T-type chloroplast DNA inSolarium tuberosum L. ssp.tuberosum was conferred from some populations ofS. tarijense Hawkes

The highly heterozygous and tetraploid nature of potato (Solanum tuberosum L. ssp.tuberosum) has hampered discovery of its wild ancestral species. Chloroplast DNA is a very reliable indicator to trace maternal ancestry of crops. Most of the common potato (grown worldwide) has unique, T-type chloroplast DNA derived from Chilean cultivated potato (both areS. tuberosum ssp.tuberosum). Analyzing seven different chloroplast DNA markers, I found all the T-type accessions of cultivated potatoes shared the same chloroplast DNA haplotype only with some accessions ofS. tarijense Hawkes and its derived hybrids. Thus, I conclude that some populations ofS. tarijense acted as the maternal ancestor of potato.     

High Levels of Heterozygosity Found for 15 SSR Loci in <Emphasis Type="Italic">Solanum chacoense</Emphasis>

Wild species-related germplasm is widely used to introduce new alleles and/or increase heterozygosity in cultivated species. Twenty-four SSR markers, specifically designed for cultivated potatoes, were evaluated to determine the extent of genetic variation within and among ten accessions of Solanum chacoense (chc). Fifteen of these markers were informative: there was no polymorphism in one of the markers, four of the markers showed evidence that more than one locus was being amplified, and the other four markers failed to consistently amplify products. Heterozygosity in these 10 accessions ranged from 33% to 87%. Variation among accessions was the largest proportion of variance for three markers, variation among genotypes within accessions was the largest proportion for three markers, and for the other nine markers variation within genotypes (chromosome to chromosome) was the largest proportion. Genetic similarity averaged 29.5% across markers. Where accessions have already been screened and found to possess the trait of interest, multiple genotypes from those accessions should be evaluated to identify genotypes with the greatest expression of the trait.     

Genetic characterization of reduced melanin formation in tuber tissue ofSolatium hjertingii and hybrids with cultivated diploids

The degree of enzymatic browning in tubers was examined quantitatively in five plant introduction (PI) accessions ofSolanum hjertingii and in hybrids of this species with cultivated diploids that had high enzymatic browning. Polyphenol oxidase activity and melanin formation inS. hjertingii accessions was subjected to an analysis of variance. There was significant variation in melanin formation within accessions but the between accession component was not significant. This indicates that it would be most advantageous to select low melanin formation by evaluating individual genotypes within an accession. Significant variation for PPO activity existed between accessions, indicating that selection on the basis of accession means would be the best means of selecting for lower PPO activity. Both parameters were much lower in allS. hjertingii genotypes compared to tetraploid cultivars known for their susceptibility to internal blackspot when mechanically damaged. The reduced browning inS. hjertingii was due to a lack of PPO activity and not the shortage of substrate. Progenies, and parents of four crosses between selectedS. hjertingii genotypes and cultivated diploids were measured for PPO activity and melanin formation. The mean performance of the progenies was closest to theS. hjertingii parent in all cases. Degree of dominance indicated nearly complete dominance or overdominance in the direction of theS. hjertingii parent. These results are discussed in light of other work which indicates that protein antigenic to PPO antibody is present inS. hjertingii. It appears that inactive PPO is present in the tubers. The pronounced dominance of low PPO activity and suppression of melanin formation in the hybrids withS. hjertingii is promising for the utility of this wild species as a source of genetic factors that, upon introgression into the cultivated potato gene pool, would suppress browning.     

利用SSR分子标记研究花生属种间亲缘关系

以5份花生栽培种资源和花生属六个区组的19份野生种资源为研究材料，通过SSR分子标记技术分析其DNA多态性并进行聚类分析。大多数从栽培种基因组分离出的SSR引物能在野生种中扩增出DNA片段，共筛选出21对多态性SSR引物；每对引物在花生基因组中扩增出的条带数为1～13条，在供试材料中扩增出的总条带数为5～40条，平均18.1条，其中多态性条带为4～40条，平均18.0条；SSR引物的多态性指数为0.92～9.04；供试材料间的遗传距离为0.33～0.91，平均0.76。结果表明，大多数花生SSR引物为多位点引物，花生属种间种质存在丰富的DNA多态性， A. duranensis是花生栽培种（A. hypogaea L.）的野生种亲本之一，与花生区组野生种亲缘关系最近的是异形花区组，最远的是大根区组。     

Evaluation of several wild tuber-bearingSolanum species for scab resistance

One hundred accessions of 18 wild diploid potato species were screened for resistance to scab through three cycles of selection, from which a total of 322 clones were selected as resistant. The putative ancestral species of the cultivated potatoes (Solanum bukasovii, S. canasense andS. multidissectum) produced resistant clones with significantly higher rates. Thus, these are primary gene sources for conferring scab resistance to cultivated potatoes.     

Evaluation of wildSolanum species for resistance to the US-8 genotype ofPhytophthora infestans utilizing a fine-screening technique

Greenhouse assays were carried out to characterizeSolanum accessions previously reported to be late blight resistant and to identify individuals within the accessions with high levels of resistance to late blight. Foliage of wildSolanum species accessions or hybrid cultivated potato x wild species (diploid or tetraploid) from Mexico, Russia, or South America was inoculated withPhytophthora infestans (US-8) and was scored for severity of foliar symptoms at 7 and 14 days after inoculation (DAI). Mexican accessions (S. brachycarpum,S. pinnatisectum,S. guerreroense, andS.fendleri) were significantly more resistant (1.1% infection at 14 DAI) than either Russian (59.1% infection at 14 DAI) or South American (53.4% infection at 14 DAI) accessions. Moreover, the genotypes within the Mexican accessions tended to be more uniformly resistant whereas genotypes within the Russian and South American accessions tended to segregate for resistance. The more resistant genotypes of Russian and South American accessions (176/546) were retested, and 56 genotypes were identified as having potential for use in potato breeding programs for resistance to late blight. Fifty percent of the selected genotypes were fromS. microdontum accessions PI498124, PI595510, and PI595511. The potential of these species for incorporation into breeding programs for late blight resistance is discussed.     

Identification of late blight, Colorado potato beetle, and blackleg resistance in three Mexican and two South American wild 2x (1EBN)Solanum species

Wild potatoes are important sources of genes for resistance to disease and insect pests. A collection of wild Mexican and South AmericanSolarium species from the US potato Genebank was evaluated under laboratory and/or field conditions for their reaction to late blight (Phytophthora infestans), Colorado potato beetle (CPB,Leptinotarsa decemlineata Say), and blackleg (Erwinia carotovora subsp.atroseptica (van Hall) Dye) in order to identify individual genotypes with multiple resistance genes. Late blight inoculations using aggressive isolates (US-8/A2 and US-11/A1 mating types) of P.infestans revealed a wide range of variation for resistance between and within the accessions of the wild species tested. For late blight, susceptible as well as moderately to highly resistant genotypes were observed in all the species tested. However, at least one accession from the three Mexican and one South American wild diploid species tested showed a relatively uniform high level of resistance toP. infestans. These includedS. bulbocastanum, S. pinnatisectum, S. cardiophyllum, andS. circaeifolium. Two accessions from South American speciesS. commersonii were highly susceptible to late blight. For the Colorado potato beetle test, only one species,S. pinnatisectum appeared uniformly resistant to CPB under field conditions. Results of screening for blackleg resistance showed that there were major differences between genotypes in the wild species. Accessions ofS. circaeifolium PI 498119 andS. bulbocastanum PI 243504 were identified as having significantly higher blackleg resistance than cultivated potato and the other wild species tested. However, genotypes from these two accessions were more susceptible to late blight and CPB. Characterization of theP. infestans isolate P1801C.16 used for late blight evaluation and multi-locus isolate tests using US-8/A2 and US-11/A1 races revealed that the resistance inS. pinnatisectum genotypes tested corresponded to a race-non-specific genetic system, which was different from any existing R genes.Solanum pin-natisectum genotypes with both high levels of late blight and CPB resistance as well as blackleg resistance genotypes identified in the present study represent a diverse gene pool that may be useful for development of new potato cultivars with multiple disease and insect resistance. The potential utilization of these valuable sources for improvement of cultivated potato is discussed.     

Screening the U.S. potato collection for frost hardiness

Potato is one of the most important world vegetables with respect to value of production and nutritional impact. Frost susceptibility reduces or precludes production on millions of hectares worldwide. In contrast to disease and pest problems, cultural or chemical treatments are not likely to be helpful in combating frost, so genetic improvement must be sought. Fortunately, wild relatives of the cultivated potato have been shown to exhibit frost tolerance far superior to that of cultivated species. In this research, over 2,600 accessions representing 101 species in the US potato collection at Sturgeon Bay, Wisconsin were visually screened after natural frosts in a uniform field in 1992. This provided a more comprehensive survey of germplasm accessions, further characterized species’ hardiness and intraspecific variation. The most hardy species wereSolanum acaule, S. albicans, S. commersonii, andS. demissum. An additional previously unreported extremely frost hardy species (Solanum paucissectum) was discovered. This information should expand the insights and germplasm options available to those intent on breeding desirable varieties with high levels of frost hardiness.     

Evolutionary pathway of T-type Chloroplast DNA in potato

Potato was domesticated in the Andes of South America. However, the presently worldwide-grown potato (Solanum tuberosum L. ssp.tuberosum, 2n=4x=48) has characteristic T-type chloroplast DNA that was introduced after late blight epidemics in the mid-19th century from the Chilean potato (2n=4x=48) grown in the southern coastal regions in Chile. Among many wild potato species, the same chloroplast DNA was found only in some populations of a diploid speciesS. tarijense Hawkes (2n=2x=24), which ranges from central Bolivia to northwest Argentina. To elucidate an evolutionary pathway of T-type chloroplast DNA fromS. tarijense to Chilean potato, 215 accessions ofS. stenotomum Juz. et Buk., considered to be the most primitive, diploid cultivated potato species, from which all the Andean cultivated species evolved, and 286 accessions of the most widely grown, Andean tetraploid cultivated speciesS. tuberosum L. ssp.andigena Hawkes (2n=4x=48) were examined in this study. No accession ofS. stenotomum had T-type chloroplast DNA, while nine accessions, mostly from northwest Argentina, ofS. tuberosum ssp.andigena had T-type chloroplast DNA. Therefore, I conclude that some populations ofS. tarijense having T-type chloroplast DNA were naturally crossed as female withS. tuberosum ssp.andigena from which the Chilean potato was selected.     

Evaluation of tuber-bearingSolanum species for symptomology,as diagnostic hosts,and sources of immunityto potato virus Y necrotic strain (PVYN)

A total of 258 Plant Introductions (PI) belonging to 69Solarium species were evaluated in the greenhouse for their reaction to the tobacco veinal necrosis strain of potato virus Y (PVY N). One hundred and thirty-one (50.7%) of the PI accessions produced mosaic symptoms ranging from mild to severe. Local lesion and veinal necrosis symptoms were observed in 19 PI accessions (7.3%) and a variety of other symptoms were observed in another 11 PI accessions (4.2%). Only 97 PI accessions (37.5%) were symptomless carriers of PVY^N. PI accession 473505 ofS. sparsipilum and PI accession 498021 ofS. brachycarpum developed local lesions and veinal necrosis with PVY^N, but necrotic spots and mosaic with PVY^o. Common mechanically-transmitted potato viruses A, S, M, and X did not interfere with PVY symptom development inS. sparsipilum andS. brachycarpum. Thus, PI 473505 and PI 498021 can be used as indicator plants for specific identification of PVY^N. PI accession 472819 ofS. chacoense developed local lesions with systemic spread in PVY^o, but without systemic spread in PVY^N. Thus, this can be used as a differential host plant for PVY strains. Two PI accessions ofS. stoloniferum, PI 160372 and 161171 were immune to PVY^N.     

Comparison of Cheng’s Index-and SSR Marker-based Classification of Asian Cultivated Rice

A total of 100 cultivated rice accessions,with a clear isozyme-based classification,were analyzed based on Cheng’s index and simple sequence repeat (SSR) marker.The results showed that the isozyme-based classification was in high accordance with that based on Cheng’s index and SSR markers.Mantel-test revealed that the Euclidean distance of Cheng’s index was significantly correlated with Nei’s unbiased genetic distance of SSR markers (r=0.466,P ≤ 0.01).According to the model-based group and cluster analysis,the Cheng’s index-and SSR-based classification coincided with each other,with the goodness of fit of 82.1% and 84.7% in indica,97.4% and 95.1% in japonica,respectively,showing higher accordance than that within subspecies.Therefore,Cheng’s index could be used to classify subspecies,while SSR marker could be more efficient to analyze the subgroups within subspecies.     

花生属不同区组种质主要植物学性状及分子特性

从主要植物学性状如主茎粗、主茎高、侧枝长、总分枝数、结果分枝数等22个性状和SSR多态性方面对花生属不同区组的19份种质资源的主要特性进行了分析。结果表明，不同种质在形态性状方面存在丰富的变异，匍匐区组的A. rigonii(G2)、花生区组的A. batizocoi（G8）和A. duranensis（G11）在形态方面具有显著区别于其他种质的特点。SSR分析结果也证实，不同野生花生种质具有多样化的分子特征，A. rigonii(G2)、A. batizocoi（G8）和A. duranensis（G11）等在形态方面具有突出特点的种质，能通过很多引物检测出来，形态性状的分析结果与SSR分析结果一致。引物10D4的检测效率很高，能鉴定19份资源中的11份。根据25对SSR引物的扩增结果，绘制了19份资源的指纹图谱。     

The dimensions of existingSolanum germ plasma collections

Analysis of the stocks available from threeSolanum germ plasm collections (Commonwealth Potato Collection, D. D. R. Sortiment and U. S. Potato Collection) shows that an adequate number of accessions are available for only a few species. Seventy-five of the 92 wild species being maintained are representd by fewer than 20 accessions. Development of activeSolanum germ plasm collections in the centers of diversity for these species eventually may provide the broader base of germ plasm needed for potato research.     

Use of activated charcoal to enhance the germination of botanical seeds of potato

The effect of activated charcoal (AC) on the germination of botanical potato seeds was tested by applying AC to seeds in petri dishes which had been pretreated with gibberellic acid (GA). A diverse sample of accessions including cultivar and cultivated species germplasm, cultivated species hybrids, wild species, and wild species known for their slow germination was tested. The time required from hydration to75% germination was significantly less for all types of seeds tested when AC was present. Cultivated species hybrids reached75% germination an average of four days sooner, wild species two days sooner, and slow germinating wild species 18 days sooner when AC was present. Only slow germinating wild species’ seeds germinated with significantly more uniformity in the presence of AC.     

A Stringent and Broad Screen of Solanum spp. tolerance Against Erwinia Bacteria Using a Petiole Test

Blackleg and stem rot caused by coliform bacteria belonging to Dickeya spp. and Pectobacterium spp. (both referred to as Erwinia in this paper) are a problem for potato growers worldwide and no sources of high tolerance are currently present in the cultivated S. tuberosum gene pool. To find sources of tolerance, 532 genotypes from 340 accessions, covering most of the known potato species, were assayed with P. wasabiae, P. carotovorum and D. ‘solani’ species in a petiole test. This petiole test was optimized later on using well responding genotypes from the broad screen. Based on the obtained data, the best developmental stage for cell wall degradation tests was identified to be the 4th-6th youngest leaf. Under the stringent biotic and climatic screening conditions used, only three genotypes were regarded as tolerant against all tested Erwinia species. These genotypes all belonged to the series Yungasensa, this series can be readily crossed with cultivated potato and is considered as a genetic source to upgrade the Erwinia tolerance level of cultivated potato.     

Response of six wild potato species to chloride and sulfate salinity

Eleven accessions belonging to six species ofSolanum (S. bulbocastanum,S. chacoense, S. gourlayi, S. microdontum, S. papita, and S.sparsipilum) were tested for resistance to salt. Resistance was measured by survival and growth (dry weight of tops) of plants treated with solutions of NaCl and Na₂SO₄. The six species could be grouped into four classes based on good to poor resistance to salt solutions (1.S. chacoense, 2.S. gourlayi, 3.S. microdontum, S. sparsipilum, S. bulbocastanum and 4.S. papita). There was a close relationship (r=0.94**) between the survival of plants and growth of surviving plants treated with salt solutions. There was no relationship between known heat or drought resistance of various accessions and salt resistance. Results indicate there is a large genetic base available to improve the salt resistance of the cultivated potato.     

两种生物型江都杂草稻不同栽播密度对水稻生长的影响及其与栽培稻的亲缘关系

 以两种生物型的江都杂草稻为材料,考查了杂草稻的生物学性状并对其进行了SSR分析, 旨在确定江都杂草稻的生物类型、遗传特性以及对栽培稻产量的影响。结果表明：杂草稻可分为两个生物型,一类是矮秆类型,包括JDWR A和JDWR C;一类是高秆类型,包括JDWR B。两种类型的杂草稻均属于籼型杂草稻。JDWR A与JDWR C亲缘关系较近,矮秆类型的杂草稻与高秆类型的杂草稻亲缘关系较远,而与杂交稻不育系亲本珍汕97A的亲缘关系较近。杂草稻与栽培稻的田间竞争实验表明,矮秆类型的杂草稻对栽培稻产量因子的影响更为严重。     

Resistance in tuber-bearing solanum species to root knot nematode,Meloidogyne incognita

Forty-one clones of 34 accessions belonging to 25 tuber-bearingSolanum species were tested for their reaction to root knot nematode,Meloidogyne incognita. A high degree of resistance was found inS. bulbocastanum, S. gandarillasii, S. lignicaule, S. ajanhuiri andS. tuberosum groupandigena. S. vernei andS. spegazzinii were the most resistant species.     

Genetic Diversity and Phylogenetic Relationships in Cotton Based on Isozyme Markers

Summary

Phylogenetic relationships among 16 diploid species, including at least one species for each of the A, C, D, E and G genomic groups, and for the natural AD tetraploid species and one synthetic AD tetraploid species were investigated using starch gel electrophoretic techniques for isozyme detection in conjunction with multivariate analysis. The species were polymorphic for phosphoglucomutase (PGM), malate dehydrogenase (MDH), shikimate dehydrogenase (SKDH), aconitase (ACO) and isozymes, but monomorphic for phosphoglucoisomerase (PGI). Similar isozyme arrays indicated close or perhaps conspecific relationships between natural tetraploids G. hirsutum and G. lanceolatum and between G. barbadense and G. darwinii. Natural tetraploid G. mustelinum was found to be relatively distinct from the other tetraploid species. The synthetic AD tetraploid was intermediate between the natural AD tetraploid and the A and D diploid clusters. The two A genome species, G. aboreum and G. herbaceum were closely related to each other. These results supported the hypothesis that the A and D genome species, or their closely related progenitors, were the ancestors of the tetraploid species. The C₁ and E2 genome diploid species differed extensively from other diploid and tetraploid species, suggesting that they are very distantly related to the diploid and tetraploid species. These genome types would be very useful resources for germplasm introgression and improvement of the cultivated diploid and tetraploid species because of their significant genetic differences.