Growth and yield of four accessions of North Maluku local sweet potato in three different locations

. The accession of North Maluku sweet potato is quite a lot and has the opportunity to be developed as a local national variety. The aim of the study was to obtain local North Maluku sweet potato accessions which had good growth and production and were adaptive in various locations. The research was conducted in three locations, namely East Halmahera, West Halmahera, and Tidore Islands from March to July 2016 using a randomized block design, consisting of 4 accessions of local sweet potato (Halteng-1, Halteng-2, Halut-1, and Halut-4), repeated 5 times. The results showed that the vegetative growth of the four accessions differed in each location. The difference lies in the length of the stem, stem diameter, number of leaves, and the length of the petiole. In the yield component, the difference is in the weight and length of the tubers. The four sweet potato accessions are not stable yet planted in various agro-ecologies.


Introduction
Genetic resources of food and agricultural crops are materials that can be used directly or indirectly to support food security.The direct use of plant genetic resources is for cultivation purposes in order to meet needs without requiring plant improvement through breeding.For plant genetic resources that are geographically unique, they can be protected in order to obtain the right to protect geographical indications.Indirect utilization of genetic resources is carried out by utilizing the diversity of genetic material contained in plant genetic resources to assemble new superior varieties through plant breeding activities.
North Maluku is an archipelago province located in a trans-equator area which is famous for its natural resource potential, agricultural diversity, and challenging environment.This potential can be seen from various potential germplasm commodities both in the oceans and on land.Sweet potato (Ipomea batatas [L.] Lam) is the third most important root and tuber plant in the world, after potato and cassava.And also grows almost worldwide and is adapted to diverse environments conditions [1].North Maluku has good germplasm potential for sweet potatoes, so it is important to develop four sweet potato accessions in three different locations.Sweet potatoes are drought resistant-plants, the rainfall required is 750 mm or more, pH 5, 6 -6,6, altitude between 0 -2.100 m asl [2].This environment is in accordance with environmental conditions in East Halmahera, West Halmahera, and Tidore Island.Therefore, it is possible to develop sweet potatoes in these three locations.
Sweet potato holds significant potential as a staple crop.Sweet potato is one of the primary carbohydrate sources with high nutritional content and an essential role as a food [3] and an important supplement for different staple products in the food industry [4].Apart from being a carbohydrate-producing food plant, sweet potato is also a source of vitamins, antioxidants, and beta carotene which are beneficial for health.Sweet potato has become an affordable source of dietary calories, protein, fiber, minerals, vitamins, and flavonoid.Sweet potato leaves are good protein, fiber, and mineral sources, especially K, P, Ca, Mg, Fe, Mn, and Cu [5].This plant is not only cultivated for human food and animal feed, but also as an industrial raw material to produce starch, alcohol, and natural pigments [6].
Sweet potato cultivars have a very high diversity [7].The phenotypic diversity of sweet potato is quite high based on the morphology of leaves, tubers and stems [8].Meanwhile, genetic diversity is an asset in obtaining superior characters in plant breeding [9].Indonesia has 74 local cultivars originating from various regions, namely Banten, West Java, Central Java, Sumatra, Kalimantan, South Sulawesi, Bali, East Nusa Tenggara, Manokwari, and Wamena [10].In North Maluku, the accession of local sweet potato is quite a lot and has the opportunity to be develop as a local national variety.Local sweet potato which has superior properties can be used as a genetic source for national local sweet potato varieties.High productivity, broad adaptability and resistance to pests and diseases are two important elements needed in forming new superior varieties.The availability of nutrients in the soil and changes in rainfall reduce tuber formation and increase vegetative growth so as to form vines that have potential as a source of animal feed [11].
A comprehensive study exploring the growth and yield characteristics of four distinct accessions of North Maluku local sweet potato across three different locations is essential for unrevealing the crop's adaptive capacity and potential contributions to local food systems.The purpose of this study was to assess the stability of the yield, the agronomic characteristics and the suitability of an accession to a particular area or environment.

Treatment and experiment design
The multi-location test was carried out in Tidore Kepulauan, West Halmahera Regency and East Halmahera Regency.The experimental design used was a randomized block design with 4 treatments in the form of clones/accessions that had high yield potential (> 20 t/ha) based on the 2015 characterization, namely V1 = Halut-4, V2 = Halut-1, V3 = Halteng-1, and V4= Halteng-2 which was repeated five times.Each experimental unit consists of 3 m x 2 m plots.In each plot, bunds were made with a base width of 60 cm, a height of 30-40 cm, and a distance between the bunds of 40 cm.Planting distance is 100 cm x 25 cm.

Data collection
Observations on vegetative variables were carried out on 3 competitive plants from each experimental plot and carried out every week which included: 1.The length of the main stem, namely the length of the main stem from the soil surface to the tip of the stem is measured at 75 DAP (days after planting) 2. Leaf size was measured at 75 DAP, i.e. at the 9th leaf from the shoot.3. The length of the petiole was measured at 75 DAP, i.e. at the 9th leaf from the shoot.4. Stem diameter was measured at 75 DAP, i.e. at the 9th leaf node from the shoot.At the time of harvest 20-24 WAP (weeks after planting) production of sample plants and plants per plot was observed which included: 1.The number of tubers worth selling and the number of tubers is small.2. The length of the bulb.This is done by measuring the length of each tuber per plant, then averaged.3. Total tuber weight, tuber weight infected by pests and diseases and healthy tuber weight, 4. The weight of tubers that can be marketed, namely tubers weighing ≥ 150 grams are not infected by pests and tuber diseases,

Data analysis
The data were analyzed by analysis of variance (ANOVA) using Minitab 18 software at p< 0.05.differences between means were compared using the Duncan multiple range test at p <0.05.

Growth performance of sweet potato accession
The results of the average stem length of the tested sweet potato accessions varied at each location (Table 1).In East Halmahera Regency, the results of statistical analysis showed that the highest main stem length was significantly produced by the Halteng-  1).A different thing happened in the Tidore where the number of branches was significantly affected by sweet potato accession.The highest number of branches resulted from the accession of Halut-1 and was significantly different from the accession of Halut-4 and Halteng-1, although not significantly different from the accession of Halteng-2.The highest number of leaves was obtained in Halteng-2 accession and the lowest was in Halteng-1.Based on Table 1, it shows that in the Tidore Islands and West Halmahera Regency, accession had a significant effect on the number of sweet potato leaves.The highest number of leaves at the Tidore Islands City location was obtained by the Halteng-1 accession, while at the West Halmahera Regency location the Halut-1 accession was obtained.At both locations, the Halut-4 accession produced the lowest number of leaves compared to the other accessions.
Leaves are organs for the photosynthesis process of plants.The results of plant photosynthesis in the form of photosynthate can be utilized by plants to develop.The number and size of leaves are influenced by genotype and environment [12].Plants that have wider leaves at the beginning of growth will grow faster because of their ability to produce higher photosynthetic than plants with narrow leaves.Sweet potato leaves that are large in size have higher tuber productivity than sweet potato leaves with small leaves because the wide leaves can photosynthesize better and more effectively than small leaves [13].
The results of statistical analysis showed that at the Tidore Islands and West Halmahera, accession had no effect on leaf length.In East Halmahera Regency, the highest leaf length was obtained by the Halut-1 accession, not significantly different from Halut-4 and Central Halmahera-1, and significantly different from Halteng-2.The character of petiole length, accession had a significant effect at each location.The Halteng-2 accession has the shortest stalk length at all three locations.Likewise with the highest stalk length, where the highest stalk length was at the three study locations.The analysis results in Table 1.show that sweet potato accession has no significant effect on the length of sweet potato stem segments.Regarding the stem diameter parameter, sweet potato accession had a significant effect on stem diameter.Stem diameter is a character that has wide genetic variability, in addition to the number of tubers and the weight of fresh tubers per clone [14].The Halut-4 accession has the largest stem diameters, namely 6.70 and 6.71 mm at the location of Kab.East Halmahera and the Tidore Islands, and the Halut-1 accession has the highest diameter in West Halmahera District.There are differences in the results of each accession in each location may be due to environmental influences including nutrients and temperature.Each variety has a different adaptation to the environment, both growing media and climate [15].

Tuber yield and yield components sweet potato accession
Table 2 shows that in the multi-site test in East Halmahera district, the average number of viable tubers for each accession was the same, only producing one viable tuber above 100 grams, with the largest tuber weight in the Halteng-2 accession with an average weight of 260.5 gram with a length of 19.02 cm.In addition, the Halut-1 sweet potato also produced tubers with an average weight of 207.5 grams and a length of 17.06 cm.The small number of tubers formed in the East Halmahera and Tidore Islands locations was possible because pruning and hilling were not carried out.Turning plants every 15 days can produce the highest tuber diameter, number of tubers planted and tuber weight, besides being able to suppress plant length, number of branches and adventitious roots [16].Apart from the effect of lack of plant maintenance, the climatic factor of rainfall also affects the formation of tubers, relatively high rainfall just before harvest can cause sweet potato tuber rot so that only a few tubers are produced.Conversely, conditions in water stress during the growth phase also affect the quantity and quality of sweet potatoes [17].The three chosen locations represent distinct agroecological zones within North Maluku, each characterized by unique environmental factors [18] In other locations in West Halmahera district, the largest number of tubers produced was in the Halteng-1 accession of 6.6 tubers per plant, while for the weight of tubers the Halut-1 accession showed the largest tuber weight of 823 grams while Halteng-2 produced an average of 819.3 grams and Halteng-1 produced 785.6 grams per plant.As for the last location in Sofifi, there was no significant difference in the number of tubers, but in terms of proper tuber weight, the Halut-4 accession showed the highest tuber weight value of 308.63 grams compared to the other accessions.
Differences in tuber yields produced by the four sweet potato accessions in three different locations may be due to environmental factors such as rainfall and soil fertility.These results indicate that the stability of the results of the four sweet potato accessions is still unknown.A variety is said to be suitable for agro-ecosystems if it is resistant to stress and waterlogging [19].Soil moisture, temperature, and nitrogen fertilizer at the beginning of planting affect the growth of sweet potatoes, especially the roots in determining root initiation; while mid and late season determines biomass and yield [20]. Soil fertility includes the physical, chemical and biological properties of soil, which is one of the production factors that plays a role in determining land cultivation and crop yields [21].
This research not only advances our understanding of crop adaptation but also has practical implications for local farmers, extension services, and policymakers in North Maluku.The insights gained from this study can contribute to the development of contextspecific agricultural practices, enhancing crop productivity and food security.Furthermore, these findings could potentially inform future breeding efforts aimed at enhancing the resilience and productivity of North Maluku sweet potato varieties.Through a comprehensive examination of growth and yield across three varied locations, our research seeks contribute valuable insights to both academic research and practical agriculture.The outcomes of this study could inform strategies for bolstering local food security, promoting sustainable agricultural practices, and guiding future breeding initiatives in North Maluku.

Conclusion
The growth and yield of the four sweet potato accessions in three locations showed a difference on stem length at 6 and 12 weeks, stem diameter, number of brances, and petiole length.The results obtained at the West Halmahera location were better than the other two locations.The existence of this difference indicates that the four sweet potato accessions are not stable yet planted in various agro-ecologies.

Table 1 .
The Growth of sweet potato at each location In East Halmahera and West Halmahera Regencies, accession had no effect on the number of sweet potato branches (Table 2 accession both at 6 weeks and 12 weeks of age.At the City of Tidore Islands, the highest stem length was obtained by accession Halteng-2 at 6 weeks of age and Halut-1 at 12 weeks of age.Whereas in the West Halmahera Regency, the main stem length was obtained by Halut-1 accessions both at 6 weeks and 12 weeks of age.

Table 2 .
Average value for large number of tubers, small number of tubers, tuber weight, tuber length, and tuber width of four sweet potato accession at three locations.