Zingiberene-mediated resistance to the South American tomato pinworm derived from Lycopersicon hirsutum var. hirsutum

The Lycopersicon hirsutum var. hirsutum accession PI 127826 is recognized as a good source of resistance to arthropod pests due to the action of the allelochemical zimgiberene, a sesquiterpene present in its glandular trichomes. Five genotypes were selected from the F₂ generation of the interspecific cross Lycopersicon esculentum ‘TOM-556’ × Lycopersicon hirsutum var. hirsutum ‘PI 127826’, based on their low levels (BPX-368-clone#56) or high levels(BPX-368-clone#92, BPX-368-clone#105,BPX-368-clone#179, BPX-368-clone#250) of zingiberene. The five F₂ genotypes were tested for resistance to the South American tomato pinworm Tuta absolutaalong with accession L. esculentum ‘TOM-556’ (pinworm susceptible), and the accessions L. hirsutum var. hirsutum ‘PI 127826’ and L. pennellii ‘LA716’ (resistant). The F₂ clones selected for high foliar zingiberene levels showed lower scores for leaflet lesion type(LLT), percent leaflets attacked (PLA) and overall plant damage (OPD) than the low zingiberene genotypes. The results indicated that zingiberene mediates resistance to the South American pinworm, based on feeding and on ovipositing deterrence, in populations derived from the interspecific cross between Lycopersicon. esculentum and Lycopersicon hirsutum var. hirsutum. Indirect selection for high foliar zingiberene content is suggested as an efficient technique for breeding tomatoes for resistance to the South American tomato pinworm. This revised version was published online in July 2006 with corrections to the Cover Date.     

Intra and interlocus interactions between alcobaça (alc), crimson (og c ), and high pigment (hp) loci in tomato Lycopersicon esculentum Mill.

The ripening mutant allele alcobaça (alc/alc) may be deployed to extend shelf life in tomatoes, but has reportedly negative effects on fruit colour development. Colour enhancing mutants crimson (og ^c /og ^c) and high pigment (hp/hp) could potentially overcome this limitation, but a detailed account of their interactions with alc is not available. In this paper, we report on intra-allelic (additive and dominant) interactions within these 3 loci, and on their possible interallelic (epistatic) interactions. Eight near-isogenic (NIL) tomato lines in background Flora-Dade were obtained, representing all possible 2ⁿhomozygous combinations in the n = 3 loci. The 8 NIL were crossed in all possible combinations (reciprocals excluded), to obtain 28 hybrids that were heterozygous in at least one locus. The 36 treatments (= 8NIL + 28 hybrids) were grown in a randomized complete block design with 4replications, and the following traits were evaluated: total yield, average fruit mass, fruit firmness at harvest (= breakerstage) and 6 days after harvest (d.a.h)., % coloured fruit surface, fruit lycopene and beta-carotene contents, fruit % soluble solids and solids/acidity ratio, internal and external fruit colour. The loci alcobaça, crimson and high pigment or their epistatic interactions had significant influence on the expression of all traits measured. Epistatic effects were responsible for most of the variation among genotypes (with a minimum of 48.1%of the total sum of squares for % coloured fruit surface and a maximum of 82.8% for total yield). External fruit colour was defficient in all alc/alc genotypes, and their commercial use is impaired, in spite of improvements in fruit internal and external colour brought about by deployment of specific genotypic constitutions in lociog ^c and hp. Some but not all alc ⁺ /alc genotypes were firmer and showed improved fruit quality over the normal Flora-Dade (alc ⁺ /alc ⁺ og ^c+ /og ^c+ hp ⁺ /hp ⁺) background. The following genotypic combinations represented good compromises between yield, long shelf life and fruit quality traits: alc ⁺ /alc og ^c+ /og ^c hp ⁺ /hp, alc ⁺ /alc og ^c /og ^c hp ⁺ /hp ⁺ and alc ⁺/alc og ^c+/og ^c+ hp ⁺ /hp     

Contents Volume 127 2002

Volume Contents

Contents Volume 127 2002     

Genome discrimination and chromosome pairing in the Hordeum chilense × Aegilops tauschii amphiploid

Tritordeum (X Tritordeum Ascherson et Graebner) is a synthetic amphiploid belonging to the Triticeae tribe, which resulted from crosses between Hordeum chilense and wheat. It presents useful agronomic traits that could be transferred to wheat, widening its genetic basis. In situ hybridisation with total genomic DNA from H. chilense and cloned, repetitive DNA sequences (pTa71 and pAs1) probes were used to discriminate the parental origin of all chromosomes, to analyse the chromosome pairing and to identify the chromosomes in pollen mother cells (PMCs) at metaphase I of the tritordeum line HT251 (H^chH^chDD, 2n = 4x = 28). The H. chilense total genomic DNA and the ribosomal sequence pTa71 probes, allowed the unequivocal discrimination of the 14 chromosomes of H^ch genome-origin and the 14 chromosomes of D genome-origin. Chromosome pairing analysis revealed meiotic irregularities such as reduced percentage of PMCs with complete homologous pairing, high frequency of univalents, most of H. chilense-origin and a reduced frequency of intragenomic multivalents from both genomes. The H. chilense genome revealed high meiotic instability. After individual chromosome identification at metaphase I with the pAs1 probe, we found the occurrence of pairing between chromosomes of different homoeology groups. The possible interest of the tetraploid tritordeum in the improvement of other Triticeae species is also discussed.     

Diversity among melon landraces (Cucumis melo L.) from Greece and their genetic relationships with other melon germplasm of diverse origins

Diversity among 17 melon landraces and inbred lines of Group Cantalupensis, Inodorus, and Flexuosus germplasm from Greece was assessed using 24 RAPD primers, 11 morphological traits of fruit, two yield-related characteristics, and resistance to powdery mildew. Accessions were genetically diverse and the greatest variation was detected in Group Flexuosus. Comparative analysis of Greek germplasm and an array of previously characterized reference accessions [RA; 68 from Africa (15), United States (U.S.; 5), Central Europe (14), Japan (19), and Spain (15)], spanning major market classes employing 19 RAPD primers (standard marker array), indicates that all but one of the accessions from Greece showed genetic affinities among themselves and with 23 RA of various origin (i.e., Japan, U.S., Central Europe, Spain and Israel) and market class. Accessions from Greece were, however, distinct from the African landraces and most Spanish melons. Greek accessions also showed little genetic affinity with the Casabas (Blanco and Crenshaw), Ogen, and U.S. Eastern Market accessions. Group Flexuosus and Inodorus accessions from Greece possessed genetic affinities with Western Asian (Group Conomon) and Mediterranean (Group Inodorus) market classes, respectively. The uniqueness of Greek melon landraces portends their potential usefulness for the enhancement of U.S., European, and Asian melon market classes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Estimation of between and within accession variation in selected Spanish melon germplasm using RAPD and SSR markers to assess strategies for large collection evaluation

The population structure of 15 Spanish melon (C. melo L.)accessions, mostly of Group Inodorus, was assessed by the analysis of 16individuals of each accession using 100 random amplified polymorphic DNA (RAPD) bands produced by 36 primers, and allelic variation at 12microsatellite (SSR) loci (23 alleles). A relatively high level of polymorphism (25.6%) was detected using RAPD markers, and eight SSR loci (66.7%) were useful in discriminating accessions. Cluster analysis using RAPD- and SSR-based genetic distance estimates resulted in similar and consistent groupings of most of the accessions studied. The mean genetic distance and standard error among accessions estimated by RAPD variation was 0.421 ± 0.099, and mean SSR-based genetic distance estimate was 0.285 ± 0.141. Albeit many dominant markers examined were fitted to a 3:1 test ratio, deviation from this ratio and from Hardy-Weinberg expectations for many SSR loci suggests that some populations were in genotypic disequilibrium. Moreover, a higher level of genetic variation was observed between Cassaba market classes than within accessions, suggesting that, depending upon the accession, allelic fixation has occurred in these populations. The relatively high level of heterogeneity observed (different band morphotypes and cluster grouping within a particular market class), however, indicates that the Spanish melons examined possess a relatively broad genetic background. An appraisal of accession population structure such as the one reported herein indicates that bulk sampling techniques coupled with molecular analysis techniques that employ a unique array of discriminating markers can provide information leading to effective strategies for diversity analyses of large collections. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genotypic differences in polyembryo formation and somatic embryogenesis increment in wheat (Triticum aestivum L.), following 2,4-D treatment

Summary In the course of experiments performed to obtain haploid wheat plants in which 2,4-dichlorophenoxyacetic acid (2,4-D) was applied to developing spikes, it was found that three cultivars showed a different ability to produce polyembryos (Thatcher 20.19%, Chris 7.06%, Dollar 0%). This behaviour was related to their capacity to form somatic embryos. Diploid immature embryos cultured in vitro after 2,4-D treatment, gave a higher frequency of embryogenic callus in Thatcher and Chris than in Dollar. As the common factor in both experiments was the 2,4-D treatment we propose that the three cultivars showed a differential sensitivity to 2,4-D.     

Vitamin production in relation to phosphate solubilization by soil bacteria

Studies were conducted to determine the relationship of vitamin production and ability to dissolve bicalcium phosphate in bacteria isolated from rhizosphere, rhizoplane and control soil. Production of vitamin B₁₂, riboflavin, niacin, pantothenate and biotin was determined using a bioassay procedure that may be useful for large-scale screening of bacteria for vitamin production.Among isolates producing one or more vitamins, 76.4, 37.5 and 57.5% of control, rhizosphere and rhizoplane isolates, respectively, solubilized phosphate. However, phosphate-solubilizing isolates from rhizosphere and rhizoplane were more active vitamin producers than solubilizing isolates from control soil, and non-solubilizing isolates from any of the three regions.Production of vitamin B₁₂, riboflavin and niacin by rhizosphere isolates and of riboflavin by rhizoplane isolates was also correlated with ability to solubilize phosphate, but similar relationships were not observed for control isolates.     

Nitrogen compound pollution associated with the use of sewage sludge compost and limestone outcrop residue under saline irrigation

Purpose

The use of composted sewage sludge and limestone outcrop residue in land rehabilitation, soil improvement, and technosol making can influence the mobility of nitrogen compounds in groundwater.

Materials and methods

This experiment analyzed this source of possible pollution under an experimental design based on the use of columns (0–30 cm) formed by both wastes and a heavy irrigation regime. Two waters of different quality (saline and non-saline) were used for irrigation. The presence of nitrate, nitrite, and ammonium in the leachates was checked.

Results and discussion

The environmental risk due to the presence of nitrogen species associated with the use of these materials was very low in general, although nitrate was the most important compound affected by the use of sewage sludge compost and saline water.

Conclusions

The combination of saline water for irrigation with the compost has to be seriously considered as a source of pollution for surface and ground waters, and the use of both resources may be a key factor to be studied (low-quality water and sewage sludge compost).

     

Optimizing conditions for the extraction of pigments in cochineals (Dactylopius coccus Costa) using response surface methodology

A simple method was developed for the extraction and determination of color pigments in cochineals (Dactylopius coccus Costa). The procedure was based on the solvent extraction of pigments in insect samples using methanol:water (65:35, v:v) as extractant. Two-level factorial design was used in order to optimize the solvent extraction parameters: temperature, time, methanol concentration in the extractant mixture, and the number of extractions. The results suggest that the number of extractions is statistically the most significant factor. The separation and determination of the pigments was carried out by high-performance liquid chromatography with UV-visible detection. Because the absorption spectra of different pigments are different in the visible region, it is convenient to use a diode array detector to obtain chromatographic profiles that allow for the characterization of the extracted pigments.