Performance of agronomic characteristics and path analysis of the highland new plant types of rice

This study aims to examine the good production characteristics and path analyses as well as the character correlation of the highland F4 new plant type of lines. The research was conducted in four paddy fields, namely Bittuang, Rantebua, Sesean, and Tallunglipu sub-districts at altitudes of 650, 850, 1400 and 1600 meters above sea level in North Toraja and Tana Toraja Regencies. This research took place from June to December 2021 and was arranged in randomized block design. The genotypes tested were 30 F4 lines and six control varieties which were repeated 3 times at each location. The results showed that lines with an average productivity of above 4 tons ha−1 at four locations namely G13 (5.17 tons ha−1), G7 (4.91 tons ha−1), G26 (4.80 tons ha−1), G15 (4.65 tons ha−1), G10 (4.55 tons ha−1), G14 (4.47 tons ha−1), and G25 (4.22 tons ha−1). The characters with the highest correlation with production were the weight of filled grain per clump, number of productive tillers, and the weight of grain per panicle, while the characters that had the highest positive direct effect were number of productive tillers, weight of filled grain per panicle and percentage of filled grain per panicle.


Introduction
The world's population is projected to reach 10 billion people in 2050, where Indonesia will contribute 300 million people [1].Based on this, it shows that the need for food sources is urgently needed in order to fulfill the balance of food and nutrition for the community.Rice is the main staple crop in Indonesia, where nearly 80% of Indonesia's population uses rice as their main daily staple food [2].Fulfillment of rice can be supported by several main factors, namely the availability of optimal cultivation land, high yielding varieties, and harvest index [3].
The availability of cultivated land is the most important thing in efforts to increase rice production.In Indonesia, paddy fields are scattered in several areas from Aceh to Papua, which range from coastal areas to the highlands, most of which are on the islands of Java, Sumatra and Sulawesi [4].Based on data from research [5] In Indonesia, there are 4 million hectares of rainfed lowland rice fields consisting of 3.2 million rainfed lowland areas and 0.8 million hectares of dry land which have the potential to support national food security, one of these potential lands is in a condition slope and elevation, namely as much as 1.54 out of 3.2 million hectares of rainfed lowland rice fields are on a slope of 3-15% of which around 1.13 million hectares are on a slope of 3-10%, and the remaining 0.50 2 million hectares on a slope of >15% or part is in the highlands.So that the middle plains and highlands are also able to support the fulfillment of national rice.
Efforts to increase rice production in the highlands have been attempted by the government in Indonesia from 1968 to the present, however, high-yielding highland varieties have yet to be found with good and quality production criteria.From this activity, the varieties Adil, Makmur, Gemar, Batang Agam, and Batang Ombilin have been released.These varieties do not grow widely in the community because they are not resistant to brown planthopper (BPH) pests and the texture of the rice is perish [6].So it is still a responsibility that continues to be carried out to find new varieties that are superior and tolerant to low temperatures in the highlands.
Low temperatures are the main obstacle faced by rice farmers in the highlands because they have an impact on decreasing crop yields, due to low temperatures resulting in disrupted growth starting from germination, tiller formation, chlorophyll, panicles become abnormal and pollination is not normal because low temperatures can inhibit pollen growth pollen, because pollen swelling occurs, pollen decay, which results in the pollination process not taking place.So that if low temperatures (<20ºC) cause the pollination process to worsen and reduce yields, low temperatures can result in a 50% decrease in rice yields [7].So based on the results of research conducted [8] stated that low temperatures can reduce rice production by up to 40-60%.
Efforts to assemble high-yielding low-temperature tolerant rice varieties in the highlands can be carried out, one of which is by crossing local upland rice that is tolerant to low temperatures with national superior varieties.Local upland rice that has been introduced and has been registered at the Plant Variety Protection Agency of the Ministry of Agriculture and most of them are in South Sulawesi, West Sumatra and Central Java [9].Among the several local rice that have been registered, there are also five Toaraja local rice namely Pare Ambo, Pare Bau, Pare Kombong, Pare Lallodo and Pare Lea [10].The five local rice have long been adapted and cultivated by local farmers in the Toraja highlands at an average altitude of 700-2000 m above sea level [11].This local rice has advantages in terms of tolerance to environmental stress and pests and diseases in the highlands, but the production is small, namely an average of 4-5 tons/ha and the age of harvest is over 150 days after sowing [12].Based on this, crosses have been carried out between the five local rice varieties with the national superior variety Inpari 4. Zuriat from crosses F2 to F3 were selected for SSD and in the third generation gave rise to different characters, so it is very important to test agronomic characters and cross-characteristics, which supports production in the highlands.Taking into account the direction of the research objective, namely the assembling of highland New Plant Type (NPT) varieties, the research was attempted at 4 locations in the highland areas.

Materials and methods
The research was conducted in four paddy fields, namely Bittuang, Rantebua, Sesean, and Tallunglipu sub-districts at altitudes of 650, 850, 1400 and 1600 meters above sea level (m asl) in North Toraja and Tana Toraja Regencies.This research took place from 2021 to December 2021.The genetic material used was 30 highland NPT F4 lines and 6 control rice varieties.Other supporting materials used include NPK, Urea, and SP-36 fertilizers.The research tools are tractors, nets, hoes, meters, digital scales, sacks, stationery and cameras.This study was arranged in the form of a randomized block design (RBD) with 3 replications at 4 different locations.The total trial plots were 108 plots at each location.Each plot consisted of 5 planting rows, with a plot size of 1.2 m x 5 m and a spacing of 25 x 25 cm.The variables observed were plant height, number of productive tillers, harvesting age, 1000 seed weight, production per clump and production per hectare.The data obtained were analyzed for variance and if there was a significant effect on the analysis of variance then tested for Least Significant Difference (LSD) with a 95% confidence level, as well as correlation and cross-link analysis.

Results and discussion
Agronomic characters are several character components that are directly related to increasing rice productivity.Agronomic characters in rice plants are a set of quantitative characters.Quantitative character is a character controlled by many genes.so that it is widely applied as an object of plant breeding research.Most of the important agronomic characters are basically the center of attention of plant breeders in the selection of segregated plants.The diversity of agronomic characters is caused by meiotic irregularities and the unequal distribution of chromosomes in offspring due to crosses between the Javanica sub-species and the Indica sub-species [13].In this study, plant height, productive tillers, harvesting age, 1000 seed weight, production per clump and production per hectare.In this study, the 4 locations used in the medium to highland plains showed the results of the agronomic characters of NPT F4 lines were different in each line with local varieties and superior varieties of rice as a comparison.The plant height characters showed that the average plant height for 36 genotypes was in the range of 76.7 cm to 148 cm (Table 4).The average plant height of the NPT lines produced was significantly shorter than all local upland rice comparisons and there were two lines that were taller than Inpari 4, namely G3 UKIT (F4UKT101-2-003) and G29 (F4UKI105-2-242) lines.The shortest average plant height character value was obtained at the Bittuang location followed by the Sesean location, this was caused by the average lineage at the two locations experiencing morphological growth abnormalities or stunting due to low temperatures which were below the normal temperature for rice growth, namely 25 °C (Figs. 1 and 2).In the opinion of [14] low temperatures greatly inhibit the growth and development of plant height because the process of cell division that takes place is not normal.This illustrates that all the expected highland PTB lines tested had plant heights in the short category.The categories of rice plant stems, based on research from [15], are short (90-115 cm), medium (115-125 cm) and tall (above 125 cm).According to Diptaningsari (2013) rice plants with too high stems cause rice to overturn easily because the tall stems are unable to support the weight of the panicles.This is also supported by a correlation analysis which shows that the character of plant height worth 0.214 has no significant effect on production (Table 5).
The number of productive tillers based on the results of the LSD 0.05 advanced test in Table 4 shows that there were three NPT lines that had the best number of productive tillers which were significantly better than G31 (Inpari 4), G34 (Pare Kombong) and G36 (Pare Lea).The number of productive tillers is a growth character that strongly supports production.These results are supported by the results of a correlation analysis of 0.772** to production (Table 4) and cross-analysis of the number of productive tillers has the highest direct effect on yield of 0.723** (Table 5).
The results of the cross-sectional analysis (Table 5) show that the character that has a very significant direct effect on production per clump is the number of productive tillers which has the highest direct effect value (0.723**) correlation coefficient which has a high contribution to the increase in production weight per hectare, this result is in line with the results of research [16] and [17]  Based on Table 4, it shows the harvesting age of the 30 new types of rice lines tested that fall into the early maturing category.This is indicated as a result of crosses with early maturing varieties Inpari 4. These results provide new information that crosses between mature rice and early maturing rice produce dominant progeny.[18] stated that crosses between deep-aged and short-lived rice would result in a shorter average harvesting age than their deep-aged parents.In addition, the harvest age has a positive correlation with the size of the plant height, namely the shorter the plant, the early harvest age.Further testing of LSD 0.05 to the weight of 1000 seeds (Table 4) showed that the weight of 1000 seeds with the tested genotype ranged from 24.4 g to 32.3 g.The best average weight is produced by local rice elders.The average size of the seeds produced by the lines is of medium size so that the weight of 1000 grains is reduced.The character weight of 1000 seeds and good grain per hill has a correlation to production per hectare of 0.424** and 0.984**, respectively (Table 4).So that the comparison strains or parents that have the highest weight on each of these characters, especially the weight per clump, will produce the best productivity (Table 6).According to [19] said that the character of the weight of 1000 grains of full grain is one of the determining parts of grain production.In addition to the weight of 1000 seeds, the weight of grain per panicle and per hill has a very high correlation with the increase in grain productivity.The average productivity at the 4 test locations is 2.09 -5.17 tons ha -1 .The best productivity at the Bittuang, Rantebua, Sesean, and Tallunglipu locations respectively G35 (Pare Lallodo) 3.99 tons ha -1 , G10 (F4UKIT102-2-032) 7.53 tons ha -1 , G33 (Pare Bau) 4.19 tons ha -1 , G13 (F4UKIT102R-2-018) 8.02 tonnes ha -1 .At the Bittuang and Sesean locations that were experiencing stress, it was shown that there were no lines that had heavier productivity compared to the five local rice controls, except Inpari 4 (Figure 1).This was caused by all the agronomical characters that were not normal.According to [20] the productivity of superior rice varieties has an average production of above 7 tons/ha, so there are several lines in this study that are classified as high production which can potentially be proposed to be released as new plant types of highland rice superior varieties.Table 6.Path analysis of several characters to productivity.

Conclusion
Based on the results of the study, it was concluded that lines with an average productivity above 4 tons -1 at four locations namely G13 (5.17 tons -1 ), G7 (4.91 tons -1 ), G26 (4.80 tons -1 ), G15 (4.65 tons -1 ), G10 (4.55 tons -1 ), G14 (4.47 tons -1 ), and G25 (4.22 tons -1 ).The characters with the highest correlation with increasing production were the weight of rich grain per clump (0.984), the number of productive tillers (0.772), and the weight of 1000 seeds (0.424).The characters of plant height and harvesting age have a negative correlation with production.While the character that has the highest positive direct influence is the number of productive tillers (0.723).
(Rohaeni and Permadi, 2014;Akhmadi et al. 2017) namely the character of the number of productive tillers and the percentage of filled grain per Panicles have the highest direct effect on production, so 1230 (2023) 012122 IOP Publishing doi:10.1088/1755-1315/1230/1/0121226 that these characters can be the main basis for selection of lines because they have a large contribution to increasing production.The harvesting age of rice plants is classified according to BB Padi (2016) namely deep age (> 155 DAS=Day After Sowing), medium (125 -150 DAS), early maturing (105 -124 DAS), very early maturing (90 -104 DAS), ultra-early maturing (<90 DAS).

Table 1 .
Characteristics of genetic material.

Table 2 .
Characteristics of the four research locations.

Table 3 .
Analysis of the combined agronomic characters of PTB upland lines at the four test locations.

Table 4 .
Average agronomic character values of 30 NPT lines at 4 highland locations.
Note: Numbers in the same column followed by letters a, b, c, d, e, f are significantly lower than Inpari 4, Pare Ambo, Pare Bau, Pare Kombong, Pare Lallodo, Pare Lea, respectively.

Table 5 .
Correlation analysis of agronomic characters of 30 hopeful rice genotypes and 6 control varieties in 4 environments.