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Immature female gametophytes and enclosed zygotic embryos of slash pine (Pinus elliottii Engelm.) collected at various developmental stages were cultured either on eight initiation media supplemented with different plant growth regulator (PGR) combinations or on LPM medium solidified with two brands of agar. Embryonal-suspensor cell masses extruded from gametophyte explants infrequently produced white or translucent mucilaginous embryogenic cultures. Variation in extrusion frequency was observed across seed sources (families), explant collection dates, agar types and culture media. Increased explant maturity (as related to collection dates) reduced cell extrusion rates. Four types of extrusions were grouped according to their morphology. One type of extrusion produced the greatest number of established and long-surviving embryogenic cultures. This extrusion type (type I) was associated with an extrusion condition termed empty in which the entirety of the embryonal-suspensor mass was extruded out of the gametophyte. Three other extrusion types (types II, III and IV) showed less culture establishment and survival. 相似文献
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Maturation of slash pine (Pinus elliottii Engelm.) somatic embryos was achieved using two protocols, each starting with a different agar incubation step to deplete plant growth regulators (PGRs) used in previous cultural steps. Strength of maturation medium (single vs. double) was found important in the first protocol to develop normal, mature embryos. In the second protocol, abscisic acid (ABA) concentrations (0, 15 and 30 M) and carbohydrate sources were tested for embryo maturation. Thirty M ABA and 6% maltose were deemed the best combination. Embryo germination was accomplished in a continuously lighted environment and embryos receiving a cold pretreatment (4 °C in darkness for 16 days) germinated better than embryos which did not receive cold pretreatment. With a survival rate of 33% after acclimation in a mist system, more than 25 plants from somatic embryos have been established in a greenhouse. Incompletely germinated embryos (lacking roots) were rooted via adventitious rooting techniques and subsequently established in the greenhouse. All established plants obtained from somatic embryogenesis appear normal in morphology. 相似文献
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Loblolly pine (Pinus taeda L.) propagules initiated adventitiously from cotyledons and via axillary-fascicular micropropagation from epicotyls were compared to seedlings grown from the same open-pollinated seedlot. Greenhouse and early field results indicate that unlike tissue culture propagules of cotyledon-origin, propagules originating via axillary-fascicular micropropagation from epicotyls do not display early reduced growth relative to seedlings. Further, axillary-fascicular micropropagules derived from cotyledon-origin adventitious shoots displayed early reduced growth. Early reduced growth and other differences between tissue culture propagules and seedlings previously observed in field plantings appear to be inherent to the cotyledon system of propagation and do not necessarily occur when other tissue culture procedures are used for propagation. 相似文献
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ABSTRACT We propose a method for defining DNA markers linked to Cronartium quercuum f. sp. fusiforme avirulence (Avr) genes. However, before this method can be successfully employed, a spore competition study was needed to determine the genetic composition of single pycnial drops and multiple drops on single galls when using the standard inoculation procedure, whether virulent (avr1) basidiospores ever predispose some resistant (Fr1/fr1) trees to infection by avirulent (Avr1) basidiospores, and whether avr1 and Avr1 basidiospores equally infect susceptible (fr1/fr1) trees. Results of this study suggest that multiple infections within a single gall are common using the concentrated basidiospore system, resulting on average in >4 infection events per tree. Due to multiple infections within a single gall, an individual pycnial drop cannot be assumed to consist of spores from only a single haploid pycnium. Roughly 57% of the drops harvested were found to consist of more than one haploid genotype, most likely due to the physical mixing of spores from genetically different pycnia. Most importantly, although multiple infections do occur in the formation of a single gall, there is no evidence to suggest that the genetics of the proposed gene-for-gene interaction are compromised. Only avr1 basidiospores were observed to cause infection on Fr1/fr1 trees, whereas both avr1 and Avr1 basidiospores were observed to cause infection on fr1/fr1 trees, albeit not at equal frequencies. 相似文献
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Hypersensitive resistance to axenically cultured Cronartium ribicola was displayed by subcultured callus of Pinus lambertiana. Cellular resistance to a destructive rust disease can now be studied at the macromolecular level through use of cloned cells of both host and pathogen in a system amenable to emerging recombinant DNA technology. 相似文献
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Fusiform rust disease remains the most destructive disease in pine plantations in the southern United States. Our ongoing research is designed to identify, map, and clone the interacting genes of the host and pathogen. Several resistance (R) genes have been identified and genetically mapped using informative pine families and single‐spore isolate inoculations. In addition, we are mapping the first of many expected corresponding avirulence (Avr) genes in the fungal pathogen. The Avr genes condition avirulence/virulence and avirulence is required for an incompatible reaction (i.e., no‐gall development) to take place within an inoculated tree that carries resistance at the corresponding R gene. We provide an overview of our methodology for identifying and mapping R and Avr genes, an update of our current progress, and a brief discussion of two approaches for predicting R gene genotypes of uncharacterized parental trees and for estimating the efficacy of specific pine genotypes at various planting locations. This paper emphasizes the critical importance of controlled genetic materials of both the host and pathogen for elucidating the genetic nature of resistance and virulence in coevolved forest pathosystems. 相似文献
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A technique was developed to isolate and grow single genotype axenic cultures of Cronartium quercuum f. sp. fusiforme from individual hyphal fragments.Multi-genotype colonies established from multiple basidiospores served as stock material for single genotype establishments via hyphal fragments. multi-genotype colonies, subcultured fifteen days earlier, were minced via scalpel chopping and streaked on fresh medium. Single fragments of hyphae liberated from the minced inoculum were dispersed along the streak line, and those fragments widely separated from others were chosen as potential precursors for single genotype cultures. Three days after streaking, the widely separated fragments of hyphae were transferred along with a small amount of supporting agar to fresh medium. On fresh medium, single genotype cultures developed from individual hyphal fragments in 1.5 to 2 months. The addition of BSA (bovine serum albumin) to the growth medium greatly enhanced establishment of cultures. Of several media tested, HGYP with 0.4% or 1% BSA yielded superior establishment frequencies of 79% and 77%, respectively.This work represents a portion of a M.S. thesis submitted to North Carolina State University by the senior author. 相似文献
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Loblolly pine (Pinus taeda) seedlings from 12 full-sib families obtained from a six-parent half diallel mating design were challenged in a greenhouse
using two basidiospore inocula of the fusiform rust fungus (Cronartium quercuum f.sp. fusiforme) at extremely high spore density. Each basidiospore inoculum originated from a mixed gall collection of aeciospores obtained
from field-infected trees. Assessments at 4.5 months after inoculation showed that rust disease levels were high for every
full-sib family and were typically above 90% for most full-sib families for both inocula. However, disease (% galled) for
family E by A progeny, even at 9 months post inoculation, was lower, around 75%. A genetic model for interaction of two pairs
of genes was proposed to explain the observed infection levels (% galled) in this diallel based on a gene-for-gene hypothesis.
The putative genotypes of host parents and virulence compositions of mixed inocula were postulated. A bulk-segregant analysis
approach based on phenotype (gall vs. no gall) was used to search for dominant molecular markers associated with the potential
resistance genes in the host parents. A few candidate marker polymorphisms were observed between the gall vs. no gall bulks;
however, none of the candidates appropriately co-segregated with phenotype when tested across the progeny set. An alternative
model involving recessive resistance controlled by a single locus was also considered, but as with the two gene model, no
markers to support the appropriateness of the recessive resistance model were observed. 相似文献
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