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Pedro B. Oliveira, Cristina M. Oliveira and António A. Monteiro

The aim of this study was to determine the effects of date of summer pruning and cane densities on growth and fruiting characteristics of the raspberry (Rubus idaeus) plant. Three summer-pruning dates (early, middle, and late July) and four cane densities (8, 16, 24, and 32 canes/m row) were imposed to the greenhouse-grown primocane-fruiting raspberry `Autumn Bliss' in 2 consecutive years (1994 and 1995). A higher light microclimate and CO2 assimilation rate were measured within the canopy at the lowest density. Some compensation in CO2 assimilation rates were observed in the upper leaves of the high-density treatments, probably in response to low light. Delayed pruning decreased yield per cane and per row. The highest yields per cane were always observed at the lowest cane density. Densities of 16 and 24 canes/m produced the highest fruit yield. Light conditions appeared to be the most important environmental factor affecting plant productivity. Fruit were a weaker sink than roots; therefore, the role of carbohydrate reserves should be investigated.

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Luisa Monte-Corvo, Luis Goulão and Cristina Oliveira

Inter-simple sequence repeat (ISSR) markers were used for cultivar identification and for determination of the phenetic relationships among 24 pear cultivars (Pyrus communis L.). The ability of several molecular marker systems including randomly amplified polymorphic DNA (RAPD), amplified fragment length polymorphisms (AFLP), inter-simple sequence repeats (ISSR), simple sequence repeats (SSR), and selective amplification of microsatellite polymorphic loci (SAMPL) to detect variation among clones of the most significant Portuguese cultivar, Rocha, was also investigated. Each of the eight ISSR primers tested was able to distinguish the 24 pear cultivars. The ISSR primers generated 337 markers, 79.5% of which were polymorphic. The cultivar dendrogram obtained with the ISSR marker data was very similar to that obtained with previous RAPD+AFLP analysis, confirming the genetic divergence of `Pérola', `Carvalhal' and `Lawson' from the other cultivars. Eight out of 15 apple [Malus sylvestris (L.) Mill. var domestica (Borkh.) Mansf.] SSR primers tested also amplified microsatellites in pear. None of the five molecular marker systems analyzed (with a total of 1082 markers) detected reproducible polymorphisms among the nine `Rocha' clones, in spite of the presence of clear phenotypic differences.

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M. Cristina Pedroso, M. Margarida Oliveira and M. Salomé S. Pais

Nodal segments and shoot tips of axenic shoot cultures of `Hayward' kiwifruit were inoculated on modified Murashige and Skoog (MS) medium supplemented with zeatin at 1 mg·liter-1 and IAA at 0.05 mg·liter-1 (H1) or on MS medium without growth regulators (H2). Inocula cultured on H2 medium all developed into normal plantlets, while those cultured on H1 medium developed into shoots, 18% of them abnormal. Rooting of H1 shoots was induced by a 24-h immersion in a solution of IRA at 20 mg·liter-1. H2 plantlets were directly transferred to soil. Statistical treatment of the results revealed no significant differences, in terms of plant development, between the two micropropagation methods used. However, the presence of a functional root system on 5-week-old H2 plantlets resulted in 100% plant survival, but only 70% of in vivo-rooted shoots from H1 survived. Nevertheless, H1 still allowed for an important reduction of costs and manipulation. Chemical names used: indole3-acetic acid (IAA).

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Luís Goulão, Luisa Monte-Corvo and Cristina M. Oliveira

Variability of commercial plum (Prunus L. sp.) cultivars is unknown since breeding often involves intercrossing hybrids with several species but has been based on a low number of parents. Molecular markers like amplified fragment length polymorphisms (AFLP) and inter-simple sequence repeats (ISSR), which sample multiple loci simultaneously, have become increasingly popular, and were used to characterize 24 diploid and four hexaploid cultivars of plum. Seven AFLP and six ISSR primers were used, and resulted in amplification of 379 and 270 products, respectively. Unweighted pair-group method with arithmetic averages (UPGMA) dendrograms, based on similarity coefficients, reflected a clear separation between diploid and hexaploid plums. Among diploid plums, two pairs of cultivars were relatively distinct from the rest, namely `Golden Japan' and `Methley' and `Ozark Premier' and `Songold'. Furthermore, several cultivars were grouped together both with AFLP and ISSR analysis: 1) `Ambra', `Red Beaut', and `Black Beaut', 2) `Black Diamond' and `Royal Diamond', 3) `June Rose', `Santa Rosa', and `Royal Red', and iv) `Freedom', `Larry Ann', and `Queen Rosa'. Although the phenetic classification obtained by the two methods were similar (r = 0.73, for the diploid group), ISSR had a higher reproducibility and percentage of polymorphisms (87.4% vs. 62.8%) than AFLP. Methodological aspects of both markers systems are discussed. Results obtained suggest that the AFLP and ISSR approaches are valuable tools for identification of specific genotypes and analysis of phenetic relationships in plum.

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Pedro B. Oliveira, Cristina M. Oliveira, Luís Lopes-da-Fonseca and António A. Monteiro

The spring shoots of `Autumn Bliss' red raspberry (Rubus idaeus L. var. idaeus; primocane-fruiting type) were cut on 2, 16, 31 July and 15 and 30 Aug. with the objective of delaying fruit harvest into the off-season under mild winter climatic conditions. Cutting shoots in August delayed fruit harvest until February and April of the following year, but shoot growth was weak and fruit yield low (4.8 and 2.1 g/cane). July cuttings delayed harvest until October to January with acceptable fruit yield (63.5, 52.8, and 26.5 g/cane for 2, 16, and 31 July, respectively). The differences in cane height and total node and fruiting node count between the three cutting dates of July were small, but there was a constant decrease in leaf area per cane from the first to the third date and a sharp decrease in fruit yield from the second to the third date. Vegetative shoot growth was less affected than yield when summer cutting was delayed until the end of July to induce a later harvest. Fruit quality always reached acceptable standards. This study confirms the practicability of using summer-cutting of primocane-fruiting red raspberries to induce off-season fruit production under protected cultivation in mild winter climates.

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Pedro Brás de Oliveira, Maria José Silva, Ricardo B. Ferreira, Cristina M. Oliveira and António A. Monteiro

In a 2-year experiment (1994 and 1995), plants of primocane-fruiting red raspberry cultivar ‘Autumn Bliss’ grown in a plastic greenhouse were destructively harvested at different growth stages to determine the effect of pruning date and cane density on dry matter distribution, carbohydrate concentration, and soluble protein concentration in different plant parts. Three summer-pruning dates (early, mid, and late July) and four cane densities (8, 16, 24, and 32 canes/m row) were imposed. Relative root biomass decreased from pruning to first flower stage and remained constant thereafter for all pruning dates. Earlier pruning dates corresponded to earlier fruit production, but yield was significantly reduced on later pruning dates and higher cane densities. Sucrose concentration was higher in fine roots than in suberized roots and had a slight decrease during flowering and the beginning of harvest. Soluble protein concentrations did not differ significantly between pruning dates. Reserve carbohydrates in the root system were unaffected by pruning and cane density, and were rapidly used during active vegetative growth, began to recover just after bloom, and were fully recovered at the end of the season. Our experiment suggested that in red raspberry plants grown under poor environmental conditions, current yield is reduced but there is enough carbohydrate accumulation to support next year's growth.

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Rita de Cássia Alves, Ana Santana de Medeiros, Mayara Cristina M. Nicolau, Francisco de Assis Oliveira, Leonardo Warzea Lima, Edna Maria M. Aroucha and Priscila Lupino Gratão

This research aimed to evaluate the yield and quality of tomato plants under different managements of salt stress by adopting the partial root-zone saline irrigation (PRSI) system. The experiment was conducted in a greenhouse at the Universidade Federal Rural do SemiÁrido (UFERSA), Mossoró, Rio Grande do Norte (RN), Brazil. The experimental design was completely randomized, with six treatments and four replicates, totaling 24 plots. The treatments consisted of six different irrigation management regimes using low and high saline water (S1–0.5 and S2–5.0 dS·m−1), applied with or without PRSI, such that one side of the root-zone was submitted to saline water whilst the other side was water low salinity irrigated. For treatments T1 (control), T2 (S2 water), and T3 (alternate irrigation system between S1 and S2, with a cycling period of 15 d for each one), the PRSI was not applied; T4 (irrigation with S1 and S2, adopting the PRSI system from phase II to phase IV), T5 (irrigation with S1 and S2 in phase II, alternating in phase III; in phase III the inversion of the remaining water was made until the end of phase IV), and T6 (irrigation with S1 and S2, adopting the PRSI system in phase II, with the water switched between low and high saline water every 15 days, remaining until the end of phase IV) treatments were under the PRSI. The number of fruit per plant, fruit weight, fruit longitudinal and transverse diameter, pulp firmness, soluble solids content, titratable acidity, pH, vitamin C, color relation (a*/b*), lycopene, and β-carotene were determined as parameters for the fruit yield and quality evaluation. Our findings reinforce the importance of the use of PRSI systems followed by irrigation managements without loss of product quality, such as demonstrated by T4 and T5 water managements.