Development of a hybrid variety system in marjoram (Origanum majorana L.)

20 accessions of marjoram (Origanum majorana L.)were characterized in two field experiments in Quedlinburg, Germany in 1997. The variation was assessed both on single plants as a base for the development of pollinator inbred lines of a prospective hybrid variety system and also on plots on a larger scale. The characterization comprised yield of leaf-flower fraction, content of essential oil and its proportion of cis-sabinene hydrate. The anther status of the regrowth after the herb harvest was used as an indicator of male fertility. The investigations revealed a high variability between and within accessions. The correlation of some traits is discussed as a clue to indirect selection. The yield rises with increasing bush diameter of the single plants and with longer vegetation periods caused by late flowering. Relations between the essential oil content and the duration of the vegetation period were not consistent and could be caused by the environment. There were no relations between the anther status and agronomical or physiological traits. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic diversity of garlic (Allium sativum L.) germplasm from China by fluorescent‐based AFLP,SSR and InDel markers

Garlic (Allium sativum L.), an asexually propagated crop, is an important vegetable and medicinal plant. China is the biggest garlic producer in the world; however, the genetic background of garlic from China is not well understood. In this study, population structure and clustering analysis of garlic germplasm was performed using amplified fragment length polymorphism (AFLP), simple sequence repeat (SSR) and insertion–deletion (InDel) markers. Among 212 accessions of garlic, genetic diversity analysis identified 546 alleles amplified by AFLP, SSR and InDel primers, and 492 of these were polymorphic. All accessions were divided into five groups by structure analysis and neighbor‐joining clustering. Most traits, including allicin content, were only slightly affected by population structure, which indicated that this germplasm can be used as populations for association mapping. The results provide a molecular basis for understanding the genetic diversity of the garlic germplasm preserved in China.     

Germplasm diversity and estimate of genetic advance of four morpho-physiological traits in a world collection of jute

Summary To improve jute productivity, locating of sources of suitable quantitative-trait genes in the recently acquired world jute collection was needed. Two hundred sixteen accessions of Corchorus capsularis and 192 accessions of C. olitorius were evaluated at a jute seed research station (87°60\s'E, 23°80\s'N) for four yield and quality linked morpho-physiological traits. The objectives were to estimate the germplasm diversity, phenotypic (PCV) and genetic (GCV) coefficients of variation, broad sense heritability (h²) and genetic advance (GA) with respect to origins and traits. Irrespective of origins all the traits showed more than 60–80% diversity in both species. Trait means of diversity were significant but not the origin means. Generally, only slightly higher PCV values than GCV were obtained for all the traits in both the species. High h² values ranging from 50% to more than 98% were also found. All the traits can be simultaneously utilized for genetic gain. Most of the C. olitorius accessions with two times higher GA estimates than those of the C. capsularis are likely to be more successful for that matter. Maximum genetic gain is expected from Mutants > China > Brazil > India > Thailand > Nepal > Burma in C. capsularis while from Thailand > Tanzania > Mutants > Kenya > Other countries in C. olitorius. C. capsularis mutants with high heterogenity for most of the traits should be useful for finding many rare alleles.     

Agronomic and qualitative traits of T. turgidum ssp. dicoccum genotypes cultivated in Italy

Summary The increasing popularity of organic agriculture and health food products has led to a renewed interest in hulled wheat species such as emmer (Triticum turgidum ssp. dicoccumSchubler). Knowledge on agronomic and quality traits is required for effective and efficient use of germplasm collections in breeding programs. The objective of this study was to estimate agronomic and grain quality traits of emmer wheat cultivated in Italy. A total of 20 emmer accessions consisting of landraces, breeding lines or cultivars selected from landraces and modern cultivars were examined under low input conditions. The study was conducted for three successive years (2002–2004) at one location of Southern Italy (Foggia). The entries were characterized for agronomic and qualitative traits [grain yield (t ha⁻¹), thousand grain weight (g), test weight (kg hl⁻¹), grain protein content (%), HMWG composition, dry gluten content (%), gluten index and yellow index, alveograph indices and Total Organic Matter (TOM) on cooked pasta]. The results showed a large genetic variability for most of the traits measured and, even if most of the accessions showed inferior bread- and pasta-making performance, modern cultivars exhibited improved quality traits with some potential to perform healthy and tasty food.     

A new method for selecting cytochimeras by the maximum number of nucleoli per cell in Allium wakegi Araki and A. fistulosum L.

Summary A new method for determining ploidy levels in cytochimeral plants was developed by examining the maximum number of nucleoli per cell. Colchicine-treated plants of Allium wakegi Araki and A. fistulosum L., which have different ploidy levels in the first (LI), the second (LII), and the third (LIII) germ layer, were used together with untreated 2-2-2 plants of the same species. Nucleoli in guard cells for LI and in mesophyll cells for LII were stained in a 50% AgNO₃ aqueous solution at 55° C for three hours under dark, humid conditions. In both species the ploidy levels of LI determined by the maximum number of nucleoli per guard cell accorded well with those determined by guard cell length. In A. fistulosum the ploidy levels of LII determined by the maximum number of nucleoli per mesophyll cell clearly agreed with those determined by pollen size. This method provided more precise and efficient identification for LI and LII ploidy than the conventional methods of using guard cell length for LI and pollen size for LII.     

Ploidy races in Actinidia chinensis

Summary Ploidy levels were examined in 26 accessions of Actinidia chinensis: 20 accessions were diploid (2n=2x=58) and 6 accessions were tetraploid (2n=4x=116). There was no evidence of variation in ploidy level within an accession. Our results are consistent with tetraploid A. chinensis coming from a restricted part of China.Interploid crosses within A. chinensis produced only low numbers of seedlings which were mainly triploid. Crossing hexaploid A. deliciosa with pollen of tetraploid A. chinensis produced a large family of plants and those checked were pentaploid.Counts on 83 genotypes of different ploidy levels (2x, 3x, 4x, and 5x) confirmed that the basic chromosome number in Actinidia is 29.     

Use of the gene pools of Triticum turgidum ssp. dicoccoides and Aegilops squarrosa for the breeding of common wheat (T. aestivum), through chromosome-doubled hybrids

Summary Triticum turgidum ssp. dicoccoides (wild emmer wheat, AABB, 2n=28) and Aegilops squarrosa (goat grass, DD, 2n=14) comprise a rich reservoir of valuable genetic material, which could be useful for the breeding of common wheat (T. aestivum, AABBDD, 2n=42). Many accessions of both wild species, most of them selected for resistance to stripe rust, were used to make amphiploids. Two strategies were applied: (1) the production of autopolyploid cytotypes of the wild species, followed by hybridisation, and (2) the production of allotriploid interspecific hybrids, followed by doubling of the number of chromosomes. The first route was unsuccessful because of failure of the crosses between the autopolyploid cytotypes, possibly due to incongruity between the two species and to reduced fertility in the autopolyploid cytotypes. The second route yielded the desired synthetic hexaploids. However, the rate of success of the crosses was low and there were great differences between years, and within years between crosses. Embryo rescue was applied to obtain the primary hybrids (2n=21), which were highly sterile and had on average 0.3 bivalents and 20.4 univalents per pollen mother cell. Various abnormalities were recorded. Doubling of the number of chromosomes sometimes occurred spontaneously or was brought about by colchicine treatment. The large scale of the interspecific hybridisation programme ensured that one-third of the female and one-sixth of the male accessions were represented in the synthetic hexaploids.     

Pollen grain size in four ploidy levels of genusAvena

Summary Pollen grain size in many genera positively correlated with chromosome number. In this study, oat (Avena) pollen grain size was examined in diploids (2×=14, one species, for accessions), tetraploids (4×=28, five species, 20 accessions), hexaploids (6×=42, one species, eight cultivars), and in 10 octoploid (8×=56) accessions. Mature anthers ready to dehisce pollen were sampled from one to six plants per accession, and pollen grains were squeezed out of the anther with tweezers. Oat pollen grains are slightly elliptical, and the length of the major axis was found to be highly correlated with the minor axis width (r=0.94^**). Pollen grain length, 39.3 m for diploids, 41.3 m for tetraploids, 47.0 m for hexaploids, and 48.8 m for octoploids, was positively correlated (r=0.86^**) with ploidy level. No genomic or species effects appeared to influence this trait. Only tetraploidAvena vaviloviana accession PI 412767 produced two distinct class sizes of pollen grains, 99% normal (43.0 m) and 1% large (52.7 m).     

Heritability estimates of spaced-plant traits in three perennial ryegrass (Lolium perenne L.) cultivars

Summary Seed yield in perennial ryegrass is low and unpredictable. Spaced-plant traits suitable for indirect selection for total seed yield in drilled plots would be very useful. The objectives of this investigation were to evaluate genetic variation for seed yield components and other traits among clones from three perennial ryegrass cultivars differing in seed yield and their open-pollinated progenies. Per cultivar, a random set of 50 genotypes was cloned and on each genotype seed was generated by open pollination. Clonal ramets of the parents were observed for 17 traits in 1986 at two locations. In 1987 and 1988, parents and progenies were observed as single plants in a randomized complete block design with two replications. There was little cultivar-environment interaction for most traits. The parents differed significantly for almost all traits. Half-sib (HS) families differed for only three to five traits. Broad-sense heritabilities (h² _b), based on variance components of the parents, were moderate to high; earliness had the highest h_b ². Narrow-sense heritabilities (h² _n), based on variance components among HS-families, were low to moderate and mostly not significant; for most traits h² _n estimates varied between years and cultivars. Flag leaf width and date of first anthesis showed the highest h² _n. Narrow-sense heritability estimates from parent-offspring regressions (h² _nPO) ranged from non-significant to high, depending on year and cultivar; they were generally higher than the corresponding h² _n estimates. Generally, h² _nPO was highest for earliness, flag leaf width, ear length and the number of spikelets per ear. Breeding methods that capitalize on additive genetic variance, such as mass selection, should result in improvement for these traits.     

New sources of major gene resistance in Lactuca to Bremia lactucae

Summary A total of 1789 accessions of several lettuce collections was screened to find new major gene resistance to the downy mildew fungus Bremia lactucae Regel. The accessions belonged to the species Lactuca sativa (N=1288), L. serriola (N=399), L. saligna (N=52) and L. virosa (N=50). A total of 20 races of B. lactucae were used, 14 of which were NL-races, isolated from cultivated lettuce in the Netherlands. The other six races were isolated from wild L. serriola in Czechoslovakia. The accessions were initially screened with two races: NL1 and NL3. Accessions with resistance to one or both of these races were tested with the other races. Phenotypes with new resistance were found in accessions of all four Lactuca species. Of L. sativa, four accessions were found with resistance phenotypes that could not be explained by combinations of known major genes. Many accessions of L. serriola had resistance phenotypes that indicated the presence of unknown resistance genes. All interactions between accessions of L. saligna and races of B. lactucae were incompatible in leaf disc tests, except for four accessions, which showed some sporulation with race NL6. Several accessions of L. virosa were resistant to all races used. Other accessions of L. virosa gave a race-specific interaction with B. lactucae.     

Pre- and post-fertilization barriers to backcrossing the interspecific hybrid between Allium fistulosum L. and A. cepa L. with A. cepa

Summary To facilitate the introgression of desirable traits of Allium fistulosum into the genome of A. cepa, several accessions of the hybrid between these species were pollinated with A. cepa as the recurrent parent, and in vitro ovary and ovule culture were performed to obtain an increase in the recovery of backcross progeny. Compared to the results obtained from seed development in planta, the increase in the number of backcross progeny was generally very limited, and in some cases even a decrease was found. Raising the sucrose concentration in the ovary culture medium resulted in a higher frequency of ovules developing back seed coats but this was not followed by an increase in the number of backcross progeny obtained. Pollen tube growth of A. cepa was disturbed in the styles of the interspecific hybrids. Per ovule, frequencies of micropylar penetration exceeded frequencies of backcross progeny only to a limited extent. Hence, it was concluded that in the tested interspecific hybrid accessions the attainable gain in viable backcross progeny by the application of in vitro culture techniques is limited by strong pre-fertilization barriers acting at the level of stylar incongruity.     

Ploidy analysis in water yam, Dioscorea alata L. germplasm

Poor reproductive development in yams (Dioscorea spp.) has often been attributed to the polyploid nature of the crop. In this study, flow cytometry was used to determine the ploidy level of 53 accessions of Dioscorea alata, mostly from West African countries, Chad and Puerto Rico. Nuclei were isolated from young leaf material and stained with DAPI(4,6-diamidino-2-phenylindole). The nuclear genome size (2C) was measured as an indicator of the ploidy level. Dioscorea rotundata genotypes with known ploidy levels were used as standards. The results showed that the majority of plants were hexaploid (84.9%) with a smaller percentage of tetraploids (15.1%). A higher number of male plants were hexaploid than tetraploids. This is at variance with earlier findings, which reported that hexaploid male plants are rare. Higher ploidy levels were not directly related to sparse or erratic flowering as previously reported as profuse flowering occurred in some male hexaploid accessions. These findings have important implications for yam breeding in relation to yam genetic resources. This revised version was published online in August 2006 with corrections to the Cover Date.     

Resistance to stripe rust in Triticum turgidum,T. tauschii and their synthetic hexaploids

Resistance to stripe rust (caused by Puccinia striiformis Westend.) of 34 Triticum turgidum L. var.durum, 278 T. tauschii, and 267 synthetic hexaploid wheats (T. turgidum x T. tauschii) was evaluated at the seedling stage in the greenhouse and at the adult-plant stage at two field locations. Mexican pathotype 14E14 was used in all studies. Seedling resistance, expressed as low infection type, was present in all three species. One hundred and twenty-eight (46%) accessions of T. tauschii, 8 (23%) of T. turgidum and 31 (12%) of synthetic hexaploid wheats were highly resistant as seedlings. In the field tests, resistance was evaluated by estimating area under disease progress curve (AUDPC). Synthetic hexaploid wheats showed a wide range of variability for disease responses in both greenhouse and field tests, indicating the presence of a number of genes for resistance. In general, genotypes with seedling resistance were also found to be resistant as adult plants. Genotypes, which were susceptible or intermediate as seedlings but resistant as adult plants, were present in both T. turgidum and the synthetic hexaploids. Resistances from either T. turgidum or T. tauschii or both were identified in the synthetic hexaploids in this study. These new sources of resistance could be incorporated into cultivated hexaploid wheats to increase the existing gene pool of resistance to stripe rust.     

Evaluation of a lucerne germplasm collection in relation to traits conferring grazing tolerance

Summary A collection of 90 accessions of different germplasm groups from the Medicago sativa complex was evaluated at Lodi, Italy, for dry-matter yield, time to anthesis, height of regrowth, plant diameter, stem density, vegetative recovery after winter, and presence of deep-set crown and ability to spread with creeping roots or rhizomes, these latter characters possibly contributing to grazing tolerance. The germplasm groups proved rather distinct for these traits, but all included types potentially suitable for grazing. Interesting types combining deep-set crown and high yield occurred mainly in subsp. x varia and materials originated from artificial crosses involving at various extent the subspecies falcata, sativa and x varia. Though belonging to subsp. sativa, mielga wild populations from Spain had aerial traits similar to those of the long-dormant, low-yielding subsp. falcata. Deep-crowned plants had greater plant diameter than shallow-crowned plants, and could be categorised into four distinct top-growth models according to their habit and vigour. One of these models combined spreading ability with high yield. The about 150 plants selected for their combination of deep crown, wide diameter, and good yield were characterised by a branch-rooted system. There was general correspondence between top-growth and root morphology of each model. Of the four deep-crowned models, three had rhizomes, with wide range of underground development and morphology, while the fourth had creeping roots. The latter model was the most rare among the examined accessions, never appearing in either cultivated or wild subsp. sativa. The implications of the results on the development of grazing-tolerant lucerne varieties are discussed.     

Starch characterisation and variability in GBSS loci of synthetic hexaploid wheats and their durum and <Emphasis Type="Italic">Aegilops tauschii</Emphasis> parents

Greater variability in starch properties is found in lower ploidy wheats than in commercial hexaploid wheats. This paper reports on the starch properties and variability in granule bound starch synthase (GBSS) loci of 17 diploid (Aegilops tauschii) and 12 tetraploid (durums) potential progenitors of wheat, compared with 29 synthetic hexaploid wheats produced from such progenitors. Starch properties examined were granule size distribution, swelling power, amylose content, gelatinisation and amylose-lipid dissociation properties. A PCR screening method was able to detect the presence or absence of each of the three GBSS genes. It also detected polymorphisms in eight diploids and nine hexaploids, all displaying the same 25 bases deletion in the D genome allele of GBSS. Two tetraploids and five hexaploids were null 4A for GBSS. There was little difference in the amylose contents and amylose-lipid dissociation peak temperatures of the synthetic hexaploids and the lower ploidy wheats. The synthetic hexaploids showed intermediate swelling power values with the durums giving the highest swelling powers. The durums also had higher B granule contents than the A. tauschii accessions, but not as high as the synthetics. However, the A. tauschii samples gave the highest gelatinisation peak temperatures. The presence of the null 4A mutation was positively correlated with swelling power, amylose content and DSC measurements. The new smaller D genome allele of GBSS was associated with slightly higher swelling power. These results confirm the value of wheat progenitor lines as sources of new starch properties for hexaploid wheat. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Heterosis breeding in Indian mustard (Brassica juncea L. Czern & Coss): Analysis of component characters contributing to heterosis for yield

Summary Divergence of 25 accessions of Brassica juncea of Indian, CIS (Commonwealth of Independent States, former USSR) and synthetic origin was studied by D² analysis. On the basis of divergence, ten accessions were selected and crossed in a diallel fashion without reciprocals to study the combining ability and heterosis. None of the accessions was found to be a good general combiner for all the nine quantitative characters that were studied. Significant heterosis over better parent for single plant yield was recorded in CIS x Indian and synthetic x CIS crosses (5 each) followed by Indian x synthetic types (3). The analysis of component characters showed that the mean performance of the majority of hybrids was intermediate for five out of six yield attributing traits, thus exhibiting dominance or partial dominance effect. To estimate the contribution of such yield attributing traits towards heterosis for yield, a comparison was made among three parameters viz. heterosis over mid parent (MP), better parent (BP) and better yielding parent (BYP) of the concerned hybrid. It was observed that estimation of heterosis from BYP was a more accurate method to determine the contribution of component characters towards yield heterosis than the analysis based on MP and BP. From the component character analysis, it was concluded that characters like number of primary and secondary branches, number of siliqua per plant and siliqua density contributed significantly towards heterosis in yield. Plot level yield trials of two selected hybrids (Skorospieka II x RH30 and Donskaja IV x Varuna) over two growing seasons revealed 29.4 to 91.8% heterosis over BYP.     

Estimation of phenotypic divergence in a collection of <Emphasis Type="Italic">Capsicum</Emphasis> species for yield-related traits

Phenotypic divergence among the 24 accessions belonging to a collection of six species of Capsicum from different geoclimatic regions available in field gene bank of CIMAP, Lucknow, India, was quantified by multivariate analysis for 12 quantitative and qualitative traits. Based on their values, all 24 accessions were grouped into six clusters such that the genetic stocks within cluster had smaller D ² values among themselves than those belonging to different clusters. The accessions of Capsicum annuum were distributed in different clusters in morphotyping representing different species, suggesting that taxonomic characteristics are not always related to agronomic traits. No parallelism/association was found between geographical and phenotypic diversity. Accessions 15 and 23 (clusters V and VI, respectively) had distinct identity. The three characteristics that played the greatest role in differentiation were fruit diameter, number of fruits per plant, and leaf diameter, which can be utilized as conventional/morphological markers for the improvement of chilli yield and obtaining good segregants in chilli breeding programs.     

Genetic distance between Triticum timopheevi Zhuk., T. aramticum Jakubz. and T. aestivum L.

The genetic distances between two cultivated wheat (Triticum aestivum L.) varieties (Martonvásári 9, Martonvásári 15), a Martonvásári 9 line possessing the crossability gene krl, and 21 accessions of T. timopheevi Zhuk. and T. araraticum Jakubz. were estimated, based on agro-morphological, physiological and biochemical analysis of data. Cluster analysis based on Mahalanobis' D² values was applied. All 21 accessions of T. timopheevi and T. araraticum could be classified into eight clusters. Clusters I and II consisted of all the T. timopheevi, while T. araraticum was located in six clusters. Discriminant analysis was applied to test significant differences between cluster pairs. The genetic distance (GD) based on the electrophoretic data of gliadins indicated two types of electrophoregrams in T. timopheevvi, distinguished as groups A and B. T. araraticum accessions were variable as regards the spectra. Mean, minimum and maximum GD were estimated within and between different wheat groups based on acid polyacrylamide gel electrophoresis.     

Reaction of wild species of the geneus Lens to drought

Summary Susceptibility to drought stress is a key factor in dry land lentil (Lens culinaris Medikus) production in the Mediterranean region of West Asia and North Africa. This study examined the response to drought stress of 121 accessions representing all subspecies of the genus Lens; cultivated, and the wild L. culinaris ssp. orientalis (Boiss.) Ponert, L. culinaris ssp. odemensis (Ladiz.), L. nigricans M.B. Godr. ssp. nigricans Godr. and L. nigricans ssp. ervoides (Brign.) Ladiz. for their potential use in breeding for dry land conditions. Accessions were grown under two moisture regimes (dry land and dry land plus supplemental irrigation) at Breda, Syria during the 1990–91 and 1991–92 seasons. The cultivated lentil had markedly superior seed and straw production than did the wild Lens species. Time to flowering accounted for less than 10% of the variation in yield of wild accessions under rainfed conditions in the two seasons, showing that, in contrast to the cultivated germplasm, drought escape was relatively unimportant in wild lentil. Performance under drought in wild lentil, measured in terms of dry land seed yield or drought susceptibility index (S), was randomly distributed among collection locations with little relation to collection site aridity. Direct selection of wild lentil germplasm for biomass yield under dry conditions is of little value and an evaluation of wild accessions in hybrid combination is needed.     

Chromosome and cytoplasm analyses of somatic hybrids between onion (Allium cepa L.) and garlic (A. sativum L.)

Chromosomes and cytoplasms were analyzed in two lines of a somatic hybrid between onion (Allium cepa L.) and garlic (A. sativum L.). One line of the somatic hybrid had 40 chromosomes and the other 41chromosomes. Genomic in situhybridization successfully revealed the chromosome constitution of the two lines. One line had 20 chromosomes from onion and17 chromosomes from garlic, and the other had 21 chromosomes from onion and 17chromosomes from garlic. Interestingly, both lines had three chimeric chromosomes. PCR-RFLP analyses of chloroplast and mitochondrial DNAs of both lines showed that these were identical to the onion parent. This revised version was published online in July 2006 with corrections to the Cover Date.