Difference in Allelopathic Potential as Influenced by Root Periderm Colour of Sweet Potato (Ipomoea batatas)

Laboratory bioassay and high‐performance liquid chromatography (HPLC) analysis were conducted to determine the allelopathic potentials of aqueous or methanol extracts from three different coloured sweet potato [Ipomoea batatas L. (Lam)] cultivars by plant part. The aqueous extracts applied on filter paper significantly inhibited root growth of alfalfa (Medicago sativa L.). Aqueous leaf leachates at 40 g dry tissue l^?1 (g l^?1) from white sweet potato cultivar ‘Sinyulmi’ showed the highest inhibition against alfalfa, followed by yellow ‘Sinhwangmi’ and purple ‘Jami’. Alfalfa root growth was significantly inhibited by methanol extracts of the same plants as the concentration increased. Aqueous and methanol extracts from leaves showed the most inhibitory effect on alfalfa root growth followed by stems and roots. By means of HPLC analysis, leaf samples of sweet potato had the highest amount of phenolic compounds followed by stems and roots. Total content of these compounds was highest for leaf extracts (37.7 mg 100 g^?1), detected in EtOAc fraction, especially trans‐cinnamic acid (20.9 mg 100 g^?1). These results suggest that sweet potato plants are allelopathic and that their activities differ depending on plant part as well as root periderm colour.     

Constitutive expression of Cry proteins in roots and border cells of transgenic cotton

Transgenic cotton plants expressing Cry1Ac and Cry2Ab, from the soil bacterium Bacillus thuringiensis (Bt), provide effective control of certain lepidopteran pests, however, little is known about the proteins below ground expression. We used ELISA to quantify in vitro expression of the Cry1Ac and Cry2Ab proteins in mucilage, root border cells and root tips in five transgenic cultivars of cotton compared to conventional cultivar Sicot 189. Expression of Cry proteins in roots and border cells of the transgenic cotton cultivars was constitutive and at detectable levels, with Cry1Ac and Cry2Ab protein expression ranging from <20 ppb to >100 pbb. To determine if genetically modified cotton demonstrated simple differences in properties of the root, when compared to an elite parental line (cv. Sicot 189), we enumerated border cells on seedling radicles. Border cell counts of 14 cultivars ranged from 0.2 to 1.1 × 10⁴ cells per root tip with an average of 5 × 10³ border cells. Border cell production in the transgenic cultivars was generally similar to that of both donor and elite parents, the exception being the cultivar Sicot 189, which had substantially more border cells than all of its transgenic derivatives. Comparison of border cell number with varietal disease resistance ranking found a limited relationship (r ² = 0.65, n = 7) between border cell numbers and the commercial resistance rank against Fusarium wilt of cotton. The implications of differences in cotton cultivar border cell number and root tip expression of Cry proteins for plant–microbe interactions in the rhizosphere and the soil ecosystem are yet to be resolved.     

Drought stress‐induced changes in starch yield and physiological traits in potato

Drought stress is an important limitation for potato (Solanum tuberosum L.) production as potato depends on appropriate water availability for high yields of good quality. Therefore, especially in the background of climate change, it is an important goal in potato breeding to improve drought stress tolerance. In this study, 34 European starch potato cultivars were evaluated for drought stress tolerance by growing under well‐watered and long‐term drought stress conditions in rainout shelters in 2 years’ pot trials. Besides yield, six physiological traits, that is free proline content, osmolality, total soluble sugar content, chlorophyll content (SPAD), cell membrane stability and crude protein content, were determined in leaves sampled during vegetative growth and during flowering to investigate their association with drought tolerance. ANOVA revealed significant treatment effects for all physiological traits and increased genotypic effects at flowering. The sensitivity of physiological traits to drought was significantly higher during flowering than during vegetative growth. Drought stress decreased starch yield significantly (p < .001), on average by 55%. Starch yield was significantly influenced by genotype and genotype × treatment interactions. Stress tolerance index (STI) calculated from starch yield ranged from 0.26 (sensitive) to 0.76 (tolerant) with significant genotype effects (p ≤ .001). STI correlated positively with cell membrane stability (r = .59) and crude protein content (r = .38) and negatively with osmolality (r = ?.57) and total soluble sugar content (r = ?.71). These contrary correlations suggest a dual adaptation strategy in potato under long‐term drought stress conditions including increased membrane stability combined with an increased osmolality due to an increased soluble sugar content.     

Plant regeneration in sweet potato (Ipomoea batatas L., Convolvulaceae)

The application of new techniques for improvement of sweet potato crops, particularly including the exploitation of somaclonal variation, gene transfer by genetic transformation and somatic hybridization, requires the control of plant regeneration from tissue cultures. Shoots can easily be regenerated from explants of stems, petioles, leaves and roots, while callus cultures do not produce any shoots. The potential of somatic embryogenesis and plant regeneration via embryogenesis was evaluated for 10 cultivars of sweet potato. Protocols for plant regeneration from cultured protoplasts have also been developed. Since mesophyll was resistant to enzyme digestion, fragments of stems and petioles, callus and cell suspensions were used as source of protoplasts of sweet potato. Series of transfers of protoplast-derived calluses, particularly those which had been obtained from in vitro plants, to media containing a high level of zeatin resulted in successful formation of shoots in only two sweet potato cultivars. In addition, the embryogenic potential was irreversibly lost through protoplast culture, since protoplasts isolated from embryogenic cell suspensions developed into non-embryogenic callus. Consequently, an alternative protocol is being successfully developed to improve plant regeneration from cultured protoplasts of sweet potato, involving first root formation from which shoots can then be regenerated. Preliminary evaluation in field conditions in Gabon revealed that plants regenerated from cultured protoplasts exhibited a great genetic variability in their growth and tuber formation in particular. This revised version was published online in July 2006 with corrections to the Cover Date.     

Production and performance of potato mini-tubers

Summary Production of mini-tubers as a source for seed potato was investigated by growing in soil micropropagated plants and micro-tubers produced from micropropagated plants. Cultures of several cultivars were initiated from indexed tubers and multiplied on modified MS medium. Cultures were micropropagated by using a modular system which allowed batch handling. Micropropagated plants produced mini-tubers in glasshouse after 70–115 days of growth in soil. A large proportion of the mini-tubers produced were between 9 and 15 mm diameter. Several factors, e.g., explant number, duration of in vitro culture and genotype influenced mini-tubers production. Micropropagated plants after culture of 86 days or longer produced micro-tubers ca. 2 to 10 mm diameter. Plants, which formed micro-tubers in vitro, produced less number of mini-tubers in soil. Micro-tubers produced 1 to 3 mini-tubers when grown in soil in chain-type paper pots, but produced conventional sized tubers when grown in soil under plastic polytunnel. Mini-tuber number varied widely between potato cultivars; cvs. Bintje and British Queen produced more mini-tubers than the other cultivars. Mini-tubers developed green hard skins when kept in light for 3 weeks, and could be stored in dark at 4° C upto 6 months. In a field trial, small mini-tubers ca. 5–10 mm diameter produced more but smaller tubers than mini-tubers ca. 15–20 mm diameter. The micropropagated plants and the plants grown from mini-tubers were genetically stable, and did not show any morphological aberrations except for one variegated plant among the several thousand produced. It is concluded that the production of mini-tubers by soil planting of micropropagated plants is a rapid and efficient method for producing seed potato tubers.The use of any trade mark and other commercial products mentioned in this paper does not constitute any recommendation or advertisement for such products on behalf of the Agriculture and Food Development Authority, Dublin, Ireland     

The Response of Sweet Potato (Ipomoea batatas Lam.) to Inter- and Relay-cropping with Maize (Zea mays L.)

Four sweet potato cultivars were inter- and relay-cropped with maize at two locations in Peru. Increasing interspecific competition drastically reduced tuber yields of all cultivars; fewer tubers m ⁻² were produced and no tolerant genotype was identified. Likewise the mean tuber weight declined linearly for two cultivars when competition became severe. Shoot development was less affected. Under intense competition the plant top was favoured in assimilate partitioning to the detriment of tuber formation. Overall reduction in assimilate production due to mixed cropping was the major cause of yield loss. Various intercropping combinations were found with the same productivity but distinct proportions of the component crops (sweet potato + maize). Land equivalent ratio (LER) exceeded sole crop productivity only for the combinations with the highest maize yields. Biomass production was clearly increased by intercropping but there was no increment in marketable yields. Relay-cropping reduced tuber and maize yields and had the lowest productivity of all combinations tested.     

山药块茎发育中物质积累及相关代谢酶变化

以桂淮5号和桂淮16两个不同山药品种为材料,根据块茎生长发育特性,在山药发育进程中测定块茎的有关生理生化指标。结果表明,随着块茎发育进程的推进,块茎长度及干物质积累持续增加,淀粉酶(AMY)活性降低;多数碳水化合物、功能性物质及过氧化物酶(POD)、酸性转化酶(AI)和蔗糖磷酸合酶(SPS)活性先持续增加,达到峰值后下降,但峰期不同;2个品种的还原糖、ADPG焦磷酸化酶(AGPase)变化不一致。t检验表明,在块茎发育全过程中,品种间的干物质(P=0.011)、淀粉(P=0.031)、皂苷(P=0.019)差异显著。可溶性糖(r₅=0.97^**,r₁₆=1.00^**)、AGPase (r₅= –0.85^*)、还原糖(r₁₆=0.87^*)与蔗糖显著相关;多糖(r₅=0.95^**)、Vc(r₅=0.83^*)、皂苷(r₁₆=0.88^**)与淀粉显著相关;干物质(r₅=0.97^**,r₁₆=0.87^*)、AMY(r₁₆= –0.95^**)、AGPase (r₁₆=–0.90^**)、蛋白质(r₁₆=0.83^*)与块茎伸长膨大显著相关。由此表明,蔗糖积累、SPS和AI活性在山药块茎发育中起关键调控作用,主要功能性物质彼此间密切相关。     

The effects of ethylene, 1-MCP and AVG on sprouting in sweetpotato roots

Exogenous ethylene is commonly used as a commercial sprouting inhibitor of potato tubers. The role of ethylene in the control of sprouting of sweetpotato roots, however, is not known. The aim of this study was to investigate the role of ethylene in control of sprouting in sweetpotato roots by observing the effect of an ethylene synthesis inhibitor, aminoethoxyvinylglycine (AVG), and the ethylene antagonist, 1-methylcyclopropene (1-MCP), in the presence and absence of exogenous ethylene on root sprouting and associated sugar accumulation. Continuous exposure to 10 μl L⁻¹ ethylene, 24 h exposure to 625 nl L⁻¹ 1-MCP or dipping in 100 μl L⁻¹ AVG all inhibited sprout growth in sweetpotato roots of two varieties over 4 weeks of storage at 25 °C. The observations that both ethylene on its own and 1-MCP, which inhibits ethylene action, inhibit sprout growth indicate that while continuous exposure to exogenous ethylene leads to sprout growth inhibition, ethylene is also required for sprouting. In potato tubers ethylene is required to break dormancy, while continuous exposure inhibits sprout growth.Monosaccharide concentrations in ethylene, 1-MCP or AVG treated roots were lower than in untreated roots, and for ethylene treated roots this was associated with higher respiration rates. This is consistent with the activation of some additional process by ethylene which uses energy through sugar metabolism. 1-MCP and AVG both inhibited this increase in respiration rate and counteracted the decrease in monosaccharide concentrations. 1-MCP presumably counteracts the ethylene stimulation of this process, while the effect of AVG is attributed to its possible inhibitory effects on protein synthesis.     

Wound-induced suberization genes are differentially expressed,spatially and temporally,during closing layer and wound periderm formation

Potato tuber (Solanum tuberosum L.) wounds incurred at harvest and upon seed cutting require rapid suberization as a major part of the healing process to prevent infection and desiccation. However, little is known about the induction and expression of genes that are essential for these processes and in particular to the two major stages of wound-induced suberization, i.e. closing layer formation and wound periderm formation. The objectives of this research were to address these needs by determining the effects of wounding on the induction and expression profiles of specific genes involved in wound-induced suberization in potato tuber (S. tuberosum L.) during the initiation and completion of closing layer formation and wound periderm formation. Although both stages critically involve suberization, there are significant differences between the two processes. Closing layer development requires rapid suberization of existing parenchyma cells bordering the wound surface to provide the initial protective barrier for the wound. Wound periderm development occurs later, i.e. after completion of closing layer formation, and requires development of a wound phellogen layer which mediates the formation of highly organized files of suberized wound-phellem cells that provide a more durable protective barrier for the tuber. The processes delineating these two separate stages of wound-induced suberization are poorly understood. This research shows that, unlike some wound responding genes such as phenylalanine ammonia lyase (StPAL-1) and anionic peroxidase (StPrx), certain genes that are specifically involved in both of these processes do not remain uniformly up-regulated during the two stages of healing (i.e. StTHT encoding Hydroxycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl)transferase, StFHT encoding a fatty ω-hydroxyacid/fatty alcohol hydroxycinnamoyl transferase, StKCS6 encoding a 3-ketoacyl-CoA synthase, StFAOH encoding a fatty acid ω-hydroxylase and StGPAT5 encoding a protein with acyl-CoA:glycerol-3-phosphate acyltransferase). Instead, they are up-regulated during closing layer formation; i.e. starting by ca. 1 d after wounding, but then slightly down-regulated or pause near completion of the closing layer (ca. 5–6 d) and then again up-regulated as wound periderm development is fully initiated (ca. 7 d) and down-regulated near completion (ca. 28 d after wounding). This differential in the expression profile, i.e. decrease between stages, was not anticipated and may be the first demonstration of measurable changes of any sort of biological flux as wound induced suberization transitions from closing layer to wound periderm development. Results were repeated using minitubers from two different crop years and demonstrate that these processes are separate, but coupled in some yet to be determined fashion. The biology of this differential expression is important because of the roles closing layer and wound periderm development play in protecting the tuber from disease and other challenges.     

云南甘薯地方主栽品种收集与脱毒复壮研究

为了更好地促进云南甘薯生产,收集云南地方主栽甘薯品种27个进行田间评价,并对其中的6个品种脱毒后进行田间对比试验。试验表明,有些品种产量较高,如‘普洱黄山芋’,产量达20.04 t/hm²,‘丘北白皮’亦达15.60 t/hm²;有些品种品质较好,如‘研和板栗薯’和‘华坪紫心’等;‘研和板栗薯’、‘建水灰薯’、‘华坪紫心’、‘马龙紫薯’、‘昆明紫薯’和‘建水紫薯’6个品种,脱毒后薯块平均增产幅度为175.8%;其中‘建水灰薯’脱毒后产量达24.00 t/hm²,比对照增产16.0 t/hm²,增幅为200.1%。通过脱毒,可以显著提高目前云南主栽甘薯品种的产量,更好为甘薯生产服务。     

Induction of mutations for heat tolerance in potato by using in vitro culture and radiation

Heat tolerant mutants were obtained in two commercial potato cultivars, `Kufri Jyoti' and `Kufri Chandramukhi' through in vitro mutagenesis of in vitro propagated plantlets. Gamma-irradiated (20 and 40 Gy) shoots were micropropagated for three cycles (M₁V₃). A large number of the micropropagated shoots produced microtubers at 28 ^°C. Microtubers induced at high temperature had distorted shape but showed normal germination in field. Under stress conditions of high temperature, the frequency of chlorophyll variants increased in the gamma irradiation-derived material, however, nearly 40% of the plants had normal leaf tissue, whereas control plants showed completely damaged leaves. This revised version was published online in July 2006 with corrections to the Cover Date.     

“渝苏303”甘薯离体形态发生过程中生理生化特性的变化

甘薯茎段、叶片和叶柄在附加有1.0 mg/L NAA的MS培养基中培养5天可产生大量的不定根,培养20 d茎段和叶片分化出不定芽。本文以甘薯品种“渝苏303”为材料,研究了甘薯外植体在不定根和不定芽分化过程中可溶性蛋白质含量、过氧化物酶（POD）和超氧化物酶（SOD）活性的变化,以及可溶性蛋白质和SOD同工酶酶谱的变化。结果表明     

Identification of somatic hybrids of dihaploid Solanum tuberosum lines and S. brevidens by species specific RAPD patterns and assessment of disease resistance of the hybrids

Summary Symmetric somatic hybrids were produced by electrofusion of protoplasts of two dihaploid tuber-bearing potato (Solanum tuberosum L.) lines and Solanum brevidens Phil., a diploid non-tuber-bearing wild potato species. A total of 985 plants was obtained. Verification of nuclear hybridity of putative hybrids was based on additive RAPD patterns, general morphological characteristics and chromosome counts. 53 (90%) calli regenerated into plants which were identified as somatic hybrids. Most of the hybrids were aneuploids at the tetraploid (4×) or hexaploid (6×) level. The 20 hybrids tested expressed a high level of resistance to potato virus Y (PVY ^N ) characteristic of the S. brevidens parent. Resistance to late blight (Phytophthora infestans (Mont.) de Bary) varied between hybrids, but was on average better than that of the fusion parents. Resistance of hybrids to bacterial stem rot (Erwinia carotovora subsp. atroseptica (van Hall) Dye) was not superior to that of commercial potato cultivars.     

The differential responses of chrysanthemum cultivars to light and temperature

Summary Chysanthemum cultivars were grown in 4 experiments in the greenhouse and in the phytotron. The growing conditions in the greenhouse varied from 14 C, 60 J cm² day^-1 to 17 C. 431 J cm² day^-1, those in the phytotron from 12 to 455 J cm^-2 day^-1 at a temperature of either 14 or 20 C.Most cultivars responded differentially to light and/or temperature, but this was only measurable when large differences in light and/or temperature were imposed. Reducing the light level in a greenhouse by 50% does not bring out cultivar×light interactions. Such interactions may be pronounced however when the performance in summer is compared with that in winter. This is also reflected in the correlation coefficients. The correlations between summer and winter performance for number of flowers per stem and the number of days to flowering are non-significant, those for the 7 other traits measured were all significant.The occurrence of interactions does not preclude the possibility of breeding cultivars adapted to a wide range of light and temperature conditions. Appropriate selection procedures are discussed.     

海拔差异对紫色甘薯品种的影响

通过对引进的‘11-07’、‘16-08’、‘Y1’和‘SCZ’ 4个紫色甘薯品种分别在云南省玉溪市3个不同海拔的山地种植,分析其生物学特性、丰产性、品质等指标。结果表明：在海拔2000 m以上,以‘11-07’和‘SCZ’的产量较高,在海拔1600 m~1700 m左右,以‘SCZ’的产量最高。综合4个品种的产量和品质,‘SCZ’可作为有价值的商品紫薯品种引到玉溪的山地推广种植,‘11-07’可作为替补品种,为玉溪市不同海拔山地选择种植优良紫色甘薯品种提供科学依据。     

Level of partial resistance to leaf rust,Puccinia hordei,in West-European barley and how to select for it

Summary The partial resistance to leaf rust (Puccinia hordei) of 40 West-European spring barley cultivars was measured in plots isolated from one another to reduce inter plot interference. The leaf area affected by leaf rust was also measured in small plots of 0.5 m² adjacent to each other, and on individual plants. The latent period was measured in the seedling stage and the adult plant stage, the infection frequency in the seedling stage only. The cultivars varied widely for partial resistance, many cultivars carrying a considerable level. Both the small adjacent plots and the single plants showed a marked inter plot interference strongly reducing the difference between cultivars. H wever, the ranking order of the cultivars was hardly, if at all, affected. Both latent period and the infection frequency showed large differences between cultivars, the latent period in the adult plant stage being highly correlated (r=0.82) with partial resistance, infection frequency in the seedling stage only rather weakly (r=–0.33).Selection for partial resistance appeared very effective in all stages tested; the seedling, the single adult plant, and the small plot stage. Selection in the small plot stage was the most effective followed by selection in the seedling stage. Selection for partial resistance therefore appears very well possible at all stages of the selection program.     

Inheritance and stability of the virus-resistant gene in the progeny of transgenic sweet potato

Viral diseases of sweet potato are very prevalent and often seriously damaging to the plants. In particular, the severe strain of the sweet potato feathery mottle virus (SPFMV‐S) causes ‘obizyo‐sohi’ disease in Japan. In order to confer viral resistance against SPFMV using current biotechnology, a transgenic sweet potato has been produced, introducing hygromycin‐resistant (hpt) and SPFMV‐S coat protein (CP) genes, which have shown a significant resistance to SPFMV‐S. In the breeding programme, it is important to confirm that the viral resistance conferred in T₀ plants can be inherited by their progeny. In the present study, progeny were obtained from crosses between the transgenic T₀ and a non‐transgenic variety of sweet potato. The results showed that the CP gene was inherited by the next generation and that the stability of viral resistance was also confirmed. Thus, this production system for the virus‐resistant transgenic sweet potato is useful in practical breeding.     

Effects of soil drought during the vegetative phase of seedling growth on the uptake of 14co2 and the accumulation and translocation of 14C in cultivars of field bean (vicia faba L. Var. Minor) and field pea (pisum sativum L.) Of different drought tolerance

During the vegetative phase of growth of two field bean and two field pea cultivars of different drought tolerance, the effect of short and prolonged soil drought on gas exchange (CO₂ i H₂O), leaf water potential (ψ), stomatal diffusive resistance (r_S), uptake of CO₂, and the distribution and accumulation of ¹⁴C was studied. Differences in the response to drought conditions between resistant and susceptible cultivars were marked. After 5 days of soil drought, the decrease in net photosynthesis and transpiration rate and the increase of stomatal resistance were greater in the drought-resistant cultivars than in the drought-susceptible ones. In contrast, after 10 days of drought the decrease of leaf P_N (CO₂ assimilation rate), E (rate of transpiration) and ψ (water potential) was greater in the susceptible cultivars than in the resistant ones. Significant differences between the resistant and the susceptible cultivars were also observed in the assimilation and translocation of ¹⁴C by the green parts of the plant. The amount of carbon accumulation in roots in drought-susceptible cultivars increased less than in the drought-resistant cultivars. For treatments in which optimal soil watering was resumed after 5 or 10 days of drought there was no evidence of effects of drought on the majority of measurements, but the drought-resistant cultivars showed a general tendency for a more rapid recovery. Our results confirm the existence of genetic variability in drought tolerance among the cultivars of field bean and field pea. The recorded differences in the response to drought of experimental cultivars may indicate that, under water deficit in the soil and in plant tissues, they may use different strategies to avoid the damaging effects of temporary limitation of water supply; for example, the drought-resistant cultivars may more effectively conserve tissue hydration through effective stomatal closure. Also, the observed changes in carbon assimilation and accumulation might be the reason for their different responses to drought. The change in radioactivity losses in the control and stressed plants may result from the differences in demand for energy to maintain cell structure and function. Similarly, the less intense carbon accumulation in the roots of the sensitive cultivars could be caused by more harmful effects of drought on root growth.     

The response of cassava cultivars to root-knot nematode infestation: An in vitro method

The aim of this study was to obtain information on the response of cassava(Manihot esculenta Crantz) to root-knot nematode infestation. To achieve this aim, a novel in vitro dual root/nematode culture method was used, where root cultures of several cassava cultivars were inoculated with axenic Meloidogyne javanica eggs. Following an incubation period,cassava roots were stained, weighed and dissected to determine the number of galls produced on the roots, as well as the number of mature females embedded in the galls. The number of eggs and larvae produced during this time were also determined. Results indicated that the modified in vitro nematode culture medium used was suitable for most root cultures of cassava cultivars. It was found that some cassava cultivars were highly susceptible to root-knot nematode infestation, with some cultivars showing very high numbers of galls and up to 50 mature females inside each gall. Some cassava cultivars screened, however, showed low numbers of galls and mature females, even though the presence of larvae was high. Some of these cultivars formed callus-like structures instead of galls, and this may be a resistance mechanism. This method may be useful as a screening tool, to determine the response and resistance or susceptibility of cassava cultivars to root-knot nematode infestation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic variation in a Norwegian germplasm collection of white clover (Trifolium repens L.)

Phenotypic (r_p), genotypic (r_g), genotype × location (r_gl) and error (r_e)correlations for important agronomic characters were estimated for eleven Norwegian populations of white clover (Trifolium repens L.), originating from between 58^°52′N and 69^°30′N latitude, and from altitudes of 10 to 450 m a.s.l. The populations were evaluated in monoculture clonal field plots for two years at two locations in Norway. All pairwise correlations between foliage height, leaflet length, dry matter yield (DMY) and general performance were positive and significant. Winter survival was positively correlated with general performance, spring growth and DMY, but negatively associated with internode length, while seed yield showed a small positive genotypic correlation with foliage height. Considerable differences were, however, revealed among populations with regard to sign and magnitude of the estimated correlations. Within-population estimates of r_g were consistently positive between DMY, general performance and most other characters; between foliage height on the one hand and leaflet length, winter survival and seed yield on the other hand, and between internode length and leaflet length, indicating pleiotropy. Correlations involving other character-combinations varied substantially among populations, and imply presence of linkage and/or coadaptation. Path coefficient analysis was used to partition the genotypic correlations between some of the characters into direct and indirect effects. Path coefficients revealed that foliage height had the highest positive direct effect on DMY, followed by winter survival and internode length. Leaflet length, which showed a positive, significant simple correlation with DMY, exhibited a negligible direct influence, counterbalanced nearly completely by the positive indirect effect on DMY via foliage height. Positive indirect effects on DMY via foliage height were also found for winter survival and internode length. The coastal populations from North and Middle Norway, and a southern highland population showed the largest expected responses to phenotypic selection for most of the characters. The results demonstrate that there is enough genetic variation in adapted local populations to develop new improved cultivars adapted to high-latitude environments that combine upright growth habit with sufficient winter-hardiness and persistency. This revised version was published online in July 2006 with corrections to the Cover Date.