Alkaloid Spectrum of Different Germplasm Lines in Opium Poppy (Papaver somniferum L.)

The opium latex of 1470 individual plant samples of 98 germplasm lines were screened for five major economic alkaloids. The alkaloids profile showed that morphine content ranged from 9.20–20.86% with an average of 15.00 ± 0.267. Codeine ranged from 1.69–6.48% with arithmetic mean of 3.35 ± 0.091, thebaine from 0.52–7.95% with an average of 2.27 ± 0.116. Narcotine ranged from 8.79–17.97% with an average 8.79 ± 0.266 and papaverine content ranged from 0.00–6.07% with an average 1.18 ± 0.167 in over all the germplasm lines. The content of different alkaloids categorized into class interval which exhibited that maximum number of plants and accessions for morphine content fall in group of 10–15% followed by 15–20%, for codeine content in group of 2–4% followed by 4–6%, for thebaine content in 1–2% followed by 2–4%, for narcotine in 5–10% followed by 10–15% and for papaverine content 0–2%. 24 germplasm lines had morphine content above 16.0%. Similarly, 37 germplasm lines for codeine and 13 for thebaine showed consistently high content, i.e., above 3%. 33 germplasm lines had narcotine content above 9% and 20 lines exhibited papaverine content above 2%. Line BR 316 was found unique having thebaine content 6.27–9.33%. The probable reasons of increase or decrease of different alkaloids based on their biosynthetic pathway has been discussed in detail.     

Inter-relation between descriptors and morphine yield in Asian germplasm of opium poppy Papaver somniferum

A set of 208 Indian and two Thai germplasm accessions of opium poppy Papaver somniferum were assessed for variation in 17 morphological characters, seed yield and content and yield of morphine from capsules and peduncles. The germplasm was found to be highly variable for all the characters evaluated. In the harvested peduncles and capsules, 13% was peduncle straw, 61% seeds and the rest capsule husk. The peduncle and capsule straw yields ranged between 0.6–2.2 and 1.4–5.3 g plant^-1, respectively. Morphine content in the peduncle varied between about 0.001–0.24% and that in the capsule from 0.02 to 1.05%. On average basis morphine content in the capsule husk was more than 9-fold higher than the peduncle straw. The plant morphine yields from peduncles and capsules ranged between 1.2 and 28.6 mg plant^-1. Four accessions yielded more than 20 mg of morphine plant^-1. Among these, in one of the accessions about 13% of the morphine was contributed by the peduncle. The plants of high morphine yielding accessions were generally small in height, and bore white flowers and large sized ungrooved capsules with a small number of seeds, on a large peduncle.     

Variation in the seed and oil yields and oil quality in the Indian germplasm of opium poppy Papaver somniferum

The variation in the seed shape, colour and yield, and content, yield and fatty acid composition of seed oil of 109 accessions of opium poppy Papaver somniferum, (majority of them Indian land races), was investigated. The seeds were white, pale yellow or light brown in colour, reniform or round in shape and varied in size up to three fold. The oil content, seed and the oil yield varied between 26 to 52%, 1.0 to 7.4 g/plant and 0.4 to 2.7 g/plant, respectively. The % content of palmitic, oleic and linoleic acid in the seed oil ranged between 9.3 to 40.0%, 7.5 to 58.4% and 0.7 to 72.7%, respectively. On average basis, the levels of major fatty acids in the seed oil were: oleic (37.1%) > palmitic (27.3%) > linoleic acid (17.2%). The palmitoleic, stearic and linolenic acids were present in the oils of only some of the accessions. Two of the accessions yielded linoleic acid rich seed oil of about the same quality as soybean and maize oils, and in four accessions, the proportion of palmitic, oleic and linoleic acids was roughly equal. The palmitic acid was relatively less and linoleic acid more in the seed oil from accessions rich in oil content. The oil that contained higher amount of oleic acid also contained higher amount of palmitic acid and relatively lower amount of linoleic acid. The correlation analyses revealed a strong positive relationship between seed yield and oil yield (r = +0.81), oil yield and oil content (r = +0.54) and oleic acid and palmitic acid content in the seed oil (r = +0.49), and a weak positive relationship between oil content and linoleic acid content of oil (r = +0.24), and a negative correlation was observed between oil content and palmitic acid content (r = –0.32), palmitic acid and linoleic acid (r = –0.55) and oleic acid and linoleic acid contents of oil (r = –0.68). The observations have permitted selection of accessions that are high seed and oil yielding and/or rich in linoleic, palmitic and oleic acids or containing palmitic, oleic and linoleic acids in about equal amounts.     

Evaluation ofFusarium wilt-resistance in primitive races ofGossypium hirsutum L.

Seven primitive races ofGossypium hirsutum L.punctatum, marie-galante, richmondi, latifolium, morrilli, palmeri, mexicanum and five F₁ crosses were inoculated withFusarium f. sp.vasinfectum physiological strain I. in the wilt field of Cixi Cotton Institute in 1987. There were highly significant differences among these primitive races.Punctatum andpalmeri were highly resistant. The resistances ofmarie-galante andmexicanum was similar with that of cultivar ‘Simian2’;richmondi, latifolium andmorrilli were susceptible. The disease incidence of F₁ in five primitive races hybridized with cultivar ‘Simian2’ was generally higher than that of mid-parent value. Inheritance of wilt resistance was partially dominant. In addition, 178 accessions of eight primitive races were evaluated for their resistance as before in 1989. There were significant differences in resistance among races and intra-race accessions. There were wilt resistance accessions among primitive races in which disease incidence was below 10%–25%. Inpalmeri, marie-galante, richmondi andpunctatum, one accession was immune with 0% disease incidence, respectively; 22.7–77.4% accessions were susceptible with 50% disease incidence. It showed that primitive races were mixed populations. They should be evaluated and screened for their utilization in cotton breeding program. Some best plants were selected from F₂ of two crosses, ‘Simian2’ ×palmeri and ‘Simian2’ ×mexicanum, based on the resistance toFusarium wilt and the response to photoperiod. 11 lines had been obtained with good fiber quality and relatively high potential production by backcrossing improvement. These lines are now being tested.     

Pattern of diversity for morphological and alkaloid yield related traits among the periwinkle Catharanthus roseus accessions collected from in and around Indian subcontinent

Thirty two accessions of periwinkle Catharanthus roseus collected from different semitemperate to tropical geographical areas of Indian subcontinent, Madagascar, Singapore and Malaysia were characterized under field conditions for 53 growth, development, morphogenesis and alkaloid yield related characters over a few seasons at Lucknow, India. Large differences were observed among the accessions for each of the characters examined. The differences among the accessions ranged 3, 80 and 15 fold for the alkaloid yield related traits – leaf dry matter yield and leaf vincristine and vinblastine concentration, respectively. Strong correlations were observed between leaf area and leaf yield with leaf alkaloid, root and root alkaloid yields, contents of dimeric alkaloid in leaves with yields of respective alkaloids, leaf number and root alkaloid content with leaf vinblastine yield and leaf vinblastine content with leaf vincristine and vinblastine yields. Multi-variate analyses allowed classification of the accessions into 5 to 7 morphologically and presumably genetically distinct groups. Generally, the accessions coming from tropical agro-climates tended to get separated from those having origins in subtropical to semi-temperate environments. Three clusters were observed to bear complementary characters for possibly cross-parenting high alkaloid yielding transgressive segregants. One of the accessions of C. roseus in which the leaf vincristine content was 5 fold and vinblastine content one and a half fold of the respective all accession means appeared suitable for the domesticated cultivation. It was proposed that accumulation of high amounts of total alkaloids and one or more dimeric alkaloids in leaves of certain accessions may be a reflection of reproductive fitness achieved under the biotic and abiotic stresses imposed on their parent populations, sometime in their evolutionary pathway.     

Identification and overcoming barriers between Brassica rapa L. em. Metzg. and B. nigra (L.) Koch crosses for the resynthesis of B. juncea (L.) Czern.

Brassica juncea (2n = 36, AABB) is an amphidiploid derived from its diploid progenitor species B. rapa (2n = 20, AA) and B. nigra (2n = 16, BB). Resynthesis of B. juncea by exploiting the wider gene pool of the present day diploids offers a powerful tool for obtaining novel genetic variation. Hybridization between the two species is difficult because of the presence of crossability barriers. Barriers to hybridization were identified using Aniline Blue Fluorescence (ABF) method. Crosses were classified as having pre- or post-fertilization barriers based on whether less than or more than one per cent ovules showed pollen tube entry. Of the 23 crosses studied, seven crosses all with B. rapa as the female parent showed pre-fertilization barriers. Only 0 to 0.3 per cent ovules were fertilized in these crosses. The remaining 16 crosses, four with B. rapa as the female parent and 12 with B. nigra as the female parent, showed post-fertilization barriers. In crosses with pre-fertilization barriers use of bud pollination and stump pollination ensured or increased fertilization. These two simple techniques were used in combination with ovary-ovule culture to ensure recovery of hybrids. In crosses with post-fertilization barriers, ovary-ovule culture alone helped to obtain hybrids. Hybrids were obtained at higher frequency with the use of direct ovule culture compared to ovary-ovule culture. The F₁ plants obtained in vitro were multiplied on MS medium + 2 mg/l Kn + 0.2 mg/l IAA. These F₁ plants were confirmed as true hybrids through morphology, leaf isozymes and cytology. In all 17 hybrids were obtained of which three were amphidiploids.     

Morphological and molecular diversity analysis among the Indian clones of <Emphasis Type="Italic">Sesuvium portulacastrum</Emphasis> L.

Sesuvium portulacastrum L. (seapurslane) is a halophyte used as pioneer species in sand dune fixation and stabilization of saline soil. Studies on the morphological and molecular diversity were carried out for the 14 clones of Sesuvium collected from the different coastal regions of India. Significant differences were observed for morphological traits viz., length, width, diameter and area of leaf, internodal distance and stem diameter for different clones when compared with the clone from Gujarat state (GJ1). A UPGMA dendrogram for morphological traits based on the Pearson’s similarity coefficient clustered the clones into three groups considering 80% polymorphism as criteria. Molecular diversity among the clones was studied using Randomly Amplified Polymorphic DNA (RAPD), Internal Transcribed Spacer (ITS) and markers specific to Ac homologous region. Of the total 749 RAPD loci amplified with 70 random primers, 294 were polymorphic with 39.25% diversity. A phylogenetic tree constructed with UPGMA and SHAN, grouped the clones into three major clades based on RAPD data. The molecular diversity studied with ITS and markers specific to Ac homologous region revealed 37.50% and 66.66% polymorphism and clustered the clones into three and four clades, respectively. The genetic diversity analysis revealed wide variations among the S. portulacastrum clones, reflecting a high level of diversity within the species which might be due to anthropogenic impact and geographic environmental conditions. Further, the various clones from the different eco-geographic coastal localities might have originated from native places of wild abundance. To the best of our knowledge, this is the first attempt to evaluate both morphological and genetic diversity among the Sesuvium clones collected from the distant habitats of the coastal regions of the India.     

Collecting spanish populations of the genusAegilops L.

Summary Several expeditions were made to the greater part of Peninsular Spain and the Balearic Islands, in order to collect samples from populations ofAegilops spp. The result has been the compilation of a collection reflecting both the presence and the distribution of the genus in Spain. The localisation and collection of two populations ofAe. cylindrica is particularly noteworthy.Ae. ovata is found all over the Peninsula except in the north and northwest of the country. It extends also to the Balearic Islands, which lie within the same biogeographical region.Ae. triuncialis also has a widespread distribution though smaller than that ofAe. ovata. In the Balearic Islands it is found only in Mallorca. All other species were found in more localised areas.Ae. neglecta was found in regions of W and SW Spain with the limits of its distribution bordering those ofAe. biuncialis, which is found in central Spain and in the South.     

Selection of parental pairs for obtaining hybrids in the genera Glycyrrhiza L. and Meristotropis Fisch. et Mey.

Summary Suitable parental partners have been selected for hybridizations between species of the genera Glycyrrhiza and Meristotropis. Further breeding work could be based upon these results which likewise could be used for estimating genetic relationships within this plant group by means of interspecific cross compatibility.     

Influence of the earthworm Aporrectodea trapezoides (Lumbricidae) on the colonization of alfalfa (Medicago sativa L.) roots by Rhizobium meliloti L5-30R and the survival of R. meliloti L5-30R in soil

A greenhouse study was performed to examine the ability of the earthworms Microscolex dubius and Aporrectodea trapezoides to transport Rhizobium meliloti L5-30R through soil. When R. meliloti L5-30R was inoculated into either ezi-mulch (a pelleted formulation of cereal-pea straw), oat hay, pea hay, or sheep dung and placed on the soil surface together with either A. trapezoides or M. dubius, >10⁴ colony-forming units (CFU) of R. meliloti L5-30R g^-1 soil were detected at 90 mm soil depth after 18 days. In the absence of earthworms, R. meliloti L5-30R was not detected at 90 mm soil depth after this time. In a second experiment using ezi-mulch as the inoculant material and in the presence of A. trapezoides (in a number equivalent to 471 or 785 m^-2), ca. 10³ CFU of R. meliloti L5-30R per 10 mm of alfalfa root were detected at 0–30, 30–60, and 60–90 mm soil depth after 18 days, while <3 CFU were detected per 10 mm of root in the absence of A. trapezoides. In a third experiment in which R. meliloti L5-30R was distributed evenly through soil at the start of the experiment, A. trapezoides (in a number equivalent to 157, 471, or 785 m^-2) significantly decreased the survival of L5-30R in soil after 40 days of incubation at 15°C, but not after 20 days. The decrease in survival of R. meliloti L5-30R was correlated with the density of A. trapezoides. These results demonstrate that A. trapezoides can increase root colonization of alfalfa by R. meliloti L5-30R, but may also reduce the ability of R. meliloti L5-30R to survive in soil.     

Phylogenetic relationships of Cajanus cajan (L.) Millsp. (pigeonpea) and its wild relatives based on seed protein profiles

Total seed storage protein of 9 accessions of cultivated C. cajan and 10 wild Cajanus species was reported and compared by sodium dodecyl sulphate polyacrylamide gel electrophoresis. A considerable variation was detected among the protein profiles of different accessions of C. cajan while those of wild species were very specific and distinctly different from each other. Relative similarities between various taxa were estimated by Jaccard's similarity index and cluster analysis was performed to produce a UPGMA dendrogram. The clustering of 10 wild species and C. cajan more or less agrees with their sectional classification and available data based on morphological characteristics, crossability, genome pairing in hybrids and nuclear RFLPs. The species closest to C. cajan is C. cajanifolia although the accessions of C. cajan also share some bands present in the profiles of C. scarabaeoides, C. goensis, C. lineatus, C. acutifolius and C. volubilis. This points towards polyphyletic origin of the cultigen which has been discussed in this paper.     

Neglected landraces of collard (Brassica oleracea L. var. viridis) from the Carolinas (USA)

A common garden crop grown in the coastal plain region of North and South Carolina (United States) is the non-heading, leafy green type of Brassica oleracea L. known as collard (B. oleracea L. subsp. oleracea convar. acephala (DC.) Alef. var. viridis L.). Predominantly a fall and winter vegetable in this region, collard is often the only green planting to be found in the yard or garden of a rural home during these cool seasons. Historically, the traditional collard patch and even commercial fields were planted with unique varieties perpetuated by individual seed savers, and collectively, the regional diversity for this crop was probably very significant for well over a century. Genetic erosion of this collard germplasm pool has been severe in recent decades as commercial hybrids have been adopted by both large-scale producers and home gardeners. Although a significant number of collard landraces are being perpetuated to this day, existing diversity among landraces still grown in the region is now in the hands of an aging population of seed savers who maintain germplasm through on-farm preservation. From 2003 to 2006, we explored the coastal plain region of North and South Carolina in search of collard gardens containing traditional landraces. Exploration trips were conducted mid-winter to early spring. About 90 samples of collard were obtained from seed savers during the course of this exploration. Observations of morphological differences of these landraces indicate that significant diversity exists in this group. Obtained landraces are being deposited into the U.S. plant introduction collection and will be available for future use. This preserved collection could prove to be an important new source of genes for B. oleracea improvement.     

Conservation of the genetic variation of Triticum tauschii (Coss.) Schmalh. (Aegilops squarrosa auct. non L.) in synthetic hexaploid wheats (T. turgidum L. s.lat. x T. tauschii; 2n=6x=42, AABBDD) and its potential utilization for wheat improvement

Triticum tauschii (Coss.) Schmalh. (Aegilops squarrosa auct. non L., 2n=2x=14, DD genome) with its diverse range of accessions and distribution provides a unique opportunity for exploiting novel genetic variability for wheat (T. aestivum L.) improvement associated with biotic/abiotic stress factors. From our working collection of 490 T. tauschii accessions we have so far produced 430 different synthetic hexaploids (2n=6x=42, AABBDD) resulting from the chromosome doubling of Triticum turgidum L. s. lat. x T. tauschii F₁ hybrids (each synthetic involving a different T. tauschii accession). We present here our results on hybrid production, plantlet regeneration, cytology, colchicine induced doubling of the 2n=3x=21 chromosome F1 hybrids, seed increase of the doubled progeny and screening for a biotic stress; Cochliobolus sativus Ito and Kuribay (syn. Helminthosporium sativum Pamm. King and Bakke); of 250 of these synthetic hexaploid (2n=6x=42) amphiploids. Application of the direct crossing methodology involving susceptible T. aestivum cultivars with resistant T. tauschii accessions is also alluded to.     

Studying the extent of genetic diversity among Gossypium arboreum L. genotypes/cultivars using DNA fingerprinting

Genetic diversity is an area of concern for sustaining crop yield. Information on genetic relatedness/diversity among Gossypium arboreum L. cultivars/genotypes is scanty. We have used random amplified polymorphic DNA (RAPD) analysis to assess the genetic divergence/relationship among 30 genotypes/cultivars of G. arboreum. Of 45 primers surveyed, 63% were polymorphic. Out of the total number of loci amplified, 36% were polymorphic. The calculated genetic similarity between the cultivars/genotypes was in the range of 47.05–98.73%. Two genotypes, HK-244 and Entry-17, were the most distantly related. The average genetic relatedness among all the genotypes was 80.46%. However, most of the cultivated varieties showed a close genetic relationship, indicating a narrow genetic base in comparison to the non-cultivated germplasm. The calculated coefficients were used to construct a dendrogram using the unweighted pair group of arithmetic means (UPGMA) algorithm, which grouped the genotypes/cultivars into two major and three smaller clusters. The study is the first comprehensive analysis of the genetic diversity of G. arboreum germplasm and identifies cultivars that will be useful in extending the genetic diversity of cultivated varieties and future genome mapping projects.     

Genetic diversity in cucumber (Cucumis sativus L.): I. A reevaluation of the U.S. germplasm collection

Genetic variation within the U.S. cucumber collection (Cucumis sativus var. sativus L. and var. hardwickii (Royle) Alef.) was assessed by examing the variation at 21 polymorphic isozyme loci and comparing the results of this investigation with a similar previous analysis of 14 loci. About 29% (15 of 51) of the enzyme systems examined in an initial survey were polymorphic. Seven loci (Ak-2, Ak-3, Fdp-1, Fdp-2, Mpi-1, Pep-gl and Skdh) which were not previously used to estimate genetic diversity, were assessed. On average, 1.4 loci were polymorphic per enzyme system and 2.2 alleles were present per polymorphic locus. The frequency of polymorphisms was relatively low for Fdp-1(2) (0.01), Mpi-1(1) (0.03), and Skdh(1) (0.02). Principal component and cluster analyses of allelic variation at polymorphic loci separated a diverse array of 757 cucumber accessions from the U.S. National Plant Germplasm Systesm's (NPGS) collection into distinct groups by country (45 nations examined). All accessions of C. s. var. sativus were isozymically distinct from C. s. var. hardwickii, which were themselves dissimilar from each other. Data suggest that C. s. var. hardwickii is not a feral derivative of extant C. s. var. sativus populations. The allelic profile of C. s. var. sativus accessions originating from Burma, Thailand, Indonesia, Hong Kong, Zimbabwe and Ethiopia were distinct from the other accessions examined. Allelic fixation has occurred at Pgd-2 in accessions from Burma, and at Ak-2 in accessions from Zimbabwe and Ethiopia. Some of the countries examined that were in close geographic proximity (e.g., Thailand, Indonesia and Hong Kong) contained accessions with similar isozyme profiles. Accessions are fixed for certain alleles [e.g., Gr(1) (100%), Fdp-1(1) (100%) and Mpi-2(2) (50%) for accessions from Thailand, Indonesia and Hong Kong]. Grouping countries by continent or sub-continent (i.e., North and South American, China, Eastern Europe, Western Europe) and by numbers of accessions examined (i.e., India/Burma, Iran, Japan, Turkey, and remaining accessions) was used to identify accessions with unique allozymic profiles [PIs 209064 (USA), 257486 (China), 188749 (Egypt), 285607 (Poland), 369717 (Yugoslavia), 357844 (Poland), 255936 (Netherlands), 183127 (India), 200818 (Burma), 200815 (Burma), 137836 (Iran), 227013 (Iran), 227235 (Iran), 451976 (Japan), 181752 (Syria), 181874 (Syria), 169383 (Turkey), 171613 (Turkey)].     

Competitive interaction among strains of Rhizobium leguminosarum bv. phaseoli in the nodulation of kidney beans (Phaseolus vulgaris L.)

We examined the competitiveness of five effective Rhizobium leguminosarum biovar phaseoli strains in the nodulation of kidney beans (Phaseolus vulgaris L.), either alone or in pairwise combination, against the indigenous strains. The results showed that the introduced Rhizobium sp. strains (B2, B17, B36, T2, or CIAT 652) occupying 64–79% of the total nodules (as single inocula) were more competitive in nodulation than the native rhizobia. However, the competitiveness of the individual Rhizobium sp. strain either increased or decreased when used in a pairwise combination of double-strain inocula. For example, strain B17, although quite competitive against the indigenous population (68% nodule occupancy), became poorly competitive in the presence of strain B2 (reduced from 68 to 2.5%). A similar reduction in nodule occupancy by strain B17 was observed in the presence of B36 or CIAT 652, indicating that two competitive strains may not always be compatible. These results suggest that it is important to co-select competitive as well as compatible rhizobia for multistrain inoculant formulation.     

RAPD and seed coat morphology variation in annual and perennial species of the genus Cicer L.

Molecular and morphological variation of six perennial and five annual species including domesticated chickpea, C. arietinum, were inferred on the basis of RAPD and S.E.M. seed coat features using three outgroup taxa (Lens ervoides, Lathyrus japonica and Pisum sativum). Of the 66 decamer arbitrary primers tested, eight primers revealed 87 informative fragments. Neighbor-joining cluster analysis using Jaccard's coefficient of similarity on the basis of polymorphic fragments indicated a narrow variation in C. arietinum and recognized two major clusters in the genus Cicer. The first one included four species of sect. Monocicer: C. echinospermum, C. arietinum, C. reticulatum and Iranian material of C. bijugum. The second cluster contained annual and perennial species belonging to sections Chamaecicer, Polycicer and Acanthocicer. The character state of morphological and ecological traits on the RAPD phenogram indicated no monophyletic incision. Our results suggested that the high genetic difference between annual and perennial species might be regarded as a rapid speciation of section Monocicer. Reconsideration of traditional classification of sections Polycicer and Acanthocicer is necessary. The Desi and Kabuli types of C. arietinum could not be separately grouped at the DNA level, and the low level of genetic variation of C. arietinum may result from a bottleneck during the domestication process.     

On the use of SSR markers for the genetic characterization of the <Emphasis Type="Italic">Agropyron cristatum</Emphasis> (L.) Gaertn. in Northern China

Genetic diversity of 69 populations of Agropyron cristatum (L.) Gaertn. originated from various regions of northern China was analyzed using 29 polymorphic microsatellite primers that were mapped on the wheat genome. The number of polymorphic bands ranged from 2 (Xgwm285, Xgwm43, Xgwm291, and Xgwm257) to 27 (Xgwm314) with an average of 10.480. The highest genetic diversity value was detected in the populations from Xinjiang Province (0.735), and the lowest was observed in populations from Qinghai Province (0.553). The proportion of diversity among and within regions was 16.9% and 83.1% of the total variation, respectively. According to the dendrogram generated by UPGMA cluster analysis based on Nei’s genetic distance matrix, all the populations of A. cristatum were distinctly clarified. At the Nei’s distance of 0.62, the populations were divided into 6 groups. The phenogram indicated that populations from similar ecogeographical regions were clustered together. The principal coordinate analysis showed that the populations from Inner Mongolia were more closely related to each other, and were less variable than the populations from Xinjiang Province.     

Cadmium-tolerant plant growth-promoting bacteria associated with the roots of Indian mustard (Brassica juncea L. Czern.)

Eleven cadmium-tolerant bacterial strains were isolated from the root zone of Indian mustard (Brassica juncea L. Czern.) seedlings grown in Cd-supplemented soils as well as sewage sludge and mining waste highly contaminated with Cd. The bacteria also showed increased tolerance to other metals including Zn, Cu, Ni and Co. The isolated strains included Variovorax paradoxus, Rhodococcus sp. and Flavobacterium sp., and were capable of stimulating root elongation of B. juncea seedlings either in the presence or absence of toxic Cd concentrations. Some of the strains produced indoles or siderophores, but none possessed C₂H₂-reduction activity. All the strains, except Flavobacterium sp. strain 5P-3, contained the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, which hydrolyses ACC (the immediate precursor of plant hormone ethylene) to NH₃ and α-ketobutyrate. V. paradoxus utilized ACC as a sole source of N or energy. A positive correlation between the in vitro ACC deaminase activity of the bacteria and their stimulating effect on root elongation suggested that utilization of ACC is an important bacterial trait determining root growth promotion. The isolated bacteria offer promise as inoculants to improve growth of the metal accumulating plant B. juncea in the presence of toxic Cd concentrations and for the development of plant-inoculant systems useful for phytoremediation of polluted soils.     

Genetic diversity of the African hexaploid species Solanum scabrum Mill. and Solanum nigrum L. (Solanaceae)

Two hexaploid species of Solanum sect. Solanum are present in Africa: Solanum scabrum and S. nigrum. Solanum scabrum is a widely cultivated species and is used as a leafy vegetable, as a source of medicine and as a source of ink dye. In previous studies a wide range of morphological diversity has been reported in this species and in some studies subspecies have been proposed. Subspecies are also recognized in S. nigrum. However, it has not been established whether or not the morphological differences are reflected at the genomic level. The present study applies AFLPs to study the genetic diversity in S. scabrum and its relationship to geographical provenance, morphological differences and the possible existence of subspecies within S. scabrum and S. nigrum. The data obtained were analyzed with cluster analysis (using UPGMA and NJ). The results indicate that the genetic variation within S. scabrum was higher within accessions than between accessions. Accessions did not cluster according to their geographical provenance, indicating that accessions from different geographical areas were not significantly different genetically. The clustering reflected neither morphological differences nor domestication status (cultivated or wild). The morphological differences exhibited by S. scabrum could be due to selection by farmers for different plant types. The AFLP derived clustering pattern did not segregate the subspecies recognized in S. scabrum and S. nigrum into separate subclusters.