Genetic diversity revealed in the apomictic fruit species Garcinia mangostana L. (mangosteen)

The novel molecular marker technique Randomly Amplified DNA Fingerprinting (RAF)was used to survey genetic relationships between 37 accessions of the tropical fruit G. mangostana (mangosteen) and among 11 accessions from eight other Garcinia species. Although mangosteen is believed to reproduce exclusively through apomixis, our results show that considerable genetic diversity exists within G. mangostana and between other Garcinia species. Among the 37G. mangostana accessions examined, nine different genotypes were identified which clustered into three distinct groups based on correspondence analysis(reciprocal averaging). For 26 (70%) of the accessions no marker variation was detected over 530 loci screened. A further eight (22%) accessions exhibited very low levels of variation (0.2–1%) suggesting at least one well conserved mangosteen genotype. The remaining three accessions (8%) showed extensive variation (22–31%)compared with the majority of accessions. The three mangosteen groups were 63–70% dissimilar to the other Garciniaspecies investigated. The genetic diversity identified in this research will assist in the conservation of Garciniagermplasm and provides a valuable framework for the genetic improvement of mangosteen. This revised version was published online in August 2006 with corrections to the Cover Date.     

Characterizing morphological traits and estimating genetic relationship for intermediate soybean collected from South Korea

Twenty‐two wild, 16 intermediate and 20 cultivated soybean varieties were used to analyse relationships among the species of subgenus Soja, genus Glycine using 11 morphological traits and simple sequence repeat (SSR) markers. These genotypes using eleven agronomic characteristics were divided into three clusters: cluster I included 20 G. max, cluster II included 12 intermediate, and cluster III included 22 G. soja and four intermediate lines. Genetic relationships among the species of subgenus Soja showed three distinct clusters. Cluster I consisted of 20 G. max cultivars and two intermediate type lines, and cluster II consisted of 13 intermediate type and two G. soja lines; however, cluster III consisted of 20 G. soja and one intermediate type lines. These phenotypic and genetic data suggest that the intermediate type lines could be distinguished between G. max and G. soja lines. However, the intermediate type could not be classified as a new species.     

Each species of Glycine collected in Taiwan has a unique seed protein pattern

Several annual and perennial species in the genus Glycine Willd., including G. soja, long-pod G. tomentella, short-pod G. tomentella and G. tabacina, collected in Taiwan and nearby islands were studied for variations of their seed proteins. SDS-PAGE and Western blotting were used to analyze the total proteins, the heat soluble proteins, six seed maturation proteins (GmPMs) and one seed storage protein. The various species had different patterns of seed heat soluble proteins. In addition,each species of Glycine collected in Taiwan exhibited unique seed maturation protein patterns. They had several cross-reactive polypeptides recognized by specific antibodies against GmPM1, GmPM2 and GmPM8, but only one polypeptide recognized by antibodies against GmPM4, GmPM5 and MP130. The long pod G. tomentella, which has been suggested as a new species and renamed as G. dolichocarpa, could be distinct from the short pod G. tomentella on the basis of the analysis of these biochemical markers. It is also indicated that these GmPM antibodies may be used to distinguish between and within other Glycine species. This revised version was published online in July 2006 with corrections to the Cover Date.     

Investigation on pre-zygotic barriers in the interspecific crosses involving Gossypium barbadense and four diploid wild species

Interspecific hybridisation has played significant role in the improvement of economically useful traits such as productivity, earliness, fibre quality and resistance to pests and diseases in cotton. However, wide crosses are often limited by the operation of either pre or/and post-fertilization barriers. The present study on pollen tube behaviour of four diploid wild species viz., G. triphyllum, G. davidsonii, G. thurberi and G. armourianum in the pistils of G. barbadense was taken up to determine the extent of pre-zygotic barriers operating in these crosses. High rate of pollen germination (∼80%) and normal growth of pollen tubes were observed upon selfing of both G. barbadense and four wild species. Pollen tubes reached the pistils and fertilization was accomplished within 8 HAP in all the five parental species. In the interspecific crosses, pollen germination was normal in the cross involving G. armourianum and drastically inhibited in the crosses involving G. triphyllum, G. davidsonii and G. thurberi. Even though delayed pollen tube growth was a general feature in all the four crosses, successful fertilization was observed only in the cross involving G. armourianum. In crosses involving G. triphyllum, G. davidsonii and G. thurberi, pollen tubes failed to reach the ovary even at 24 HAP due to the presence of strong stylar and ovarian incompatibility. Abnormalities in pollen tubes such as swelling, twisting, intense callose plug formation, breakage, branching and reverse orientation were frequently observed among the incompatible crosses.     

Use of morphological,molecular markers and cytology to differentiate between closely related <Emphasis Type="Italic">Gaura coccinea,G. drummondii</Emphasis> for breeding purposes

Collection of wild species is critical to increase crop germplasm gene pools. Gaura coccinea has been identified as an important source of cold tolerance (winter hardiness) for hybridization with non-cold tolerant G. lindheimeri. Identification of species in the wild is often complicated by diagnostic, morphological characteristics that may not be present at the time of collection. G. drummondii, however, can be misidentified as G. coccinea even when using some diagnostic and quantitative traits. Therefore, additional methods of distinguishing between the species are needed. Fifteen populations of both G. coccinea and G. drummondii collected for potential breeding purposes in Texas, California, and Minnesota were used to identify species-specific molecular markers and morphological characteristics. A dendrogram based on randomly amplified polymorphic DNA (RAPD) markers separated the genotypes into two groups, G. coccinea and G. drummondii. One unique RAPD marker was identified in all G. drummondii genotypes, but absent in G. coccinea. Dendrograms based on morphological data separated genotypes into three distinct groups: G. coccinea, G. drummondii, and G. sp. (393-1). Petal/sepal lengths and leaf width were smaller in G. coccinea, while fruit/stipe lengths were smaller in both G. coccinea and genotype 393-1. Cytological analysis of G. coccinea confirmed that most populations were tetraploid (2n = 4x = 28) with one hexaploid (2n = 6x = 42) genotype from Texas (1000-1). G. drummondii were primarily tetraploid (2n = 4x = 28). Occasional triploids were found. These markers, along with screening for cold tolerance, will allow for accurate identification of G. coccinea genotypes for hybridization with G. lindheimeri.     

Interspecific hybridization in Gossypium L.: characterization of progenies with different ploidy‐confirmed multigenomic backgrounds

Cytological and molecular investigations were undertaken for parent and progeny derived from a trispecific line [2(Gossypium arboreum × G. anomalum) × G. hirsutum var. BWR], which was crossed with G. hirsutum var. JLH168. Cytomorphological analysis of the F₁ (G. arboreum × G. anomalum), its amphidiploid and progeny from trispecies hybrid showed distorted ploidy segregation with monovalents to hexavalents and high intergenomic (small A₂ and large B₁) allosynthetic chromosome pairing. Microsatellite analysis identified three fragments associated with G. arboreum and G. anomalum and six fragments associated with G. hirsutum in derivates of the trispecies line × G. hirsutum var. JLH168. Inter‐Retrotransposon Amplified Polymorphism (IRAP) analysis revealed fragments of G. arboreum and G. anomalum, only in F₁ and amphidiploid. Chromosomal association and microsatellite analysis of three progeny genotypes (i.e. haploid, hexaploid and tetraploid no. 1) confirmed that they share multigenomic background from the three cotton species (A₂, A_hD_h and B₁ genome). The interspecific hybrid cotton genotypes studied are likely to be useful for the introgression of genes from diploid species to commercial upland cultivars.     

A set of differential Glycine hosts for the identification of races of Phakopsora pachyrhizi Syd.

Summary Variation in the responses of a wide range of accessions of four native Australian species of Glycine (viz. G. canescens, G. clandestina, G. tabacina and G. tomentella) to infection by eight Australian isolates of Phakopsora pachyrhizi was analyzed.Differences in the infection type responses of the various wild Glycine species were sufficient to recognize six different virulence combinations amongst the eight pathogen isolates.A set of differential hosts useful in the identification of different races of the pathogen is presented to facilitate further examination of the virulence structure of the pathogen population.     

Evaluation of wild perennial Glycine species for resistance to soybean cyst nematode and soybean rust

The genetic base for soybean cultivars is narrow compared to most other crop species. Twenty-seven wild perennial Glycine species comprise the tertiary gene pool to soybean that may contain many genes of economic importance for soybean improvement. We evaluated 16 accessions of G. argyrea, G. clandestina, G. dolichocarpa, and G. tomentella for resistance to Heterodera glycines (HG), also known as the soybean cyst nematode, and to multiple isolates of Phakopsora pachyrhizi, the causal fungus of soybean rust. All 16 accessions were classified as resistant to H. glycines HG Type 2.5.7, based on number of cysts per root mass with plant introductions (PIs) 483227, 509501, 563892, and 573064 (all G. tomentella) void of any cysts indicating no reproduction by this pest. All 16 accessions had an immune reaction to one isolate of P. pachyrhizi. Regardless of isolate, no sporulating uredinia were observed on G. argyrea (PI 505151) and G. tomentella (PIs 483227, 509501, and 573064). These results demonstrate that some accessions within the perennial Glycine species harbour resistance to both H. glycines and P. pachyrhizi and would be good candidates for wide hybridization programs seeking to transfer potentially unique multiple resistance genes into soybean.     

New sources of resistance to the potato cyst nematodes Globodera pallida and G. rostochiensis in the Commonwealth Potato Collection

The Commonwealth Potato Collection contains 77 species following the incorporation of the personal collection of Professor JG Hawkes. The material originates from several expeditions to the Americas and represents a potentially valuable source of resistance to pests and pathogens, including potato cyst nematodes (PCN). The germplasm from the Hawkes collection screened in this study included taxa mainly from Mexico, Bolivia, Argentina and Peru. Seedlings of 198 accessions, from 63 different species were screened for reaction to the PCN species G. pallida and G. rostochiensis. Of the 198 accessions tested, 56% contained G. pallida-resistant clones and 53% contained clones resistant to G. rostochiensis. Twelve species in this survey are believed to contain novel, previously unreported sources of resistance. The geographical distribution of resistance indicated a contrast between the two PCN species. Although, as in previous studies, resistance to G. rostochiensis was centred on Bolivia and Argentina, G. pallida resistance was found across the geographical range of tuber-bearing Solanum. The possibility of cross-resistance arising from selective pressure from the more northern species G. mexicana is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Are Beta procumbens Chr. Sm. and Beta webbiana Moq. Different Species?

Different Origins of Beta procumbens and B. webbiana, which are wild species of the section Procumbentes, were investigated by means of electrophoretical techniques. The isozyme patterns did not show any differences between the two species. Assignment of accessions to either one of the two species was not possible using the differences occurring in the banding patterns of some enzyme systems. One can raise the question, therefore if the classification of B. procumbens and B. Webbiana into two species is justified.     

Alien chromosome transmission and somatic elimination in monosomic addition lines of Gossypium australe F. Muell in G. hirsutum L.

The efficiency of using monosomic alien addition lines (MAALs) to introgress agronomical traits of interest carried by wild diploid Gossypium species into the main cultivated cotton species G. hirsutum depends on the opportunities of confronting the alien chromosome with the recipient background genome at each generation and on the occurrence of translocations and homoeologous recombinations. The selfed-progeny of five MAALs of G. australe in G. hirsutum was screened with SSR markers to determine the transmission frequency of the alien chromosome and monitor its integrity. Three MAALs revealed a transmission frequency significantly lower than the expected ratio and one MAAL presented an exclusive transmission of the additional chromosome. In these four MAAL the alien chromosome was transmitted almost unaltered. With the fifth MAAL the alien chromosome was normally transmitted but was altered in half of the plants carrying it. In one MAAL, normally carrying brown fiber, the emergence of some plants carrying white and brown fiber revealed the somatic elimination of the additional chromosome. The loss of this chromosome seems to be triggered by its deletion.     

Kunitz trypsin inhibitor polymorphism in the Korean wild soybean (Glycine soja Sieb. & Zucc.)

Kunitz trypsin inhibitor (KTi) in 1368 accessions of wild soybean (Glycine soja Sieb. & Zucc.), collected from three regions of Korea, was examined for allelic diversity and geographical distribution. Five electrophoretically distinguishable KTi forms were detected: three were common (Tia, Tib and Tia/Tib) and two were previously unreported (Tib^i7‐1 and Tibⁱ⁵). The Tia allele was predominant (93.49%). Alleles Tib, Tib^i7‐1 and Tibⁱ⁵ were detected with the frequencies of 3.47, 0.55 and 0.11%, respectively. The heterozygous form (Tia/Tib) was detected with the frequency of 2.26%. The nucleotide sequence of Tib^i7‐1 was identical to that of the Tib‐derived variant allele Tif, with the exception of three nucleotides: A→G at position +244, A→C at position +286 and G→C at position +601. The latter two were similar to Tia, suggesting that Tib^i7‐1 is an intermediate allele between Tia and Tib. The gene for Tibⁱ⁵ showed 100% similarity with the Japanese intermediate allele Tibⁱ⁵. This study demonstrates that Korean wild soybeans are remarkably rich source of new KTi alleles not reported before.     

Pollen donor impact on progenies of pseudogamous blackberries (Rubus subgen. Rubus)

A series of intra- and interspecific crosses in Rubus was evaluated with DNA markers to assess the proportion of apomictically vs. sexually derived progeny plants. The species were well separated from each other with these markers and the interspecific hybrids were easy to ascertain. Ten plants each were derived by selfing of R. hartmanni, R. polyanthemus and R. vestitus, and evaluated with RFLP. Of these plants, only one R. hartmanni plant appeared to be sexually derived, whereas the remainder appeared to have arisen by apomixis. Between 10 and 19 progeny plants, derived by open pollination of R. Hartmanni, R. infestus, R. laciniatus and R. vestitus, respectively (total of 63plants), were evaluated with RFLP. Of these, 6 plants (approx. 10%) showed as lightly deviating band pattern, which may indicate sexual seed set but could also result from experimental artefacts. The three species combinations 1) R. hartmanni and R. sprengelii, 2) R. infestus and R. vestitus, and 3)R. laciniatus and R. polyanthemus were cross-pollinated reciprocally and the resulting progenies evaluated with RAPD (combinations 1 and 2)and leaf shape (combination 3). Combination1 produced 20% (3 out of 15 progenies)sexually derived progenies, combination 2produced 100% (26 progenies) and combination 3 produced 64% (16 out of 26progenies), respectively. The hybrid progenies appeared to have been derived through pollination of unreduced as well as reduced egg cells. The ability to produce interspecific hybrid progenies is most probably dependent upon the species combination. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic variability for seed oil content and seed index in some wild species and perennial races of cotton

A 3‐year study was made on genetic variability of seed oil content and seed index with 20 wild species, two cultivated species and six perennial races of Gossypium arboreum cotton maintained at the Central Institute for Cotton Research, Nagpur, India. The mean seed oil content varied from 10.26 to 22.89% in 22 species of Gossypium and six races of G. arboreum. In this material the weight of delinted seed varied from 43.33 to 54.54 mg/seed. The highest seed oil content was recorded in the species G. lobatum followed by G. harknessii. On average, for both traits, the means were higher for G. arboreum and its races. However, G. africanum and G. harknessii reached the level of G. arboreum and its races for seed weight, while five wild species surpassed the best races and G. arboreum in seed oil content, among them was G. harknessii. To breed simultaneously for seed oil content and seed weight, crosses between races of G. arboreum and wild species of Gossypium seem to be promising.     

Identifying lettuce species (Lactuca subsect. Lactuca, Asteraceae): A practical application of flow cytometry

The wild lettuce species L. serriola, L. saligna, and L. virosa are important genitors in lettuce (L. sativa) breeding. Identifying these wild species can be problematic because in some cases they look very similar. Flow cytometry was tested for its reliability and general applicability as a tool to distinguish them. Three series of tests were conducted: (1) Tests with three accessions of L. sativa and one accession of each of the wild species, repeated three times throughout the year. In each repeat, the mean relative DNA amount of L. serriola was significantly higher than that of L. saligna, but significantly lower than that of L. virosa. The mean relative DNA amount of L. sativa did not differ from that of L. serriola.(2) Tests with each wild species represented by 10 accessions. Significant differences between the accessions within each species demonstrated the presence of intraspecific variation. Notwithstanding this intraspecific variation, the relative DNA amounts of all accessions of L. serriola were significantly higher than that of all L. saligna accessions, and significantly lower than that of all L. virosa accessions. Therefore, all accessions could be assigned to the appropriate species on the basis of their DNA amounts. (3) Tests with single plants from 10 accessions of each of the wild species. These test revealed that individual plants of L. serriola, L. saligna, and L. virosa can be reliably identified with flow cytometry, when aL. serriola sample of established identity is used as internal reference. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characterization of resistance gene analogs from <Emphasis Type="Italic">Gossypium arboreum</Emphasis> and their evolutionary relationships with homologs from tetraploid cottons

Four cotton species (genus Gossypium) produce spinable fiber. The two diploid species of Asiatic origin, Gossypium arboreum and G. herbaceum, have been largely replaced by G. hirsutum. However, these diploid species are potentially a rich source of genes for the improvement of G. hrisutum, particularly in terms of providing resistance against biotic and abiotic stresses. As a first step towards understanding the mechanisms of resistance in cotton, we designed 24 non-degenerate primers based on resistance gene analogs (RGAs) cloned from G. hirsutum for screening a number of cotton species with the A and D genomes. Most of these RGAs are conserved on the A genome (G. arboreum), suggesting a bias towards this genome. The amplified RGAs from G. arboreum were cloned and their nucleotide and amino acid sequences compared with RGA sequences available in public databases. The majority of the RGAs identified were homologous to those isolated from G. hirsutum and G. barbadense, but their diversity was greater than expected at both the nucleotide and amino acid levels. These RGAs provide useful tools for the identification of full-length resistance genes from bacterial artificial chromosome and cDNA libraries.     

Hybridizations among Brassica napus, B. rapa and B. juncea and their two weedy relatives B. nigra and Sinapis arvensis under open pollination conditions in the field

The rate of natural crosses occurring among the cultivated Brassica species B. napus, B. rapa, and B. juncea and their two weedy relatives B. nigra and Sinapis arvensis was studied in co-cultivation experiments under field conditions in Saskatchewan, Canada, with special reference to evaluation of the possibility of transgene escape from the cultivated to the weedy species. Natural crosses occurred among B. napus, B. rapa, and B. juncea, indicating that hybridizations among these three species do occur under field conditions. On the other hand, no natural crosses occurred between the cultivated species and B. nigra or S. arvensis. It is concluded that the crosses between the cultivated and weedy species are practically impossible under field conditions in Saskatchewan, and that the escape of transgenes from transgenic cultivars of B. napus, B. rapa and B. juncea into B. nigra and S. arvensis is basically zero in this region.     

New genetic sources of resistance in the genus <Emphasis Type="Italic">Phaseolus</Emphasis> to individual and combined aluminium toxicity and progressive soil drying stresses

Bean species and genotypes show wide phenotypic variability in relation to aluminium (Al) resistance and progressive soil drying. The objective of this study was to identify and characterize sources of resistance to Al toxicity and progressive soil drying among six genotypes of common bean (Phaseolus vulgaris), four of runner bean (P. coccineus), and one of tepary bean (P. acutifolius), using hydroponic and soil cylinder screening methods. One experiment on hydroponic screening of Al resistance was carried out using a basal nutrient solution with and without 20 μM Al. Two experiments were carried out using two oxisols in 80 cm long soil cylinders with high Al (HAl) and low Al (LAl) saturation treatments. The three experiments showed an average of 36.9–53.5% inhibition of root growth with HAl compared with LAl treatments. Differences in root development and distribution were observed among genotypes and species. Two accessions of P. coccineus (G35346-2Q, G35464-5Q) and one Andean common bean genotype (ICA Quimbaya) were outstanding in root and shoot growth in the HAl treatments. P. coccineus accession (G35346-3Q) was outstanding under combined stress of Al-toxic acid soil and progressive soil drying. Accessions of P. coccineus may represent unique sources of Al resistance for the improvement of common bean through interspecific crosses.     

Simple sequence repeats as useful resources to study transcribed genes of cotton

Microsatellites or Simple Sequence Repeats(SSRs) are informative molecular genetic markers in many crop species. SSRs are PCR-based, highly polymorphic, abundant, widely distributed throughout the genome and inherited in a co-dominant manner in most cases. Here we describe the presence of SSRs in cDNAs of cotton. Thirty one SSR primer pairs of 220 (∼14%) tested led to PCR amplification of discrete fragments using cotton leaf cDNA as template. Sequence analysis showed 25% of 24randomly selected cDNA clones amplified with different SSR primer pairs contained repeat motifs. We further showed that sequences from the SSR-containing cDNAs were conserved across G. barbadense and G. hirsutum, revealing the importance of the SSR markers for comparative mapping of transcribed genes. Data mining for plant SSR-ESTs from the publicly available databases identified SSRs motifs in many plant species,including cotton, in a range of 1.1 to4.8% of the submitted ESTs for a given species. This revised version was published online in August 2006 with corrections to the Cover Date.     

Waxy proteins and amylose content in tetraploid wheats Triticum dicoccum Schulb, Triticum durum L. and Triticum polonicum L.

This paper reports the waxy proteins and apparent amylose contents of the tetraploid species Triticum dicoccum, Triticum polonicum and Triticum durum. Three waxy proteins were found in the three species; two showed the same electrophoretic mobility as the alleles Wx-A1a and Wx-B1a of the hexaploid variety ‘Chinese Spring’, while the third showed the same mobility as the allele Wx-B1e belonging to the hexaploid wheat variety ‘Bai Huo’. In apparent amylose content no significant differences between the alleles Wx-B1a and the Wx-B1e were found for each species. However, the mean amylose contents of T. durum and T. polonicum were significantly greater than that of T. dicoccum, regardless of which allele was present. This revised version was published online in July 2006 with corrections to the Cover Date.