Identification of the physiological characteristics of some local Aceh rice (Oryza sativa L.) germplasms

The identification of local rice germplasms resources is essential for determining morphological and anatomical traits for agronomic applications. In this study, we have screened several local rice germplasms from Aceh, conducted in Gampong Paloh Lada and Agroecotechnology Laboratory, Agriculture Faculty, Universitas Malikussaleh, Aceh Utara Regency, from February to June 2023. The study employed Randomized Block Design Non-Factorial, consisting of 7 lines of local germplasms, including Unsyiah Cakep, Unsyiah Seumeulu, Cot Bada, Sigunca, Sigupai, Cot Bada and Rajasa (control). Flowering age, net assimilation rate, relative growth rate, root length, shoot – root ratio and 1000- grain weight was observed. The results of this study showed that there were significant differences between several rice strains on the variables of flowering age, net assimilation rate 40-20 DAP, relative growth rate 60-40, shoot-root-ratio at 60 DAP and harvest, root length, 1000 seed weight. Cotbada eight and Cotbada four strains gave the best effect compared to Rajasa (control) and other strains, seen in the parameters of relative growth rate two, number of grains per clump, weight of 1000 seeds and yield tonnes/ha. Cotbada four strain with a production of 7.24 tonnes/ha and followed by Cotbada eight strain with a yield of 6.48 tonnes/ha.


Introduction
Rice (Oryza sativa L.) is the most important food crop of the developing countries, including Indonesia and it plays a crucial role in the country's diet, agriculture and food security, enabling it to be strategic commodity [1].The key to success in increasing rice production is the use of superior varieties.Superior rice varieties are one of the technical components that play a very important role in increasing domestic rice production.Superior varieties should also have advantages in certain ecolocations and other important agronomic traits, such as good adaptability to the environment, low water and nutrient requirements, and tolerance to extreme weather [2].The use of superior varieties indirectly displaces the existence of local rice that has high quality such as fluffy and aromatic flavours.The diversity of local rice cultivars has a very important role in the future, especially in the assembly of superior rice varieties Local rice is a potential genetic source to be utilised in the assembly of new varieties [3].
According to data Central Bureau of Statistics [4], in 2022 national rice production reached around 54.75 million tonnes or an increase of 333.68 thousand tonnes or 0.61 percent compared to national rice production in 2021 which reached around 54.42 million tonnes.Meanwhile, for Aceh province, rice paddy production reached around 1.53 million tonnes or decreased by 101.5 thousand tonnes (6.21%) compared to rice paddy production in 2021 which reached around 1.63 million tonnes.The development of rice production must continue to be carried out through the use of superior varieties that are in accordance with the conditions of the adaptation environment.In addition, the development of local Aceh rice is also one of the efforts to increase production in realizing food selfsufficiency.
Local rice that is still widely cultivated by farmers, especially in the West-South region of Aceh, is very diverse.Bakhtiar et al. [5] stated that local varieties of Aceh rice are very diverse.However, the potential of local rice as a gene source has not been evaluated and identified, due to the widespread use of national superior varieties.Therefore, identification of agronomic characters is needed so that it can be used in plant breeding programmes [6], and can be used as an initial step in the identification of genotypes as elders for the establishment of basic populations, as well as the basis for applying for plant variety protection [7].
Food crop germplasm is a very important asset that must be preserved.Local rice is a potential germplasm as a source of genes that control important traits in rice plants.High genetic diversity in local rice can be utilised in rice breeding programmes in general.Identification of important traits found in local rice needs to be carried out in order to know its potential in breeding programmes [8].Exploration and identification of local rice germplasm is essential to assess morphological and anatomical traits for agronomic purposes.Observation and characterization of germplasm is an essential part of varietal improvement [9].Acquah [10] suggests that breeding materials developed conventionally or molecular biology for the evaluation of phenotypic appearance under environmental stress is very important for variety assembly.Exploration activities, inventory, and preservation of local rice germplasm in Aceh are considered necessary to identify physiological characters and yield components of local Aceh rice (Oryza sativa L.) germplasm research on the identification of local Aceh rice characteristics.

Study area
We conducted the research in Paloh Lada village, North Aceh district, Indonesia and Agroecotechnology Laboratory, Agriculture Faculty, Universitas Malikussaleh, from February to June 2023.

Preparation of Planting Media
Top layer of paddy soil obtained from Teupin Punti Village, Aceh Utara.These soils were placed into polybags (40 cm x 60 cm) covered with plastic, where these plastics applied to prevent water from escaping the polybags.

Seed preparation
The 7 tested seeds were submerged into salt water before sowing to screen the healthy seeds.These screened (healthy) seeds were treated with fungicide Anthracol 70 WP with active ingredient Propine 70% for 20 minutes with dose 1.4g/litre.The seeds were rinsed thoroughly with clean water 3 times, and then submerged for 48 hours.The seeds were then incubated in the sacks for 48 hours for the growth of the roots.

Nursery
Germinated seeds were sown into planting media applied with soil 50% and cow manure 50% (1:1).The seeds were sown after 1 day of sowing media is made or 2 days after germination.

Plant cultivation
Seedling removal is required before planting, where it applied after 21 days of sowing (DAS).Before planting, the media needed to be submerged with water (5 cm above soil surface) for 2-3 days.Independent 2 seedling was planted into a planting hole with distance between polybags 10 x 10 cm.The media submersion was maintained (5 cm) for 2 weeks before harvest time.

Fertilization
Fertilizer N (Urea) 300 kg/ha was applied 3 times (with TSP and KCl) at 77 days after planting and at 99 days after planting (DAP).

Plant maintenance
Watering is carried out to keep the water level up to 5 cm from the polybag´s surface, utilizing some wooden sticks as a marker.Water stayed preserved up to one week before harvesting.Mechanical weed management is carried out by eliminating weeds from the study area.Pest control was performed manually using handpicking method, where the insect pests were collected and discarded.

Harvesting time
The type of rice and the harvesting specifications determine harvesting age for rice.The essential and characteristic phenomena of the ripening stage of rice is the yellowing of leaves begins to develop, the panicles bend with their own weight, curved panicles formed, yellowed hulls and matured grains.
The rice was manually harvested by cutting the crop using simple hand tool like sickle.

Shootroot ratio.
The shoot-root ratio was calculated by comparing the dry biomass of the upper plant (leaves, stems, flowers and fruits) with the dry biomass of the lower plant (roots).
2.11.6.Grain weight per clump and 1000-grain weight.Weight of 1,000 kernels of grain is the weight of 1,000 kernels of grain that have been cleaned and dried to a moisture content of approximately 14% per clump.

Flowering age
The average value the effect of rice strains (G) gave a very significant difference on flowering age.The results were presented in Table 1.  1 shows the plants with faster flowering age from others are found in rice strains G7 (Rajasa) which is 79.55 days which is very significantly different from G4 (SG02) which is 81.66 days, G2 (US20) which is 82.88 days, G5 (UA12) which is 83.99 days, G1 (UC 77) which is 84.66 days, G6 (CBD 04) which is 88.22 days and G3 (CBD 08) which is 90.33 days.
The difference in flowering time is caused by differences in the character of the plants used.Each variety must have different flowering age criteria.The findings in this study are in line with research from [11] who found that each plant has distinctive features influencing particular plant characteristics.Furthermore, environmental variables and plant demands might create disparities in plant development.Each plant has unique environmental needs, such as soil type, air temperature, humidity, sunshine, and nutritional requirements.These environmental standards are required for the plants to develop well and healthy.Nazirah et al [12] also confirmed that environment plays an important role in plant development beside the genetic factor.

Net Assimilation Rate (LAB)
The result of variance analysis shows that the effect of rice strains (G) gave a significant difference to the Net Assimilation Rate at the age of 40 -20 HST, while the Net Assimilation Rate at the age of 60 -40 HST and Harvest -60 HST was not significantly different.The results of further tests on the variable wet weight of rice plants have been presented in Table 2.
The rate of assimilation is influenced by leaf area size [13] which states that the net assimilation rate will increase in line with the increase in leaf area to a certain extent and then decrease because in a canopy with a high leaf area value, young leaves are able to absorb the most light, have a high photosynthetic rate, and transfer most of the photosynthate to other parts of the plant including the lower leaves.Whereas in the lower leaves, the rate of photosynthesis is slower because it is shaded by the upper leaves.Likewise, the relative growth rate is influenced by the dry weight of the plant where if the plant is optimized for growth, the dry weight will also increase.As stated by [14] which states that plants that grow optimally will increase photosynthetic yields.High photosynthesis results will increase plant dry weight so that the relative growth rate will also increase.

Relative Growth Rate (LTR)
The result of variance analysis shows that rice strains (G) showed no significant difference to the Relative Growth Rate (LTR) at the age of 60-40 HST, while the Relative Growth Rate (LTR) at the age of 20-40 HST and Harvest-60 HST was not significantly different.The results of further tests on the variable Relative Growth Rate (LTR) of rice have been presented in Tabel 3.

Tabel 3. Relative Growth Rate (LTR)
The number values in the same column followed by the same letter are not significantly different (P>0.05) based on Duncan's Multiple Range Test Based on Tabel 3, it can be seen that plants with the highest relative growth rate at LTR I is found in rice lines G1 (UC77) and G2 (US20) which is 0.91 and plants with the lowest relative growth rate at LTR I is found in rice lines G7 (Rajasa) which is 0.89.Plants with the highest relative growth rate at LTR II were found in rice lines G3 (CBD 08) and G7 (Rajasa), namely 0.89 and plants with the lowest relative growth rate at LTR II were found in rice lines G1 (UC77), namely 0.84.And at LTR III for all rice strains have the same value of 0.73.

Root length
The average value the (G) significantly differs the root length at 20, 40 and 60 DAP and harvesting time (Table 4).Based on Tabel 4. The highest root length at 20, 40 and 60 DAP was exposed by line G3 (CBD 08), 20.83, 32.17 and 39.00 cm, and the lowest by G5 (UA12), 12.50, 16.67 and 24.33 cm.Rice line G3 (CBD08) also showed the best root length, 48.17 cm and the lowest was presented by line G1 (UC77), 33.67 cm.Root length determines the ability of plants to acquire water and nutrients from soils.Its length could be the indicator of water deficit in rice plants, well-performed root system is important in plant growth.The study by [15] discovered that root length is vital for rice plants, which it could be an indicator for water deficit in rice by accelerating the length as an act of water-deficit resistance, demonstrating potential characteristic.Hasanah et al [16] also agreed that Rooting capacity in rice has been linked to productivity under drought stress.

Shoot-root-ratio
The analysis described that the rice line (G) significantly differs the shoot-root ratio at 20, 40 and 60 DAP and harvesting time.The results were given in Table 5.

Grain weight per clump and 1000-grain weight
The analysis revealed that rice lines (G) differ significantly on grain weight per clump, 1000-grain weight and yield (tons) per ha.The results were described in Table 6.Rice line G6 (CBD 04) exhibited the highest weight per clump (72,44 g) and the lowest by G2 (US20), 41.65 g and G3 (CBD 08) demonstrated the highest 1000-grain weight (32.10 g) and the lowest was G2 (US20), 22,14 g.The highest yield was shown by rice line G6 (CBD 04), 7.24 g and the lowest was rice line G2 (US20), 4.17 g.
Each rice line exhibited different 1000-grain weight.This due to differences in size and shape of the rice.This result corroborates with the finding of [1], where they confirmed that grain size affecting the weight, that the larger the grain size, the heavier the grains are and vice versa.Therefore, to calculate the 1000-grain weight, the size of grains must be taking into account.
Vary results in yield is contributed by both genetic and environmental factors.[18] confirmed that genetic and environmental factors are linked to the plant productivity and yield.There are genetic differences between varieties affecting the rice production.In addition, According to [19], the higher the number of panicles produced, the higher yield obtained.From those statements above, we can conclude that that higher number of panicles contributed to higher yield.Nonetheless, this phenomenon also influenced by other factors such as soil quality, nutrient availability and weather conditions.If one of important factors is not required, optimal yield would not be reached.Therefore, it is important to consider all important requirements to provide the plants better environment to have better performance.

Conclusion
In this study, we found the rice lines Cotbada eight and Cotbada four to be the best compared to other rice lines and control, observed from its tiller number at 20 DAP, leaf width, 1000-grain weight and yield 7.24 tons per ha followed by rice line CBD 08 with yield 6.48 tons per ha.The two best lines produced in this study have the potential to be tested on a wider research scale, one of which is on a demonstration plot scale in farmers' fields.
[20]ering age observations were made when the vegetative phase of rice stopped and entered the generative phase marked by the presence of flowers and the appearance of grains on rice.Observation of flowering age is done by observing each individual plant, carried out every week.unit of observation in days after transplanting (DAP).2.11.2Net assimilation rate (LAB).Calculation of net assimilation rate is done based on dry weight with plant leaf area per unit time using the formula[20].2.11.3.Relative growth rate (LTR).The calculation of relative growth rate is based on plant dry weight per unit time using the equation[20].2.11.4.Root length.Root length observations were made by measuring the longest root after cleaning it from the attached soil.Observations of this parameter were made when the plants were 20, 40 and 60 after planting, which were taken from destructive plant samples.

Table 1 .
Flowering age of Aceh local rice germplasm

Local rice straits (G) Flowering age (days)
The number values in the same column followed by the same letter are not significantly different (P>0.05) based on Duncan's Multiple Range Test

Table 4 .
Root length and agronomic traits of local rice germplasms (Oryza sativa) in Aceh

Table 5 .
Shoot-root-ratio and agronomic traits of local rice germplasms (Oryza sativa) in Aceh

Table 6 .
Grain weight per clump, 1000-grain weight, yield weight and agronomic traits of local rice germplasms (Oryza sativa) in Aceh