The pressure due to global population increase and rising environmental damage has the unfortunat... more The pressure due to global population increase and rising environmental damage has the unfortunate consequence that world food production may shortly become inadequate to feed all the mouths of the world. It is therefore indispensable that agricultural productivity be significantly improved within next couple of decades. To achieve this, agricultural practices are approached in a more sustainable and eco-friendly manner. Further, the substantial use of chemical fertilizers and pesticides in conventional farming has led to the accumulation of harmful chemical remnants and heavy metals in the environment leading to degradation of agroecosystem and incidence of unpredictable chronic diseases in human. Therefore, biofilmed biofertilizers (BFBFs) have become a viable alternative for chemical fertilizers in agriculture. BFBFs, in addition to their fertilizing task, accomplish a variety of processes such as reinstating agroecosystem, maintaining regulated metabolic and biochemical processes, improving soil quality, suppression of pests and diseases, amelioration of plants from stress and synthesis of plant hormones. The consortia of microbes in BFBFs add an array of benefits together for the soil-plant system to support plant growth and development thereby to enhance the yield. Moreover, BFBF itself is a sustainable system which can ensure the sustainability of agroecosystem. Therefore, the use of BFBFs in agriculture would lead to a more eco-friendly approach in crop production with many health, environmental and economic benefits.
American Journal of Agriculture and Forestry, 2015
Ixora or Jungle Geranium (Ixora coccinea) is an invaluable plant in tropical landscapes for its b... more Ixora or Jungle Geranium (Ixora coccinea) is an invaluable plant in tropical landscapes for its beautiful foliage, easiness of growing and fabulous flowers freely formed and artfully presented. Sri Lanka exports Ixora hybrids as planting materials after rooting the Ixora cuttings on a coir dust media. Exporting potted Ixora plants with flowers is more beneficial than that without flowers as flowers increase product quality and gain customer attraction. In commercial floriculture venture, flower induction at young age using plant growth regulators and fertilizers is a popular practice. An experiment was conducted to investigate the most effective combination of a plant growth regulator and fertilizers for early flower initiation of Ixora hybrids; Vulcanus, Chanmai, Nora grant and Kontiki under outdoor and shaded conditions. Six-month-aged healthy plants of Ixora hybrids grown in containers were treated with a flowering hormone containing Nitrobenzene in combination with two fertilizer types: F1-Bloom special and F2-Krista K 44. Flowering hormone was sprayed in four concentrations; H1= 0.075% (V/V), H2 = 0.100% (V/V), H3 = 0.125% (V/V) and H4 = 0.150% (V/V) once in two weeks. Both fertilizers were applied as a liquid spray in same concentration (1 g/L of water) once a week. All the cultural practices were similarly applied to the plants under two light levels (outdoor light 'L1'and shaded conditions 'L2'). There were 16 treatment combinations and control, each with five replicates. Each treatment combination consisted of three plants. The number of flower-initiated plants per treatment combination was recorded as a percentage for five weeks. Percentage values after five weeks of treatments were transformed into log values and used for the analysis of variance. All the hybrids except Vulcanus showed a significant flower induction compared to the control. Outdoor light and shaded conditions were not significantly different to each other showing the potentiality of early flower initiation of hybrids under shaded condition. However, no significant difference in flower induction was observed among four levels of the flowering hormone and the two types of fertilizers (p> 0.05) in all four Ixora hybrids despite differences among the hybrids. Therefore, it could be concluded that the least expensive combination of hormone and fertilizer type could play a profitable and a positive role in early flower induction of Ixora at an age of six months.
American Journal of Environmental Protection, 2015
Cyanobacterial toxins available in drinking water pose a major health problem to humans and anima... more Cyanobacterial toxins available in drinking water pose a major health problem to humans and animals. Nuwara wewa and Nachchaduwa wewa are two important reservoirs supplying water for domestic purposes in Anuradhapura, Sri Lanka. As cyanobacterial toxins are resistant to deactivation by heat, it is important to control the proliferation of cyanobacteria in these reservoirs. Therefore, making an inventory of cyanobacterial variations with respect to time and space is imperative. Distinct temporal variations of temperature, pH, turbidity, dissolved oxygen and cyanobacteria density were observed in both reservoirs. Strong positive correlations existed between the above physico-chemical parameters of water and the cyanobacterial density in both reservoirs. These parameters can therefore be used as good indicators to assess the status these reservoirs with respect to cyanobacterial density and distribution.
A method of historical inference that accounts for ascertainment bias is developed and applied to... more A method of historical inference that accounts for ascertainment bias is developed and applied to single-nucleotide polymorphism (SNP) data in humans. The data consist of 84 short fragments of the genome that were selected, from three recent SNP surveys, to contain at least two polymorphisms in their respective ascertainment samples and that were then fully resequenced in 47 globally distributed individuals. Ascertainment bias is the deviation, from what would be observed in a random sample, caused either by discovery of polymorphisms in small samples or by locus selection based on levels or patterns of polymorphism. The three SNP surveys from which the present data were derived differ both in their protocols for ascertainment and in the size of the samples used for discovery. We implemented a Monte Carlo maximum-likelihood method to fit a subdivided-population model that includes a possible change in effective size at some time in the past. Incorrectly assuming that ascertainment bias does not exist causes errors in inference, affecting both estimates of migration rates and historical changes in size. Migration rates are overestimated when ascertainment bias is ignored. However, the direction of error in inferences about changes in effective population size (whether the population is inferred to be shrinking or growing) depends on whether either the numbers of SNPs per fragment or the SNP-allele frequencies are analyzed. We use the abbreviation "SDL," for "SNP-discovered locus," in recognition of the genomic-discovery context of SNPs. When ascertainment bias is modeled fully, both the number of SNPs per SDL and their allele frequencies support a scenario of growth in effective size in the context of a subdivided population. If subdivision is ignored, however, the hypothesis of constant effective population size cannot be rejected. An important conclusion of this work is that, in demographic or other studies, SNP data are useful only to the extent that their ascertainment can be modeled.
Additional file 1: Supplementary Data 1. Consensus sequence of endogenous geminiviral elements of... more Additional file 1: Supplementary Data 1. Consensus sequence of endogenous geminiviral elements of macadamia initially developed by computational approach and pairwise sequence alignment and contig assembly methods.
Additional file 3: Supplementary Figure 2. Detection of circular forms of geminiviral DNA using t... more Additional file 3: Supplementary Figure 2. Detection of circular forms of geminiviral DNA using the TempliPhi assay, a sequence non-specific amplification method.
Aquatic ecosystems are contaminated with heavy metals by natural and anthropogenic sources. Whils... more Aquatic ecosystems are contaminated with heavy metals by natural and anthropogenic sources. Whilst some heavy metals are necessary for plants as micronutrients, others can be toxic to plants and humans even in trace concentrations. Among heavy metals, cadmium (Cd), arsenic (As), chromium (Cr), lead (Pb), and mercury (Hg) cause significant damage to aquatic ecosystems and can invariably affect human health. Rice, a staple diet of many nations, and other aquatic plants used as vegetables in many countries, can bioaccumulate heavy metals when they grow in contaminated aquatic environments. These metals can enter the human body through food chains, and the presence of heavy metals in food can lead to numerous human health consequences. Heavy metals in aquatic plants can affect plant physicochemical functions, growth, and crop yield. Various mitigation strategies are being continuously explored to avoid heavy metals entering aquatic ecosystems. Understanding the levels of heavy metals in...
Background Ziziphus jujuba is an important fruit crop which is increasingly becoming popular amon... more Background Ziziphus jujuba is an important fruit crop which is increasingly becoming popular among consumers due to its medicinal properties. Increasing worldwide demand for the fruit poses new challenges to the industry which includes the need for accelerated cultivar development of jujubes. To embark on cultivar development with improved traits such as high yield and disease resistance, molecular and conventional breeding, and genetic engineering become imperative. But inadequate trait-enhancing alleles or gene pleiotropism limit the direct use of several identified genes. To overcome these issues, microRNAs (miRNAs) can be utilized in breeding of jujubes as genetic modulators to fine-tune the regulation of gene expression, thus the discovery of miRNAs becomes important. Methods and results In this study using a computational approach, we identified one potential miRNA (zju-miR-215-3p) from 2904 expressed sequence tags. The miRNA showed down regulation of five target proteins (AP-...
Total agricultural land of the globe becomes insufficient due to the progressive nature of primar... more Total agricultural land of the globe becomes insufficient due to the progressive nature of primary and secondary salinity. High salt content in the irrigation water or soil is a serious restriction factor to the cultivation of many crops. Salinity has significant influence in maintaining the balance nature of osmosis, the availability of water and nutrients, and the formation of free radicals in plant. The consequence of these factors causes undesirable effect on photosynthesis, growth, and development of numerous economically important plants. This review evaluates the management practices or strategies based on the combination of approaches through management of soil-borne pathogens, root-zone salinity management, quality irrigation, and cultural practices to accelerate the removal of salts and cultivation of salt-tolerant plants. Root-zone salinity is mainly controlled by different irrigation systems and leaching and by the use of appropriate plants to maintain the water table. There is a diverse strategy that can be applied through quality irrigation and cultural practices. Different modes of irrigation, tillage, and bio-drainage, addition of organic matters and gypsum, and application of sulfur are some of them. However, growing salt-tolerant plants along with the traditional methods of managing the saline environment take a momentum to reduce the effect of high salinity. Genetic engineering approach through the deep understanding of physiological response of plants to salinity would augment the identification of potential gens for developing transgenic plants. Application of microbes, organic matters, and green remediation also has proved the improvement of plant health and productivity under salinity and biotic stress. These management strategies provide an insight to the effective crop production under saline environment.
This study examines teachers' understanding of the connections between key concepts of biotec... more This study examines teachers' understanding of the connections between key concepts of biotechnology and underlying biological principles that are critical for an in-depth understanding of biotechnology education in school. Many teachers in Sri Lanka avoid addressing biotechnology topics available in the A-level biology curriculum (age 16-18). We aimed to explore the factors that influence teachers' practice. Using a structured questionnaire, we examined randomly selected teachers' understanding of these relationships at school level in the Eastern Province in Sri Lanka. Findings from this study were as follows. Teachers strongly believe that biotechnology is interesting and important for life improvement and this attitude influences their practice in biotechnology education. Almost all the teachers had a good knowledge of biotechnology but not the relationship between application and basic knowledge. The teachers were willing to buy genetically modified (GM) foods if th...
Abnormal vertical growth (AVG) causes significant yield losses to the Australian macadamia indust... more Abnormal vertical growth (AVG) causes significant yield losses to the Australian macadamia industry and the cause is unknown. Studies on the spread of AVG and molecular analysis of trees with AVG symptoms suggest the involvement of a slow spreading pathogen that does not produce copious amount of inoculum nor is spread by flying insects. The possibility that Bacillus megaterium, elements of a bipartite geminivirus and phytoplasmas are associated with AVG aetiology was investigated using specific PCR assays. Leaf samples from 118 trees including wild accessions of the four Macadamia species, and commercial cultivars of Hawaiian and Australian selections with and without AVG symptoms were tested. The assays detected geminiviral elements and B. megaterium, but not phytoplasma in trees with and without AVG symptoms. The absence of phytoplasmas together with no statistically significant relationship between the presence of either B. megaterium or geminiviral elements and AVG symptoms, suggests that all three agents are not the cause of the disease. The frequency of detection of B. megaterium was higher in samples from trees without AVG (66%) than trees with AVG (34%). In contrast, the frequency of detection of geminiviral elements was higher in trees with AVG (64%) than trees without AVG (36%). Geminiviral elements were detected in the wild accessions of the four Macadamia species, whereas B. megaterium was only detected in M. integrifolia and M. jansenii. The Hawaiian and Australian selections were positive for B. megaterium and geminiviral elements.
Australian macadamia production is threatened by a disorder known as abnormal vertical growth (AV... more Australian macadamia production is threatened by a disorder known as abnormal vertical growth (AVG), for which the etiology is unknown. AVG is characterized by vigorous upright growth and reduced lateral branching, flowering, and nut set that results in over 70% yield loss annually. Six commercial macadamia orchards were surveyed in 2012 and again in 2018 to examine spatiotemporal dynamics of the epidemic. Data were subjected to point-pattern and geostatistical analyses. AVG incidence in all orchards showed a better fit to the beta-binomial distribution than the binomial distribution. AVG incidence in the different orchards varied between 5 and 47% in 2012, and 13 and 55% in 2018 and the rate of spread was slow, averaging at about 2% increase in disease incidence per annum. Spatial patterns of AVG were highly aggregated on both survey years and spread was mainly between neighboring trees in a row or trees that were opposite to each other in different rows. Semivariograms showed larg...
The pressure due to global population increase and rising environmental damage has the unfortunat... more The pressure due to global population increase and rising environmental damage has the unfortunate consequence that world food production may shortly become inadequate to feed all the mouths of the world. It is therefore indispensable that agricultural productivity be significantly improved within next couple of decades. To achieve this, agricultural practices are approached in a more sustainable and eco-friendly manner. Further, the substantial use of chemical fertilizers and pesticides in conventional farming has led to the accumulation of harmful chemical remnants and heavy metals in the environment leading to degradation of agroecosystem and incidence of unpredictable chronic diseases in human. Therefore, biofilmed biofertilizers (BFBFs) have become a viable alternative for chemical fertilizers in agriculture. BFBFs, in addition to their fertilizing task, accomplish a variety of processes such as reinstating agroecosystem, maintaining regulated metabolic and biochemical processes, improving soil quality, suppression of pests and diseases, amelioration of plants from stress and synthesis of plant hormones. The consortia of microbes in BFBFs add an array of benefits together for the soil-plant system to support plant growth and development thereby to enhance the yield. Moreover, BFBF itself is a sustainable system which can ensure the sustainability of agroecosystem. Therefore, the use of BFBFs in agriculture would lead to a more eco-friendly approach in crop production with many health, environmental and economic benefits.
American Journal of Agriculture and Forestry, 2015
Ixora or Jungle Geranium (Ixora coccinea) is an invaluable plant in tropical landscapes for its b... more Ixora or Jungle Geranium (Ixora coccinea) is an invaluable plant in tropical landscapes for its beautiful foliage, easiness of growing and fabulous flowers freely formed and artfully presented. Sri Lanka exports Ixora hybrids as planting materials after rooting the Ixora cuttings on a coir dust media. Exporting potted Ixora plants with flowers is more beneficial than that without flowers as flowers increase product quality and gain customer attraction. In commercial floriculture venture, flower induction at young age using plant growth regulators and fertilizers is a popular practice. An experiment was conducted to investigate the most effective combination of a plant growth regulator and fertilizers for early flower initiation of Ixora hybrids; Vulcanus, Chanmai, Nora grant and Kontiki under outdoor and shaded conditions. Six-month-aged healthy plants of Ixora hybrids grown in containers were treated with a flowering hormone containing Nitrobenzene in combination with two fertilizer types: F1-Bloom special and F2-Krista K 44. Flowering hormone was sprayed in four concentrations; H1= 0.075% (V/V), H2 = 0.100% (V/V), H3 = 0.125% (V/V) and H4 = 0.150% (V/V) once in two weeks. Both fertilizers were applied as a liquid spray in same concentration (1 g/L of water) once a week. All the cultural practices were similarly applied to the plants under two light levels (outdoor light 'L1'and shaded conditions 'L2'). There were 16 treatment combinations and control, each with five replicates. Each treatment combination consisted of three plants. The number of flower-initiated plants per treatment combination was recorded as a percentage for five weeks. Percentage values after five weeks of treatments were transformed into log values and used for the analysis of variance. All the hybrids except Vulcanus showed a significant flower induction compared to the control. Outdoor light and shaded conditions were not significantly different to each other showing the potentiality of early flower initiation of hybrids under shaded condition. However, no significant difference in flower induction was observed among four levels of the flowering hormone and the two types of fertilizers (p> 0.05) in all four Ixora hybrids despite differences among the hybrids. Therefore, it could be concluded that the least expensive combination of hormone and fertilizer type could play a profitable and a positive role in early flower induction of Ixora at an age of six months.
American Journal of Environmental Protection, 2015
Cyanobacterial toxins available in drinking water pose a major health problem to humans and anima... more Cyanobacterial toxins available in drinking water pose a major health problem to humans and animals. Nuwara wewa and Nachchaduwa wewa are two important reservoirs supplying water for domestic purposes in Anuradhapura, Sri Lanka. As cyanobacterial toxins are resistant to deactivation by heat, it is important to control the proliferation of cyanobacteria in these reservoirs. Therefore, making an inventory of cyanobacterial variations with respect to time and space is imperative. Distinct temporal variations of temperature, pH, turbidity, dissolved oxygen and cyanobacteria density were observed in both reservoirs. Strong positive correlations existed between the above physico-chemical parameters of water and the cyanobacterial density in both reservoirs. These parameters can therefore be used as good indicators to assess the status these reservoirs with respect to cyanobacterial density and distribution.
A method of historical inference that accounts for ascertainment bias is developed and applied to... more A method of historical inference that accounts for ascertainment bias is developed and applied to single-nucleotide polymorphism (SNP) data in humans. The data consist of 84 short fragments of the genome that were selected, from three recent SNP surveys, to contain at least two polymorphisms in their respective ascertainment samples and that were then fully resequenced in 47 globally distributed individuals. Ascertainment bias is the deviation, from what would be observed in a random sample, caused either by discovery of polymorphisms in small samples or by locus selection based on levels or patterns of polymorphism. The three SNP surveys from which the present data were derived differ both in their protocols for ascertainment and in the size of the samples used for discovery. We implemented a Monte Carlo maximum-likelihood method to fit a subdivided-population model that includes a possible change in effective size at some time in the past. Incorrectly assuming that ascertainment bias does not exist causes errors in inference, affecting both estimates of migration rates and historical changes in size. Migration rates are overestimated when ascertainment bias is ignored. However, the direction of error in inferences about changes in effective population size (whether the population is inferred to be shrinking or growing) depends on whether either the numbers of SNPs per fragment or the SNP-allele frequencies are analyzed. We use the abbreviation "SDL," for "SNP-discovered locus," in recognition of the genomic-discovery context of SNPs. When ascertainment bias is modeled fully, both the number of SNPs per SDL and their allele frequencies support a scenario of growth in effective size in the context of a subdivided population. If subdivision is ignored, however, the hypothesis of constant effective population size cannot be rejected. An important conclusion of this work is that, in demographic or other studies, SNP data are useful only to the extent that their ascertainment can be modeled.
Additional file 1: Supplementary Data 1. Consensus sequence of endogenous geminiviral elements of... more Additional file 1: Supplementary Data 1. Consensus sequence of endogenous geminiviral elements of macadamia initially developed by computational approach and pairwise sequence alignment and contig assembly methods.
Additional file 3: Supplementary Figure 2. Detection of circular forms of geminiviral DNA using t... more Additional file 3: Supplementary Figure 2. Detection of circular forms of geminiviral DNA using the TempliPhi assay, a sequence non-specific amplification method.
Aquatic ecosystems are contaminated with heavy metals by natural and anthropogenic sources. Whils... more Aquatic ecosystems are contaminated with heavy metals by natural and anthropogenic sources. Whilst some heavy metals are necessary for plants as micronutrients, others can be toxic to plants and humans even in trace concentrations. Among heavy metals, cadmium (Cd), arsenic (As), chromium (Cr), lead (Pb), and mercury (Hg) cause significant damage to aquatic ecosystems and can invariably affect human health. Rice, a staple diet of many nations, and other aquatic plants used as vegetables in many countries, can bioaccumulate heavy metals when they grow in contaminated aquatic environments. These metals can enter the human body through food chains, and the presence of heavy metals in food can lead to numerous human health consequences. Heavy metals in aquatic plants can affect plant physicochemical functions, growth, and crop yield. Various mitigation strategies are being continuously explored to avoid heavy metals entering aquatic ecosystems. Understanding the levels of heavy metals in...
Background Ziziphus jujuba is an important fruit crop which is increasingly becoming popular amon... more Background Ziziphus jujuba is an important fruit crop which is increasingly becoming popular among consumers due to its medicinal properties. Increasing worldwide demand for the fruit poses new challenges to the industry which includes the need for accelerated cultivar development of jujubes. To embark on cultivar development with improved traits such as high yield and disease resistance, molecular and conventional breeding, and genetic engineering become imperative. But inadequate trait-enhancing alleles or gene pleiotropism limit the direct use of several identified genes. To overcome these issues, microRNAs (miRNAs) can be utilized in breeding of jujubes as genetic modulators to fine-tune the regulation of gene expression, thus the discovery of miRNAs becomes important. Methods and results In this study using a computational approach, we identified one potential miRNA (zju-miR-215-3p) from 2904 expressed sequence tags. The miRNA showed down regulation of five target proteins (AP-...
Total agricultural land of the globe becomes insufficient due to the progressive nature of primar... more Total agricultural land of the globe becomes insufficient due to the progressive nature of primary and secondary salinity. High salt content in the irrigation water or soil is a serious restriction factor to the cultivation of many crops. Salinity has significant influence in maintaining the balance nature of osmosis, the availability of water and nutrients, and the formation of free radicals in plant. The consequence of these factors causes undesirable effect on photosynthesis, growth, and development of numerous economically important plants. This review evaluates the management practices or strategies based on the combination of approaches through management of soil-borne pathogens, root-zone salinity management, quality irrigation, and cultural practices to accelerate the removal of salts and cultivation of salt-tolerant plants. Root-zone salinity is mainly controlled by different irrigation systems and leaching and by the use of appropriate plants to maintain the water table. There is a diverse strategy that can be applied through quality irrigation and cultural practices. Different modes of irrigation, tillage, and bio-drainage, addition of organic matters and gypsum, and application of sulfur are some of them. However, growing salt-tolerant plants along with the traditional methods of managing the saline environment take a momentum to reduce the effect of high salinity. Genetic engineering approach through the deep understanding of physiological response of plants to salinity would augment the identification of potential gens for developing transgenic plants. Application of microbes, organic matters, and green remediation also has proved the improvement of plant health and productivity under salinity and biotic stress. These management strategies provide an insight to the effective crop production under saline environment.
This study examines teachers' understanding of the connections between key concepts of biotec... more This study examines teachers' understanding of the connections between key concepts of biotechnology and underlying biological principles that are critical for an in-depth understanding of biotechnology education in school. Many teachers in Sri Lanka avoid addressing biotechnology topics available in the A-level biology curriculum (age 16-18). We aimed to explore the factors that influence teachers' practice. Using a structured questionnaire, we examined randomly selected teachers' understanding of these relationships at school level in the Eastern Province in Sri Lanka. Findings from this study were as follows. Teachers strongly believe that biotechnology is interesting and important for life improvement and this attitude influences their practice in biotechnology education. Almost all the teachers had a good knowledge of biotechnology but not the relationship between application and basic knowledge. The teachers were willing to buy genetically modified (GM) foods if th...
Abnormal vertical growth (AVG) causes significant yield losses to the Australian macadamia indust... more Abnormal vertical growth (AVG) causes significant yield losses to the Australian macadamia industry and the cause is unknown. Studies on the spread of AVG and molecular analysis of trees with AVG symptoms suggest the involvement of a slow spreading pathogen that does not produce copious amount of inoculum nor is spread by flying insects. The possibility that Bacillus megaterium, elements of a bipartite geminivirus and phytoplasmas are associated with AVG aetiology was investigated using specific PCR assays. Leaf samples from 118 trees including wild accessions of the four Macadamia species, and commercial cultivars of Hawaiian and Australian selections with and without AVG symptoms were tested. The assays detected geminiviral elements and B. megaterium, but not phytoplasma in trees with and without AVG symptoms. The absence of phytoplasmas together with no statistically significant relationship between the presence of either B. megaterium or geminiviral elements and AVG symptoms, suggests that all three agents are not the cause of the disease. The frequency of detection of B. megaterium was higher in samples from trees without AVG (66%) than trees with AVG (34%). In contrast, the frequency of detection of geminiviral elements was higher in trees with AVG (64%) than trees without AVG (36%). Geminiviral elements were detected in the wild accessions of the four Macadamia species, whereas B. megaterium was only detected in M. integrifolia and M. jansenii. The Hawaiian and Australian selections were positive for B. megaterium and geminiviral elements.
Australian macadamia production is threatened by a disorder known as abnormal vertical growth (AV... more Australian macadamia production is threatened by a disorder known as abnormal vertical growth (AVG), for which the etiology is unknown. AVG is characterized by vigorous upright growth and reduced lateral branching, flowering, and nut set that results in over 70% yield loss annually. Six commercial macadamia orchards were surveyed in 2012 and again in 2018 to examine spatiotemporal dynamics of the epidemic. Data were subjected to point-pattern and geostatistical analyses. AVG incidence in all orchards showed a better fit to the beta-binomial distribution than the binomial distribution. AVG incidence in the different orchards varied between 5 and 47% in 2012, and 13 and 55% in 2018 and the rate of spread was slow, averaging at about 2% increase in disease incidence per annum. Spatial patterns of AVG were highly aggregated on both survey years and spread was mainly between neighboring trees in a row or trees that were opposite to each other in different rows. Semivariograms showed larg...
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