In three field trials on the epidemiology of blast disease in upland rice, different methods of s... more In three field trials on the epidemiology of blast disease in upland rice, different methods of sampling spores of Pyricularia grisea were compared to study aerial concentration, deposition, survival, and infectiousness of conidia of the pathogen. The methods included a Burkard spore trap, glass slides and rods, several trap-plant treatments, and leaf prints from trap plants. The results were mostly highly intercorrelated and revealed a unimodal pattern of disease progression, with peaks before or at the middle of the cropping seasons. The number of conidia per square centimeter deposited on leaf surfaces as measured by leaf prints made up one-fourth of the number caught with glass slides [...]
Systems Approaches for Sustainable Agricultural Development, 1997
ABSTRACT Yield gaps, and factors causing them are of prime importance for agricultural production... more ABSTRACT Yield gaps, and factors causing them are of prime importance for agricultural production. There are too many yield constraining factors in the variable rainfed lowland rice agroecosystems to be studied in full factorial experiments. An empirical-exploratory attempt is presented to characterize yield gaps and attainable yield levels as related to agroecosystem variables and to adjust yield expectations and identify research and management needs. Data on crop and pest management practices, soil conditions, weather, crop performance, and biotic and abiotic stresses were collected in over 600 plots in farmers' rainfed lowland ricefields in nothwest Luzon (Philippines), northeast Thailand, and the Mekong River Delta (south Vietnam) from 1992 to 1994. The CERES Rice simulation model was used to estimate weather and nitrogen (N) limited attainable yield levels while a simple empirical model was used to estimate yield trends based on fertilizer N and soil organic matter. Results of simulation runs indicated that the weather-adjusted yield gaps, i.e. the deviations of the observed yields from the weather-limited simulated yields, averaged about 35% in the Philippines, 45% in Vietnam, and 55% in Thailand. They were mainly due to N limitation in Thailand, where soil-N and fertilizer use is low, while in the other two countries they were mainly related to other constraints. In multiple regression analyses, terms related to soil carbon content and/or amount of N fertilizer captured the main yield trend well. The remaining yield variation could partly be explained by interactions between these main terms and severity levels of diseases and pest damage, water stress, and other variables related to soil conditions, crop and pest management, and weather. Factor and canonical correspondence analyses gave further insights into links among actual yield, estimated attainable yield levels and corresponding yield gaps, and other agroecosystem variables. The approach is useful for quantifying attainable yield levels and yield gaps at various constraint levels and leads to a better understanding of complex relationships between agroecosystem variables, improved yield expectations, and a better understanding of the role of yield determining factors. This can be instrumental for prioritizing research on yield-limiting factors and guiding crop and pest management decisions.
ABSTRACT Two glasshouse experiments were conducted to determine the potential for Armillaria spec... more ABSTRACT Two glasshouse experiments were conducted to determine the potential for Armillaria species to infect fireweed and subsequently use it as a food base for attacking lodgepole pine. Aspen segments colonized by A. mellea and A. ostoyae were used to inoculate fireweed roots. Both species caused infection, although the former was more pathogenic, attacking 28 of 42 inoculated fireweed roots as opposed to 8 of 60 in the case of the latter species. None of the nine pines inoculated with segments of fireweed roots colonized by A. ostoyae became infected, even though the isolates were pathogenic on pine when aspen segments were used as the food base. In contrast, 8 of 29 pine seedlings inoculated with fireweed colonized by A. mellea were killed, thus suggesting that fireweed could play some role in the epidemiology of this disease.
Single plant yield loss due to brown girdling root rot (Rhizoctonia solani) and cabbage root magg... more Single plant yield loss due to brown girdling root rot (Rhizoctonia solani) and cabbage root maggot (Delia spp.) damage was assessed in canola (Brassica rapa cvs. Reward and Tobin) to quantify the effects of root rot on yield and determine whether yield losses due to root rot are compounded by maggot damage. At crop ripening during 1998 and 1999, 2,000 plants from six growers' fields were scored for both root rot and maggot injury. The assessed roots were separated into eight categories constructed by crossing four classes of root rot severity based on degree of girdling and two classes of maggot damage based on percentage of the root surface with maggot tunnels. A ninth category was defined for partially to completely decayed roots for which it was not possible to determine maggot damage. There was no root rot by maggot injury interaction on any of the yield parameters measured. Furthermore, maggots had no adverse effects on yield at the observed damage levels. In contrast, pla...
... 2 Materials and methods 261 Biological species determination Four isolates oi Armillaria were... more ... 2 Materials and methods 261 Biological species determination Four isolates oi Armillaria were collected from the roots of infected trees at both sites and were paired with an Armillaria ostoyae diploid tester and examined for the presence of a black line. ...
... Many empirical damage functions for blast losses are known, but their validation and use in d... more ... Many empirical damage functions for blast losses are known, but their validation and use in disease management is still to be researched. Work on coupling blast effects to rice simulation models is under way in several laboratories. ...
Brown girdling root rot (BGRR) is a serious and widespread disease of canola (Brassica rapa L.) i... more Brown girdling root rot (BGRR) is a serious and widespread disease of canola (Brassica rapa L.) in the Peace River region of northwestern Canada. There is no chemical control treatment for the pathogen, and farmers have observed that the disease is more severe when canola follows red fescue (Festuca rubra L.) or clover (Trifolium spp.) compared to summer fallow. A field study was conducted to determine how crop sequences following red fescue termination can be combined with residue and tillage management to reduce BGRR infection and increase canola yield. The five treatments consisted of rotations of: continuous canola (CCC) and oat (Avena sativa L.)-oat-canola (OOC), both managed using reduced tillage (RT), and wheat (Triticum aestivum L.)-wheat-canola (WWC), managed using RT, conventional tillage (CT) or no-till (NT). Canola yield followed the trend: OOC (RT) = WWC(RT) > WWC(CT) > CCC(RT) = WWC(NT). BGRR infection increased with tillage intensity: WWC(CT) > CCC(RT) = WWC(...
Brown girdling root rot is a devastating disease of canola (Brassica rapa) in the Peace river reg... more Brown girdling root rot is a devastating disease of canola (Brassica rapa) in the Peace river region. Breeding for resistance to this disease up to now has relied on field screening, with every alternate row as a check. Examination of the distribution of brown girdling root rot from spaced rows of Brassica rapa ‘Tobin’ revealed that there would be a minimal loss of precision in breeding programs by reducing the frequency of check rows to one in four, which represents a considerable saving in cost compared with the current practice. Key words: Turnip rape, Brassica rapa, brown girdling root rot, resistance, selection technique
S-alleles W1 and T2 and an incompletely dominant white petal character were introgressed into the... more S-alleles W1 and T2 and an incompletely dominant white petal character were introgressed into the self-compatible (SC) summer rape (Brassica napus L. ssp. oleifera {Metzg.}) cultivars Global, Topas and Westar. The derived self-incompatible (SI) lines were evaluated for strength of incompatibility by ultraviolet fluorescence of pollen tubes, and by seed set. Pollen tube and seed set analyses showed the W1 and T2 alleles were strongly, moderately and weakly expressed in Topas, Global and Westar, respectively. Seed set data showed a significant difference between SI lines, but not between S-alleles, or between homozygous or heterozygous lines from the same SI cultivar. SI cultivar yellow petal (wild type) lines were field pollinated with SC white petal lines. Seed collected from the SI cultivars were evaluated for proportion of outcrossed progeny by recording the frequency of yellow petal and cream petal plants, which were the result of self- and cross-pollination, respectively. The pr...
Juvenile lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) were excavated at three sit... more Juvenile lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) were excavated at three sites near Hinton, Alberta. In all cases in which Armillariaostoyae (Romagn.) Herink had become established in the root collar or taproot, it was also able to colonize lateral roots. In cases in which only lateral roots were infected, subsequent colonization generally was primarily distal to the point of infection. Rhizomorphs were associated with 89% of 21 infected roots, whereas only 19% of 70 roots with no associated rhizomorphs were infected. Stumps, roots, and debris from the previous generation of trees were the inoculum sources for 78% of 36 infected juvenile trees, and infected regeneration served as the inoculum source for the remaining trees. Rhizomorphs occasionally were attached to the roots or rhizomes of plants other than pine, especially fireweed (Epilobiumangustifolium L.). There was no spatial relationship between stumps and symptomatic trees. Nearest neighbor analysis indi...
Camelina is a relatively new oilseed crop to western Canada. Currently there is little research a... more Camelina is a relatively new oilseed crop to western Canada. Currently there is little research available for camelina seeding rates in western Canada. A field study was conducted in 2007 and 2008 for 9 site years at locations in western Canada to determine the effect of seeding rate on various agronomic aspects of camelina like yield, days to maturity, lodging, and plant height. The seeding rates used were 12, 25, 50, 100, 200, 400, 800, and 1600 seeds m. Camelina exhibited a plastic yield response to seeding rate. Maximum yield was reached at 450-500 seeds m. Small yield increases were seen with seeding rates greater than 100 seeds m. Days to maturity decreased by up to seven days as seeding rate increased. The optimum seeding rate was approximately 500 seeds m2 because of the positive effect on maturity, plant height, and yield. 500 seeds m would supply enough seeds to produce an acceptable plant density under poor seeding conditions to help prevent crop failure due to poor emerg...
In three field trials on the epidemiology of blast disease in upland rice, different methods of s... more In three field trials on the epidemiology of blast disease in upland rice, different methods of sampling spores of Pyricularia grisea were compared to study aerial concentration, deposition, survival, and infectiousness of conidia of the pathogen. The methods included a Burkard spore trap, glass slides and rods, several trap-plant treatments, and leaf prints from trap plants. The results were mostly highly intercorrelated and revealed a unimodal pattern of disease progression, with peaks before or at the middle of the cropping seasons. The number of conidia per square centimeter deposited on leaf surfaces as measured by leaf prints made up one-fourth of the number caught with glass slides [...]
Systems Approaches for Sustainable Agricultural Development, 1997
ABSTRACT Yield gaps, and factors causing them are of prime importance for agricultural production... more ABSTRACT Yield gaps, and factors causing them are of prime importance for agricultural production. There are too many yield constraining factors in the variable rainfed lowland rice agroecosystems to be studied in full factorial experiments. An empirical-exploratory attempt is presented to characterize yield gaps and attainable yield levels as related to agroecosystem variables and to adjust yield expectations and identify research and management needs. Data on crop and pest management practices, soil conditions, weather, crop performance, and biotic and abiotic stresses were collected in over 600 plots in farmers' rainfed lowland ricefields in nothwest Luzon (Philippines), northeast Thailand, and the Mekong River Delta (south Vietnam) from 1992 to 1994. The CERES Rice simulation model was used to estimate weather and nitrogen (N) limited attainable yield levels while a simple empirical model was used to estimate yield trends based on fertilizer N and soil organic matter. Results of simulation runs indicated that the weather-adjusted yield gaps, i.e. the deviations of the observed yields from the weather-limited simulated yields, averaged about 35% in the Philippines, 45% in Vietnam, and 55% in Thailand. They were mainly due to N limitation in Thailand, where soil-N and fertilizer use is low, while in the other two countries they were mainly related to other constraints. In multiple regression analyses, terms related to soil carbon content and/or amount of N fertilizer captured the main yield trend well. The remaining yield variation could partly be explained by interactions between these main terms and severity levels of diseases and pest damage, water stress, and other variables related to soil conditions, crop and pest management, and weather. Factor and canonical correspondence analyses gave further insights into links among actual yield, estimated attainable yield levels and corresponding yield gaps, and other agroecosystem variables. The approach is useful for quantifying attainable yield levels and yield gaps at various constraint levels and leads to a better understanding of complex relationships between agroecosystem variables, improved yield expectations, and a better understanding of the role of yield determining factors. This can be instrumental for prioritizing research on yield-limiting factors and guiding crop and pest management decisions.
ABSTRACT Two glasshouse experiments were conducted to determine the potential for Armillaria spec... more ABSTRACT Two glasshouse experiments were conducted to determine the potential for Armillaria species to infect fireweed and subsequently use it as a food base for attacking lodgepole pine. Aspen segments colonized by A. mellea and A. ostoyae were used to inoculate fireweed roots. Both species caused infection, although the former was more pathogenic, attacking 28 of 42 inoculated fireweed roots as opposed to 8 of 60 in the case of the latter species. None of the nine pines inoculated with segments of fireweed roots colonized by A. ostoyae became infected, even though the isolates were pathogenic on pine when aspen segments were used as the food base. In contrast, 8 of 29 pine seedlings inoculated with fireweed colonized by A. mellea were killed, thus suggesting that fireweed could play some role in the epidemiology of this disease.
Single plant yield loss due to brown girdling root rot (Rhizoctonia solani) and cabbage root magg... more Single plant yield loss due to brown girdling root rot (Rhizoctonia solani) and cabbage root maggot (Delia spp.) damage was assessed in canola (Brassica rapa cvs. Reward and Tobin) to quantify the effects of root rot on yield and determine whether yield losses due to root rot are compounded by maggot damage. At crop ripening during 1998 and 1999, 2,000 plants from six growers' fields were scored for both root rot and maggot injury. The assessed roots were separated into eight categories constructed by crossing four classes of root rot severity based on degree of girdling and two classes of maggot damage based on percentage of the root surface with maggot tunnels. A ninth category was defined for partially to completely decayed roots for which it was not possible to determine maggot damage. There was no root rot by maggot injury interaction on any of the yield parameters measured. Furthermore, maggots had no adverse effects on yield at the observed damage levels. In contrast, pla...
... 2 Materials and methods 261 Biological species determination Four isolates oi Armillaria were... more ... 2 Materials and methods 261 Biological species determination Four isolates oi Armillaria were collected from the roots of infected trees at both sites and were paired with an Armillaria ostoyae diploid tester and examined for the presence of a black line. ...
... Many empirical damage functions for blast losses are known, but their validation and use in d... more ... Many empirical damage functions for blast losses are known, but their validation and use in disease management is still to be researched. Work on coupling blast effects to rice simulation models is under way in several laboratories. ...
Brown girdling root rot (BGRR) is a serious and widespread disease of canola (Brassica rapa L.) i... more Brown girdling root rot (BGRR) is a serious and widespread disease of canola (Brassica rapa L.) in the Peace River region of northwestern Canada. There is no chemical control treatment for the pathogen, and farmers have observed that the disease is more severe when canola follows red fescue (Festuca rubra L.) or clover (Trifolium spp.) compared to summer fallow. A field study was conducted to determine how crop sequences following red fescue termination can be combined with residue and tillage management to reduce BGRR infection and increase canola yield. The five treatments consisted of rotations of: continuous canola (CCC) and oat (Avena sativa L.)-oat-canola (OOC), both managed using reduced tillage (RT), and wheat (Triticum aestivum L.)-wheat-canola (WWC), managed using RT, conventional tillage (CT) or no-till (NT). Canola yield followed the trend: OOC (RT) = WWC(RT) > WWC(CT) > CCC(RT) = WWC(NT). BGRR infection increased with tillage intensity: WWC(CT) > CCC(RT) = WWC(...
Brown girdling root rot is a devastating disease of canola (Brassica rapa) in the Peace river reg... more Brown girdling root rot is a devastating disease of canola (Brassica rapa) in the Peace river region. Breeding for resistance to this disease up to now has relied on field screening, with every alternate row as a check. Examination of the distribution of brown girdling root rot from spaced rows of Brassica rapa ‘Tobin’ revealed that there would be a minimal loss of precision in breeding programs by reducing the frequency of check rows to one in four, which represents a considerable saving in cost compared with the current practice. Key words: Turnip rape, Brassica rapa, brown girdling root rot, resistance, selection technique
S-alleles W1 and T2 and an incompletely dominant white petal character were introgressed into the... more S-alleles W1 and T2 and an incompletely dominant white petal character were introgressed into the self-compatible (SC) summer rape (Brassica napus L. ssp. oleifera {Metzg.}) cultivars Global, Topas and Westar. The derived self-incompatible (SI) lines were evaluated for strength of incompatibility by ultraviolet fluorescence of pollen tubes, and by seed set. Pollen tube and seed set analyses showed the W1 and T2 alleles were strongly, moderately and weakly expressed in Topas, Global and Westar, respectively. Seed set data showed a significant difference between SI lines, but not between S-alleles, or between homozygous or heterozygous lines from the same SI cultivar. SI cultivar yellow petal (wild type) lines were field pollinated with SC white petal lines. Seed collected from the SI cultivars were evaluated for proportion of outcrossed progeny by recording the frequency of yellow petal and cream petal plants, which were the result of self- and cross-pollination, respectively. The pr...
Juvenile lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) were excavated at three sit... more Juvenile lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) were excavated at three sites near Hinton, Alberta. In all cases in which Armillariaostoyae (Romagn.) Herink had become established in the root collar or taproot, it was also able to colonize lateral roots. In cases in which only lateral roots were infected, subsequent colonization generally was primarily distal to the point of infection. Rhizomorphs were associated with 89% of 21 infected roots, whereas only 19% of 70 roots with no associated rhizomorphs were infected. Stumps, roots, and debris from the previous generation of trees were the inoculum sources for 78% of 36 infected juvenile trees, and infected regeneration served as the inoculum source for the remaining trees. Rhizomorphs occasionally were attached to the roots or rhizomes of plants other than pine, especially fireweed (Epilobiumangustifolium L.). There was no spatial relationship between stumps and symptomatic trees. Nearest neighbor analysis indi...
Camelina is a relatively new oilseed crop to western Canada. Currently there is little research a... more Camelina is a relatively new oilseed crop to western Canada. Currently there is little research available for camelina seeding rates in western Canada. A field study was conducted in 2007 and 2008 for 9 site years at locations in western Canada to determine the effect of seeding rate on various agronomic aspects of camelina like yield, days to maturity, lodging, and plant height. The seeding rates used were 12, 25, 50, 100, 200, 400, 800, and 1600 seeds m. Camelina exhibited a plastic yield response to seeding rate. Maximum yield was reached at 450-500 seeds m. Small yield increases were seen with seeding rates greater than 100 seeds m. Days to maturity decreased by up to seven days as seeding rate increased. The optimum seeding rate was approximately 500 seeds m2 because of the positive effect on maturity, plant height, and yield. 500 seeds m would supply enough seeds to produce an acceptable plant density under poor seeding conditions to help prevent crop failure due to poor emerg...
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