speed of germination, germination seed and maximum growth potential values.

Table 5 .
Average Germination Test Results, vigor index, speed of germination, radicle emergence, mean germination time, maximum growth potential and sprout growth rate of 4 sorghum varieties.Graph of Correlation Test Average Results for Germination, Vigor Index, Growth Speed, Mean Germination Time, Maximum Growth Potential and Sprout Growth Rate with Radicle emergence values of 4 varieties of sorghum.