Molecular Analysis of Local Potato Cultivars from Tenerife Island Using Microsatellite Markers

We have used 19 SSR markers to fingerprint 41 local potato cultivars from 10 locations of Tenerife Island. These varieties represent relicts of the early introductions originating from South America and have been characterised previously morphologically and ecophysiologically. The SSR primers generated a varying degree of polymorphisms. A total of 67 alleles were observed, 12 of them were present in all cultivars. Several accession and group specific alleles were detected. Similarity coefficients were computed from the molecular data and cluster analyses were performed. Generally, cultivar groups with identical or related common names showed the same SSR patterns or clustered closely together. According to the molecular patterns misleading or confounded names were evident for four accessions. The dendrogram clusters were generally in good agreement with previous classifications of the accessions as Solanum tuberosum subsp. andigena, S. tuberosum subsp. tuberosum and Solanum chaucha genotypes. However in four cases the molecular patterns showed discrepancies with previous species assignments suggesting the need for a more detailed and comparative study of these accessions.     

Usefulness of Andigena (Solanum Tuberosum SSP. Andigena) Genotypes as Parents in Breeding Early Bulking Potato Cultivars

Summary Seven Solanum tuberosum ssp. tuberosum and three Solanum tuberosum ssp. andigena accessions were crossed to produce 12 Tuberosum × Tuberosum (T × T) and 9 Tuberosum × Andigena (T × A) progenies. These families were evaluated for five important traits for two successive clonal generations under short day sub-tropical plains. The differences in yield, average tuber weight and tuber number between {T × T }and T × A families in an early (75 days) crop were not significant. Compared to conventional intra-Tuberosum families, T × A families had significantly higher % tuber dry matter and specific gravity. In contrast to intra-Tuberosum crosses, T × A crosses exhibited a positive heterosis for tuber yield. Compared to T × T families, T × A families showed significantly higher heterosis for yield and tuber number. Comparison of T × T and T × A families and parents using canonical analysis led to the identification of superior hybrid families and superior parents. Some T × A progenies were close to breeding goal and thus can be used for selecting high-yielding cultivars. This revealed the usefulness of Andigena genotypes as parents in developing early bulking potato cultivars with broad genetic base for short day sub-tropical plains.     

A maternally inherited DNA marker,descended from Solanum demissum (2n = 6x = 72) to S. tuberosum (2n = 4x = 48)

A Mexican hexaploid wild potato species, Solanum demissum (dms), was only used as a female in previous breeding programs. The resulting clones with dms cytoplasm produced abundant, but non-functional pollen. A 170 bp DNA fragment, named Band 1, was originally detected in the F₁ hybrid between dms and S. tuberosum. In this study, the sequenced region was extended to 1,032 bp; nevertheless, it did not show any homology to known sequences. This extended region harboring Band 1 was, without introns, all transcribed to mRNA and was maternally inherited from dms to S. tuberosum through backcrosses. Three dms accessions, 168 accessions of 38 cultivated and closely related wild species, and 158 varieties and breeding lines were surveyed, which demonstrated that Band 1 was specific to dms and varieties and breeding lines with dms cytoplasm. Thus, Band 1 is a useful marker to distinguish dms cytoplasm, which enables us to design efficient mating combinations in breeding programs.     

The Use of Potato Haploids to Put 2x Wild Species Germplasm into a Usable Form

An effective method of incorporating germplasm of wild 2x Solanum species into the cultivated potato is through hybridization with haploids of 4x S. tuberosum Group Tuberosum. This procedure provides for the introduction of desirable traits and genetic diversity from wild species into potato. Haploid and wild species genotypes can be evaluated for parental value based on the presence of good tuberization, desirable traits, fertility, and 2n gametes in their hybrid progeny. Haploid-wild species hybrids may be intercrossed and evaluated at the 2x level to take advantage of diploid genetic ratios. Selected 2x genotypes may then be brought to the 4x level through sexual polyploidization with 2n gametes.     

Characterization of resistance to Globodera rostochiensis pathotype Ro1 in cultivated and wild potato species accessions from the Vavilov Institute of Plant Industry

Potato cyst nematodes (PCN) collected in six localities in the Leningrad region of North West Russia were identified as Globodera rostochiensis pathotype Ro1 and were used for subsequent resistance tests. Seventy‐nine accessions of cultivated and closely related wild potato species from the VIR collection in Russia were screened on resistance to G. rostochiensis pathotype Ro1 and on the presence of molecular markers for H1 and Gro1‐4 resistance genes. No associations were detected between the resistance level of diploid and tetraploid Andean and tetraploid Chilean potato landraces (indigenous cultivars) and their related wild species and their geographical distribution or presence of PCR‐based markers that are associated with the H1 and Gro1‐4 genes. At the same time, all susceptible genotypes lacked such markers. New sources of resistance were found and could be used in breeding.     

Creation of long-day adapted tetraploid potatoes from crosses of <Emphasis Type="Italic">Solanum tarijense</Emphasis> females with Andigena males

T-type is a common chloroplast DNA type among modern potato varieties (Solanum tuberosum), their progenitor Chilean tuberosum, and a diploid wild species S. tarijense. To recreate Chilean tuberosum, we made 983 pollinations between 10 accessions of T-type chloroplast DNA-holding S. tarijense used as females and 32 Andean tetraploid landraces (Andigena) used as males, from which 14 tetraploid hybrids were obtained. These interspecific hybrids grew vigorously with long stolons, flowered well with high male and female fertilities, and matured 1 month later than modern varieties. Seedlings of selfed and sib-crossed interspecific hybrids were artificially selected for tuber yield under long days. The selected clones were grown in the field, of which two clones produced over 1 kg of edible tubers per plant. These results lend experimental support to the hypothesis that the Chilean tuberosum originated by selection for long-day adaptability from tetraploid hybrids that occurred by fertilization of a 2n egg of S. tarijense and n pollen of Andigena.     

The Importance of the Bolivian Wild Potato Species in Breeding for Globodera pallida Resistance

Screening for resistance to the potato cyst nematode, Globodera pallida, in potatoes from. Bolivia, was carried out in 1983 and 1984, using a mixture of four nematode populations representing pathotypes Pa₁, Pa₂ and Pa₃ From the 66 accessions of 17 species and subspecies evaluated, highly resistant genotypes were identified in 21 accessions from seven species. All had Pf/Pi values of 2 or less, whereas the susceptible control, Solanum tuberosum cv. ‘Disiree’ had Pf/Pi values of more than 2G in both tests. Two diploid wild species, S. brevicaule and S. leptophyes, showed the best resistant. The geographical distributional of resistant populations and the evolution of resistance in wild potato populations are discussed.     

Geographic distribution of insect resistance in potatoes

Potato germplasm accessions representing 92 Solanum species and associated with known coordinates of latitude, longitude, and elevation were rated for resistance to one or more of the following potato insect pests: green peach aphid, Myzus persicae (Sulzer); potato aphid, Macrosiphum euphorbiae (Thomas); Colorado potato beetle, Leptinotarsa decemlineata (Say); potato flea beetle, Epitrix cucumeris (Harris); and potato leafhopper, Empoasca fabae (Harris), in Minnesota field trials (1966–1986). Chi-square tests were used to determine if the proportion of resistant accessions differed from expected among altitude classes, small geographic quadrants (4° latitude by 4° longitude), and larger geographic regions (Mexico-USA, Colombia-Ecuador, Peru, Bolivia, and Argentina). Resistant potatoes were not evenly distributed throughout North and South America. Fourteen quadrants were identified that had greater or fewer resistant accessions than expected. The Mexico-USA potatoes as a group had more resistance than expected to all insects except Colorado potato beetle. Potatoes from Colombia and Ecuador were less resistant than expected to all but green peach aphid. Potatoes from Peru were more resistant than expected to green peach aphid. Potatoes from Bolivia were less resistant than expected to potato aphid, but more resistant than expected to Colorado potato beetle, potato flea beetle, and potato leafhopper. Potatoes from Argentina were more resistant than expected to Colorado potato beetle and green peach aphid, but less resistant than expected to potato aphid and potato leafhopper. Potatoes from North America and collected at or below 2,500 m were more resistant than expected to green peach aphid, Colorado potato beetle and potato flea beetle. Potatoes from South America and elevations greater than 3,000 m were more resistant than expected to green peach aphid and potato aphid and those collected at or below 3,000 m were more resistant than expected to Colorado potato beetle, potato flea beetle and potato leafhopper.     

Immunity to Clavibacter michiganensis subsp. sepedonicus: Screening of exotic Solanum species

Summary Accessions from exotic Solanum species, including diploid and tetraploid species, were screened for immunity to Clavibacter michiganensis subsp. sepedonicus, the causal agent of potato ring rot. The diploid species included S. infundibuliforme, S. lesteri, S. megistacrolobum, S. tuberosum Group Phureja, S. polyadenium, S. pinnatisectum, S. raphanifolium, S. sparsipilum, S. sanctae-rosae, S. tuberosum Group Stenotomum, S. toralapanum, and S. verrucosum. The tetraploid species included S. tuberosum Group Andigena, S. acaule, S. fendleri, S. hjertingii, S. oplocense, S. polytrichon, and S. stoloniferum. Apparent immunity was initially found in several diploid species, but was not present during subsequent retesting. Immunity was found in nine accessions of tetraploid S. acaule. These accessions maintained their immunity during testing over an eight-month period. S. acaule appears to be a good source of immunity for introgression studies.     

Change of leaf size in the evolution of the tuberosum potatoes

Summary A selection experiment designed to recreate the Tuberosum Group potatoes from their South American (Andigena Group) ancestors has made good progress. Leaf size (estimated by a simple linear measurement) showed a correlated response to selection for general adaptation and productivity, growing at about nine percent per generation. Extrapolation suggests that the Andigena populations should equal Tuberosum in about five generations. Conscious selection for large leaves may also have contributed to the evolution of the Tuberosum Group but it seems likely that the unconscious, correlated response was the most important factor in the change.     

Early selection for extreme resistance to potato virus Y and tobacco etch virus in potato using a β-glucuronidase-tagged virus

The Ry_sto gene from Solanum stoloniferum introduced into potato cultivars (Solanum tuberosum L. ssp. tuberosum) confers resistance to potato virus A, potato virus V and potato virus Y (PVY). In addition to PVY, tobacco etch virus (TEV) and a TEV construct that encodes β‐glucuronidase (TEV‐GUS) were inoculated to determine the inheritance of resistance to these viruses in progenies obtained from potato cultivars containing the Ry_sto gene. While cultivars ‘Karlena’ and ‘Delikat’ were susceptible, ‘Bettina’ and clone 927eY were resistant to PVY, TEV and TEV‐GUS, as determined by enzyme linked immunosorbent assay, biotest and GUS assay, respectively. The segregation ratios obtained from the progenies of ‘Bettina’בDelikat’ and 816eY בKarlena’ indicate that resistances to PVY and TEV are governed by one dominant gene or two genes tightly linked in coupling phase. Evidently, Ry_sto confers broad spectrum resistance to potyviruses. TEV resistance could be reliably detected 4 days after inoculation with the TEV‐GUS construct by GUS assay. Therefore, the GUS‐tagged TEV construct can be used for early selection for resistances based on the gene Ry_sto or closely linked genes.     

Characterization of the resistance to <Emphasis Type="Italic">Phytophthora infestans</Emphasis> in local potato cultivars in Bolivia

This experiment was carried out to investigate whether and how much field resistance to late blight, caused by Phytophthora infestans, is present in the local cultivated potato germplasm. In total 36 entries were compared in a field experiment in an area highly conducive to late blight development. Of the 36 cultivars 32 were local cultivars belonging to five Solanum species, S. tuberosum (1 accession), S. andigena (18), S. juzepczukii (2), S. stenotomum (9) and S. ajanhuiri (2). The other four cultivars were derived from breeding programmes, one being the Dutch cultivar Alpha used as a highly susceptible control. The 36 cultivars were planted according to a simple 6 × 6 lattice design with three replicates. Each replicate was divided in six incomplete blocks each with six cultivars. The disease severity was assessed weekly during 9 weeks starting 48 days after planting. The area under the disease progress curve (AUDPC) was used as a measure of the field resistance. Nine isolates from surrounding potato fields were tested for their virulence to the resistance genes R1–R11 using 22 differential cultivars. The components of the field resistance of 19 of these cultivars were compared in the greenhouse using a local isolate with virulence to all known R-genes, except to R9. The nine isolates represented seven races with a race complexity varying from 7 to 10 virulence factors. All isolates carried virulence against R1, R2, R3, R7, R10 and R11, while virulence against R9 was absent. The AUDPC among the 32 local cultivars ranged from very large, significantly larger than that of ‘Alpha’ to very small. The AUDPC from S. stenotomum accessions ranged from very large to intermediate, those from S. andigena accessions from large to very small. Especially among the S. andigena accessions interesting levels of field resistance were found. Four components of field resistance were assessed, latency period (LP), lesion size (LS), lesion growth rate (LGR) and relative sporulation area (RSA). All four showed a considerable variation among the cultivars. The LP ranged from 3½ to 6 days. The LS ranged from 225 mm² to 20 mm². The LGR varied about six-fold, the RSA more than 10-fold. The components tended to vary in association with one another. LP and LGR were well associated with each other and had a significant correlation with the AUDPC.     

马铃薯品种遗传多样性分析

为解析一套(559份)从世界各国收集的马铃薯种质资源的遗传多样性,用16个表型性状和36个SSR标记进行了聚类和多样性参数分析。对454份表型数据完整材料的UPGMA聚类分析表明,在欧氏距离14.66处被聚成2个类群(A_1和A),其中A_1在欧氏距离12.74处被分为A_(11)和A_(12)亚群;454份材料在欧氏距离11.73处被划成9个类群,包括4个小类(A、B、C和H)和5个大类(D、E、F、G和I),其中类群I所包括的材料占总数的57.5%,该结果较好地揭示了马铃薯种质材料之间的形态差异,区分生态类型不同和遗传差异明显的亲本。36个SSR标记在559份材料中共检测出134个多态性位点,每对引物检测1~7个等位变异,平均3.72个,引物多态性信息量(PIC)为0.1545~0.7743,平均为0.5783,说明品种间有丰富的遗传多样性。NJ系统进化树分析表明,559份材料可分为3个大群。类群I为一个混合群,各地区品种均有分布,包括133份马铃薯材料,占总数的23.8%;类群II中欧洲、北美及中国东北和西北地区的材料所占比重较大,数量为187,占33.5%;类群III中北美、南美以及中国东北和西南地区马铃薯材料所占比重较大,包含239份材料,占42.8%。表型性状聚类与SSR分子标记聚类结果相似,均与地理位置有很大相关性,应结合共同用于评价马铃薯品种遗传多样性。     

Comparison of yield based drought tolerance indices in improved varieties, genetic stocks and landraces of potato (Solanum tuberosum L.)

Drought strongly influences potato (Solanum tuberosum) production and quality. Potato being a drought susceptible crop, the development of varieties with enhanced tolerance to water stress could highly improve productivity in drought prone areas. The objective of this study was to evaluate the ability of several yield based indices to be used in large scale screening for drought tolerance. The experiment included improved varieties, genetic stocks and landraces potatoes grown under drought and irrigated conditions. A group of accessions with high yield under both conditions was identified. Mean productivity (MP), geometric mean productivity (GMP), tolerance (TOL), drought tolerance index (DTI), drought susceptible index (DSI) and yield stability index (YSI) were calculated from tuber yield under drought and irrigated conditions. The relationships between these indices and yield were analyzed. The Fleiss’ Kappa concordance test was used to analyze the correspondence between accessions previously identified as highly productive under both drought and irrigated conditions and accessions with optimal values for the different indices. MP, GMP and DTI allowed identifying genotypes combining high yield potential and high yield under drought within the three subsets of genotypes. Conversely, DSI, YSI and TOL showed low and variable concordance values across subsets, suggesting that their efficiency in screening genotypes highly depends on the nature of the tested genetic material.     

The Use of RFLPs (Restriction Fragment Length Polymorphisms) Detects Germplasm Introgressions from Wild Species into Potato (Solanum tuberosum ssp. tuberosum) Breeding Lines

The germplasm of the potato (S. tuberosum ssp. tuberosum) has been modified since the beginning of this century by breeders who introgressed important agronomic traits, for example disease resistance genes, from several wild and cultivated Solanum species of the Americas. In this paper we show that the Rflp analysis of potato-breeding material can be used to detect chromosomal regions descended from more-distantly related Solanum species. The Rflp patterns of individuals of ten Solanum species, ten breeding lines of S. tuberosum ssp. tuberosum and the cultivated variety ‘Bintje’ were analyzed. Rflp data for each of eight single loci of known genomic position were used for the computation of locus-specific phenograms by distance matrix methods. Several of the potato-breeding lines deviated clearly from the clustered species S. tuberosum, S. stenotomum and S. canasense for one or more of the loci considered. These deviations indicated the presence of “exotic” germplasm at a particular locus. The possibility of detecting such germplasm has implications for mapping the agronomic traits for which the wild species were introgressed and which may still be linked to “foreign” chromosome fragments.     

Genetic variation of sweet potatoes (Ipomoea batatas L.) cultivated in Chile determined by RAPDs

RAPD (randomly amplified polymorphic DNA) technology was applied to analyze the genetic variability of sweet potato germplasm existing in Chile and elsewhere. Analysis of 28 cultivars from all over the world showed polymorphic bands with all 18 primers tested. A total of 124 RAPD bands were scored with an average of 6.9 polymorphic bands per primer. These results confirm that sweet potato exhibits high genetic variation. Two groups were distinguished: one containing Peruvian cultivars, and another containing cultivars from the rest of the world. Analysis of 14 accessions from Central Chile and one from Northern Chile showed polymorphic bands with 24 of 26 primers tested, but almost all of the 140 polymorphic bands merely showed the distinctness of the Northern accession. The almost complete uniformity of the other 14 accessions shows that sweet potato germplasm collected in Central Chile has very little genetic variability and may be derived from a single cultivar. Based on these results and on historical records, some hypotheses are proposed to explain the origin of sweet potatoes cultivated in Chile. This revised version was published online in July 2006 with corrections to the Cover Date.     

Resistance to late blight (<Emphasis Type="Italic">Phytophthora infestans</Emphasis>) in ten wild <Emphasis Type="Italic">Solanum</Emphasis> species

Nineteen accessions of the tuber-bearing species Solanum berthaultii, S. chacoense, S. leptophyes, S. microdontum, S. sparsipilum, S. sucrense, S. venturii, S. vernei and S. verrucosum were tested for their resistance to late blight in two years of field experiments. Plants were artifically inoculated with zoospores of race 1.2.3.4.5.7.10.11 and the development of the disease was followed. Resistance ratings, calculated as the areas under the disease progress curves (ADPC), demonstrated a high resistance in all accessions except in S. sparsipilum, S. leptophyes and their interspecific hybrid. Segregations suggest that major genes for resistance are present in S. sucrense and S. venturii, and may also play a role in S. verrucosum. It is not yet certain wether the resistance of the other accessions is comparable to the partial and durable resistance of S. tuberosum cultivars like Pimpernel, as inheritance and mechanism have yet to be established. However, segregations suggesting the presence of single major genes with complete dominance were not found in these other accessions. Tuber initiation in the field occurred in only one accession, S. tuberosum ssp. andigena, and maturity of the clones was not related to their resistance. In the other accessions maturity types could not be assessed, as the clones require short day conditions for tuber initiation.     

蚂蚱麦和小白麦衍生系的遗传多样性分析

陕西关中蚂蚱麦和山西平遥小白麦是我国北方小麦品种的原始骨干亲本,解析蚂蚱麦和小白麦及其衍生系的遗传多样性对于小麦品种改良具有重要的参考意义。本研究利用小麦660KSNP芯片对蚂蚱麦、小白麦及其衍生品种(系)进行全基因组扫描,分析其遗传多样性。结果表明,小麦3个基因组的多态性SNP标记数为BAD,第4同源群的多态性标记数最少, 149份供试材料基因多样性(H)范围为0.095～0.500,平均值为0.336;核苷酸多样性指数(π)范围为0.272～0.435,平均值为0.340;而遗传相似系数(GS)变幅为0.335～0.997,平均值达0.619,表明蚂蚱麦和小白麦衍生系的遗传多样性较低。聚类分析表明蚂蚱麦和小白麦紧密地聚在亚群I,其衍生品种(系)分为5个亚群,其中2000年以前以蚂蚱麦或小白麦的单一衍生系为主,分在亚群I、II、III, 2000年以后多数品种同时拥有蚂蚱麦和小白麦血缘,分在亚群IV、V,遗传多样性较高,且与大面积推广品种聚为一类。因此,应加强优异基因资源导入,拓宽小麦品种的遗传基础,最终提高育种水平。     

Chromosome numbers in potato cultivars hypersensitive to late blight

The chromosomes of twenty-four blight resistant potato cultivars produced from S. demissum x S. tuberosum hybrids were counted. Twenty-two cultivars had 2n=4x=48 chromosomes and two cultivars had 2n=4x+1=49 chromosomes. The implications of these results are discussed briefly in relation to previous studies and to potato breeding methods.     

PCR-based INDEL markers co-dominant between Oryza sativa,japonica cultivars and closely-related wild Oryza species

Wild relatives genetically close to cultivars are precious genetic resources for plant breeding. Oryza rufipogon, O. barthii, O. glumaepatula, O. meridionalis and O. longistaminata are such wild species, and are also categorized as AA genome species based on their structural similarities. Chromosome segment substitution lines (CSSLs) are a powerful resource in breeding and genetics, and numerous rice CSSLs have been produced. This study aimed to develop DNA markers for evaluation of CSSLs directly by PCR and subsequent gel electrophoresis. We confirmed that up to 155 of 188 markers developed for detection of japonica-indica INDELs could also detect INDELs between rice cultivars and wild AA-species accessions. Percentages of applicable markers were higher in O. rufipogon accessions (61.7 to 85.6%), and lower in accessions of other four AA species (39.8 to 51.4%). These markers were distributed throughout the rice chromosomes, and will be useful for genotyping of CSSLs and other genetic resources derived from crosses between rice cultivars and closely related wild species.