Seed purity assessment of two local upland rice cultivars of Southeast Sulawesi based on agronomic characteristics

This research intended to purify upland rice seeds that have presumably been unintentionally mixed with various types of rice seeds, causing decreased quality or nature of the superior upland rice cultivars. Seed purification effort is needed to restore the purity of the seeds of promising local upland rice cultivars. The second long term goal of this research was to produce basic pure seeds, that are required for further breeding programs, and/or for the purpose of releasing new varieties. This study was the second generation of purification effort, aimed to further select the same or uniform agronomic characteristics of the local upland rice cultivars in each seed lot. Similar with the first generation, the experiment used a Randomized Block Design (RBD) consisting of 15 seed lots as treatment and each seed lot consisted of 4 “grids” (replications). This research was conducted at the Field Laboratory, Experimental Garden II, Faculty of Agriculture, Halu Oleo University. The results showed several characters (i.e., plant height, leaf number, and tiller number etc.) of the two rice cultivars were seem more uniform as compared to the first generation of purification. This indicates that the seeds are gradually purer.


Introduction
Cultivars that have been cultivated for a long time tended to be mixed with other varieties, so that its characteristics no longer match the actual description.Seed purification approach is very important to overcome this problem [1].Purification is an effort to restore the quality of cultivars and to ensure the stabile superior characteristics of a local variety.
The Southeast Sulawesi's local upland rice genotypes of Wakawondu and Wangkariri are known to have a good taste, fluffier, fragrant, high anthocyanin content, and highly popular rice cultivars in the community [2].Both rice cultivars have been marketed in many areas, even abroad.However, in the field, due to repeatedly cultivation without systematic breeding efforts, causing the local superior rice seeds mixed with other varieties.Every effort to purify the mixed seeds are very necessary, to restore the nature or original characteristics of the rice produced.This even more important when this potential local cultivar is prepared for release.Seed purity is one of the characteristics of quality seeds.Purification effort can be done through mass selection method.Mass selection for seed purification aims to obtain uniform plants by selecting plant characters from a mixed population where each individual might have different characteristics [3,4].This study aimed to further select (2 nd generation) the same, or at least, uniform morphological characteristics of the two local upland rice cultivars (Wakawondu and Wangkariri) [2] in each seed lot and to find out which seed lots show high uniformity.

Materials and Methods
In general, the experiment methods used were similar to the methods used during the first-generation experiment [5].The seed materials used were the selected seeds resulted from the first generation of purification.

Place and period
This research was carried out at the Field Laboratory II, Faculty of Agriculture, Halu Oleo University, Kambu District, Kendari City during 2022.

Materials
The seed materials used in this study were Wakawondu and Wangkariri rice seeds, NPK fertilizer, and organic fertilizer (cow feces).The main tools used in this study were tractors, white nets (fine net for preventing insects and birds entering the field), and warring nets.

Research design
Research design used was a Randomized Block Design (RBD) which consisted of 15 seed lots as treatment and each seed lot was made into 4 "grids" (replications), so that 60 grids were obtained in one experimental land.In each, four sample plants were chosen randomly.

Land preparation
Land preparation included measuring land area (7 m x 20 m), land clearing, plowing using tractors and rotary.The plots were made of 15 seed lots with a size of 5.5 m x 1 m.Each seed lot was divided into 4 grids with a size of 1.5 m x 1 m.

Seed germination
Both rice seeds were soaked in water for 2 x 24 hours to accelerate the germination process.The soaked seeds were then be sown evenly on a nursery medium.The seedling medium used were husk charcoal and soil with a ratio of 1:1.

Seed planting
The 14-days-old rice seedlings were then transplanted to the experimental land that has been prepared.Planting was conducted by taking 2 seedlings, planting in each planting hole, with a planting space of 20 cm x 25 cm.The total population was 25 plants in one grid, so there were 1,500 plants in the experimental land.

Grain harvesting
Harvesting was done when at least 85% of the grain in the experimental field has turned yellow.

Observed variables
Measured research variables were based on [6].Growth components: plant height (cm), number of leaves per clump (strands), and number of tillers per clump (stems).In this paper, only data on vegetative characters were reported.

Data analysis
Observed data were tabulated, and later will be analyzed by analysis of variance (ANOVA) if the Fcount was not significant, it means that the plants in each seed lot or between seed lots were uniform, it could be assumed that the purity level was high.If there is a significant effect in the analysis of variance, it will be continued with the Scott Knott group test = 0.05.

Results and discussion
Data on Table 1 and Table 2 show that the average values of variables plant height, leaf number, and tiller number on each line of each cultivar, the age of 49 days after planting, were in general seemed to be uniform/similar.This indicated both cultivars had progressed to uniformity, except for a few lines (e.g., lines 1, 5, 8, 13 for cultivar Wangkariri; and lines 2, 5, 9, 14 for cultivar Wakawondu) the values were not uniform, or considered as outliers (too high and/or too low).Uniform seeds or lines can be used for further research program and/or seed progression.

Discussion
Pure seeds will ultimately produce uniform plants and minimize the number of deviant plants.Genetic purification efforts must always be carried out to ensure whether the population is still diverse or already uniform [1].The use of pure seeds maintains a better production.According to [7], purification approach is conducted to optimize crop production results.
Seed purification method based on morphological and agronomic characteristics is not always easy to conduct, because the plant phenotypes are influenced by genetics and the environment [8].However, purification techniques based on morphological and agronomic characters can still be used.This argument is similar to opinion of [3], if the character is stable in diverse environment, that although the plant phenotypes are strongly influenced by the environment, purification techniques using morphological characteristics are generally used to maintain the cultivar purity.Similarly, [4] stated that to detect diversity can be done by observing the phenotype.
Seed purity was assessed by looking at seed lots that are uniform in each statistically observed variable based on analysis of variance.If there is no significant effect, it is assumed that the seeds to be uniform and if there is a significant effect, it is assumed still to be diverse or not uniform.This is similar to the research results by [1], stating that if the results are not significantly different, this indicates that the results of observations and measurements of a quantitative character between the two varieties tested do not differ in value.If the characters are significantly different, indicate the observed results of the characters have different average values, meaning that the characters are still diverse.
Rice is a self-pollinating crop, making less potential for the seeds to have a high diversity, as compared to cross-pollinated ones.Self-pollinating plants generally have a homozygous genetic composition, resulting in plant populations with a high uniformity [1].
The generally uniform of Wakawondu and/or Wangkariri rice plants can be seen in the variables of plant height, number of leaves, and number of tillers (Table 1 and Table 2).Uniform appearance of a plant population is because the genotype used is from the same genotype as the parents [9].
The occurrence of a few varied results (Table 1 and 2) can be caused by environmental factors that affect these properties.Plant morphological diversity is influenced by two factors, namely genetic and environmental [10].Genetic factors are originated from parents and environmental factors dependent on rainfall, temperature, land conditions etc. [11,12].