Potato Tuber Resistance to Phytophthora infestans and its Relation to Maturity

Tuber resistance to P. infestans was evaluated in the progeny of potato genotypes differing in levels of resistance and maturity. Two methods of tuber evaluation were used: testing whole tubers and testing tuber slices. In the progeny, some genotypes were superior in resistance to the more resistant parent. This superiority was never associated with early maturity. The results of both tuber-testing methods were positively correlated but the interaction genotypes X years was more pronounced in the reaction of tuber slices. It is concluded that: (1) transgression in tuber resistance may be obtained, (2) a high level of tuber resistance is difficult to combine with early maturity and (3) the expression of genes for specific resistance was more pronounced in testing tuber slices than in testing whole tubers.     

转基因纯合四倍体马铃薯多酚氧化酶活性及同工酶谱的变异

选择14个已插入反义PPO基因的纯合四倍体马铃薯“GD-9-qc”系列,进行叶片、微型薯PPO活性检测和同工酶分析,结果表明,不同品系间的叶片、微型薯PPO活性存在极显著差异,其中2个品系的叶片及8个品系的微型薯PPO活性明显低于对照;供试转基因品系间的叶片PPO同工酶谱带的颜色深浅表现差异,所示结果与PPO活性检测基本一致;     

Components of Visual Selection in Early Clonal Generations of a Potato Breeding Programme

In the first two clonal generations of a potato breeding programme, clones are visually selected for ‘plant appearance’. Selection for plant appearance based on unreplicated small plots is unreliable, due to significant genotype × environment interaction and high error variance. In order to improve the selection efficiency, component traits of plant appearance were identified and the effect of selection for these components was studied. Tuber yield was found to be the principal component of plant appearance while stolon length and tuber appearance contributed significantly, but to a lesser extent. Tuber yield had a higher heritability than plant appearance. Characters determining the appearance of stolons and tubers were found to have equal or lower heritabilities than plant appearance at 80 days after planting and somewhat higher heritabilities than plant appearance at 145 days after planting. Hence, since the expected and observed selection responses of the component characters have been found to be equivalent to that of plant appearance, selection for plant appearance cannot be improved upon by separately selecting for characters like tuber yield and tuber appearance.     

Effect of Presprouting on Yield of Maincrop Potatoes (Solanum tuberosum L.) in Organic Farming

From 1991 to 1993 field trials at two sites (Bruchkobel and Gladbacherhof) were carried out to study the coti-tribtition of presprouting in securing the yield of main-crop potatoes (cvs. Agria. Granola. Linda and Nicola) in organic farming. In several cases presprouting diminished significantly the number of stems and tubers per plant. While in July (sample harvest) presprouting resulted in significant higher total yields with nearly all cultivars, in September (main harvest) the presprouting effect on total yield differed from year to year and partially from site to site, Presprouting reduced the percentage of undersized tubers, especially in 1992. Significant increases of the percentage of oversized tubers caused by presprouting were found especially with cv. Agria. The presprouted potatoes showed significantly higher marketable yields in 1991 at Bruchkobel (+28%), in 1992 at Bruchkobel (+ 14%) and Gladbacherhof (+ 18%) and in 1993 at Bruchkobel (+ 3%), Considerable yield increases caused by presprouting were observed when the foliage was destroyed early in the growing season by the Colorado beetle (Bruchkobel 1991) or by late blight (both sites 1992). Presprouting proved to be an important method to ensure yields in a farming system using no chemical pesticides.     

Genetic analyses for bioactive potential in tetraploid potato (Solanum tuberosum L.)

A total of four traits related to bioactive potential of the tetraploid potato were studied in a North Carolina II cross‐experiment. The objectives of this study were to estimate genetic parameters for target bioactive compounds in a tetraploid potato population, to determine phenotypic and genotypic correlations and to calculate combining ability effects of cultivars and breeding lines included in the crossing scheme. Total monomeric anthocyanins, phenolics, carotenoids and hydrophilic antioxidant capacity were measured by spectrophotometric methods. The sources of variation female (GCA_f), male (GCA_m) and their interaction (SCA) were significant for bioactive compounds and antioxidant capacity. Narrow‐sense heritability estimates (h²) were moderate for all the traits (0.413–0.657). Both phenotypic and genotypic correlations were highly significant for phenolic compounds and antioxidant capacity. As regards combining ability, positive and negative GCA and also SCA effects have been identified for bioactive compounds and antioxidant capacity. These results indicate that hybrid breeding lines can be obtained by choosing parents with significant GCA, whose bioactive potential can also be further enhanced if the crosses have a significant SCA.     

StGATA12对马铃薯(Solanum tuberosum)生长发育的影响

GATA转录因子是广泛存在于真核植物中的一类转录因子,它是锌指蛋白家族的成员,具有锌指结构,可以识别和特异性结合DNA序列。在调控植物开花时间、叶片延伸、花的发育以及光周期和光信号转导、叶绿素合成和碳、氮代谢调节等生物学过程中发挥重要作用。研究GATA家族的基因可以为作物增产提供一定的理论基础。本研究对转StGATA12基因的株系进行了生理生化分析,结果表明:转基因株系表现出叶面积、茎直径及单株结薯量增加的性状;叶绿素含量、淀粉含量增加;激素含量发生变化。由此可知,StGATA12转录因子在马铃薯叶绿素合成及激素平衡方面起着重要的调控作用。本研究初步阐明了StGATA12转录因子在马铃薯发育过程中的生物学功能和作用机制,丰富了植物GATA12基因的功能研究,并为培育优良的马铃薯新品种提供理论参考。     

Genetic characterisation of tetraploid potato (Solanum tuberosum L.) emphasising genetic control of total glycoalkaloid content in the tubers

Two segregating resource populations were constructed, one of 216 clones using the tetraploid clones Cara and LT7 as parents and one of 176 clones using the tetraploid clones NT8 and LT7 as parents. The populations were used, in replicates, to estimate genetic parameters for total glycoalkaloid (TGA) content in the tubers, and for other agronomic and morphological traits such as tuber weight, dormancy and plant height. In both populations, the parental clones differed markedly in TGA-content and the progeny population was normally distributed for this trait after logarithmic transformation. Broad sense heritability estimate of TGA-content was 0.54 in Cara × LT7 and 0.50 in NT8 × LT7 and the trait proved to be inherited in a non-dominant manner. The minimum number of genes contributing to TGA-content was estimated to be between 3 and 7. None of the other traits recorded in this study showed a statistically significant genetic association with TGA-content. This suggests that tuber TGA-content may be genetically modulated without any significant adverse effects on other agronomic traits. The genetic parameters estimated in this study indicate that these populations are suitable for DNA-marker analysis for TGA-content in tubers. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effects of Root Zone Temperature on Root Activity of Two Potato (Solanum tuberosum L.) Clones with Different Adaptation to High Temperature

Under controlled environmental conditions, the effect of optimal (20 °C) and supraoptimal (30 °C) root-zone temperature on root activity (respiration, soluble sugar content, ethylene release, nitrogen uptake and translocation) was studied in water culture with two potato clones differing in the heat tolerance of their root systems. Root respiration was little affected by raising temperature from 20 °C to 30 °C. However, in both clones assimilate allocation to the roots was strongly depressed. In the heat sensitive clone LT-1 exposed to 30 °C root-zone temperature, concentrations of soluble sugars in the apical root zone (0–10 mm) increased with time, presumably as a result of the cessation of root growth. The rate of nitrate absorption was not significantly affected by root-zone temperature. However, the export of nitrogen (xylem exudate) was depressed in the heat tolerant clone whereas in the heat sensitive clone the export of total nitrogen and the proportion of nitrate increased. No effect of root-zone temperature on ethylene release was observed in our experiments.     

云南省马铃薯品种的配合力分析及亲本选配

本研究选用Mira等lO个当地马铃薯品种,通过不完全双列杂交遗传设计配制成22个杂交组合,对杂交组合后代群体在无性一代的晚疫病抗性、生长势等7个植株性状以及块茎产量、淀粉含量等8个块茎性状的群体遗传效应和配合力效应进行了分析。其中,对马铃薯的块茎肉色、开花性、株形分离、株高分离、茎色分离和花色分离的配合力研究是首次报道。通过对当地四类主要的马铃薯品种的遗传分析,结果表明:(1)晚疫病抗性和单个块茎重的父本效应分别达65.2％、56.7%,群体遗传主要受父本效应影响;淀粉含量的遗传主要受母本效应和亲本间非加性效应的影响,其遗传效应分别达40.5%、44.9％;株形分离、株高分离、开花性、茎色分离、皮色、结薯数和块茎产量等7个性状的非加性效应在66.8％-93.0％之间,群体遗传主要受亲本间遗传差异的影响;植株生长势、花色分离、薯形、肉色和块茎外观等5个性状的加性和非加性效应同等重要。(2)HZ23、HZ88、K6、N7是4个综合性状优良的亲本,ZHXW、XWYY是2个紫色肉质的特色亲本;Mira×K6、Hui-2×K6、HZ23×K6、Hui-2×N7、HZ88×N7等5个组合是综合性状评价较好的杂交组合;HZ23×N7是一个优良杂交实生籽组合;HZ88×ZHXW、HZ23×ZHXW是综合性状优良的特色杂交组合,可从中筛选出紫色或红色肉质的优良     

Effects of Root-Zone Temperature on Growth and Development of Roots of Two Potato (Solanum tuberosum L.) Clones as Influenced by Plant Age, Nutrient Supply, and Light Intensity

The effects of supraoptimal root-zone temperature (30 °C) on growth and development of roots were investigated in water and soil culture with cuttings of two potato clones DTO-2 (heat tolerant) and LT-1 (heat sensitive) at different plant ages, with different compositions of the nutrient solution, and different light intensities. It is suggested that the negative relation between cutting age and heat susceptibility observed in our experiments, is a reflection of the decreasing shoot/root dry weight ratio rather than of age. Heat damage of root systems increased with the concentration of the nutrient solution, nitrate being the main factor responsible. The influence of light intensity on temperature mediated restriction of root growth was relatively small. However the roots of plants grown under low light intensity (60 W m⁻² PAR) appeared to be less stressed by supraoptimal temperature, i.e. roots appeared brighter, thinner and more ramified than plants growing at high light intensity (190 W m⁻²).     

Molecular breeding for resistance to Phytophthora infestans (Mont.) de Bary in potato (Solanum tuberosum L.): a perspective of cisgenesis

Late blight caused by Phytophthora infestans is one of the most devastating diseases in potato cultivation and is mostly controlled by the application of chemicals. However, introduction of combinations of resistance ( R ) genes conferring broad-spectrum resistance from wild Solanum species into cultivated potatoes is considered the most practical and promising approach to achieve durable resistance. This can be realized via classical breeding or genetic modification (GM). Because classical breeding is very time-consuming and is often hampered by linkage drag, a GM approach seems logic in this heterozygous and vegetatively propagated crop. During the last decades, many R genes have been identified in several wild Solanum species. Some have been cloned and more will follow. When these genes are derived from species crossable with cultivated potato (so-called cisgenes), application in resistance breeding using a GM approach is similar to an introgression breeding approach, in that the exploited genes are indigenous to the crop. Pending deregulation or derogation of cisgenesis, the use of cisgenic R genes would be an ideal strategy to accomplish durable resistance in potato.     

Impact of nitrogen supply on leaf water relations and physiological traits in a set of potato (Solanum tuberosum L.) cultivars under drought stress

Improved adaptation of potato to limited water availability is needed for stable yields under drought. The maintenance of the cell water status and protection of cellular components against dehydration are important for drought tolerance, and the N status of plants affects the regulation of various respective metabolic processes. A 2‐year pot trial with 17 potato cultivars was conducted under a rain‐out shelter including two water regimes and two N‐levels to investigate genotypic differences concerning osmotic adjustment (OA) and relevant biochemical traits in relation to nitrogen (N) supply. Drought stress resulted in a rapid decrease in the leaf osmotic potential. The N, protein and proline contents increased under drought, while the N protein/N_Kjeldahl ratio decreased. Initially, total soluble sugars increased at both N‐levels but dropped back to the control level at high N‐availability under prolonged drought while remaining high in N‐deficient plants. Results indicate that potatoes have only a limited capacity of active OA and that increasing sugar and proline concentrations are rather associated with the protection of cellular components. High N supply promoted the N protein/N_Kjeldahl ratio at short‐term drought and enhanced proline accumulation. Significant genotypic differences were observed for all investigated traits.     

Early Generation Selection for Grain Yield in Narrow-Leaf Lupin (Lupinus angustifolius L.)

Experiments were conducted with early segregating generations of a selected narrow-leaf lupin cross to determine the effectiveness of selection for yield based on alternative criteria. F2 plants were selected on the basis of seed yield and several other yield-related characters to generate separate F3 populations. Randomly selected plants from each population were grown over the summer (off-season) in a glasshouse to generate F4 populations. Analyses of relationships between F2 plant measurements and F3 progeny mean yields revealed significant correlations only for those characters with the highest heritabilities - flowering time, 100 seed weight and harvest index. However, selection for the earliest flowering F2 plants followed by selection within this group of plants with the highest number of pod bearing branches would result in the greatest increase in F3 mean yield. The F2-derived F4 populations with the highest seed yields were those obtained by selection for total plant dry weight, number of pod bearing branches and number of pods per plant. Improvement in commercial crop yield should therefore be obtained through selection in early generations for those characters contributing to the greatest number of pods per unit area. A scheme involving selection for early flowering and high number of pod bearing branches in the F2 combined with replicated yield tests in the F4 is proposed.     

Tolerance to low temperatures and tuber soft rot in hybrids between Solanum commersonii and Solanum tuberosum obtained through manipulation of ploidy and endosperm balance number (EBN)

The objectives of this study were to evaluate the tolerance to low temperatures and tuber soft rot in hybrids between Solanum commersonii and Solanum tuberosum. The experimental materials consisted of F₁ triploid, BC₁ pentaploid‐near pentaploid and BC₂ tetraploid–near tetraploid hybrids. The F₁ triploids had a freezing tolerance and acclimatization capacity closest to S. commersonii. This indicated that the endosperm barriers which prevent the introgression of 1EBN S. commersonii into 4EBN S. tuberosum had been overcome. Indeed, the triploids produced 2n eggs, thus giving a compatible maternal to paternal EBN ratio in the hybrid endosperm generated by the 3x(2EBN) × 4x(3EBN) crosses. The tolerance to low temperatures of BC₁ and BC₂ hybrids was lower than that of the F₁. However, a number of genotypes were identified which were able to withstand temperatures down to ‐5°C. Some BC₂ hybrids were also tested for their tolerance to tuber soft rot, and some resistant hybrids were detected. A number of them combined the capacity for cold acclimatization with tolerance to tuber soft rot. These hybrids have an EBN of 4; they are fertile and have been used in backcrosses with 4EBN S. tuberosum.     

Evaluation of seedling selection for salinity tolerance in potato (Solanum tuberosum L.)

Summary Salt-tolerance in potato (Solanum tuberosum L.) was selected on the basis of germination and survival of seed sown in trays of perlite suspended in either 75 or 150 mM NaCl. Salinity reduced the germination of seed. Genetic differences in salt-tolerance were apparent with salt reducing germination more in seed collected from cv. Cara than in that collected from cv. Maris Piper. Progeny from the seedling selection were then grown to maturity to produce tubers.The relative tolerance of the parental cultivars and of unselected and selected progeny to long-term exposure to salinity was examined in a pot experiment in which plants were irrigated with either fresh water or 50 mM NaCl solution from one week after plant emergence. In this experiment, salinity significantly reduced leaf conductance, total dry matter production and partitioning of assimilate to tubers. Salinity reduced dry matter production and assimilate partitioning to tubers to a greater extent in Cara than in M. Piper. Progeny selected for short-term salt-tolerance did not exhibit greater long-term salt-tolerance than unselected progeny, and both were more sensitive than M. Piper.These results demonstrate genetic variation in salt-tolerance in potato. However, although there was a correlation between the performance of the parent to long-term salinity and survival of progeny in the seedling selection, there was no correlation between short- and long-term salt-tolerance. This suggests that characters underlying short-term tolerance may contribute to long-term tolerance but do not of themselves confer long-term tolerance. Future progress in selecting for improved salt-tolerance depends on understanding the effects of salinity on the physiological processes underlying growth and carbon partitioning.     

Somaclonal variation for resistance to Verticillium dahliae in potato (Solanum tuberosum L.) plants regenerated from callus

Summary Plant tissue culture is recognized as an important tool to generate useful genetic variability for crop improvement. Regenerated plants from callus induced from stem explants of Solanum tuberosum cv Désirée were assessed by in vitro selection, for resistance to Verticillium dahliae. This fungus is the causal agent of Verticillium wilt, a serious vascular wilt disease both in crops and wild species.The rate of in vitro multiplication by single node cuttings was used as a parameter of screening in two selection cycles with different concentrations of V. dahliae filtrate. One resistant clone was selected and then evaluated by inoculation in the growth chamber. Induced damage, and morphological traits (dry weight, leaf area and tuber production) were estimated. The selected clone was comparable to the resistant control, cv Kondor.The results suggest that genetic variation induced in tissue culture cound be utilized to generate disease resistance.     

Effectiveness of early generation selection under two plant densities in faba bean (Vicia faba L.)

The effectiveness of early generation selection under low and high plant density was evaluated in faba bean (Vicia faba L.). For this, the faba bean cv. 'Polycarpe' was pollinated by eight higher yielding cultivars of different origin. The F₁'s and F₂'s together with 'Polycarpe' and the pollinator with the highest yielding ability (cv. 'Effe') were evaluated under high plant density with adjacent controls and under low plant density in a honeycomb design. It was found that the eight hybrids had a different ranking at low than at high plant density for both generations (F₁and F₂). Hybrid Pol.x A-58 had the best combined yield performance in the F₁and F₂under high and hybrid Pol.x A-37 under low plant density. Application of individual plant selection in the F₂and F₃generation of the two crosses (Pol.x A-58 and Pol.x A-37), under both low plant density according to UNR-O honeycomb design and high plant density using a moving average, resulted in the selection of four groups with 20 selected F₃plants each. Within each group, equal numbers of seeds from each plant were mixed to establish four mixtures. These mixtures together with two controls ('Polycarpe' and 'Effe') were evaluated in a randomized complete block design (22 plants/m²) in one location for two years. It was found that the material selected continuously under low plant density had a significantly higher yield than the material selected under high plant density. In addition, the material selected from Pol.x A-37 (H₁R₂) under high plant density had a lower mean yield than that selected continuously under low plant density (H₁H₂). Their average yield over years was significantly higher than the yield of the material selected from Pol.x A-58 under both plant densities. Furthermore, the material selected from Pol.x A-58 under low plant density, had a significantly higher mean yield over years than its sibs selected under high plant density. It was concluded that honeycomb selection at low plant density can be used effectively for early generation selection in faba bean.     

Chloroplast DNA diversity in brinjal eggplant (Solanum melongena L.) and related species

Chloroplast DNA (cpDNA) samples of brinjal eggplant (S. melongena) and representative related species including S. incanum sensu lato (or S. campylacanthum sensu stricto), S. lichtensteinii, S. marginatum, S. macrocarpon, S. anguivi and S. aethiopicum and also S. nigrum as an outgroup taxon, were digested by 14 restriction enzymes and analyzed by using electrophoresis and a cpDNA probe. All the species used here were clearly separated in the cpDNA analysis, except the pair S. anguivi and S. aethiopicum. From the dendrogram constructed by the unweighted pair-group method, it is suggested that S. incanum is the closest to S. melongena and the next closest species is S. macrocarpon followed by S. aethiopicum (and S. anguivi), S. lichtensteinii, S. marginatum and finally the outgroup taxon S. nigrum. The tree derived by the neighbour-joining method suggests phyletic relationships that agree with those indicated by crossability and seed coat anatomy, but conflict with conventional classifications based on morphology. In particular, members of sections Oliganthes and Melongena are not separated and no cpDNA variation was found within either of the morphologically diverse cultigens, S. aethiopicum and S. melongena. Paradoxically, the morphologically similar species S. incanum, S. lichtensteinii and S. marginatum have diverged greatly in their cpDNA. The significance of these results is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

A comparative assessment of DNA fingerprinting techniques (RAPD, ISSR, AFLP and SSR) in tetraploid potato (Solanum tuberosum L.) germplasm

Several DNA marker systems and associated techniques are available today for fingerprinting plant germplasm but information on their relative usefulness in particular crops is limited. The study investigated PCR based DNA fingerprinting in a set of 39 potato cultivars using RAPDs (20 primers), ISSRs (6 primers), AFLPs (2 primers) and SSRs (5 primer pairs). Results show that each of the four techniques can on their own, individually identify each cultivar, but that techniques differ in the mean number of profiles generated per primer (or primer pair) per cultivar, referred to as Genotype Index (GI). The order of merit based on this criterium and in this material was AFLPs (GI = 1.0), a multi-locus SSR (GI = 0.77),RAPDs (GI = 0.53), ISSRs (GI = 0.47) and single locus SSRs (GI = 0.36). Problems in relating banding patterns to individual loci and alleles for polyploid genomes, using these techniques as they are currently employed, are also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

马铃薯HD-Zip I家族ATHB12基因的克隆及功能鉴定

HD-Zip I是一类植物特异转录因子, 在植物应对外界逆境胁迫过程中有重要的调控作用。本研究从马铃薯栽培品种甘农薯2号中克隆了HD-Zip I转录因子ATHB12基因, 其开放阅读框为759 bp, 编码252个氨基酸残基。该基因位于马铃薯1号染色体, 其启动子区含有ABRE、LTRECOREATCOR15和WBOXATNPR1等多种响应非生物胁迫(ABA、低温、脱水及高盐)的顺式作用元件。ATHB12基因在马铃薯根、茎和叶中均有表达, 其根中表达量最高。qRT-PCR分析证实该基因的表达受聚乙二醇(PEG)、NaCl和ABA诱导, 受低温抑制。构建了由组成型表达启动子CaMV 35S驱动的ATHB12基因的过表达载体, 通过农杆菌介导法转化马铃薯获得了转基因植株。干旱处理后, 转基因植株叶片中丙二醛含量显著低于非转基因植株(P<0.05), 而脯氨酸含量显著高于非转基因植株(P<0.05); 转基因植株根鲜重和干重均高于非转基因植株; 说明马铃薯ATHB12基因可能参与了逆境胁迫的响应。