Progress in Research and Development on Yams (Dioscorea spp.) in Maluku Islands, Indonesia: Achievements and Challenges

Tuber crops, including yams (Dioscorea spp.) have been playing an important role in the menu of the community of Maluku islands...


Materials
University-USAID [5]. Field experiments were mostly conducted at the experimental/collection fields/stasion at the Faculty of Agriculture, Pattimura University. The others were done at the farmers field at different places in Ambon Island as well as Seram

Island.
Taxonomic studies were accomplished using 17 cultivars Europe and Asia and Africa were planted in green houses and the description of morphological characters were done as the plants were growing and developing.
Chromosome observation was done implementing the squash method using the fixative solution reported by Okada [6,7]. Yams tubers were culivated in the soil with high composition of sands and organic matter in plastic bags in the laboratory. The soft roots developed from the tubers were than obtained for preparat preparation leading to microscopic observations. Root tips of about 4mm were disected and fixed in the fixative solution of 3 : 1 ratio of absolute alcohol and glacial acetic acid for 2 hours in room temperature. The root tips were than washed with destilated water, placed on preparat glass and further trimmed into about 2 mm in size. One drop of aceto orcein (2%) staining solution was given to the root specimen, further covered with cover glass than squashed using finger tip and/or a small wooden stick. The excesive staining solution was cleaned using tissue, passed quickly through a fire flame from a bunsen burner to dry the preparat and finally observed under the microscope. Observation was done by first using 10 X magnification of oculer lense and 10X objective lence. When cells with good mitosis division appeared, the obective tubers were first weighted normally using the scale to determine their weight (grafity) in the air (AG) than further weighted in the water to determine their weight in the water (WG). The SG was than calculated using a formula of SG=AG/(AG-WG).
Yams distributed along the tropics and subtropics, small number of species distributed within the temperate region. The highest diversity of yams species, however, distributed within the wet climatic area [9]. Certain species , such as that of D. rotundata Poir macroura (Knuth) Pax. [10] D. pentaplylla L. [11] are also produce aerial tubers (bulbils). In green house cultivation at the IPK Gatersleben Germany, the aerial tubers produced by D. bulbifera Onwueme [12] reported that field cultivated yams in Tropical Africa especially D. alata and D. esculenta L., rarely produce flowers. Yams cultivation at the experimental station of the joint project, Faculty of Agriculture, Pattimura University -USAID indicated similar case as that reported by Onwueme [12] accept that D. pentaphylla

Dioscorea in Maluku Islands
In the year 1978, when the scientists of Bogor Agriculture Institute conducted a survay, in Indonesia distributed 33 species of Dioscorea, eight of them were found in Maluku Islands [14].    [5,4]. In addition, several initial studies on taxonomy, genetics and breeding were also conducted in the joint work with a Netherland scientist, Lieuwe S. Anema BSc., who assisted the establishment of genetics and plant breeding laboratory at the Faculty of Agriculture Pattimura University.

Field Studies
Experiments on the methods of land preparation before soil cultivation evaluated the practices implemented by farmers in yams growing areas. Theoretically, in the growth and development of Dioscorea spp., a great amount of organic matter is needed, and the practices of burning the field after felling down the trees or burning the bushes can readily provide organic matter to be used. The experiment implemented two treatments, with and without land burning on the cultivation of ubi kelapa (D. alata.), found that the highest production at the amount of 26 tons/ha was obtained from the field burning treatment. However, this result was not significantly different, statisticly, than that without burning. The results shown that the best yield of peagon pea was obtained at the combination of two peagon pea crops with one white yam, while the best yield of white yam was obtained at monoculture system (without peagon pea). Multiple croppyng system with leguminose (peagon pea) is intended to provide Nitrogen in the soil needed for the vegetative development of yams. This study indicated, however, that the presence of legume promote competitive effects rather than supporting effects to yams. while that of solid medium, 5g/l agar was added to the MS medium.

Tissue Culture Studies
Each treatment with 5 replications were placed in the cultivated room of 29 0 C, with light intensity of 1600 lux from incandescent lamp. After six to eight weeks cultivation followed by observations, it was concluded that different yams cultivars responded differently to the cultivated media. As well, liquid medium, with the use of shaker, showed better shoots, roots and leaves growth and development for most of the cultivars. On the experiments of transplanting, it was concluded that there is a need for the plantlets to be cultivated in rooting medium before transplanting, to ensure further successfull growth and development.

Studies at the Genetics and Plant Breeding Laboratory
In addition to the studies at the tuberous crops project, several researches were conducted by the author for the copletion of the research thesis entitle "Taxonomy of several yams specimens, carbohydrate-diosgenin ratio and their impact on yams breeding". Basic cromosome number of Dioscorea reported to be x=9 for new world yams [16] and x=10 for old world yams [17]. Later findings indicated, however, basic chromosome number of D. alata to be x=20 [18]. cayenensis with 2n=140 have been counted by different researchers [12]. Martin and Ortiz [16] reported New world species such as D. floribunda Mart. and Gal. with 2n=6x=54, 8x=72, 16x=144, D.
Understanding karyotype of the cromosome is not only important for taxonomical purposes but also breeding purposes. The linier regression coeficient of R=0.78 is considered quite high for practical uses, that is to estimate carbohydrate content of the tuber without laboratorium analysis (only by weighing the tuber).
A note on this regression is that the tuber flesh should be white in color, or other color of tuber flesh (purple, in this case) will reduce the value of regression coefficient. Purple color of the tuber flesh is assumed to contain more of other compound than carbohydrate (anthocyanin, for example). This experiment, surely still have to be repeated several times, utilizing higher number of samples to be able to increase its precision and reliability. However, the benefits of using the regression are reduction of the cost of analysis, or when the study is conducted in a remote area and carbohydtae content need to be determined, roughly. Results of the diosgenin analysis on 17yams specimens at the Utrech University the Netherlands indicated very low percentages (below 1%), mostly zero, diosgenin content. Diosgenin, C 27 H 42 O 3 , a steroid chemical compound has been used widely in pharmaceutical industry especially for treating cancers [19] and as an active ingradiend in contaceptive pill [20]. Based on the results of the analysis of carbohydrate and diosgenin contents of the tuber, it is concluded that development of yams species and cultivars in Maluku islands should be directed to their use as cabohydrate source or as food crops and not as diosgenin source crops, and breeding efforts can be directed partly to improve their carbohydrate contents. It is assumed that in a very long process, community of the Maluku islands, maybe unconciously, have selected the present cultivars for the purpose of consuming their carbohydrate or as food crops from generation to generation. This assumption is justifiable since diosgenin has a bitter taste and present in wild species/varieties and therefore, the commuinty did not consume species/varieties/genotypes with high diosgenin content, but cultivate and consume varieties which has no bitter taste and in the process, selected for genotypes with high carbohydrate content.

Implementation of the Experimental Results and Further Development
Achievements of the joint project, "crop potetntial of tons [24] with the possibility of development as fresh tuber for human consumtion, processing for animal feed, processing as flour for bread making, especielly for D. alata [25]. As part of the roots and tuber crops, development vision for Dioscorea in the year 2020 are to contribute to the world food system through its integration into emerging markets through eficient and environmentally friendly products as well as high quality, competitive products as sources of food, feed, and industry [25]. Copyright@ Semuel Leunufna | Biomed J Sci & Tech Res | BJSTR. MS.ID.004764.

Germplasm Erosion and Solution Alternatives
In recent years, it is seldom to run into Dioscorea spp. in traditional markets, even more in super markets in Ambon city.
When present, mainly of cultivars coconut yam (ubi Kelapa- Figure   3E) and white yam (ubi Putih- Figure 3D) of D. alata, and one or two cultivars of D. esculenta ( Figure 3A,B). In fact, it has been the case for quite a long time since only a few cultivars of certain species are preferable by the consumers, the others are cultivated only for family consumption or for other purposes. For example; snake yam (ubi Ular) of D. alata with a long, rounded and waify or coiled tuber is cultivated at the border of the farmers field or gardens and twining its stem on the fence or function as the fence.
The scarcity of yams commodity found in the market, can also be an indication of yams genetic erosion, aside from the survays data indicated previously. Economic preasure might also have caused the farmers to abandone cultivars, chich are not well sold in the marked, utilizing the lands they have, efficiently, to cultivate the species and cultivars attracted to the consumers only. The lost of yams germplasm, not only means the scarcity of food crops, which may support diversification in food and nutrition as well as maintaining food security, but also means narrowness of crops genetic diversity, from which, selections and coss-breedings can be made to obtain superior varieties in the future. A hope for the conservation of yams' genetic resources is present on the inter-situ conservation method through seasonal cultivation by the farmers or on-farm management. This method is supported by the traditional culture or indigenous practices, which assigned a certain family to cultivate or manage a certain cultivar or the tradition, which identify a certain family with certain yams cultivar. Another cultural practice is having a competition, periodically, on variety of food products prepared from various yams cultivars. This hope, however, is getting faded away as the local wisdoms or traditional cultural practices of germplasm conservation are dissapearing [26].
The joint project of USAID-Pattimura University, which collected more than 120 accessions, mostly Dioscorea spp., both field and in vitro cultures is obviously not only a research project but also an effort to conserve yams germplasm. The mehods and techniques used are considered to be effective and economics since they are the only methods available for the ex-situ conservation of recalcitrant and semi-recalcitrant seeds, as well as vegetatively propagated crops. The in-vitro conservation may than followed by protocol development for cryopreservation, that is a technique/ method of preserving biological materials in liquid nitrogen for an unlimited time period. These three methods or techniques of ex-situ germplasm conservation mainly implemented in the world today, each with its advantages and disadvantages, will complement each other, in which, cryopreservation will be a long-term germplasm Conservation efforts through on-farm management supported by local wisdoms and practices seems to be slowing down due to the continuing dissappearance of the local wisdoms and practices. There have to be a concerted efforts of government and community in the conservation of yams germplasm, so that yams (Dioscorea spp.) can be continuosly play an even bigger role in the diversification policy in Maluku islands. A gene bank or/and a community gene bank are proposed to contribute to yams germplasm conservation.