António A. Monteiro

Initial in vitro evaluations of the antibacterial activities of glucosinolate enzymatic hydrolysis products against plant pathogenic bacteria.

Aims:  The aim of the study was to evaluate the in vitro antibacterial effects of glucosinolate hydrolysis products (GHP) against plant pathogenic micro‐organisms namely Agrobacterium tumefaciens, Erwinia chrysanthemi, Pseudomonas cichorii, Pseudomonas tomato, Xanthomonas campestris and Xanthomonas juglandis.

Numerical taxonomy of Portuguese Tronchuda cabbage and Galega kale landraces using morphological characters

SummaryA morphological study was carried out to determine the relationships among Portuguese cole landraces using 58 accessions belonging to: (i) Portuguese Tronchuda cabbage (Brassica oleracea var. tronchuda Bailey syn. var. costata De Candolle, Couve Tronchuda); (ii) Portuguese Galega kale (B. oleracea var. acephala De Candolle, Couve Galega); and (iii) other economically less important coles such as Algarve cabbages (B. oleracea var. capitata L., Couve do Algarve or B. oleracea var. sabauda L., Couve Repolho-lombarda do Algarve). The cole accessions were collected from the growers, studied under field conditions during two consecutive years, and characterized using 46 morphological characters from seedling stage to ripe silique. Morphological data were analysed by numerical taxonomy techniques using UPGMA (Unweighted Pair Group Method Using Arithmetic Averages) and by principal component analysis (PCA). Phenograms based on correlation and distance coefficients showed the existence of 8 main groups (A-H). Five of these groups correspond to Tronchuda cabbage landraces: (A) “Couves de Trás-os-Montes”; (B) “Couves do Minho”; (C) “Couves from Central Portugal”; (D) “Couve Portuguesa”; (E) “Couves from Southern inland Portugal”. The three other groups correspond to: (F) cabbages; (G) miscellaneous coles; and (H) Galega kales. Landrace groups are primarily associated with morphological differences among accessions and secondly with accession geographical origin. The interannual character variation did not affect the clustering patterns of the accessions and therefore the stability of landrace classification. PCA was congruent with the landrace groups defined by the phenograms and gave supplementary information on the usefulness of the characters for the definition of the various groups.

The use of auxins for the production of greenhouse tomatoes in mild-winter conditions: A review

Abstract This review summarizes the research on the effects of synthetic auxins on fruit setting and development of greenhouse-grown tomatoes in mild-winter conditions. The concepts of mild winter and fruit setting are analysed in relation to the use of auxins on tomato under protected cultivation. Particular emphasis is placed on horticultural uses of auxins, especially on active chemicals and concentration, methods of application and timing of the treatment. Features of auxins in fruit development are reviewed in relation to fruit-setting and parthenocarpy, fruit size, fruit number, fruit earliness, fruit yield and fruit quality. Auxin effects are discussed arguing the importance of environmental conditions at the time of auxin application, the type of auxin and the concentration used, the number of clusters and their position on the plant and the cultivar under investigation.

Inheritance of downy mildew resistance at cotyledon and adult-plant stages in 'Couve Algarvia' (Brassica oleracea var. tronchuda)

The progeny of several crosses between the resistant ‘Couve Algarvia’ of Brassica oleracea var. tronchuda Bailey and susceptible hosts was evaluated with the objective of determining the mode of inheritance of resistance to downy mildew (DM) (Peronospora parasitica (Pers. ex Fr.) Fr.) at cotyledon and adult-plant stages and to find out whether the resistance observed at the two plant developmental stages was under the same genetic control. In an assay, conducted under controlled environment with artificial inoculation, the F2 of a cross between resistant ‘Couve Algarvia’ and susceptible ‘Penca de Chaves’ segregated 15 resistant:1 susceptible, indicating that ‘Couve Algarvia’ cotyledon resistance was controlled by two duplicate dominant genes. In a field assay under natural DM infection, the F2 of a cross between resistant ‘Couve Algarvia’ and susceptible ‘Couve de Corte’ segregated 3 resistant:1 susceptible, indicating that ‘Couve Algarvia’ adult-plant resistance was under the control of a single dominant gene. The 15:1 segregation at cotyledon stage and the 3:1 segregation at adult-plant stage were confirmed in the progeny of a cross between a susceptible doubled-haploid rapid-cycling B. oleracea line and the resistant ‘Couve Algarvia’. Besides, the inoculation of the same plants at cotyledon and adult-plant stages showed that the F2 segregation for resistance at cotyledon was independent from the F2 segregation for resistance at adult-plant stage, evidencing that ‘Couve Algarvia’ DM resistance at cotyledon and adult-plant stage was under the control of two different genetic systems. Therefore, field resistance cannot be predicted from cotyledon resistance.

Molecular taxonomy of Portuguese tronchuda cabbage and kale landraces using nuclear RFLPs

SummaryRFLPs were used to study the genetic relationships of 31 Portuguese coles (Brassica oleracea L.) representing the different ecotypes or landraces grown in Portugal. Other cole crops such as Jersey kale, Chinese kales, common cabbages, broccolis and cauliflower, two nine-chromosome wild species, and one accession of turnip also were included to determine the evolutionary relationships of Portuguese coles to other related coles. Principal coordinates and cluster analyses were conducted using a package of computer programs and RFLP data from 55 nuclear DNA probes, detecting 291 polymorphic restriction fragments. The results showed that the 48 accessions clustered into five groups: (a) a dispersed group with turnip and the wild brassicas; (b) Chinese kales; (c) broccolis and cauliflower; (d) a disperse group including Algarve and Jersey kales, thousand head kale, cabbages, and savoy cabbage; (e) a large and compact group containing all Portuguese tronchuda cabbages and kales. This unique and closely related group containing Portuguese tronchuda cabbages and kales could be further divided into five subgroups corresponding to the major areas of cultivation. The phenetic groupings of Portuguese tronchuda cabbages and kales based on RFLP data corresponded more with their geographic origins (collecting sites) than with their morphological similarities. A mechanism involving geographic isolation and frequent intercrossing within local areas is proposed to explain genetic relationships among Portuguese tronchuda cabbages and kales.

Inheritance of downy mildew resistance in mature broccoli plants

The objective of this study was to determine the mode of inheritance of field resistance to downy mildew (Peronospora parasitica (Pers. ex Fr.) Fr.) in broccoli (Brassica oleracea var.italica) at the adult plant stage. The F1, F2 and F3 progeny of resistant and susceptible plants of broccoli were tested in the field under natural infection, in central Portugal, from August to December in two successive years. The plants were evaluated for resistance to downy mildew at maturity using a five-class scale of increasing susceptibility to the disease, which took into account the number of infected leaves and the size of the sporulating lesions. The F1 was completely resistant, the F2 segregated a clear 3 resistant: 1susceptible and the F3 confirmed the F2 segregation, which suggests a dominant character controlled by a single locus. This resistance has good potencial for direct use in commercial broccoli breeding or for transfer to other Brassica vegetables.

Screening Portuguese cole landraces for resistance to seven indigenous downy mildew isolates

Abstract Twenty-nine Brassica oleracea accessions, including Portuguese cole landraces, were screened for resistance to crucifer downy mildew using seven Portuguese isolates of Peronospora parasitica. Seven-day-old seedlings were inoculated on the cotyledons with two 10 μl droplets of a water suspension containing 5 × 105 conidiospores ml−1. Host-pathogen interaction phenotype (IP) was evaluated 7 days after inoculation using an increasing susceptibility (1–9) scale. The screening revealed high variable reaction for downy mildew resistance within Portuguese cole landraces. Some accessions were very susceptible with most of the plants scoring in IP classes 7 and 9, but most of the accessions showed high variability in interaction phenotype with plants scoring in all IP classes. Four accessions belonging to landraces ‘Couve Algarvia’, ‘Couve Murciana’ and ‘Couve Coracao de Boi’ expressed high resistance to all downy mildew isolates, with over 42% of seedlings in the non-sporulating IP class 1. Downy mildew isolates Pp504 (Batalha), Pp503 (Condeixa), and Pp507 (Faro) showed slightly higher aggressiveness than isolates Pp505 (Loures), Pp502 (Vila Real), Pp506 (Odemira), and Pp501 (Povoa). There was no significant interactions between accession and downy mildew isolate, which shows that the geographic origin of the host and pathogen had no influence on the interaction phenotype. This study confirms the high potential of Portuguese cole landraces as sources of resistance to downy mildew and has identified accessions with a high valuable resistance.

Expression of resistance to downy mildew at cotyledon and adult plant stages in Brassica oleracea L.

This research compared the expression of resistance to downy mildew at cotyledon and adult plant stages in seven Brassica oleracea genotypes against two P. parasitica isolates of different virulence. Seven day old seedlings were dual inoculated under controlled environment by depositing two 10 μl droplets of a spore suspension of a different isolate on each cotyledon and the interaction phenotype (IP) evaluated 7 days later using a 0–5 scale of increasing susceptibility. The seedlings were transplanted to 16 cm pots and grown in the greenhouse for 110 days (15 to 28 leaves). Adult plants were tested using a single leaf inoculation method that allowed the same plant to be simultaneously inoculated with the two P. parasitica isolates. Leaves were scored 10 days after inoculation using a 0–5 scale of increasing susceptibility. The inoculation of the same plant with the two isolates produced different combinations of cotyledon (CT) and adult-plant (AP) interaction-phenotype according to the genotype. CrGC 3.1 was susceptible at CT and AP stages, ‘Algarvia’ resistant at CT and AP stages, and broccoli ‘A’ susceptible at CT and resistant at AP stage against the two isolates. ‘Murciana’ and broccoli ‘B’ were differential at CT and AP stages. Savoy and Shetland cabbages were differential at CT stage and resistant to both isolates as adult plants. Cotyledon resistance could not be used to predict adult-plant resistance since the two types of resistance were very poorly correlated. Resistance can be race specific either at cotyledon or at adult-plant stage.

Internal transcribed spacer 2 amplicon as a molecular marker for identification of Peronospora parasitica (crucifer downy mildew)

Aims:  The purpose of the study was to characterize the internal transcribed spacer (ITS) regions of Peronospora parasitica (crucifer downy mildew) in order to evaluate their potential as molecular markers for pathogen identification.

Genetic diversity and taxonomy of Portuguese Tronchuda cabbage and Galega kale landraces using isozyme analysis

SummaryIsozyme analysis was used to study the genetic variation and the genetic relationships of a collection of 48 Brassica spp. including 31 Portuguese coles (Brassica oleracea L.) accessions representative of the different landraces cultivated in Portugal. Other brassicas included in this experiment were Jersey kale, kailaan, common cabbages, broccolis, cauliflower, nine-chromosome wild brassica and turnip. Nine enzymes used in the starch gel electrophoresis included: PGM, PGI, AAT, LAP, TPI, FBP, SOD, IDH and GR. Twenty-one putative loci were revealed, with 3 showing invariance and the other 18 contained 50 alleles. The allelic frequencies at these loci represented by 40 plants per accession were used to calculate the following estimators of genetic variation: % of polymorphic loci, average number of alleles per polymorphic loci, average number of alleles per locus, and index of heterozygosity. The genetic relationships were evaluated considering Nei (1978) and Rogers (1972) genetic distances between each pair of accessions whose matrices were hierarchically clustered by the UPGMA method. The accessions were also studied using the principal coordinate analysis.Portuguese Tronchuda cabbages and Galega kales have shown high genetic diversity in comparison with the other accessions. This indicates their potential variation for use in breeding programs. The UPGMA results show that the 48 accessions, with the exception of B. insularis, B. cretica, and turnip, can be clustered into 6 groups: (a) Portuguese Tronchuda cabbages, Galega kales and Algarve cabbages; (b) common cabbages and kales; (c) Couve Poda do Algarve and broccoli; (d) Algarve cabbage and common cabbages; (e) kailaan; (f) broccoli and cauliflower. The groupings obtained by the isozyme analysis are difficult to interpret considering the origin of the Brassica spp. and the morphological resemblance among the accessions.