Isozyme Genotypes Research Articles

Effect of the male parent on pericarp and seed weights in several Floridian mango cultivars

Self- and cross-pollination effects on mango pericarp and seed weights were studied. Fruit was collected from cultivar `6–6' trees caged with, and without, `Tommy Atkins' (`Tommy') as the pollenizer, and from plots consisting of adjacent blocks of `Maya' and `Tommy' or `Maya' and `Kent' cultivars. Selfed and outcrossed offspring were identified using the triosephosphate isomerase (TPI) isozyme system. Selfed `Keitt' progeny showed no significant relationship between TPI isozyme genotypes and pericarp and seed weights. No significant differences in pericarp or seed weights were found between outcrossed and selfed fruit for `Maya', `Tommy' or `Kent'. In contrast, pericarp and seed weights from fruit of `6–6' originating from cross-pollination were >50% heavier than self-pollinated fruit.

Colonization history and introduction dynamics of capsella bursa-pastoris (Brassicaceae) in north america: isozymes and quantitative traits

Multilocus isozyme genotypic composition for aspartate aminotransferase (AAT), leucine aminopeptidase (LAP) and glutamate dehydrogenase (GDH) was studied for Capsella in the source continent, Europe (9000 plants from 593 populations), and in the colonized continent, North America (2700 plants from 88 populations). North America was depauperate in the number of genotypes (by approximately 50%), but in terms of frequencies, a few genotypes were common and shared by both continents. Although some, very rare, genotypes were, however, unique for North America, our data provided no evidence to indicate that the introduced gene pools were reconstructed on a multilocus genetic basis after introduction. Instead, they argued for a considerable number of independent introduction events. Geographical distribution patterns of multilocus genotypes in Europe and North America were pronounced and enabled us to trace the colonization history of Californian Capsella back to Spanish ancestral populations and those of temperate North America back to temperate European gene pools. A random-block field experiment with 14 Californian populations from different climatic regions revealed that variation patterns of quantitative traits reflect ecotypic variation, and the ecological amplitude of Capsella in North America is similar to that in Europe, which can be traced back to the introduction of preadapted genotypes. It appears that certain multilocus isozyme genotypes are associated with certain ecotypes. The variable European gene pool of Capsella was essentially introduced into North America without major genetic changes.

Genotypic variation in progeny of the agamic grass complexPennisetum sectionBrevivalvula in West Africa

The genotypic variation of 1180 progeny from 118 genitors belonging to five taxa ofPennisetum sect.Brevivalvula has been estimated by isoenzyme electrophoresis with observations on five enzymatic systems, in order to compare the type of reproduction in polyploid and diploid taxa. A total of 112 different isozyme genotypes has been found, over all taxa. Genotypic variation was found among all progeny of the diploid populations ofP. polystachion andP. subangustum, as a consequence of their sexual reproduction system. At the polyploid level the type of reproduction appears to be predominantly agamic, but genotypic variation in the progeny was not rare: five tetraploid and one hexaploidP. pedicellatum, one pentaploid and one hexaploidP. polystachion and one hexaploidP. hordeoides, in a total of 90 genitors. Genetic relationships have been observed between the diploid sexualP. polystachion andP. subangustum, and, to a lesser extent, with the tetraploids of the same taxa as well. TetraploidP. polystachion andP. pedicellatum share genotypes with most other chromosomal taxa.

Variation in pathogenicity among South African isolates of Phytophthora cinnamomi

Phytophthora cinnamomi isolates from South Africa were evaluated for differences in growth rate in vitro and levels of pathogenicity towards Eucalyptus smithii in the field. Inoculations were conducted in the field in summer and winter in two subsequent years at two locations in South Africa using 59 P. cinnamomi isolates. The isolates differed significantly in growth rate in vitro, as well as in levels of pathogenicity to E. smithii in the field. Growth rate in vitro was significantly influenced by interactions with culture age, geographic origin and genetic background as determined using isozymes. Levels of pathogenicity in the field were influenced by season of inoculation and average minimum temperatures at trial sites. The host from which P. cinnamomi isolates were originally obtained did not significantly affect levels of pathogenicity in the field. Culture age had a significant negative effect on growth rate in vitro and pathogenicity in the field. Significant differences in levels of pathogenicity could be found for different multilocus isozyme genotypes. Geographic origin and mating type of P. cinnamomi isolates had no significant effect on levels of pathogenicity in the field. A positive correlation was found between growth rate in vitro and levels of pathogenicity in the field. Levels of variation for pathogenicity within A1 mating type isolates were significantly lower than for A2 mating type isolates. Results of this study provide valuable information on selection of P. cinnamomi isolates for future resistance/tolerance screening assays of Eucalyptus germplasm in South Africa.

The extinction of genetic resources of Asian wild rice, Oryza rufipogon Griff.: A case study in Thailand

Natural populations of wild rice, Oryza rufipogon Griff., are now threatened with the disturbance of their natural habitats by various human activities. To obtain basic information on genetic erosion or loss of genetic diversity in wild rice, we investigated how environmental changes of habitat affected the genetic structure of its natural population at a study site in the central plain of Thailand. During 10 years from 1985 to 1994, the wild-rice population at this site was seriously destroyed and fragmented. Using two sets of seed sample collected in 1985 and 1994 from the same population, allozyme variability at 17 loci of 11 enzymes were examined. Isozyme genotypes of mother plants of seed samples were estimated by the segregation in each progeny, and we calculated genetic parameters for the population. Gene diversity severely decreased in the 1994 sample compared with the 1985 sample. It is supposed that declining and fragmentation of the wild rice population, which happened during the 10 years, caused loss of genetic variability and forced the habitually outbreeding plants to inbreed, accelerating a reduction in gene variability. Pgi1-1 allele which was common in Indica rice cultivars of this region was found in the wild rice plants growing at the side of rice fields. Probably, introgression has occurred between wild and cultivated rice plants, and consequently the intrinsic nature of wild rice was gradually blurred by cultivar genes. We must realize that the genetic erosion of wild rice is rapidly proceeding and that an action for their conservation in natural environment, so called in situ conservation, is urgently needed.

First Report of A1 and A2 Mating Types of Phytophthora infestans on Potato and Tomato in Nepal.

Late blight caused by Phytophthora infestans (Mont.) de Bary is an important disease of potato and tomato that occurs annually in the hills and occasionally in the terai (plain) of Nepal. In 1996 and 1997, each year, 50 samples of late blight-infected potato and tomato leaves were collected from the hill and terai areas. The pathogen was cultured on Rye A agar. Each isolate was paired on clear V8 agar with reference isolates DN111 (A1 mating type) and DN107 (A2 mating type) received from Hokkaido University, Japan, and examined for oospore formation after 10 to 15 days of incubation at 20°C. The proportion of A2 isolates was 6% in 1996 and 42% in 1997. The A2 isolates were mainly from the high hills (2,000 to 2,500 m) where local and Andean types of potatoes are grown. Analysis of genotypes of isolates at the glucosephosphate isomerase (GPI-1), malic enzyme (ME), and peptidase (PEP-1) (1,2) isozyme loci revealed genetic diversity between A1 and A2 isolates. A1 isolates from potato were either homozygous (100/100) or heterozygous (86/100) for GPI-1, whereas all A1 isolates from tomato were heterozygous (86/100). All A1 isolates were homozygous (100/100) at the ME locus and heterozygous (92/100) at the PEP-1 locus. A2 isolates were homozygous (100/100) at all isozyme loci. The results show that both A1 and A2 mating types of P. infestans are present in Nepal, and that they display different isozyme genotypes. It is speculated that the A1 type may have migrated with potatoes from Europe while the A2 type may have been introduced with Andean potatoes from Latin America more recently. The simultaneous occurrence of both mating types may allow the fungus to increase its pathogenic diversity and to survive by means of oospores.

Lack of detectable isozyme variability in British populations of Potamogeton epihydrus (Potamogetonaceae)

Outside North America Potamogeton epihydrus Raf. is confined to two areas of Britain. An investigation of British material from apparently native sites in the Outer Hebrides and from a canal in northern England (where it is believed to be introduced) revealed only a single isozyme genotype. Ten putative loci were resolved. The IDH phenotype was uniform and three-banded, consistent with heterozygosity (possibly caused by a duplicated locus or preserved by clonal growth). All other enzyme loci were homozygous.

Classification of the Cultivars of Japanese Taro (Colocasia esculenta (L.) Schott) by Isozyme Analyses.

To classify cultivars of Japanese taro (Colocasia esculenta (L.) Schott), isozyme variations at the five loci, Gpi-2 of glucose-6-phosphate isomerase, Aat-1 and Aat-3 of aspartate aminotransferase, Skdh of shikimate dehydrogenase and Idh of isocitrate dehydrogenase, were examined in the 58 cultivars. Allele a at the Aat-3 was recognized specifically in all the examined triploid cultivars, and this allele clearly discriminated the triploid cultivars from the diploid ones. This suggests that these triploid cultivars did not originate as bud mutations or from crosses between diploid ones. Combinations of isozyme genotypes at the five loci divided the 58 cultivars into only 11 groups, which indicates that the Japanese cultivars originated from a relatively small number of progenitors. Isozyme variations in each of the 14 cultivar groups proposed by Kumazawa et al. (1956) were not recognized except those in the Akame and Kurojiku groups. Therefore, wide morphological variations between the cultivars in each of the cultivar groups seem to have occurred as bud mutations in many cases. Cultivars in the Akame and Kurojiku groups seem to have been derived from the several ancestral cultivars of different origins.

The biology of Canadian weeds. 108. Erucastrum gallicum (Willd.) O.E. Schulz

A review of biological information is provided for Erucastrum gallicum (Willd.) O.E. Schulz. A European native, it was introduced into Canada and the United States in the early 1900s and spread rapidly along the railroads. The species occurs in all the provinces and the Northwest Territories and is particularly abundant in the Prairie provinces and mid-western United States. It is a summer annual, rarely a winter annual or biennial species, and is characterized by high reproductive output. Plants occur most commonly on waste ground and along roadsides and railroads, followed by agricultural fields. Erucastrum gallicum is of allopolyploid origins (n = 15, 7 + 8 chromosomes), and contains a single multi-locus isozyme genotype. The species is a close relative of Brassica and is capable of limited genetic exchange with the canola species, B. rapa and B. napus. The possible transfer of genes from transgenic canola varieties to Erucastrum gallicum poses a remote, but potential, environmental risk. Populations of Erucastrum gallicum, including both Old World and North American populations, constitute a valuable germplasm resource as potential sources of beneficial agronomic traits, such as disease resistance for canola crop improvement. Key words: Dog mustard, Erucastrum gallicum, weed biology, risk assessment, germplasm, canola

Population Structure of Phytophthora cinnamomi in South Africa

ABSTRACT Phytophthora cinnamomi isolates collected from 1977 to 1986 and 1991 to 1993 in two regions in South Africa were analyzed using isozymes. A total of 135 isolates was analyzed for 14 enzymes representing 20 putative loci, of which four were polymorphic. This led to the identification of nine different multilocus isozyme genotypes. Both mating types of P. cinnamomi occurred commonly in the Cape region, whereas, predominantly, the A2 mating type occurred in the Mpumalanga region of South Africa. A2 mating type isolates could be resolved into seven multilocus isozyme genotypes, compared with only two multilocus isozyme genotypes for the A1 mating type isolates. Low levels of gene (0.115) and genotypic (2.4%) diversity and a low number of alleles per locus (1.43) were observed for the South African P. cinnamomi population. The genetic distance between the Cape and Mpumalanga P. cinnamomi populations was relatively low (D(m) = 0.165), and no specific pattern in regional distribution of multilocus isozyme genotypes could be observed. The genetic distance between the "old" (isolated between 1977 and 1986) and "new" (isolated between 1991 and 1993) P. cinnamomi populations from the Cape was low (D(m) = 0.164), indicating a stable population over time. Three of the nine multilocus isozyme genotypes were specific to the "old" population, and only one multilocus isozyme genotype was specific to the "new" population. Significant differences in allele frequencies, a high genetic distance (D(m) = 0.581) between the Cape A1 and A2 mating type isolates, significant deviations from Hardy-Weinberg equilibrium, a low overall level of heterozygosity, and a high fixation index (0.71) all indicate that sexual reproduction occurs rarely, if at all, in the South African P. cinnamomi population.

Genetic variability of the Japanese eel Anguilla japonica (Temminck & Schlegel) related to latitude

Abstract— Isozyme genotypes of 400 glass eels recruiting to 4 localities along the east Asian coast, stretching from Taiwan to the Yalu River of northeastern China, were studied using starch gel electrophoresis. Geographic cline was found to exist in two loci: NADP‐isocitrate dehygenase‐1 and 6‐phosphogluconate dehydrogenase. Frequencies of the most common allele of these two loci increased from south to north. In the latitudinal range of 25°N to 40°N, the magnitude of difference of IDH100 and PGD100 was 13% and 9% respectively. However, deviations from Hardy‐Weinberg equilibrium were found to be insignificant in both loci at three of the four localities. The cline was, therefore, unlikely to have resulted from selection. Migration time‐lag from different parts of the continent to the spawning ground in the western Pacific was suggested to be a possible reason for the formation of the cline.

Complex constitutive nature of Japanese upland rice, Oryza sativa L.

Two rice ecotypes, the so-called lowland and upland populations, which carry different isozyme genotypes mostly at a single locus, are cultivated in Japan. The aim of this study was to examine the origin and the mechanism for keeping these genetic differences. The upland population is cultivated in upland fields and carries a different allele for a particular isozyme gene, Pgd-1, which has never been found in the lowland population. RFLP markers showed a weak trend for genetic differentiation between the two ecotypes. On the other hand, morphological, and physiological traits showed marked differences between the two ecotypes. Furthermore, based on the genotypic difference, two Japonica subgroups are defined in the upland population. Subgroup I is the minor group and carries key lowland characters, including the genotype for PGD. Subgroup II carries different traits and the genotype for PGD of the alternative subgroup. As an allelic difference for Pgd-1 is known to occur between the two ecospecies, Tropical (Tr) and Temperate (Tm) Japonicas, upland cultivars can be classified by diagnostic characters which distinguish a variety into Tr or Tm type. The upland population consists of three types of cultivars, Tr-, Tm- and intermediate-type. In contrast, the lowland population consists of a uniform Tm type Japonicas. As Japanese upland cultivars still have an isozyme allele specific to the Tr type, the upland population has a rather complex constitution which is presumably now being introgressed by lowland genetic material, but still represents a major difference at some genetic levels. Upland rice carries several stress-resistant genes which would be useful for lowland rice breeding. The genetic difference would be efficient for tagging upland specific traits by upland specific genetic markers.

Isozyme Genotype of Major Cultivar Groups Resistant to Bacterial Blight in Asian Rice.

Isozyme types were determined for six cultivar groups carrying different resistance to rice bacterial blight in Asia. The temporarily proposed Isozyme genotypes would be associated with the differentiation of the reaction of resistance. The predominant type of the Java 14 group was Isozyme type VI-1, and type II-4 was involved as the second predominant type. The majority of the DZ 192 group belonged to type II-1 and II-2. A newly assigned TN 1 group consisted of Isozyme type I and VI / . The predomi-nant occurrence of I-1 and I-2 was common among the TKM 6, Cas 209, Mond Ba and TN I groups. However, frequent involvement of IM-1 and IM-2 were specific to the TKM 6 group. The frequent presence of I-4 and I-5 was the characteristic of the Cas 209 and Mond Ba groups. Based on these observations the ecotypic diversity of each group was discussed.

Genetic diversity in the top onion,Allium �proliferum (Alliaceae), analysed by isozymes

Polymorphisms for six enzyme systems (GPI, IDH, PDG, PGM, SKD, and TPI) were analysed in the top onion,Allium ×proliferum. Five multilocus isozyme genotypes were found. The banding patterns of top onions were compared with those ofA. ×wakegi, A. cepa, A. fistulosum, A. altaicum, and artificial hybrids between these three species. One top onion type and one artificial hybrid had identical banding patterns. Shallots andA. altaicum, the wild progenitor ofA. fistulosum, cannot be distinguished from the common onion andA. fistulosum, respectively; these species are also potential contributors to the top onion's gene pool.

8-Hydroxydeoxyguanosine in human leukocyte DNA and daily health practice factors: effects of individual alcohol sensitivity.

A typical oxidative DNA damage, 8-hydroxydeoxyguanosine (8-OHdG), was evaluated in human polymorphonuclear leukocytes (PMN) and mononuclear leukocytes (MN) by an anaerobic determination method. The mean 8-OHdG values were the lowest level ever reported [PMN, 3.07 +/- 1.45; MN, 2.37 +/- 1.21 8-OHdG/10(6) deoxyguanosine molecules (dG); n = 92]. According to a self-administered questionnaire to 92 healthy male workers, the relationship was investigated between 8-OHdG in leukocytes and daily health practice factors, that is, the frequency of physical exercise, smoking status, alcohol drinking, nutritional balance, and the degree of mental stress. A significant difference was observed only in alcohol drinking in subjects classified by aldehyde-dehydrogenase 2 isozyme (ALDH2) genotype. Habitual alcohol intake appeared to increase 8-OHdG in PMN from ALDH2-deficient subjects. Neither age, body mass index, nor any other factors examined showed any significant correlation with the 8-OHdG levels in leukocytes.

8-Hydroxydeoxyguanosine in Human Leukocyte DNA and Daily Health Practice Factors: Effects of Individual Alcohol Sensitivity

A typical oxidative DNA damage, 8-hydroxydeoxyguanosine (8-OHdG), was evaluated in human polymorphonuclear leukocytes (PMN) and mononuclear leukocytes (MN) by an anaerobic determination method. The mean 8-OHdG values were the lowest level ever reported [PMN, 3.07 +/- 1.45; MN, 2.37 +/- 1.21 8-OHdG/10(6) deoxyguanosine molecules (dG); n = 92]. According to a self-administered questionnaire to 92 healthy male workers, the relationship was investigated between 8-OHdG in leukocytes and daily health practice factors, that is, the frequency of physical exercise, smoking status, alcohol drinking, nutritional balance, and the degree of mental stress. A significant difference was observed only in alcohol drinking in subjects classified by aldehyde-dehydrogenase 2 isozyme (ALDH2) genotype. Habitual alcohol intake appeared to increase 8-OHdG in PMN from ALDH2-deficient subjects. Neither age, body mass index, nor any other factors examined showed any significant correlation with the 8-OHdG levels in leukocytes.

Isozyme Variation in Lychee (Litchi chinensis Sonn.)

A genetic diversity analysis involving 49 Iychee (Litchi chinensis Sonn.) accessions using eight enzyme systems encoding 12 loci (Idh-1, Idh-2, Mdh-2, Per-1, Pgi-2, Pgm-1, Pgm-2, Skdh, Tpi-1, Tpi-2, Ugpp-1, and Ugpp-2) revealed moderate to high levels of genetic variability. Cluster analysis of the isozyme data from 40 genetically different accessions of the total 49 identified three groups at the 50% level of genetic similarity, the largest of which contained 32 of the 40 accessions distributed in three sub-groups. The groups including the three subgroups differed in frequency and composition of alleles at different loci. Polymorphism was observed in 77% of the loci, with an overall mean of 2.2 alleles per locus and an observed heterozygosity of 0.387. The unbiased genetic identities (I) between groups ranged from 0.809 to 0.937. Summing over all 11 polymorphic loci, 16% of gene diversity was due to differentiation between groups and 84% within groups. Comparison of isozyme fingerprints revealed that some accessions with identical names, particularly of `No mai tsz', `Kwai mi', and `Hak ip', possessed different isozyme genotypes, while other accessions with different names displayed identical isozyme genotypes. Isozyme fingerprinting will be useful in revealing and resolving questions of clonal identity, which are common in Iychee germplasm collections.

Isozyme variation in lychee ( Litchi chinensis Sonn.)

A genetic diversity analysis involving 49 lychee ( Litchi chinensis Sonn.) accessions using eight enzyme systems encoding 12 loci ( Idh-1, Idh-2, Mdh-2, Per-1, Pgi-2, Pgm-1, Pgm-2, Skdh, Tpi-1, Tpi-2, Ugpp-1, and Ugpp-2) revealed moderate to high levels of genetic variability. Cluster analysis of the isozyme data from 40 genetically different accessions of the total 49 identified three groups at the 50% level of genetic similarity, the largest of which contained 32 of the 40 accessions distributed in three sub-groups. The groups including the three sub-groups differed markedly both in frequency and composition of alleles at different loci. On average, 77% of the loci were polymorphic with an overall mean of 2.2 alleles per locus and an observed heterozygosity of 0.387. The unbiased genetic identities ( I) between groups ranged from 0.809 between Groups 1b and 2 to 0.937 between Groups 1b and 1c. Group 2 has diverged from the other groups with an average genetic identity of 0.821. Summing over all 11 polymorphic loci, 16% of gene diversity was due to differentiation between groups and 84% to that within groups. Comparison of isozyme fingerprints revealed that some accessions identically named, such as ‘No mai tsz’, ‘Kwai mi’, and ‘Hak ip’, possessed different isozyme genotypes, whereas some others with different names displayed identical isozyme genotypes.

Isozyme Variability in Wild and Cultivated Carica papaya

Populations of wild Carica papaya, previously designated as Carica peltata, were sampled from its native range on the Caribbean coast of Central America (Mexico, Belize, Guatemala, Honduras) and cultivated Carica papaya from both Central and South America were examined for isozyme variability. Thirteen loci from nine enzyme systems (Pgm, Pgi, Idh, Mdh, 6Pgd, Ugpp, Skdh, Aco, Tpi) were scored for all populations. Ten loci were polymorphic and a total of 31 alleles were detected. Isozyme genotypes as determined through segregation analysis were used in the genetic interpretation for eight loci and 18 alleles while six additional loci and 13 alleles were postulated on the basis of phenotypic variation found throughout the species. Nei's genetic identity, I, for both cultivated and wild Carica papaya was >0.9, which is consistent with conspecific populations. Wild papaya populations from different geographic areas appear more related to one another than to domesticates in the same geographic region.

Genetic Diversity in Nephelium

Fifty-six accessions involving five taxa of Nephelium (N. Iappaceum varieties lappaceum and pallens, N. hypoleucum, N. ramboutan-ake, and N. cuspidatum) were fingerprinted and evaluated for genetic diversity using isozyme polymorphism. All five taxa were polymorphic for most of the enzymes encoded by 10 putative loci. Number of alleles per locus ranged from three for Pgi-1 to nine for Pgi-2 with a total of 57 alleles. Thirty-eight accessions out of 56 possessed unique isozyme genotypes, indicating a high level of diversity in the collection. On average, 80% of the loci were polymorphic and the expected and observed heterozygosities were 0.374 and 0.373, respectively. The cluster analysis of the isozyme data revealed five distinct clusters representing the five taxa included in the study. Genetic differentiation within N. Iappaceum var. Iappaceum was evident from the cluster analysis. Isozyme data indicated that N. ramboutan-ake is the closest relative of N. Iappaceum var. Iappaceum, followed by N. hypoleucum, N. Iappaceum var. pallens, and N. cuspidatum. Interestingly, the varieties of N. Iappaceum exhibited genetic divergence far beyond that of the congenerics, N. hypoleucum and N. ramboutan-ake and may require a taxonomic revision.