Coconut Seedlings Research Articles

Ex vitro rooting using a mini growth chamber increases root induction and accelerates acclimatization of Kopyor coconut (Cocos nucifera L.) embryo culture-derived seedlings

Ex vitro rooting using a mini growth chamber to maintain relative humidity has been used to mass produce true-to-type Kopyor coconut (Cocos nucifera L.) seedlings through embryo culture. This new process was found to (1) improve the proportion of seedlings successfully transferred to soil (from 40 to 90% for seedlings with roots); (2) achieve this step in the shortest time possible (a reduction from 10 to 4 mo in in vitro culture); (3) improve root formation using indolebutyric acid (IBA; an improvement in the number of primary roots from 2 to 5); and (4) improve the vigor of seedlings ex vitro (improvements of fresh weight, shoot length, number of opened leaves, leaf thickness, amount of epicuticular wax, and stomatal density). The best ex vitro rooting and rapid acclimatization protocol was obtained when 4-mo-old seedlings with two opened leaves were kept in the mini growth chamber for 3 mo before being transferred into soil, and when the mini growth chamber was flooded with a quarter strength hybrid embryo culture (HEC) medium with 1 μM IBA but depleted of vitamins and sugar. This protocol was efficient in delivering high-value Kopyor seedlings to the field (90% success rate), with a decreased risk of contamination and lower labor cost. The improved process was found applicable to both tall and dwarf Kopyor and other coconut types.

Physiological and ionic changes in dwarf coconut seedlings irrigated with saline water

ABSTRACT Salt-tolerant plants are important to cope with salinity and/or sodicity problems in semiarid regions. The dwarf coconut palm (Cocos nucifera L.) has emerged as a salt-tolerant crop once established. However, little is known about the mechanisms that contribute to the survival of coconut seedlings under salinity stress. This study aimed to evaluate the effect of saline water on morpho-physiological and biochemical responses of dwarf coconut seedlings. Treatments were composed of five levels of water salinity, expressed by its electrical conductivity (ECw), as follows: 0.9 (control); 5.2; 10.1; 15.3 and 19.3 dS m-1 in a completely randomized design with four replications. The high levels of organic solutes (carbohydrates and soluble amino-N) and Na+ in roots, that contribute to the low values of Na+/K+ ratio in the leaves, suggest that roots play an important role in the mechanism of salt tolerance of coconut seedlings. The use of brackish water with ECw of 5.2 dS m-1 allows seedling production, with no loss of quality. Based on total dry matter accumulation, seedlings were classified as moderately tolerant to the salinity of 10.1 dS m-1.

Limitation in the use of spectral analysis to detect Weligama coconut leaf wilt disease affected palms in Southern Sri Lanka

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.

Effectiveness of Arbuscular Mycorrhizal Fungi based biofertilizer on early growth of coconut seedlings

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.

Identification and utilization of informative EST-SSR markers for genetic purity testing of coconut hybrids

<p>Coconut palms are categorized into two forms, <em>viz</em>., ‘talls’ and ‘dwarfs’ which are being utilized to produce hybrids through the process of inter-varietal or intra-varietal crosses. Hybrid coconut seedlings are generally identified and selected based on morphological traits by plant breeders, which is quite difficult and requires expertise. Even minor errors in identification may adversely affect breeding programs in coconut, which is spread over many decades. In this study, we have utilized thirty EST-SSR markers, derived from existing coconut leaf transcriptome data, for screening polymorphism between eighteen coconut parental lines. The polymorphic primers capable of differentiating the parental palms were then utilized successfully for assessment of purity of hybrids derived from these parents. Thus, the current study demonstrates the utility of EST-SSR markers in determining<br />the genetic purity of hybrids in coconut.</p>

ESTABLISHMENT OF YOUNG “DWARF GREEN” COCONUT PLANTS IN SOIL AFFECTED BY SALTS AND UNDER WATER DEFICIT

ABSTRACT The aim was to analyze the establishment of young “Green Dwarf” coconut plants in soils affected by salts and under water stress, by evaluating leaf area, biomass production and allocation. In the experiment, conducted in protected environment in Fortaleza, CE, in statistical design of randomized blocks in a split plot arrangement, the effects of different water deficit levels (plots) were evaluated, by imposing different percentages of replacement of water losses by potential crop evapotranspiration - ETpc (20, 40, 60, 80 and 100%), associated with subplots consisting of increasing soil salinity levels (1.72, 6.25, 25.80 and 40.70 dS m-1) provided by soil collected at different parts of the Morada Nova Irrigated Perimeter - PIMN. Leaf area and biomass production were sharply reduced by the conditions of water stress and high soil salinity, apparently being more critical to the crop under water restriction condition. The degree of water stress can increase the susceptibility to salinity and plants can be considered, in general terms, as moderately tolerant to the effects of salinity, when combined with water deficiency. Coconut seedlings show full capacity of establishment in PIMN saline soils, corresponding to the level of electrical conductivity of 6.50 dS m-1, but only when the water supply remains adequate. For higher salinity levels, plants survive, but their size is reduced by around 50%, even when fully irrigated.

Enzyme Activities and Nutrient Status in Coconut (Cocos nuciferaL.) Seedling Rhizosphere Soil after Exposure to Elevated CO2and Temperature

The elevation of CO2 and temperature could affect soil microbial mineralization and nutrient cycling in perennial crop systems. To understand this, microbial enzyme activities in the rhizosphere soil and soilplant nutrient status in coconut (Cocos nucifera L.) seedlings were investigated. Coconut seedlings were grown in elevated CO2 at 550 ([CO2]550) and 700 ([CO2]700) μmol mol−1 and elevated temperature (2°C higher than ambient control; [T]+2°C) for three years (2007–2010) in controlled field facility called open top chambers (OTCs). Activities of soil dehydrogenase (62, 27 and 69%) and phosphatase (18, 47 and 49%) were reduced under [T]+2°C, [CO2]550 and [CO2]700, respectively, while activity of cellulase (5, 24 and 33%) was increased. Soil was more acidic in elevated CO2 conditions with higher activity of amylase (9 and 32%) and lower activity of urease (54 and 49%). Though elevated temperature did not influence soil pH, it increased the activities of soil urease (19%) and invertase (23%) but decreased the activity of amylase (32%). The soil electrical conductivity was increased (67, 64 and 53%, respectively), but total soluble sugars concentration was decreased (42, 21 and 39%, respectively) in [T]+2°C, [CO2]550 and [CO2]700, respectively. While soil respiration (6%) and total phenols (4%) increased in the [CO2]550 condition. At the same time soil free amino acids were decreased (3%) in [CO2]700. Reductions of soil potassium (K, 7%), iron (Fe, 9%) and sodium (Na, 6%) content at elevated temperature and calcium (Ca, 5%) content in elevated CO2 indicates higher uptake by plant as it is evident from leaf tissue nutrient status. Changes in concentration of other major and minor nutrients in leaf tissue and soil indicates effects of CO2 and temperature on soil organic matter mineralization, nutrient uptake, microbial community and pH. The study reveals that elevated CO2 and temperature can affect soil microbial mineralization and nutrient cycling and better soil management may be required in coconut plantations under future climatic conditions.

First Report of Leaf Spot Disease in Coconut Seedling Caused by Bipolaris setariae in China.

Coconut (Cocos nucifera L.), an important oilseed as well as a multipurpose perennial plantation crop, is distributed and planted in humid tropical areas. In October 2012, a new leaf spot disease was observed on 3-year-old coconut seedlings in Wenchang, Hainan Province, China. The symptom first appeared as spindly or elliptical and brown flecks with water-soaked lesions that became yellow with the progress of the disease. In the later stage of the disease, the lesions merged together, gradually expanding to the leaf apex. In recent years, the disease has been prevalent in all the nursery gardens surveyed. Once young leaves got infected and nearly all the leaves of the tree showed diseased symptoms, the coconut eventually became defoliated. The pathogen was isolated from the lesion margin, surface sterilized with 75% ethanol and 0.1% mercury bichloride, washed by sterile distilled water, and then placed excising pieces of leaves from the leision margin onto potato dextrose agar (PDA). Plates were incubated at 25°C for 4 days. After 7 days, the colony was grayish black and produced black pigment in the medium. Aerial mycelium was fluffy, septate, and branched, the conidiophores were slightly flexuous or straight, 5 to 11 μm thick, and produced curved, spindle-shaped, or fusiform, septate conidia with 4 to 10 septa, measuring 39 to 86 × 9 to 16 μm, with a slightly protuberant hilum, truncated. Based on the symptoms and mycelial and conidial characters above, the fungus was identified as Bipolaris setariae (1). The pathogenicity was established and repeated for six times by following Koch's postulates. Two 1-year-old coconut seedlings were washed with sterilized water and six leaves were wounded with a sterile needle and then inoculated by spraying them with a suspension of conidia of the isolate. The seedlings were kept in two incubators at 25°C for 12 days. Inoculated leaves showed typical symptoms similar to those described above. The pathogen was re-isolated from inoculated leaves. Morphological characteristics were identical to the original isolated fungus. In contrast, the control leaves did not show any symptoms. The genomic DNA of this fungus was extracted, amplification of the internal transcribed spacer (ITS) region was performed with primer ITS1 and ITS4, and the purified PCR product was sequenced (GenBank Accession No. KJ605157). BLASTn analysis revealed 99% sequence similarity with four B. setariae isolates (HE792936.1, JX462256, GU073108.1, and FJ606786.1). Morphologic characters and sequence analysis of the ITS rDNA confirmed that the pathogen was B. setariae. Bipolaris incurvata has been reported causing disease on coconut (2), but B. setariae was not previously reported on coconut. So far, this is the first report of B. setariae caused coconut seedling leaf spot disease in Hainan, China.

Effect of elevated CO2 and temperature on oxidative stress and antioxidant enzymes activity in coconut (Cocosnucifera L.) seedlings

Increasing atmospheric CO2 concentration is one of the factors driving climate change. We have investigated the individual effect of elevated CO2 and temperature on oxidative stress and antioxidant enzymes activity in coconut (Cocosnucifera L.) seedlings. Three cultivars (WCT, LCT and COD) and two hybrids (WCT × COD and COD × WCT) were grown in six open top chambers (OTCs) and responses were analyzed after three years. In two OTCs the CO2 was set at 550 and 700 µmol mol−1 and control chamber had ambient level of 393 µmol mol1. In two separate OTCs, air temperature was elevated by 2 °C above the ambient control chamber. Remaining two chambers served as chamber control. Elevated CO2 and temperature increased the activities of superoxide dismutase and catalase , whereas it reduced polyphenol oxidase activity. On the other hand, peroxidase (POX) activity was decreased in elevated temperature, while it increased under elevated CO2 conditions. The POX activity and membrane stability index (MSI) were positively correlated. By virtue of greater MSI and lower MDA content, WCT and hybrid COD × WCT were observed to be tolerant to oxidative stress among the five cultivars under elevated CO2 and temperature conditions. These cultivars may adapt better to changing climates.

Leaf spot disease of coconut seedling and its eco-friendly management

The effect of weather on prevalence of seedling diseases of coconut during 2010-11 and 2011-12 in different areas of Bangladesh was studied to develop an environment friendly disease management practice. Pestalotia palmarum was isolated and identified from leaf having spot. Incidence and severity of grey leaf spot at seedling stage were determined and significant variations were observed depending on weather factors as well as locations. Occurrence of seedling disease was significantly influenced by temperature, rainfall and relative humidity. Comparative effectiveness of BAU-Biofungicide either alone or in combination with two fungicides viz. Bavistin or Dithane M-45 was evaluated on coconut seedling in the nursery. Among the treatments applied, Trichoderma harzianum based BAU-Biofungicide either alone or in combination with Bavistin (0.2%) as an excellent biocontrol means in controlling leaf spot disease of coconut. DOI: http://dx.doi.org/10.3329/jbau.v11i2.19894 J. Bangladesh Agril. Univ. 11(2): 199-208, 2013

Improving acclimatization through the photoautotrophic culture of coconut (Cocos nucifera) seedlings: an in vitro system for the efficient exchange of germplasm

An in vitro photoautotrophic step based on the supply of CO2-enriched air (1,600 μmol mol−1) during the light phase and ambient air (350 μmol mol−1 CO2) during the dark phase has been used to promote the ex vitro establishment of coconut (Cocos nucifera L.) seedlings. The introduction of this step into a previously developed in vitro protocol was found to improve the quality of the seedlings (as assessed by fresh weight increase, physical stature, leaf area and thickness, stomatal density, and chlorophyll a content, and primary and secondary root production), the proportion of seedlings successfully transferred to soil (improvement from 40% to 100%) and achieved in a shorter time (reduction from 10 to 6 mo). Best results using this photoautotrophic growth step were obtained when a low medium concentration of sucrose (43.8 mM or lower) was used, when it was applied to seedlings that had already reached 4 or 5 mo of age in the in vitro culture step, and when seedlings were cultured in the photoautotrophic system for 2 mo or more before transfer to soil. Our improved protocol is more efficient and it reduces the cost per plant for the international exchange of coconut germplasm.

Comparative Evaluation of Different Organic Fertilizer Effects on Soil Fertility, Leaf Chemical Composition and Growth Performance of Coconut (Cocos nucifera L.) Seedlings

Comparative Evaluation of Different Organic Fertilizer Effects on Soil Fertility, Leaf Chemical Composition and Growth Performance of Coconut (Cocos nucifera L.) Seedlings

Pengaruh Pemberian Pupuk Kandang Kotoran Ayam dan Pupuk NPK Mutiara Yaramila terhadap Pertumbuhan Bibit Kelapa Sawit (Elaeis Guineensis Jacg.) pada Pembibitan Pre Nursery

This study aims: (1) to determine the effect of chicken manure and Yaramila NPK fertilizer on the growth of oil palm seedlings in pre-nursery nurseries and (2) to determine the single factor of chicken manure and Yamila pearl NPK fertilizer on the growth of coconut seedlings palm in pre-nursery nurseries. This experiment used factorial completely randomized design with three factors and three replications. The second factor studied was: Factor I: Giving Chicken Manure (P) which consists of 4 levels, namely: P0 = 0 ton / ha, P1 = 20 ton / ha, P2 = 30 ton / ha, and P3 = 40 ton / ha. Factor II: Fertilizer Giving NPK Mutiara Yaramila (Y) consisting of 4 levels, namely: Y0 = 0 kg / ha, Y1 = 200 kg / ha, Y2 = 300 kg / ha, and Y3 = 400 kg / ha.As for the number of leaf parameters, the interaction between them does not produce real or very real.The parameters of seed height were 4, 8 and 12 MST (17.9 cm, 34.4 cm and 44.3 cm), stem diameter aged 4, 8 and 12 MST (0.57 cm, 0.60 cm and 0.92 cm), parent root length (25.3 cm) and fresh seed weight (16.87 grams) per day. Chicken Manure Fertilizer at a dose of 40 tons / ha and Yaramila Pearl NPK Fertilizer at a dose of 400 kg / ha (P3Y3).

Nucleic acid based detection technique for Ganoderma lucidum in coconut

Basal stem rot caused by Ganoderma lucidum is the most serious disease in coconut and arecanut gardens. Twenty-five Ganoderma isolates were collected from different parts of India and the pathogenicity of Ganoderma was proved on coconut seedlings. Mature sporophores developed within 10–13 weeks after inoculation of pathogen under in vivo. To detect the pathogen at early stage, DNA-based technology, polymerase chain reaction was used. In this, the primers Gan1 and Gan2 produced a product of 167 bp in size for all the Ganoderma isolates tested. Simultaneously, ITS 1 and ITS 4 primers amplified a fragment of 680 bp in the Ganoderma isolates. In addition, Ganoderma isolates showed polymorphism in the random amplified polymorphic DNA analysis.

First Report of Marasmiellus palmivorus Causing Post-Emergence Damping Off on Coconut Seedlings in Malaysia.

In April and June 2010, coconut seedlings with symptoms of very slow growth, yellowing of leaves, and general abnormal leaf growth were observed in germination beds in Teluk Intan, Perak, Malaysia. The roots were soft, rotten, and brown, extending upward and downward from these lesions. Rhizomorphs and basidiocarps were produced on coconut seeds near the germination eye and identified as Marasmiellus palmivorus according description by Turner (2). Three isolates were obtained by plating surface sterilized symptomatic roots and basidiocarp on malt extract agar (MEA) amended with 85% lactic acid (1 ml added to 11 of the medium). To confirm the identity of the fungus, genomic DNA was extracted from mycelia and basidiocarps of isolates and the large subunit (LSU) region was amplified and sequenced using LR0R/LR7 primers (3). All isolates had identical LSU sequences (GenBank Accession No. JQ654233 to JQ654235). Sequences were identical to each other and 99% similar to a M. palmivorus sequence deposited in the NCBI database (Accession No. AY639434).To confirm pathogenicity, three isolates of M. palmivorus that were obtained from symptomatic plant tissue was inoculated onto seeds of Malaysian Red Dwarf variety. Each isolate was grown in 100 ml of malt extract broth in 250 ml Erlenmeyer flasks and incubated at 27 ± 2°C for 5 days on an orbital shaker (125 rpm). The resulting culture was passed through two layers of sterile cloth. Mycelial suspension was obtained by blending mycelia in 100 ml of sterile water. Seeds were sterilized by soaking in 10% v/v sodium hypochlorite in distilled water for 3 min. The seeds were then rinsed three times over running tap water. The calyx portion of the seed was removed and five holes were made around the germination eye. The seeds were inoculated by injecting 2 ml of suspension into each hole. The control seeds were inoculated with sterile distilled water only. The seeds were transferred to 40-cm diameter plastic pots containing a mixture of sand, soil, and peat in the ratio of 3:2:1, respectively, and steam treated at 100°C for 1.5 h. Pots were placed in the glasshouse with normal exposures to day-night cycles, temperatures of 29 ± 4°C, and high relative humidity (85 to 95%) achieved by spraying water twice daily. After 2 months, 75% of the inoculated seeds failed to germinate. It was speculated that the artificial inoculum was higher than under germination bed conditions. Rhizomorphs and basidiocarps were produced on husk seeds near the germination eye. Seedlings that emerged successfully developed symptoms similar to those observed in the germination bed. No symptoms developed in the noninoculated seeds and seedlings. At 80 days post inoculation, basidiocarps were observed emerging from three diseased seedlings near the germination eye. Three reisolations were made on MEA from root lesions surface sterilized. Pathogenicity tests and LSU sequence analyses indicated that M. palmivorus is the causal agent of the symptoms observed on coconut seedlings. M. palmivorus was first recorded on coconuts and oil palm in the 1920s (1) and attacks the fruit and the petiole on oil palm (2). To our knowledge, this is the first report of M. palmivorus causing post-emergence damping off on coconut seedlings.

Development of a RAPD-derived SCAR marker associated with tall-type palm trait in coconut

Coconut palms are classified into two major types, viz. ‘talls’ and ‘dwarfs’, based on plant stature. The selection of coconut seedlings in the nursery, presently relying solely on morphological markers, often results in selection of out-crossed seedlings. Hence, identification of molecular markers for distinguishing tall/dwarf character at an early stage of growth assumes importance. In the present investigation, a RAPD marker for tall-type palm trait was identified using a pooled DNA approach. Screening of tall and dwarf palm bulked DNA with 200 decamer primers revealed a primer OPA09, producing a unique band of around 260bp exclusively in tall accessions. The primer was used for screening and validation in individual tall and dwarf coconut accessions representing different geographic regions. The band was present in all the tall accessions, but absent in the dwarfs. Furthermore, sequence characterized amplified region (SCAR) primers were designed from the unique RAPD amplicon. The primers produced a specific 260-bp amplicon in tall accessions, but not in dwarf accessions. The SCAR marker was utilized in assessing the purity of hybrid seedlings of D×T (Dwarf×Tall) cross. The results pave the way for ensuring genuineness/quality of hybrid seedlings of coconut.

Effect of Soil Physical and Water Stress on Biochemical Aspects of Coconut Seedlings (Cocos nucifera) in Sri Lanka

The Journal of Agricultural Sciences is a peer reviewed journal aiming to publish high quality articles on topical issues in Agriculture. The journal provides a forum for Sri Lankan and international scholars especially in Asia and Africa to publish authoritative and well referenced articles in agriculture related areas. The journal publishes original research works, book reviews, short communications and comparative articles. JAS is published by the Faculty of Agricultural Sciences of the Sabaragamuwa University of Sri Lanka.The journal adheres to the publication ethics as portrayed by the Committee on Publication Ethics (COPE) and is a member of this Organisation,The Journal is also available on the Sabaragamuwa University of Sri Lanka website http://www.sab.ac.lk/agri-journalIt is indexed in Web of Science (WoS) as an ESCI journal , Scopus, DOAJ and EBSCO.According to Google Scholar ,Citation years: 3 (2018-2020)Citations/paper: 1.23Hirsch h-index: 4 Egghe g-index: 5

Impact of Glyphosate on Weed Biomass and Growth of Coconut Seedlings in Nurseries

The effects of five different weed management systems on growth of coconut seedlings were evaluated to determine an economical and effective method for controlling weeds in coconut nurseries in the low country of the wet zone in Sri Lanka. The treatments comprised of manual weeding (T1), application of glyphosate at 1.44 kg ai/ha (T2), 1.08 kg ai/ha (T3), 0.72 kg ai/ha (T4) and 0.36 kg ai/ha (T5) applied at three-month intervals. Treatments 1 and 2 significantly reduced the weed biomass when compared to other treatments. The growth of coconut seedlings (in terms of height and girth) increased significantly (P<0.05) with the application of glyphosate at 1.08 kg ai/ha (T3) at the end of the nursery growth period. At the higher concentration (1.44 kg ai/ha) the growth of seedlings was reduced at the latter part of the experiment. Therefore, the most costeffective treatment of controlling weeds in the study was to apply glyphosate at the rate of 1.08 kg ai/ha (3l of commercial mixture/ha). Manual weeding was neither effective no economical. DOI: http://dx.doi.org/10.4038/cocos.v19i1.4750

The Effect of Different Concentration of Glyphosate on the Growth of Coconut Seedlings

Coconut (Cocos nucifera L) is one of the predominant plantation crops in Sri Lankan economy which is known to have existed for over thousands of years. During the past decades coconut production had been reduced by a significant quantity. The usage of poor quality planting materials is a major reason for the low coconut production. Thus much attention needs to be paid in coconut nurseries. Weed management is a critical management practice in the nursery. Though glyphosate application is becoming popular in nurseries it can affect weeds as well as coconut seedlings growth. Therefore the effects of glyphosate were evaluated by determining the growth of shoot and root of coconut seedlings. Poly bag nursery was prepared and three treatments were used. Treatments were no glyphosate and manual weeding (T1), application of glyphosate 1.08 ai kg ha-1 at 2 monthly interval (T2) and application of glyphosate 1.44 ai kg ha-1 at 2 monthly interval (T3). Application of glyphosate at early stage of seedling growth had a no significant effect on growth parameters tested. However, the concentrations of glyphosate negatively affected numbers, volumes and dry weights of secondary, tertiary and quaternary roots at the latter stage of seedling growth. The leaf area and the height of seedling were significantly reduced by the highest concentration of glyphosate. Among the growth parameters tested, seedling girth and shoot dry weight were not affected by the application of glyphosate. These results revealed that the usage of glyphosate at both concentrations negatively affected root growth of coconut seedlings. Based on these results, the both concentration levels of glyphosate should be applied to coconut nurseries before sprouting the seed nuts.

Multifarious beneficial traits and plant growth promoting potential of Serratia marcescens KiSII and Enterobacter sp. RNF 267 isolated from the rhizosphere of coconut palms (Cocos nucifera L.)

Two plant growth promoting bacteria designated as KiSII and RNF 267 isolated from the rhizosphere of coconut palms were identified as Serratia marcescens and Enterobacter sp. based on their phenotypic features, BIOLOG studies and 16S rRNA gene sequence analysis. Both bacteria exhibited phosphate solubilization, ammonification, and production of indole acetic acid, β-1, 3 glucanase activities and 1-aminocyclopropane-1-carboxylate-deaminase activity. They could also tolerate a range of pH conditions, low temperature and salinity (NaCl). In addition, S. marcescens KiSII exhibited N- fixation potential, chitinase activity, siderophore production and antibiotics production. Seed bacterization with these bacteria increased the growth parameters of test plants such as paddy and cowpea over uninoculated control in green house assay. In coconut seedlings, significant increase in growth and nutrient uptake accompanied with higher populations of plant beneficial microorganisms in their rhizospheres were recorded on inoculation with both the PGPRs. The present study clearly revealed that PGPRs can aid in production of healthy and vigorous seedlings of coconut palm which are hardy perennial crops. They offer a scope to be developed into novel PGPR based bioinoculants for production of elite seedlings that can benefit the coconut farming community and the coconut based ecology.