A universal primer for isolation of fragments of a gene encoding phytoene desaturase for use in virus-induced gene silencing (VIGS) studies

We have been using Virus-Induced Gene Silencing (VIGS) to test the function of genes that are candidates for involvement in floral senescence. Although VIGS is a powerful tool for assaying the effects of gene silencing in plants, relatively few taxa have been studied using this approach, and most that have are in the Solanaceae. We typically use silencing of phytoene desaturase (PDS) in preliminary tests of the feasibility of using VIGS. Silencing this gene, whose product is involved in carotene biosynthesis, results in a characteristic photobleaching phenotype in the leaves. We have found that efficient silencing requires the use of fragments that are more than 90% homologous to the target gene. To simplify testing the effectiveness of VIGS in a range of species, we designed a set of universal primers to a region of the PDS gene that is highly conserved among species, and that therefore allows an investigator to isolate a fragment of the homologous PDS gene from the species of interest. We report the sequences of these primers and the results of VIGS experiments in horticultural species from the Asteraceae, Leguminosae, Balsaminaceae and Solanaceae

Effect of precooling and ethylene absorbent on the quality of Dendrobium "Pompadour" flowers

We studied the effect of precooling and the use of an ethylene absorbent (based on potassium permanganate) in the flower boxes, on the vase life of Dendrobium `Pompadour` flowers, after simulation of air shipment (3 days at 25°C). Precooling at 10°C (85-95%RH) for 60 minutes reduced ethylene production, ACC activity, and the concentration of 1-aminocyclopropane-1-carboxylic acid (ACC) in the flowers, during shipment. Precooling for 90 minutes or longer did not have a positive effect on the chilling-sensitive Dendrobium flowers. The presence of an ethylene absorbent in the cardboard boxes further reduced ethylene concentration in the boxes. The combination of 60 min precooling and the ethylene absorbent was optimal to reduce epinasty of the buds and flowers, to promote bud opening and to prevent abscission of open flowers. It also considerably delayed the time to in visible petal withering

Physiological and biochemical changes during banana ripening and finger drop

Fruit drop of banana is due to breaking at the junction of the pedicel and pulp, and we found no true abscission zone. The breakage seems therefore due to weakening of the peel. We investigated pectin hydrolysis and some properties at the rupture zone, using `Hom Thong` (Musa acuminata, AAA Group) and `Namwa` (Musa x paradisiaca, ABB Group) fruit, which show massive drop and no drop, respectively. During the period of finger drop, the water content of the peel in `Namwa¿ was similar to that of `Hom Thong` and thus water content does not account for the high breakage in `Hom Thong`. The peel thickness at the rupture area in the two cultivars was not significantly different. During the period of finger drop, the level of water-soluble pectin in the peel at the rupture area of `Hom Thong` was higher than that of `Namwa`, indicating pectin degradation. CDTA soluble pectin and insoluble pectin was lower in `Hom Thong`, also indicating more pectin breakdown in this cultivar. Polygalacturonase activity in the peel at the rupture area of `Hom Thong` bananas rapidly increased, but not clearly more than in `Namwa` bananas. Pectinesterase activity in the peel at the rupture area of `Hom Thong` was much lower than that of `Namwa` bananas, and thus does not account for the breakage. Pectate lyase in the peel of `Hom Thong` was considerably higher than in that of `Namwa`. The present data indicate that the much higher pectate lyase activity in `Hom Thong` might be responsible, at least partially, for the finger drop

Effect of precooling and ethylene absorbent on the quality of Dendrobium "Pompadour" flowers

We studied the effect of precooling and the use of an ethylene absorbent (based on potassium permanganate) in the flower boxes, on the vase life of Dendrobium `Pompadour` flowers, after simulation of air shipment (3 days at 25°C). Precooling at 10°C (85-95%RH) for 60 minutes reduced ethylene production, ACC activity, and the concentration of 1-aminocyclopropane-1-carboxylic acid (ACC) in the flowers, during shipment. Precooling for 90 minutes or longer did not have a positive effect on the chilling-sensitive Dendrobium flowers. The presence of an ethylene absorbent in the cardboard boxes further reduced ethylene concentration in the boxes. The combination of 60 min precooling and the ethylene absorbent was optimal to reduce epinasty of the buds and flowers, to promote bud opening and to prevent abscission of open flowers. It also considerably delayed the time to in visible petal withering

Effect of temperature on softening and the activities of polygalacturonase and pectinesterase in durian fruit

Durian fruit (Durio zibethinus Murr. cv Chanee) were ripened at 12, 27 and 34 °C (85±5 H). When held at 27 °C, the aril of durians softened rapidly, concomitant with a decrease in alkali-soluble pectin, a marked increase in water-soluble pectin and a large increase in polygalacturonase (EC 3.2.1.15) activity. Pectinesterase (EC 3.1.2.11) activity was high at harvest and changed little. Fruit stored at 34 °C showed the same rate of softening as fruit held at 27 °C, whereas polygalacturonase activity (and the amount of water-soluble pectin) was considerably lower. Durians stored at 12 °C showed virtually no softening and had low polygalacturonase and pectinesterase activities and small changes in water-soluble pectin. It is concluded that there is a positive correlation between softening and pectin degradation. No correlation was found between softening and pectinesterase activity, while the softening is correlated with polygalacturonase activity

Aplicação em pré-colheita de cloreto de cálcio no controle do despencamento natural dos frutos de bananeira 'FHIA-18'

RESUMO: O objetivo deste trabalho foi avaliar o efeito da aplicação de CaCl2 em pré-colheita, em diferentes doses e épocas no controle do despencamento natural de frutos da bananeira 'FHIA-18'. O delineamento experimental foi o de blocos casualizados, em esquema fatorial 3x3+1 testemunha, sendo testadas as doses de 2, 4 e 6% de CaCl2 aos 60, 90 e 120 dias após a emissão do cacho, com cinco repetições e uma planta por parcela. Observou-se redução linear da resistência ao despencamento e do tempo de maturação do fruto com o acréscimo das doses de CaCl2. Os frutos apresentaram maior firmeza com três aplicações de CaCl2. Os teores de cálcio da casca e da polpa não foram alterados significativamente com as doses e épocas de aplicações do CaCl2, indicando que o cálcio não é absorvido efetivamente pelo fruto. A aplicação de CaCl2 na pré-colheita não reduz o despencamento dos frutos da bananeira 'FHIA-18'