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Raspberries (Rubus idaeus L.) are important vegetatively propagated fruit plants. They are used as food, as medicinal plants, and in pharmaceutical and cosmetic industry. For the protection of inte...

Antioxidant activity (AOA) in fruits of Sambucus nigra and several new elderberry interspecific hybrids involving S. javanica (JA), S. nigra subsp. nigra (NI), S. nigra subsp. nigra ‘Black Beauty’ (BB), S. nigra subsp. cerulea (CER) and S. racemosa (S. racemosa subsp. racemosa (RAC), S. racemosa subsp. racemosa var. miquelii (MIQ), S. racemosa subsp. tigranii (TIG), S. racemosa subsp. kamtschatica—coreana (KOR) at five maturity stages were investigated by applying DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)), FRAP (ferric reducing antioxidant power) and ORAC (oxygen radical absorption capacity) assays. The aim of the study was to compare different assays for estimating AOA in elderberries, to plan the appropriate harvest time and to determine whether the most promising genotypes could be predicted in advance. All assays used showed that AOA increased significantly during maturation. All assays were significantly correlated with each other and could be reliably used for the AOA determination of elderberries. In fully mature berries, significant correlations were also found between total phenolic (TP) content and AOA by all assays, but no significant correlations were found between total ascorbic acid (TAA) content and AOA by all assays. At the fully mature stage, (the most appropriate stage for harvesting), berries of (JA × NI) × BB and (JA × NI) × MIQ were found to be superior in AOA and TP content. Genotypes with higher/lower AOA and TP content could not be predicted in advance, while TAA showed the opposite.

In view of growing requirements of the food industry regarding elderberries (genus Sambucus), a need to increase their productivity and improve their chemical composition has emerged. With this purpose in mind, numerous elderberry interspecific hybrids have been created. In the present work, the content of minerals in their crucial plant parts was studied. It was also investigated whether superior genotypes regarding the mineral composition of berries and inflorescences could be predicted at early stages of plant development. The results showed that elderberry leaves contained the highest amounts of Ca, Mg, Mn, Zn, and Sr, while K and P were predominant in fruit stalks. Fe and Al prevailed in roots and Cu in bark. Although berries showed lower mineral content compared to other plant parts, their mineral content is not negligible and could be comparable to other commonly consumed berries. Genotypes with a favorable mineral content of inflorescences and berries could be predicted on the basis of known mineral composition of their shoots and leaves. The study also indicates that S. nigra genotypes and the majority of interspecific hybrids analyzed are suitable for further genetic breeding or cultivation.

Phenotypic and genotypic variations within the genus Sambucus are limited. They could be efficiently increased by genetic recombination involving different species. The aim of the presented investigation was to assess the possibility of using molecular approach (i.e., microsattelites) in determination of unknown hybrid structures. The study involved 47 Sambucus genotypes (parental species and intespecific hybrids), and six microsatellite loci were analysed. The clustering method grouped the analysed genotypes into four main groups. The first main group involved two sub-groups: one with taxons and hybrids involving S. racemosa (in broad sense) and the other involving two botanical varieties of S. nigra. In the second main group, there was a sub-group involving hybrids between S. javanica and S. nigra, and a sub-group involving F1 hybrids between S. javanica and S. ebulus. The third main group contained a sub-group with hybrids between S. javanica and S. nigra ‘Black Beauty’, a sub-group with hybrids involving S. javanica, S. nigra and S. racemosa (miquelii), a sub-group with backcrosses S. javanica × (S. javanica × S. ebulus), and un unknown hybrid. The fourth main group included a subgroup with F1 hybrids S. javanica × S. ebulus, a sub-group involving various taxons of S. racemosa (in broad sense), and a sub-group involving hybrids between S. cerulea and S. javanica, with and without S. nigra. Our study shows that molecular analysis can be helpful in determining some of the unknown but simple interspecific hybrids of Sambucus. In the cases of complex hybrid combinations, the use of SSRs is most probably not the best solution.

Taro (Colocasia esculenta L. Schott) is considered a dietary staple food crop for millions of people throughout tropical and subtropical regions. Depending on the cultivar, taro may contain oxalic acid deposited in plant tissues as calcium oxalate crystals, causing a very unpleasant burning sensation in the mouth. In the present study, oxalate content was quantified in four different parts of the taro corm, as well as variation in dry matter, Ca, and the oxalate content of corms harvested at different developmental stages, from 5 months after planting (MAP) to 13 MAP. The results revealed that the level of oxalates varies according to corm part and cultivar. The cultivars with the lowest and highest water-soluble and total oxalate content in the central part, which is critical for human nutrition, were VU268 (87 and 134 mg 100 g−1 DW) and VU384 (182 and 230 mg 100 g−1 DW, respectively). Water-soluble oxalates accumulate mainly in the central and lower parts, while insoluble oxalates are concentrated in the marginal part of the corm. Their content can be almost halved by removing a 1 cm thick marginal layer (peeling). The oxalate/Ca molar ratio ranged from 0.78 in the upper to 1.31 in the central part, suggesting that the bioavailability of Ca in corms could be low. The dry matter content and Ca, insoluble and total oxalate levels vary according to the harvest time. The lowest total oxalate content was determined at 8 MAP (the usual time for taro harvest), while water-soluble oxalates increased with growing period. The proper assessment of corm maturity before harvest is, therefore, a critical step in controlling corm quality. Taro breeding programs aimed at reducing corm acridity need to take into consideration these results when designing protocols for optimum nutritional quality improvement of new cultivars.

Differences in the content of sugars, organic acids, total phenolics and antioxidative activity have been evaluated among three different elderberry species (Sambucus nigra, Sambucus cerulea, Sambucus javanica) and seven interspecific hybrids. The highest content of sugars has been determined in the fruits of JA×CER hybrid and the lowest in fruits of (JA×NI)×cv. Black Beauty hybrid. S. nigra berries contained highest levels of total organic acids. S. nigra and (JA×NI)×CER flower extracts were characterized by 1.3- to 2.8-fold higher content of total sugars compared to other species/hybrids analyzed. Total phenolic content (TPC) in berries ranged from 3687 to 6831 mg GAE per kg FW. The highest TPC has been determined in S. nigra fruits and flowers. The ABTS scavenging activity differed significantly among species and hybrids and ranged from 3.2 to 39.59 mM trolox/kgF W in fruits and 44.87-118.26 mM trolox/kg DW in flowers.

UNLABELLED The aim of this study was to investigate a detailed composition and content of phenolic compounds in fruits of 4 elderberry species (Sambucus nigra, S. cerulea, S. ebulus, and S racemosa) and 8 interspecific hybrids. Hydroxycinnamic acids (HCAs) represented the major share of phenolics in analyzed elderberries; caffeoylquinic and p-coumaroylquinic acids were most abundant. Flavanols (catechin, epicatechin, and different procyanidins) were the second major phenolic group detected in range from 2% to 30% of total analyzed phenolics. From the group of flavonols, 13 different quercetin glycosides, 7 kaempferol glycosides, and 8 isorhamnetin glycosides have been quantified. Rutin was the major flavonol in all studied genotypes. S. ebulus was characterized by the highest level of total HCAs, catechin, epicatechin, and most flavonols. Some elderberry hybrids, for example JA × RAC, CER × NI, and JA × (JA × NI), are perspective for further studies because they have high content of phenolic compounds. The results of research could contribute to breed cultivars, which may prove interesting for food-processing industries. PRACTICAL APPLICATION Different levels of phenolic compounds have been measured in fruit of analyzed elderberry species and interspecific hybrids. Natural evaluation of elderberry genetic resources, the identification of phenolic compounds, and assessment of their properties are of great interest to breeders and directly valid for pharmaceutical and food industry.

Our investigation was based on a molecular study of the genetic relationships among raspberry genotypes collected around selected medieval castles, Carthusian monasteries and nearby villages. We assumed that the hypothetical medieval raspberry genotypes could be traced to isolated medieval settlements that used to be highly prosperous during the feudal era but were later abandoned. Some of these genotypes could have survived in natural conditions without seed multiplication for at least three centuries. The molecular genetic analysis was based on microsatellite data. A total of 155 alleles were detected at 18 microsatellite loci. The clustering method grouped the analysed genotypes into seven main clusters. The analyses indicated that the most probable medieval genotypes had been collected around the ruins of two abandoned Carthusian monasteries: Zice and Jurkloster. They were morphologically very similar, vigorous and primitive but obviously not wild genotypes. The plants could be more than 2.3 m high, the canes were medium waxy, the lower and upper parts of the canes were covered by sparse short spines, the mid part was more or less completely smooth, the fully developed leaves were 15–25 cm long and the inflorescences were loose. In addition, the flowers were relatively small, the fruit setting was poor and the fruits were small, ovoid to conical and more aromatic than those of modern cultivars.

The main purpose of the present study was to evaluate the diversity and content of various phenolic compounds in floral infusions of 14 elderberry genotypes (3 species and 9 interspecific hybrids). Detailed phenolic analysis was performed using HPLC-MS. Hydroxycinnamic acids (HCAs) were the major phenolic group identified and 3-, 4-, and 5-caffeoylquinic acids were detected in infusions prepared from all analyzed species and interspecific hybrids. Several flavonols were identified in elderberry floral infusions: 8 isorhamnetin derivatives, 6 quercetin derivatives, 2 flavanones, and 6 kaempferol derivatives. The main flavonols detected in all samples were isorhamnetin-3-rutinoside, isorhamnetin dihexoside, quercetin-3-rutinoside, kaempferol-3-rutinoside, and kaempferol dihexoside. The highest levels of flavonols and hydroxycinnamic acids were measured in interspecific hybrid infusions of Sambucus javanica x S. cerulea, (S. javanica x S. nigra) x S. nigra cv. Black Beauty, (S. javanica x S. nigra) x S. nigra, and S. javanica x S. racemosa.

The adaptive plasticity of Norway spruce (Picea abies) against attack by Ips typographus depends on systemic acquired resistance which involves salicylic acid (SA), and an antioxidant system both recognized as valuable stress markers in ecophysiological studies. In the presented field experiment, 100 mM SA was applied to the bark sections of Norway spruce prior to being attacked by bark beetles, in order to study interactions with antioxidants and its significance for mediating stress-tolerance under natural conditions. SA-treatments significantly elevated the total SA levels over the whole sampling period. Total glutathione (tGSH) and total cysteine (tCys) increased by 167% and 80%, respectively, two weeks after treatment, in comparison with controls. In contrast, SA-treatment caused an initial deterioration in total ascorbic acid (tASC) and enhanced the percentage of dehydroascorbic acid (DHA), but activated tASC levels over later sampling dates. The initial bark beetle attack was characterized by a significant decline in total SA levels, which was accompanied by a transient degradation and oxidation of their ascorbate-glutathione system. This initial reaction was significantly alleviated by SA-application and characterized by 175% higher tGSH contents, when compared to moderately-affected untreated trees. One month after pheromone dispensers were placed on trees, an intensification of ascorbate-glutathione system occurred within moderately-affected bark, but to a greater extent after SA-treatment. Total SA levels within SA-treated moderately-affected trees remained at the control level until June. In contrast, strong attack was characterized by a successive increase in total SA up to 252% following SA-treatment in June, whereas a 110% increase of SA was determined within severely affected control-bark. A strong attack was further characterized by a degradation of tGSH and total phenolics (tPH), a moderate increase in tASC and an oxidation of the ascorbate-glutathione pool within untreated bark. In the SA-treated trees the redox state was unaffected by severe colonization and the degradation of antioxidants was significantly alleviated. In addition, SA-treated bark had significantly less entrance holes and exhibited fewer and shorter maternal galleries than control-bark. From this perspective, exogenous SA was successfully implicated as an activator of systemic acquired resistance in Norway spruce, providing tolerance against the complex interactive effects of bark beetle attack and environmental factors.

International audience; Thermogenesis and heat generating tissues in inflorescences of the giant taro (Alocasia macrorrhizos (L.) G. Don) were studied from December 2005 to February 2006, on the Island of Espiritu Santo, Vanuatu. Temperatures were recorded in the ambient air, in the peduncle tissue, and on 12 positions within spadices during periods of maximum thermogenic activity, in the early morning hours of the female and male phases. The study showed that there were three thermogenic tissues: the sterile appendix, the fertile male part, and the differentiated sterile area below the fertile male part. During the female phase, heat was generated by the sterile appendix and the differentiated sterile area below the fertile male part, the smallest region of the spadix (mean ± SD = 0.86 ± 0.24 cm, 3.17% of the spadix length), and most probably by the fertile male part. Within the spadix, average temperatures gradually increased from the base of the female part and reached the first peak at the midpoint of the differentiated sterile area below the fertile male part (36.11 ± 1.54 °C). After that, they gradually decreased towards the midpoint of the fertile male part and increased again, reaching a second (main) peak at 1/4 of the sterile appendix height (44.83 ± 1.87 °C). From 1/4 to 1/2 of the appendix height they remained at more or less the same level, and then they decreased towards the tip of the spadix. During the male phase, heat was generated only within the fertile male part.; La thermogenèse et les tissus thermogénétiques du taro géant (Alocasia macrorrhizos (L.) G. Don) ont été étudiés de Décembre 2005 à Février 2006 sur l’île d’Espiritu Santo au Vanuatu. Les températures ont été mesurées dans l’air ambiant, dans le pédoncule ainsi que dans 12 emplacements à l’intérieur des spadices pendant les périodes d’activité thermogénétique maximale, au petit matin et pendant les phases femelles et mâles. L’étude a montré l’existence de trois tissus thermogénétiques : l’appendice stérile, la partie mâle fertile et la zone stérile différenciée située sous la partie mâle fertile. Durant la phase femelle, la chaleur était générée par l’appendice stérile et par la zone stérile différenciée sous la zone mâle fertile, soit la plus courte zone (0,86 ± 0,24 cm de long, soit 3,17 % du spadice), enfin très probablement par la zone mâle fertile elle-même. Á l’intérieur du spadice, les températures augmentaient progressivement à partir de la base de la partie femelle et atteignaient leur premier pic à la moitié de la zone stérile différenciée sous la zone mâle fertile (36,11 ± 1,54 °C). Ensuite, elles diminuaient graduellement vers le milieu de la zone mâle fertile, augmentaient à nouveau avant d’atteindre le second pic (le principal) au quart de la hauteur de l’appendice stérile (44,83 ± 1,87 °C). Entre le quart et la moitié de la hauteur de l’appendice, elles conservaient plus ou moins le même degré de température, puis décroissaient vers l’apex du spadice. Durant la phase mâle, la chaleur n’était générée que par la partie mâle fertile.

Taro (Colocasia esculenta) is an important staple crop distributed throughout many tropical and subtropical regions. Very little information is available about the nitrate content and its distribution within taro corms. The aim of this study, based on ion chromatography, was to analyze the concentration and distribution of nitrate within four crucial parts (upper, central, marginal, basal) of taro corms of 8 representative cultivars. The results revealed that the levels of nitrate in taro corms were variable depending on the cultivar and corm parts. The highest levels were determined in the upper part of the corm which is used for the multiplication and establishment of a new crop. Therefore, the size of this part is closely associated with the quality of the planting material. As there are no roots, the initial growth of the new taro plant depends entirely on the nutrients accumulated in the upper part of the corm. During the growth season, this part of the corm gradually becomes the lower (basal) part containing the oldest and the least biochemically active tissue, which has the lowest concentration of nitrate ions. The nitrate content in the central part, which is the most important for human nutrition, was relatively low and varied between 29 and 313 mg/kg fresh weight. (Resume d'auteur)

Attempts were made to produce hybrids among various Sambucus species in order to change the plant structure of S. nigra, a medicinal plant of increasing agricultural importance. The first successful genetic recombination, involving four species, was conducted after the introduction of S. javanica from a South Pacific island. A series of genetic analyses of the involved species and some relatives was performed in order to obtain reliable data on genetic similarity among parental species and to confirm the hybrid nature of putative hybrids. The nuclear 2C DNA content revealed by flow cytometry of nine species showed limited variation, the greatest being in S. nigra (28.6 pg) and the smallest in S. caerulea (23.9 pg). Maximum parsimony analysis of seven Sambucus species was used to form two dendrograms, one based on the sequenced nuclear ribosomal DNA (nrDNA) internal transcribed spacer (ITS) region and the other based on the cpDNA trnT-trnF region. The results showed similar clustering into distinct groups; on both dendrograms S. nigra and S. javanica ES were closely related. Analysis of hybrid origin was based on the sequenced cpDNA region, genome size differences and PCR–RFLP analysis of the nrDNA ITS region. The seed parent and maternal origin of cpDNA was confirmed for all hybrids, while the pollen parent was confirmed in 21 of 22 putative hybrid plants tested.

The aim of this study was to investigate a detailed composition and content of phenolic compounds in fruits of 4 elderberry species (Sambucus nigra, S. cerulea, S. ebulus, and S racemosa) and 8 interspecific hybrids. Hydroxycinnamic acids (HCAs) represented the major share of phenolics in analyzed elderberries; caffeoylquinic and p-coumaroylquinic acids were most abundant. Flavanols (catechin, epicatechin, and different procyanidins) were the second major phenolic group detected in range from 2% to 30% of total analyzed phenolics. From the group of flavonols, 13 different quercetin glycosides, 7 kaempferol glycosides, and 8 isorhamnetin glycosides have been quantified. Rutin was the major flavonol in all studied genotypes. S. ebulus was characterized by the highest level of total HCAs, catechin, epicatechin, and most flavonols. Some elderberry hybrids, for example JA × RAC, CER × NI, and JA × (JA × NI), are perspective for further studies because they have high content of phenolic compounds. The results of research could contribute to breed cultivars, which may prove interesting for food-processing industries.Different levels of phenolic compounds have been measured in fruit of analyzed elderberry species and interspecific hybrids. Natural evaluation of elderberry genetic resources, the identification of phenolic compounds, and assessment of their properties are of great interest to breeders and directly valid for pharmaceutical and food industry.

Pulsatilla grandis is a rare and endangered species in Central Europe. A field experiment was set up to test the effects of disturbances on its germination and survival rates after artificial seeding. Disturbances were simulated by the following treatments: burning, hoeing, and removal of vegetation. The germination percentage decreased rapidly with time, to only 2% in 2-year-old fruits. The germination rate of fresh fruits was the highest in hoed plots (29.2 ± 12.9%), followed by removedvegetation plots (21.8 ± 17.3%) and burned plots (1.8 ± 2.2%). No germination was observed in control plots. The survival rate of seedlings was monitored over the next 5 years. In the year following the treatment, all the seedlings survived in the burned plots; in the hoed and in removed-vegetation plots, survival rates were 38.5 ± 2 and 55 ± 27%, respectively. Approximately half of them were alive after 5 years. Grassland vegetation in burned quadrates recovered very quickly, whereas in other disturbed plots the numbers ...

La thermogénèse de la floraison du taro (Colocasia esculenta (L.) Schott) a été étudiée pendant la période la plus chaude de l'anné (Décembre 2002 à Février 2003), au sein d'une collection importante de germoplasmes présentant une forte diversité, sur l'île de Espiritu Santo, au Vanuatu. Sur chacune des inflorescences étudiées, les températures des trois principales zones du spadice et de l'air ambient ont été enregistrées pendant une période de 38 h. Ce travail indique qu'il existe une thermogénèse significative des inflorescences de taro, et qu'elle a lieu durant deux nuits successives: (1) durant la nuit où l'inflorescence devient odorante (phase femelle); et (2) une nuit plus tard, lorsque la microsporogénèse approche sa phase finale (phase mâle). Les plus fortes différences entre les températures moyennes et la température de l'air ont été enregistrées durant la phase femelle, à 0500 (la température moyenne de l'appendice stérile est alors de 29,1°C ± 0,9°C (P = 0,05) soit 6,8°C de plus que la température de l'air ambiant). L'activité de la thermogénèse est synchronisée avec la protogynie de l'espèce et la pollinisation entomophile durant les premières heures du jour. Ses fonctions supposées sont: (1) de réduire les écarts de température de l'air ambient durant les périodes critiques de la pollinisation; et (2) de promouvoir les pollinisations croisées. Cette activité cesse entre 1 h et 1,5 h après l'émission de pollen.

Branching in taro (Colocasia esculenta) corms is a complex, undesired, and rare trait, which is expressed because of proliferation of lateral buds. The evaluation of the Vanuatu national taro germplasm collection showed that the frequency of this trait was significantly high (9.51% of the accessions were characterised by genetically controlled branching). Such a high frequency can be considered as an indication of close relationships among the majority of the Vanuatu cultivars. The expression of branching depends on the genetic structure, specific environmental conditions, interactions between the genetic structure and the environment, and interactions between various developmental stages of a particular genotype and the environment. The genetic control is complex and involves the interaction of at least two loci. The present study suggests that the existing genetic diversity of taro in Vanuatu (and probably also in other geographically isolated Pacific areas) is insufficient for a successful longterm breeding programme and should include introductions from other countries, especially from the centres of diversity.

The investigation includes the analysis of genome sizes of 11 Cucurbita species (some represented by several botanical varieties). In the majority of species, the genome size was measured for the first time. Values obtained by flow cytometry were based on propidium iodide (PI) staining technique. In contrast to the uniform chromosome number, the genome size differences within this genus appeared to be large, 2C values ranging from 0.686 pg in C. foetidissima to 0.933 in C. ficifolia. PI determined genome sizes of five cultivated species were 0.864 pg (C. pepo), 0.887 pg (C. maxima), 0.933 pg (C. ficifolia), 0.708 pg (C. moschata) and 0.748 pg (C. argyrosperma). The investigation also included several interspecific crosses among cultivated species, using embryo rescue technique. F1 hybrid plants were obtained from crosses: C. maxima×C. pepo (and vice versa), C. pepo×C. moschata, C. ficifolia×C. maxima, (C. maxima×C. moschata)×C. pepo, C. argyrosperma×C. moschata (and vice versa). The formation of plantlets in the last combination, where C. moschata was used as the female parent, had not been previously reported. The interspecific origin of regenerants was confirmed by evaluating relative nuclear DNA content, estimated by DAPI staining. In all hybrid combinations, the relative nuclear DNA contents in interspecific hybrids was intermediate and differed significantly from those determined in parental species. The results show that differences in genome size within the genus Cucurbita are big enough to be used efficiently in determination of interspecific hybrids.

A total of 19 different anthocyanins have been detected in four elderberry species and eight hybrids and quantified with the use of HPLC-MS(n). The profile and content levels of anthocyanins varied considerably among the analyzed elderberry species and hybrids. Cyanidin-3-O-sambubioside and cyanidin-3-O-glucoside were the most abundant anthocyanins in Sambucus nigra fruits. On the other hand, the prevalent anthocyanin in S. javanica hybrids was identified as cyanidin-3-(E)-p-coumaroyl-sambubioside-5-glucoside. The highest content of total analyzed anthocyanins (TAA) was determined in berries of the interspecific hybrid S. javanica × S. racemosa, followed by S. nigra, (S. javanica × S. nigra) × cv. Black Beauty, and (S. javanica × S. nigra) × S. cerulea. Berries of S. nigra var. viridis contained significantly lower levels of TAA. Our results provide novel information for nutritional research in addition to breeding programs, which strive to create new hybrids or cultivars with enhanced levels of bioactive components.

Green cover in vineyards on steep slopes may play an important role in the reduction of soil erosion. The main objective of this study was to investigate the effect of a permanent green cover (PGC) on soil erosion, together with any loss of nutrients, and to compare it with periodic soil tillage (PST). PST took place in the spring (May) and summer (August), in each second area between rows, in a vineyard with permanent green cover. In the case of PST experimental treatments, on average, 1892 kg of soil ha-1 yr-1 eroded, together with the nutrients. In the case of PGC treatments, the amountof soil erosion was only 92 kg ha-1 yr-1. The greater portion of erosive events occurred after tillage in summer, which was accompanied by heavy rainfall and slow renewal of grass cover (slower than in spring). PGC treatment provided a better environment for the activities of soil macro-organisms (i.e., earthworms belonging to the family Lumbricidae), and mostof the organisms were close to the soil surface. In PST treatment, the majority of macro-organisms were below the area disturbed by the tillage (between 10 and 20 cm). The results of our investigation indicate that, in order to adjust wine production activities to climatic changes in vineyards with permanent green cover, PST in area between rows is more advisable in spring (end of May) than in summer (first decade of August) owing to an earlier establishment of effective grass cover.

International audience; Aroids are an economically important source of food for numerous tropical countries. They are mostly consumed for their corms and cormels but leaves and petioles can also be part of the diet. According to FAO databases (www.fao.org 2007) taro (Colocasia esculenta (L.) Schott) and cocoyam (Xanthosoma sagittifolium (L.) Schott) produce the lowest average yields (6.5 tons/ha) of all root crops. World production in 2006 was approximately 11.9 million fresh tons from 1.8 million hectares but significant taro producers such as India, Bangladesh, Burma, Indonesia, Papua New Guinea, and Cuba do not supply production figures. Since taro production was around 4 million tons in 1961, its cultivation is stable or even growing and follows the global trend of demographic growth. Aroids are considered minor crops but they are a staple food for numerous poor populations from tropical countries.

International audience; Taro (Colocasia esculenta) breeding, as other root crop breeding, is based on the production and evaluation of large numbers of hybrids. The selection of parents is based on their phenotypic value in the absence of information concerning general combining ability (GCA), specific combining ability (SCA), or genetic distances between varieties. By combining data from heritability trials and from genetic diversity studies conducted with AFLP and SSR markers, we aimed at studying the relationship between hybrid vigour and genetic dissimilarity between parents. The traits studied included number of suckers, corm weight, corm dimensions, and dry matter content. Correlation coefficients between hybrid gain and dissimilarity values were calculated. The prediction of hybrid performance based on the mid-parent value was compared to the prediction based on a modified expression that takes into account the genetic relationships between parents. Correlations were all but one positive but not statistically significant for all traits, with the exception of the number of suckers, when using SSR markers for dissimilarity calculations. Accordingly, the genetic dissimilarities in the prediction of hybrid performances did not increase the correlation between predicted and observed hybrid vigour values. However, large differences were observed among the residual means from the regression between predicted and observed values when using AFLP or SSR markers, mainly due to the much higher polymorphism revealed by the latter. Models need to be further adapted to the type of molecular marker used, since their ability to reveal different rates of polymorphism will have a direct incidence on the calculation of genetic dissimilarities between genotypes. Nevertheless, since SSR markers are more polymorphic and more informative than AFLP markers, they should be preferentially used for these studies. Low genetic dissimilarity of parents yielded weak heterosis effects and future studies need to be conducted by using a broader genetic base. This is the first study assessing the relationship of hybrid vigour with the genetic distances between parents, conducted on a tropical root crop.

The thermogenesis and flowering biology of Colocasia gigantea (Blume) Hook. f. were studied from December 2005 to February 2006 on Espiritu Santo, Vanuatu (South Pacific). Endogenous thermogenesis was measured in two ways: (1) continuously over 5-day periods, and (2) over 3 h during maximum heating. The study showed that heat was generated by the male part of the spadix and probably the lower zone of the sterile region. The temperatures of the male part peaked twice: (1) between 0625 and 0640 (during the female phase) and (2) 24 h later (during the male phase). The average maximum temperature was 42.25 +/- 0.14 degrees C during the female phase (16.63 degrees C above the ambient temperature) and 35.14 +/- 0.22 degrees C during the male phase (10.61 degrees C above the ambient temperature). In the lower zone of the sterile region, thermogenesis was documented only during the female phase. The average maximum temperature was 35.44 +/- 0.41 degrees C (9.82 degrees C above the ambient temperature). Thermogenic heating appeared to be closely associated with the activities of pollinating insects.

International audience; This investigation was aimed at understanding the morphological variation and reproductive biology of wild populations of giant tar (Alocasia macrorrhizos) in Vanuatu. It is an aroid species, which grows in vigorous, relatively small and dense populations, consisting of phenotypically uniform or very similar individuals. The most variable traits observed in wild populations are number of inflorescences, number of infructescences per plant, and corm length. These traits are highly variable even within genetically uniform populations and are highly influenced by age differences between plants. Flowering is frequent and most of the plants are highly fertile. However, sexual reproduction is rare due to self-incompatibility (between plants genetically homogeneous within the same population) and the absence of efficient pollinators. Self-incompatibility can be partly overcome by repeated self-pollination. Thermogenesis was studied on a large sample of inflorescences and little variation concerning the thermogenic potential was observed. Our results showed that, despite optimal flowering conditions (concerning pollen fertility, stigma receptivity, and thermogenic potential), propagation of wild Alocasia macrorrhizos populations in Vanuatu was mainly vegetative. Giant taro plants might have been carried beyond the range of their most effective pollinators. Other factors were considered: the presence of numerous earwigs (Labidura truncata) insects within inflorescences, which could have a competing effect with the usual pollinators of giant taro, and the long distances between genetically homogeneous populations.

Equipe DGB, ex-UMR PIA; International audience; The increase of production of an important root crop such as taro [Colocasia esculenta (L.) Schott, Araceae] implies the development of new varieties through an efficient breeding scheme. The breeding of new taro cultivars is a complex process which requires experience, adequate genetic resources, and reliable data about inheritance of crucial agronomic traits. To obtain these data, 2-yr heritability taro trials were conducted in Vanuatu with 42 full-sib families of variable sizes. In the first clonal generation (Cl), a fully randomized complete block design was planted with plots of 16 datum plants. During the second clonal generation (C2), parents were included with their offspring in two alpha incomplete block designs with elementary plots of 12 and 4 datum plants, respectively. Both family and narrow-sense heritabilities were higher for the number of suckers and dry matter content than for corm weight or its components (corm length and width). A high percentage of valuable hybrids were observed among a small number of families. These results, combined with the moderately high family heritability values for several traits, recommend the creation of a small number of large full-sib families when working with a narrow genetic base and the creation of numerous small full-sib families when dealing with a broad genetic base

The paper presents the first taro (Colocasia esculenta L. Schott) genetic maps. Taro is an important vegetatively propagated root crop species in most subtropical areas. It is an allogamous and protogynous species with a basic chromosome number of x = 14. Two F1 progenies of 123 and 100 individuals obtained from crosses between local cultivars from Vanuatu (VU101 × VU104 and VU373 × VU314) were chosen for this study. Both genetic maps contained 169 markers, mainly AFLPs and 8 SSRs, and were characterised by a high density of markers and a short map length. The maps had 14 and 18 linkage groups (LG) respectively and were not completely saturated. Twenty-four markers were identified across the two progenies and a good co-linearity was observed for the majority of these markers. A QTL detection study was conducted on both progenies with 91 and 89 individuals respectively. Several putative QTLs were identified for corm yield and corm dimensions (which were highly correlated traits) whereas no QTL was detected for dry matter content. This result was relatively unexpected since dry matter content was a more highly heritable trait than corm yield or corm dimensions. A major dominant gene, responsible for the yellow colour of the corm flesh, was also identified. Further mapping studies on taro should include a larger number of SSR markers, larger progenies should be created and other important traits related to yield and eating quality should be included in the QTL analyses.

L'activité thermogénétique des inflorescences de populations sauvages d'Alocasia macrorrhizos (L.) G. Don a été enregistrée à Espiritu Santo (Vanuatu, Pacifique Sud), entre décembre 2002 et février 2003, puis entre février 2004 et mars 2004. Les températures ont été mesurées à l'aide de six thermocouples cuivre-constantan (type T) de taille infra-millémétrique, reliés à une centrale d'acquisition automatique Campbell Scientific 10X. La période thermogénétique dure de 36 à 42 heures et ne fut détectée que sur la partie mâle et sur l'appendice stérile. On enregistre les plus hautes températures sur les appendices stériles. Ces températures commencent à monter lentement avant minuit, et atteignent un pic entre 05h45 et 06h00, lorsque l'odeur de l'inflorescence devient plus intense. La température maximale moyenne des 59 inflorescences mesurées était de 43,9 ± 0,6 °C. Le maximum absolu fut de 47,4 °C. L'écart maximal à la température ambiante fut de 25,6 °C. L'activité thermogénétique de la partie mâle démarrait 10 à 15 heures avant que l'inflorescence ne devienne très odorante, et s'arrêtait 2 à 3 heures après la libération du pollen. Deux pics furent enregistrés: le premier apparaissait 15 min après celui de l'appendice stérile, alors que le deuxième apparaissait au moment de la libération du pollen. Les insectes visiteurs les plus abondants étaient des perce-oreilles (Labidura truncata Kirby, Labiduridae, Dermaptera). La production de graines était extrêmement rare.

This paper addresses the preservation and use of minor root crop genetic resources, mostly aroids and yams. Conservation is fraught with difficulty: ex situ collections are expensive to maintain and methods for on-farm conservation have not been studied. Conventional breeding strategies present serious limitations when applied to these species. Furthermore, the evaluation and distribution of improved material are as problematical as its conservation. The similarities shared by these species regarding their domestication, breeding constraints and improvement strategies as well as farmers' needs, are briefly reviewed. Based on these biological constraints, we propose a practical alternative to current conservation and breeding strategies. This approach focuses on the geographical distribution of allelic diversity rather than localized ex situ and/or in situ preservation of genotypes. The practical steps are described and discussed. First, a core sample representing the useful diversity of the species is assembled from accessions selected for their diverse and distant geographic origins, wide genetic distances, quality, agronomic performances and functional sexuality. Second, the geographical distribution of this core sample, in vitro via a transit centre, allows the direct use of selected genotypes by farmers or for breeding purposes. Third, the distribution of genes is realized in the form of clones resulting from segregating progenies and, fourth, farmers select clones with local adaptation.

Taro (Colocasia esculenta (L.) Schott) is an allogamous and polymorphic species with thousands of cultivars. Tremendous morphological variation can be created by artificial genetic recombination. The breeding of taro is expensive, especially when the breeders have to deal with large populations of 10 000 or more individuals. One of the most efficient ways to improve the breeding efficiency is to start selection at an early stage of development, without uprooting the plants, which usually takes place 15 months after the germination of seeds. Such an approach has been considered for determining taro corm flesh and corm fibre colours, as these traits are very important for marketing. In the present study, phenotypic correlation analysis shows that most of the colours of the corm flesh and corm fibres can be determined by scoring the colour of the petiole base and the colour of the lower part of the petiole (2-3 mm above the base). This can be done in an early stage of development and speeds up the recurrent selection process. (Resume d'auteur)

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