One hundred and forty-seven primer pairs originally designed to amplify microsatellites, also kno... more One hundred and forty-seven primer pairs originally designed to amplify microsatellites, also known as simple sequence repeats (SSR), in black walnut (Juglans nigra L.) were screened for utility in persian walnut (J. regia L.). Based on scorability and number of informative polymorphisms, the best 14 loci were selected to analyze a di- verse group of 47 persian walnut accessions and
Exotic insect pests and pathogens have dramatically reduced the quantity and quality of several t... more Exotic insect pests and pathogens have dramatically reduced the quantity and quality of several trees species in North America. Butternut (Juglans cinerea L.) is one such species. This review discusses the identification of butternut, the current status of butternut, and the nature of the threats that influence its survival, all in the context of what forest managers need to know to make difficult choices they face when managing butternut. Options for encouraging regeneration are presented, as well the current status of recovery efforts.
Once trees are planted and begin growing, damage from wildlife can threaten their quality. In thi... more Once trees are planted and begin growing, damage from wildlife can threaten their quality. In this publication we discuss how to identify and manage injury to hardwoods from wildlife to minimize losses.
Since the early 1960s, researchers in programs to improve black walnut for timber have struggled ... more Since the early 1960s, researchers in programs to improve black walnut for timber have struggled to meet some basic breeding objectives. Promising avenues of research had been identified by the early 1950s, and conventional methods to breed forest trees were widely adopted as suitable for walnut. Progress has been slow however, due to practical problems related to field plot establishment
We evaluated eight-year-old seedlings in a black walnut (Juglans nigra L.) progeny test for two q... more We evaluated eight-year-old seedlings in a black walnut (Juglans nigra L.) progeny test for two quantitative and two qualitative traits. We also used 12 microsatellite markers to genotype the 328 progeny and their maternal parents. Seedling family growth and quality was evaluated based on the progeny test map. These values were compared to family growth and quality after seedlings were genotyped and reassigned to families by parentage assignment software. After genotyping and parentage analysis, about 80 % of the offspring were assigned to the same half-sib family indicated on the planting map. Considerable differences were observed between the ranks of half-sib families based on the planting-map versus the ranks of the families based on the exclusion/assignment of progeny to their family based on genotypes. Analysis of the data without genotypic assignment of progeny to their correct family revealed that the family effect for height was significant, as was family effect for diameter. After seedlings were reassigned to half-sib families based on genotypic information, neither the family effect for height nor the family effect for diameter was significant. The efficiency of the mixed model ANOVA, as measured by Akaike Information Criterion improved by about 30 % after genotyping and exclusion/reassignment of progeny. These results show that genotyping progeny can have a significant effect on the rank of families and potential selection of individuals from a progeny trial, the quality of data analysis, and the efficiency and efficacy of breeding operations.
Cytokinins elevate ethylene biosynthesis in etiolated Arabidopsis seedlings via a post-transcript... more Cytokinins elevate ethylene biosynthesis in etiolated Arabidopsis seedlings via a post-transcriptional modification of one isoform of the key biosynthetic enzyme ACC synthase. In order to begin to dissect the signaling events leading from cytokinin perception to this modification, we have isolated a series of mutants that lack the ethylene-mediated triple response in the presence of cytokinin due to their failure
Information about the natural patterns of genetic variability and their evolutionary bases are of... more Information about the natural patterns of genetic variability and their evolutionary bases are of fundamental practical importance for sustainable forest management and conservation. In the present study, the genetic diversity of 164 individuals from fourteen natural populations of Crataegus pontica K.Koch was assessed for the first time using three genome-based molecular techniques; inter-retrotransposon amplified polymorphism (IRAP); inter-simple sequence repeats (ISSR) and start codon targeted (SCoT) polymorphism. IRAP, ISSR and SCoT analyses yielded 126, 254 and 199 scorable amplified bands, respectively, of which 90.48, 93.37 and 83.78% were polymorphic. ISSR revealed efficiency over IRAP and SCoT due to high effective multiplex ratio, marker index and resolving power. The dendrograms based on the markers used and combined data divided individuals into three major clusters. The correlation between the coefficient matrices for the IRAP, ISSR and SCoT data was significant. A higher level of genetic variation was observed within populations than among populations based on the markers used. The lower divergence levels depicted among the studied populations could be seen as evidence of gene flow. The promotion of gene exchange will be very beneficial to conserve and utilize the enormous genetic variability.
Approaches for the development of disease-resistant butternut (Juglans cinerea L.) are reviewed. ... more Approaches for the development of disease-resistant butternut (Juglans cinerea L.) are reviewed. Butternut is a threatened fine hardwood throughout its natural range in eastern North America because of the invasion of the exotic fungus, Sirococcus clavigignenti-juglandacearum Nair, Kostichka and Kuntz, which causes butternut canker. Early efforts were made to identify and collect putatively resistant germ plasm, identify vectors and to characterize the disease. More recently, molecular techniques have been employed to genetically characterize both the pathogen and the resistant germ plasm. Much of the host resistance may originate from hybridization with a close Asian relative, Japanese walnut (Juglans ailanthifolia Carr.), and from a few natural phenotypic variants. Further genetic characterization is needed before classical breeding or genetic modification can be used to produce canker-resistant trees.
A regional center for hardwood tree improvement, genomics, and regeneration research, development... more A regional center for hardwood tree improvement, genomics, and regeneration research, development and technology transfer will focus on black walnut, black cherry, northern red oak and, in the future, on other fine hardwoods as the effort is expanded. The Hardwood Tree Improvement and Regeneration Center (HTIRC) will use molecular genetics and genomics along with traditional breeding, selection, and vegetative propaga-
The Arabidopsis mutants eto1 (ethylene overproducer) and eto3 produce elevated levels of ethylene... more The Arabidopsis mutants eto1 (ethylene overproducer) and eto3 produce elevated levels of ethylene as etiolated seedlings. Ethylene production in these seedlings peaks at 60 to 96 h, and then declines back to almost wild-type levels. Ethylene overproduction in eto1 and eto3 is limited mainly to etiolated seedlings; light-grown seedlings and various adult tissues produce close to wild-type amounts of ethylene.
With the transport of plants around the globe, exotic species can readily spread disease to their... more With the transport of plants around the globe, exotic species can readily spread disease to their native relatives; however, they can also provide genetic resistance to those relatives through hybrid breeding programmes. American chestnut (Castanea dentata) was an abundant tree species in North America until its decimation by introduced chestnut blight. To restore chestnut in North America, efforts are ongoing to test putative blight-resistant hybrids of Castanea dentata and Chinese chestnut (Castanea mollissima), but little is known about the ecology of C. mollissima. In a forest in northeastern USA in which C. mollissima has become established, we explored questions of stand dynamics, health and genetic relationships of C. mollissima offspring to an adjacent parent orchard. We found that C. mollissima was adapted and randomly distributed among native species in this relatively young forest. The genetics of the C. mollissima population compared with its parents indicated little eff...
Butternut (Juglans cinerea L.) is a native, cold-tolerant, hard-mast species formerly valued for ... more Butternut (Juglans cinerea L.) is a native, cold-tolerant, hard-mast species formerly valued for its nuts and wood, which is now endangered. The most immediate threat to butternut restoration is the spread of butternut canker disease, caused by the exotic fungus Sirococcus clavigignentijuglandacearum Nair, Kostichka & Kuntz. Other threats include the hybridization of butternut with the exotic Japanese walnut (Juglans ailantifolia Carr.) and poor regeneration. The hybrids, known as buartnuts, are vegetatively vigorous, highly fecund, more resistant than butternut to butternut canker disease and difficult to identify. We review the vegetative and reproductive morphological traits that distinguish butternut from hybrids and identify those that can be used by field biologists to separate the taxa. No single trait was sufficient to separate butternut from hybrids, but pith color, lenticel size, shape and abundance, and the presence or absence of a notch in the upper margin of leaf scars, can be used in combination with other traits to identify butternuts and exclude most hybrids. In at least one butternut population, reduced symptoms of butternut canker disease were significantly associated with a dark barked phenotype. We also describe two randomly amplified polymorphic DNA (RAPD) markers that differentiate butternuts from hybrids based on DNA polymorphism. Together, these results should assist in the identification and testing of non-hybrid butternut for breeding and reintroduction of the species to its former habitats.
Life history traits, historic factors, and human activities can all shape the genetic diversity o... more Life history traits, historic factors, and human activities can all shape the genetic diversity of a species. In Italy, walnut (Juglans regia L.) has a long history of cultivation both for wood and edible nuts. To better understand the genetic variability of current Italian walnut resources, we analyzed the relationships among the genetic structure of local walnut populations (inferred by SSR markers) and human migrations along ancient routes, using the territory of Royal Tratturo Candela-Pescasseroli (RT) as a case study. Sixteen J. regia provenances were collected along RT and compared with 13 Italian provenances and the landrace Sorrento. Although the level of SSR polymorphism we observed was moderately high, AMOVA revealed that most of the diversity was located within individuals (92.58%), and geographical differentiation was low (D est = 0.076). Evidence for human-mediated domestication bottleneck events was detected in about 95% of walnut provenances. A Bayesian approach divided 456 walnut samples into three clusters: (1) Sorrento genotypes, (2) trees from the island of Sicily, and (3) the remaining germplasm. The UPGMA tree based on Nei's distances distinguished northeastern provenances and weakly grouped 12 of 16 prove-nances of RT. The observed genetic differences derived mainly from gradations in allele frequencies. Separation of the Sicilian provenance from the mainland may be explained in terms of founder effects and prolonged geographic isolation. Two contrasting forces, selection, and frequent inter-regional transfer of propagules, appear to drive the patterns of genetic variability for J. regia.
The management of threatened and endangered species can be improved by understanding their patter... more The management of threatened and endangered species can be improved by understanding their patterns of ge- netic diversity and structure. This paper presents the results of the first analysis of the population genetics of butternut (Ju- glans cinerea L.) using nuclear microsatellites. Butternut once was an economically and ecologically valuable hardwood, but now its numbers are rapidly decreasing throughout its
The ascomycete Geosmithia morbida and the walnut twig beetle Pityophthorus juglandis are associat... more The ascomycete Geosmithia morbida and the walnut twig beetle Pityophthorus juglandis are associated with thousand cankers disease of Juglans (walnut) and Pterocarya (wingnut). The disease was first reported in the western United States (USA) on several Juglans species, but has been found more recently in the eastern USA in the native range of the highly susceptible Juglans nigra. We performed a comprehensive population genetic study of 209 G. morbida isolates collected from Juglans and Pterocarya from 17 geographic regions distributed across 12 U.S. states. The study was based on sequence typing of 27 single nucleotide polymorphisms from three genomic regions and genotyping with ten microsatellite primer pairs. Using multilocus sequence-typing data, 197 G. morbida isolates were placed into one of 57 haplotypes. In some instances, multiple haplotypes were recovered from isolates collected on the same tree. Twenty-four of the haplotypes (42%) were recovered from more than one isolate; the two most frequently occurring haplotypes (H02 and H03) represented 36% of all isolates. These two haplotypes were abundant in California, but were not recovered from Arizona or New Mexico. G. morbida population structure was best explained by four genetically distinct groups that clustered into three geographic regions. Most of the haplotypes isolated from the native range of J. major (Arizona and New Mexico) were found in those states only or present in distinct genetic clusters. There was no evidence of sexual reproduction or genetic recombination in any population. The scattered distribution of the genetic clusters indicated that G. morbida was likely disseminated to different regions at several times and from several sources. The large number of haplotypes observed and the genetic complexity of G. morbida indicate that it evolved in association with at least one Juglans spp. and the walnut twig beetle long before the first reports of the disease.
Azafenidin, sulfometuron, pendirnethalin, and simazine were applied alone and in combination to 1... more Azafenidin, sulfometuron, pendirnethalin, and simazine were applied alone and in combination to 1-0 seedlings of nine hardwood and one conifer species. Percent bare ground at 30, 60, and 90 days, diameter and height growth of the seedlings were determined for 16 herbicide treatments, tillage and a control. Azafenidin applications alone and in combination with sulfometuron resulted in about 85% bare ground 90 days post-treatment. There were significant differences for diameter, height growth, and volume among the treatments for every species. No single treatment ranked best for all species, but comparison of the mean ranks of the treatments for all species indicated that azafenidin andpendimethalin resulted in the most growth. Azafenidin-treated seedlings also had the greatest volume at the end of the season. North. J. Appl. For. 19(3):101-105.
Approaches for the development of disease-resistant butternut (Juglans cinerea L.) are reviewed. ... more Approaches for the development of disease-resistant butternut (Juglans cinerea L.) are reviewed. Butternut is a threatened fine hardwood throughout its natural range in eastern North America because of the invasion of the exotic fungus, Sirococcus clavigignenti-juglandacearum Nair, Kostichka and Kuntz, which causes butternut canker. Early efforts were made to identify and collect putatively resistant germ plasm, identify vectors and to characterize the disease. More recently, molecular techniques have been employed to genetically characterize both the pathogen and the resistant germ plasm. Much of the host resistance may originate from hybridization with a close Asian relative, Japanese walnut (Juglans ailanthifolia Carr.), and from a few natural phenotypic variants. Further genetic characterization is needed before classical breeding or genetic modification can be used to produce canker-resistant trees.
One hundred and forty-seven primer pairs originally designed to amplify microsatellites, also kno... more One hundred and forty-seven primer pairs originally designed to amplify microsatellites, also known as simple sequence repeats (SSR), in black walnut (Juglans nigra L.) were screened for utility in persian walnut (J. regia L.). Based on scorability and number of informative polymorphisms, the best 14 loci were selected to analyze a di- verse group of 47 persian walnut accessions and
Exotic insect pests and pathogens have dramatically reduced the quantity and quality of several t... more Exotic insect pests and pathogens have dramatically reduced the quantity and quality of several trees species in North America. Butternut (Juglans cinerea L.) is one such species. This review discusses the identification of butternut, the current status of butternut, and the nature of the threats that influence its survival, all in the context of what forest managers need to know to make difficult choices they face when managing butternut. Options for encouraging regeneration are presented, as well the current status of recovery efforts.
Once trees are planted and begin growing, damage from wildlife can threaten their quality. In thi... more Once trees are planted and begin growing, damage from wildlife can threaten their quality. In this publication we discuss how to identify and manage injury to hardwoods from wildlife to minimize losses.
Since the early 1960s, researchers in programs to improve black walnut for timber have struggled ... more Since the early 1960s, researchers in programs to improve black walnut for timber have struggled to meet some basic breeding objectives. Promising avenues of research had been identified by the early 1950s, and conventional methods to breed forest trees were widely adopted as suitable for walnut. Progress has been slow however, due to practical problems related to field plot establishment
We evaluated eight-year-old seedlings in a black walnut (Juglans nigra L.) progeny test for two q... more We evaluated eight-year-old seedlings in a black walnut (Juglans nigra L.) progeny test for two quantitative and two qualitative traits. We also used 12 microsatellite markers to genotype the 328 progeny and their maternal parents. Seedling family growth and quality was evaluated based on the progeny test map. These values were compared to family growth and quality after seedlings were genotyped and reassigned to families by parentage assignment software. After genotyping and parentage analysis, about 80 % of the offspring were assigned to the same half-sib family indicated on the planting map. Considerable differences were observed between the ranks of half-sib families based on the planting-map versus the ranks of the families based on the exclusion/assignment of progeny to their family based on genotypes. Analysis of the data without genotypic assignment of progeny to their correct family revealed that the family effect for height was significant, as was family effect for diameter. After seedlings were reassigned to half-sib families based on genotypic information, neither the family effect for height nor the family effect for diameter was significant. The efficiency of the mixed model ANOVA, as measured by Akaike Information Criterion improved by about 30 % after genotyping and exclusion/reassignment of progeny. These results show that genotyping progeny can have a significant effect on the rank of families and potential selection of individuals from a progeny trial, the quality of data analysis, and the efficiency and efficacy of breeding operations.
Cytokinins elevate ethylene biosynthesis in etiolated Arabidopsis seedlings via a post-transcript... more Cytokinins elevate ethylene biosynthesis in etiolated Arabidopsis seedlings via a post-transcriptional modification of one isoform of the key biosynthetic enzyme ACC synthase. In order to begin to dissect the signaling events leading from cytokinin perception to this modification, we have isolated a series of mutants that lack the ethylene-mediated triple response in the presence of cytokinin due to their failure
Information about the natural patterns of genetic variability and their evolutionary bases are of... more Information about the natural patterns of genetic variability and their evolutionary bases are of fundamental practical importance for sustainable forest management and conservation. In the present study, the genetic diversity of 164 individuals from fourteen natural populations of Crataegus pontica K.Koch was assessed for the first time using three genome-based molecular techniques; inter-retrotransposon amplified polymorphism (IRAP); inter-simple sequence repeats (ISSR) and start codon targeted (SCoT) polymorphism. IRAP, ISSR and SCoT analyses yielded 126, 254 and 199 scorable amplified bands, respectively, of which 90.48, 93.37 and 83.78% were polymorphic. ISSR revealed efficiency over IRAP and SCoT due to high effective multiplex ratio, marker index and resolving power. The dendrograms based on the markers used and combined data divided individuals into three major clusters. The correlation between the coefficient matrices for the IRAP, ISSR and SCoT data was significant. A higher level of genetic variation was observed within populations than among populations based on the markers used. The lower divergence levels depicted among the studied populations could be seen as evidence of gene flow. The promotion of gene exchange will be very beneficial to conserve and utilize the enormous genetic variability.
Approaches for the development of disease-resistant butternut (Juglans cinerea L.) are reviewed. ... more Approaches for the development of disease-resistant butternut (Juglans cinerea L.) are reviewed. Butternut is a threatened fine hardwood throughout its natural range in eastern North America because of the invasion of the exotic fungus, Sirococcus clavigignenti-juglandacearum Nair, Kostichka and Kuntz, which causes butternut canker. Early efforts were made to identify and collect putatively resistant germ plasm, identify vectors and to characterize the disease. More recently, molecular techniques have been employed to genetically characterize both the pathogen and the resistant germ plasm. Much of the host resistance may originate from hybridization with a close Asian relative, Japanese walnut (Juglans ailanthifolia Carr.), and from a few natural phenotypic variants. Further genetic characterization is needed before classical breeding or genetic modification can be used to produce canker-resistant trees.
A regional center for hardwood tree improvement, genomics, and regeneration research, development... more A regional center for hardwood tree improvement, genomics, and regeneration research, development and technology transfer will focus on black walnut, black cherry, northern red oak and, in the future, on other fine hardwoods as the effort is expanded. The Hardwood Tree Improvement and Regeneration Center (HTIRC) will use molecular genetics and genomics along with traditional breeding, selection, and vegetative propaga-
The Arabidopsis mutants eto1 (ethylene overproducer) and eto3 produce elevated levels of ethylene... more The Arabidopsis mutants eto1 (ethylene overproducer) and eto3 produce elevated levels of ethylene as etiolated seedlings. Ethylene production in these seedlings peaks at 60 to 96 h, and then declines back to almost wild-type levels. Ethylene overproduction in eto1 and eto3 is limited mainly to etiolated seedlings; light-grown seedlings and various adult tissues produce close to wild-type amounts of ethylene.
With the transport of plants around the globe, exotic species can readily spread disease to their... more With the transport of plants around the globe, exotic species can readily spread disease to their native relatives; however, they can also provide genetic resistance to those relatives through hybrid breeding programmes. American chestnut (Castanea dentata) was an abundant tree species in North America until its decimation by introduced chestnut blight. To restore chestnut in North America, efforts are ongoing to test putative blight-resistant hybrids of Castanea dentata and Chinese chestnut (Castanea mollissima), but little is known about the ecology of C. mollissima. In a forest in northeastern USA in which C. mollissima has become established, we explored questions of stand dynamics, health and genetic relationships of C. mollissima offspring to an adjacent parent orchard. We found that C. mollissima was adapted and randomly distributed among native species in this relatively young forest. The genetics of the C. mollissima population compared with its parents indicated little eff...
Butternut (Juglans cinerea L.) is a native, cold-tolerant, hard-mast species formerly valued for ... more Butternut (Juglans cinerea L.) is a native, cold-tolerant, hard-mast species formerly valued for its nuts and wood, which is now endangered. The most immediate threat to butternut restoration is the spread of butternut canker disease, caused by the exotic fungus Sirococcus clavigignentijuglandacearum Nair, Kostichka & Kuntz. Other threats include the hybridization of butternut with the exotic Japanese walnut (Juglans ailantifolia Carr.) and poor regeneration. The hybrids, known as buartnuts, are vegetatively vigorous, highly fecund, more resistant than butternut to butternut canker disease and difficult to identify. We review the vegetative and reproductive morphological traits that distinguish butternut from hybrids and identify those that can be used by field biologists to separate the taxa. No single trait was sufficient to separate butternut from hybrids, but pith color, lenticel size, shape and abundance, and the presence or absence of a notch in the upper margin of leaf scars, can be used in combination with other traits to identify butternuts and exclude most hybrids. In at least one butternut population, reduced symptoms of butternut canker disease were significantly associated with a dark barked phenotype. We also describe two randomly amplified polymorphic DNA (RAPD) markers that differentiate butternuts from hybrids based on DNA polymorphism. Together, these results should assist in the identification and testing of non-hybrid butternut for breeding and reintroduction of the species to its former habitats.
Life history traits, historic factors, and human activities can all shape the genetic diversity o... more Life history traits, historic factors, and human activities can all shape the genetic diversity of a species. In Italy, walnut (Juglans regia L.) has a long history of cultivation both for wood and edible nuts. To better understand the genetic variability of current Italian walnut resources, we analyzed the relationships among the genetic structure of local walnut populations (inferred by SSR markers) and human migrations along ancient routes, using the territory of Royal Tratturo Candela-Pescasseroli (RT) as a case study. Sixteen J. regia provenances were collected along RT and compared with 13 Italian provenances and the landrace Sorrento. Although the level of SSR polymorphism we observed was moderately high, AMOVA revealed that most of the diversity was located within individuals (92.58%), and geographical differentiation was low (D est = 0.076). Evidence for human-mediated domestication bottleneck events was detected in about 95% of walnut provenances. A Bayesian approach divided 456 walnut samples into three clusters: (1) Sorrento genotypes, (2) trees from the island of Sicily, and (3) the remaining germplasm. The UPGMA tree based on Nei's distances distinguished northeastern provenances and weakly grouped 12 of 16 prove-nances of RT. The observed genetic differences derived mainly from gradations in allele frequencies. Separation of the Sicilian provenance from the mainland may be explained in terms of founder effects and prolonged geographic isolation. Two contrasting forces, selection, and frequent inter-regional transfer of propagules, appear to drive the patterns of genetic variability for J. regia.
The management of threatened and endangered species can be improved by understanding their patter... more The management of threatened and endangered species can be improved by understanding their patterns of ge- netic diversity and structure. This paper presents the results of the first analysis of the population genetics of butternut (Ju- glans cinerea L.) using nuclear microsatellites. Butternut once was an economically and ecologically valuable hardwood, but now its numbers are rapidly decreasing throughout its
The ascomycete Geosmithia morbida and the walnut twig beetle Pityophthorus juglandis are associat... more The ascomycete Geosmithia morbida and the walnut twig beetle Pityophthorus juglandis are associated with thousand cankers disease of Juglans (walnut) and Pterocarya (wingnut). The disease was first reported in the western United States (USA) on several Juglans species, but has been found more recently in the eastern USA in the native range of the highly susceptible Juglans nigra. We performed a comprehensive population genetic study of 209 G. morbida isolates collected from Juglans and Pterocarya from 17 geographic regions distributed across 12 U.S. states. The study was based on sequence typing of 27 single nucleotide polymorphisms from three genomic regions and genotyping with ten microsatellite primer pairs. Using multilocus sequence-typing data, 197 G. morbida isolates were placed into one of 57 haplotypes. In some instances, multiple haplotypes were recovered from isolates collected on the same tree. Twenty-four of the haplotypes (42%) were recovered from more than one isolate; the two most frequently occurring haplotypes (H02 and H03) represented 36% of all isolates. These two haplotypes were abundant in California, but were not recovered from Arizona or New Mexico. G. morbida population structure was best explained by four genetically distinct groups that clustered into three geographic regions. Most of the haplotypes isolated from the native range of J. major (Arizona and New Mexico) were found in those states only or present in distinct genetic clusters. There was no evidence of sexual reproduction or genetic recombination in any population. The scattered distribution of the genetic clusters indicated that G. morbida was likely disseminated to different regions at several times and from several sources. The large number of haplotypes observed and the genetic complexity of G. morbida indicate that it evolved in association with at least one Juglans spp. and the walnut twig beetle long before the first reports of the disease.
Azafenidin, sulfometuron, pendirnethalin, and simazine were applied alone and in combination to 1... more Azafenidin, sulfometuron, pendirnethalin, and simazine were applied alone and in combination to 1-0 seedlings of nine hardwood and one conifer species. Percent bare ground at 30, 60, and 90 days, diameter and height growth of the seedlings were determined for 16 herbicide treatments, tillage and a control. Azafenidin applications alone and in combination with sulfometuron resulted in about 85% bare ground 90 days post-treatment. There were significant differences for diameter, height growth, and volume among the treatments for every species. No single treatment ranked best for all species, but comparison of the mean ranks of the treatments for all species indicated that azafenidin andpendimethalin resulted in the most growth. Azafenidin-treated seedlings also had the greatest volume at the end of the season. North. J. Appl. For. 19(3):101-105.
Approaches for the development of disease-resistant butternut (Juglans cinerea L.) are reviewed. ... more Approaches for the development of disease-resistant butternut (Juglans cinerea L.) are reviewed. Butternut is a threatened fine hardwood throughout its natural range in eastern North America because of the invasion of the exotic fungus, Sirococcus clavigignenti-juglandacearum Nair, Kostichka and Kuntz, which causes butternut canker. Early efforts were made to identify and collect putatively resistant germ plasm, identify vectors and to characterize the disease. More recently, molecular techniques have been employed to genetically characterize both the pathogen and the resistant germ plasm. Much of the host resistance may originate from hybridization with a close Asian relative, Japanese walnut (Juglans ailanthifolia Carr.), and from a few natural phenotypic variants. Further genetic characterization is needed before classical breeding or genetic modification can be used to produce canker-resistant trees.
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Papers by Keith Woeste