Abstract: After the identification of the Weligama Coconut Leaf Wilt Disease (WCLWD) in 2006, a three km wide boundary zone was declared which stretched from Galle to Tangalle. All suspicious palms recorded within the boundary zone were removed. Gradual removal of affected palms in the core area was also continued. These actions along with many other precautionary steps were taken with the objective to prevent the spread of the disease further beyond the demarcated boundary. After taking continued precautionary measures for more than 7 years, it was timely to find out the presence of any disease affected palms beyond the boundary. Therefore, a sample survey was conducted along a 4 km wide belt beyond the boundary. Uniform sampling locations were ensured by selecting sample sites on a I km grid drawn on the areal image of the area. Each grid covered an area of I km2 (100 ha). Four sampling locations/plots of approximately I ha in extent were selected within each grid. All coconut palms within selected plots were examined for morphological symptoms of the WCLWD and necessary information was recorded. The total area covered by the sample survey was about 40,000 ha and the extent closely examined was about 1600 ha, which was approximately 4% of the total land area covered by the survey. The results revealed that the precautionary measures taken by relevant authorities to prevent the spread of the WCLWD have had a significant effect in containing the disease within the demarcated area. However, some spread of the disease beyond the boundary was detected in a few places within the four-km-belt beyond the boundary. Thus altogether 18 affected palms were identified in 10 plots in Galle and Malara districts. They were in Akmeemana, Imaduwa and Yakkalamulla DSD in Galle district and Kamburupitiya and Mulatiyana DSD in Malara district. Most of those locations were adjacent to the boundary. However, any detection of even a few affected palms outside the boundary in a sample survey indicates the possibility of having such palms elsewhere in the study area. A comprehensive palm to palm survey is needed for precise detection of such palms. Considering the impending threat from the disease, a palm to palm survey at least within a 4 km belt outside the boundary is suggested to effectively prevent the spread of the disease, despite the cost and the man power required for such an operation. Published on 2016-11-02 00:00:00
Abstract: In Sri Lanka, coconut (Cocos nucifera L.) has been classified into three varieties, typica, nana and aurantiaca based mainly on their stature and breeding behaviour. Typica and nana are tall and dwarf coconuts respectively while aurantiaca includes intermediate types. Different phenotypes within a variety have been classified as forms of coconut. Current Sri Lankan coconut classification includes 19 different forms within three varieties. There are four different forms of coconut within variety nana, as green, yellow, red and brown dwarfs based on the colour of the epicarp of the fruit. They all conform to the morphological features of variety nana except the yellow dwarf population which was observed to be a phenotypic mixture of different types of coconut. The current study was conducted to differentiate the phenotypes within the Sri Lankan Yellow Dwarf (SLYD) population and to classify them based on existing criteria. A sample of 200 yellow dwarf palms were studied to determine their breeding behaviour, and the morphological characteristics related to stem, leaf, inflorescence and fruit morphology and yield. Based on quantitative and qualitative data generated, the pure Sri Lanka yellow dwarf coconut form could be distinguished and in addition a new coconut form which was named as Sri Lanka Yellow Semi Tall (SLYST) which was classified within the variety aurantiaca, was identified within the yellow dwarf population. There was a further group of coconuts which could not be placed within the existing varietal classification and they were hypothesized to be a population resulting from cross pollination between SLYD and SLYST. Published on 2016-11-02 00:00:00
Abstract: The coconut palm is an important cash crop mostly in the sub-tropical countries which provides almost all the necessities of life to the mankind. Genetic improvement for increased productivity is a prioritized research area of coconut palm. In vitro cloning of elite palms via somatic embryogenesis seems to be a promising method due to its potential for massive propagation. Based on the Sri Lankan experience, this paper summarizes the notable achievements towards developing a reliable protocol for clonal propagation of coconut and also dihaploid plant production. The newel explants described by Coconut Research Institute Sri Lanka (CRISL), unfertilized ovaries dissected from immature inflorescences collected from -4 stage (inflorescence to be opened in 4 months time), is a somatic tissue which causes minimal damage to the mother palm while collecting. Limited number of female flowers in an inflorescence which limits large scale culturing could overcome by callus multiplication phase to produce higher number of plants. Somatic embryogenesis and germination of somatic embryos was achieved by reduction of auxin concentration in the culture medium followed by an addition of cytokinin. AINTEGUMENTA-LIKE (ANT-like) gene isolated from coconut genome which shows higher conserved domain sequence similarities with BABYBOOM gene will assist development of suitable molecular markers to assess the morphogenic potential of in vitro cultured coconut tissues and callus. Successful plant regeneration from cultured anthers was reported by culturing anthers at three weeks before splitting (3-WBS) inflorescence stage which contains late uninucleate microspores. Heat pretreatment of anthers for six days at 38°C induced androgenesis in coconut upon culturing in 2, 4-D and 1-naphthyl acetic acid (NAA) added medium. Current clonal propagation protocol is efficient when responsive genotype is in use.Further improvement to current protocol will enable commercially viable protocol for coconut micropropagation. Published on 2016-11-02 00:00:00
Abstract: Sri Lanka tall (variety Typica, form typica) is the most widely cultivated coconut form in Sri Lanka. Sri Lanka tall coconuts display variation in fruit colour ranging from green to divergent brownish red (rathi). The growers' perception is that rathi seedlings are more vigorous and higher yielding than the green phenotype. A study was conducted to evaluate and compare the nut and copra yield and seedling vigour of phenotypic groups of green, rathi and intermediate coloured fruits. Secondary data for nut yield recorded over 21 years and husked nut weight of 30 nuts per palm collected over a year in 30 palms in each of the three phenotypes were used for analysis. Furthermore, primary data for seedling girth, height and leaf number in 30 palms each of rathi and green phenotypes were collected for analysis. The data was subjected to Analysis of variance using MINITAB 16. Nut yield or the husked nut weight of the three phenotypes was not significantly different. Significant differences were observed in seedling collar girth between rathi and green phenotypes, with rathi seedlings appearing more vigorous as indicated by the thicker stem compared to the green seedlings. It is concluded that, there are no differences in the nut and copra yield among different colour forms of Sri Lanka Tall coconuts while the rathi seedlings appear superior due to their thicker seedling girth. Published on 2016-11-02 00:00:00
Abstract: Weligama Coconut Leaf Wilt Disease (WCLWD) was first reported in late 2006 in the Weligama Divisional Secretariat Division (DSD) in Matara District in the Southern Province of Sri Lanka. Surveys conducted in 2012 revealed that 65,838, 251,980 and 14,344 palms affected by the disease in Galle, Malara and Hambanlota districts respectively. It has been confirmed by the Coconut Research Institute that the disease is caused by a phytoplasma which has some resemblance to the phytoplasma of Coconut Root (Wilt) disease in India. A 3 km wide boundary was demarcated covering the area affected by the disease and all suspicious palms were removed in the boundary zone. In the core area, affected palms were gradual removed. The disease prevailing area spanned > 680 km2 and the detection of affected coconut palms across such a large area became practically difficult. Therefore, the objective of the present study was to find alternative methods to detect affected coconut palms with yellowing leaves prominent at the middle stage of the disease, using multispectral satellite images of 0.5 m resolution. It was envisaged to use this technique as a supportive management tool at field level, if successful. Normalized Differential Vegetation Index (NDVI) which is the standard and widely used algorithm for detecting vegetation under stress conditions did not reveal an appreciable isolation of canopies of affected coconut palms. Of the different customized algorithms tested, the best outcome was obtained by the algorithm (Red + Green) - 2 x (Blue). When this algorithm was applied to the multispectral satellite images of 0.5 m resolution in the affected area, adult coconut palms in advanced stage of the disease could be distinguished with an accuracy of above 80%. However, a detection of palms in the early stages of the disease where leaf flaccidity is the major morphological symptom could not be made with an acceptable level of accuracy. Moreover, the detection of affected coconut seedlings was much more difficult. Thus, only an overall accuracy of 60 - 70% could be achieved by this approach with multispectral satellite images of 0.5 m resolution. Although the level of accuracy is not sufficient for a comprehensive field level application, there is scope for further improvement using images with higher resolution. Published on 2016-11-02 00:00:00
Abstract: Coconut (Cocos nucifera L) is one of the predominant plantation crops in Sri Lanka. The success of a coconut plantation, in terms of its establishment as well as its future performance, is heavily dependent on the quality of the seedling used. Thus attention needs to pay to raise healthy seedlings in coconut nurseries. Coconut nurseries adopt different agronomic practices to produce good quality seedlings. In this process, applying mycorrhizal inoculants is becoming an increasingly common practice in plant nurseries. Therefore the effects of mycorrhizae based biofertilizer on root and shoot development of coconut seedlings was evaluated under nursery conditions for a period of seven months. The treatments were the presence of mycorrhizae based biofertilizer (T1) and absence of mycorrhizae based biofertilizer (T2). Application of mycorrhizae based biofertilizer had no significant effect on growth parameters tested in the early stages of seedling development up to four months. In contrast, the bio fertilizer significantly increased the numbers, volumes and dry weights of primary, secondary, tertiary and quaternary roots and stem girth at the latter stages of seedling growth. The leaf area and seedling height were not significantly increased by application of biofertilizer during the nursery period. These results revealed that the usage of mycorrhizae based biofertilizer positively affected root development and stem girth of coconut seedlings. The application of the mycorrhizae based biofertilizer seems to be beneficial to produce high quality seedlings with well developed roots and thus obtain good field establishment, thereby reducing the number casualties at early field establishment. Published on 2016-11-02 00:00:00
Abstract: The potential production ofdifferent lands varies depending on the quality of the.land. The land suitability class S4; moderately suitable and S5; marginally suitable lands yielding 5,000 to 10,000 nuts ha–1 yr–1 and 2,500 to 5,000 nuts ha–1 yr–1 for coconut respectively are regarded as low potential productivity lands. These lands have limitations which are moderately severe and reduce the level of coconut productivity. Thus, these lands require inputs like fertilizer and agricultural practices like contour drains or terracing, husk pits, cover crops and mulch around the palms to break even cost and bring about profit to moderate level. Fertlizer application is one of the important inputs for such lands. The information on macro and micronutrient removal by Typica x Typica (CRI 60) coconut palms and required fertilizer input to compensate the loss of nutrients in low potential productivity lands are not available. Therefore, the objective of this study was to estimate the macro and micronutrient removal by coconut palms in low yielding lands and to compare nutrient removal with fertilizer inputs and soil reserves.Harvested nuts, fallen fronds and fallen inflorescences were collected monthly interval for three years from ten coconut palms of Typica x Typica (CRI 60) grown on moderately suitable Boralu series soil (Red Yellow Podzolic). The macro and micronutrients in plant components and nutrient reserves in experimental site were determined. The results reavealed that the major nutrient removed by all plant parts were 164,53,37; 22,19 and 9.85 kg–1 ha–1 yr–1 for K, N, Na, Ca, Mg and P respectively. The amount of N, P, K, Ca and Mg applied annually as fertilizers were 58, 11.5, 125.9,69.9 and 19 kg–1 ha–1 respectively. Except K and Mg, the other macronutrients, input by application of fertilizer slightly exceeds the nutrient removal. The N, P, Ca and Mg reserves of soil was high and would not deplete rapidly. The K input by application of 3.3 kg of APM fertilizer mixture was about 76.7 % of the K removal. This leads to depletion of exchangeable K pool rapidly, if the harvested nuts and fallen plant components are all removed from the plantation. Hence, the depletion should be compensated for either by adding extra 80 kg ha–1 of Muriate of Potash or recycling of fallen fronds and residues of the inflorescences or mulching the manure circle using fresh coconut husks or addition of organic manure.The mironutrient removed through all plant parts were 0.93, 0.53, 0.28, 0.15 and 0.09 kg–1 ha–1 yr–1 for Fe, Mn, Zn, B and Cu respectively. The reserves of available Fe, Mn, Cu and Zn in Boralu series soil was very high and the gap between the soil reserves and the plant removal rates were high. Hence, micronutrient containing fertilizers would not be required as the depletion of micronutrient reserves in soil would not occurre significantly. Published on 2016-10-19 00:00:00
Abstract: Weligama Coconut Leaf Wilt Disease has been reported to infect the coconut palms in Southern Sri Lanka. Intra-cellular pathogen phytoplasma has been identified as the causal organism of this disease. So far there have been no known control methods to cure diseases caused by intra-cellular pathogens. Integration of resistant varieties into management programmes has been identified as a viable option in management strategies of such diseases. For this, it is essential to identify the resistance of available genetic resources. This study was carried out in the Weligama and Matara area of Southern Sri Lanka to screen the coconut germplasm for resistance to Weligama Coconut Leaf Wilt Disease. Infected and healthy palms were differentiated using symptomatology; flaccidity of leaves, yellowing of leaves and marginal necrosis of leaflets. Sri Lanka Tall, Sri Lanka Green and yellow dwarfs, Gon thembili tall and king coconut were among the main coconut forms studied. Out of them Sri Lanka Green Dwarf recorded a high level of resistance (98%). Within the Sri Lanka Yellow dwarf and Gon thembili tall, certain individual genotypes were observed to be resistant while king coconut was identified to be susceptible. The most popular commercial coconut variety, Sri Lanka tall was highly susceptible to the disease although there were certain individual genotypes which were resistant. Although Sri Lanka Green dwarf has not so far been viable as a commercial coconut cultivar the presence of resistant genes within the coconut germplasm was recognized as a great advantage in breeding coconuts for resistance to Weligama Coconut Leaf Wilt Disease. Published on 2016-10-19 00:00:00
Abstract: Vermicomposting is a well known technology that produces a valuable organic fertilizer from Organic waste. Weeds in coconut plantations are good organic sources for vermicompost production. The experiment was carried out to evaluate the quality of vermicompost produced by different weed or plant species commonly available in coconut plantations and also to evaluate the effect of these residues on the earth worm activity in the vermicomposting process. Vermicomposts were produced using different plant or weed species collected from coconut plantations in combination with cattle manure.The highest N content and worm growth was found in the vermicompost produced using Puereria phasioloides, Gliricidia sepium and Tithonia diversifolia. The highest P content was recorded in vermicompost samples produced using Tithonia diversifolia and Panicum maximum. Tithonia diversifolia, Puereria phasioloides and Gliricidia sepium showes significantly higher K content than the other plant species residues. Organic Carbon content was significantly high in vermicompost made with Tithonia diversifolia, Gliricidia sepium, Tephrosia purpurea, Chromoleana odorata, Panicum maximum and Hyptis suaveolens. Worm multiplication rate was significantly lower % by Lantana camara, Chromoleana odorata, Hyptis suaveolens and Vernonie zeylanica substrates, possibly due to chemical compounds present in these plant species. The results shows that Gliricidia sepium, Puereria phasioloides and Tithonia diversifolia are the best species for vermicomposting when compared with other weed species in coconut plantations. Published on 2016-10-19 00:00:00
Abstract: This study investigated the effect of heat treatment (100°C and 150°C) with or without addition of tocopherol (0 mg/L - 300 mg/L) in the formation of free fatty acids in differently processed coconut oil, dry processed virgin coconut oil (DYCO), wet processed virgin coconut oil (WYCO), white coconut oil (WCO), paring coconut oil (PCO) and soya oil. FFA content of all oils stored for a period of 3 months were determined. The results show that WVCO had the lowest FFA content (0.035 %) followed by DYCO, WCO, Soya and paring oil. The initial FFA content reduced when the respective oils were heated to 100°C or 150°C. This indicates that heat treatment can improve the quality of coconut oil. Addition of tocopherol to DYCO, WYCO and WCO in 100 mg/L, 200 mg/L and 300 mg/L had a significant effect on controlling FFA development of the oil. Addition of tocopherol in 200 mg/L had significantly lower FFA content in DVCO both with and without heat treatment. WVCO and WCO had lowering effect of FFA due to addition of tocopherol in 200 mg/L. However it was not significant. Published on 2016-10-19 00:00:00
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