The effects of an osmoregulator, carbohydrates and polyol on maturation and germination of ‘Golden THB’ papaya somatic embryos

This study evaluated the effect of osmoregulators and carbohydrates on the maturation and germination of somatic embryos of papaya ‘Golden THB’. Cotyledon explants from papaya seedlings germinated in vitro on basal MS medium were cultured on somatic embryogenesis induction medium (IM) containing MS salts, myo-inositol, sucrose, agar and p-chlorophenoxyacetic acid. After 50 days, embryogenic calli were transferred onto maturation media (MM) for 45 additional days. For experiment 1, a MS-based medium supplemented with abscisic acid, activated charcoal and concentrations of PEG 6000 (0; 40; 50; 60 and 70 g L^-1) was used, whereas for experiment 2 malt extract concentrations (0; 0.1; 0.2; 0.3 and 0.4 g L^-1) were assessed. The normal cotyledonary somatic embryos produced in experiment 2 were transferred to the germination medium (GM). The GM consisted of full-strength MS medium, sucrose, agar and was supplemented with myo-inositol at varying concentrations (0; 0.275; 0.55 and 0.825 mM). The PEG concentrations tested impaired the maturation of ‘Golden THB’ papaya somatic embryos. The MM, supplemented with malt extract at 0.153 g L^-1, promoted the greatest development of normal somatic embryos (18.28 SE calli^-1), that is, two cotyledonary leaves produced 36.56 SE calli-1. The supplementation with 0.45 mM myo-inositol provided the highest germination percentage (47.42%) and conversion to emblings

Vegetative rescue of adult genotypes of annatto ( Bixa orellana L.) by air layering

Este trabalho teve por objetivos avaliar a t\ue9cnica de alporquia visando ao resgate vegetativo de gen\uf3tipos de urucum ( Bixa orellana L.) e a obten\ue7\ue3o de plantas fornecedoras de prop\ue1gulos para processos de propaga\ue7\ue3o clonal. Foram utilizadas dez plantas matrizes de urucum, com 12 anos de idade, obtidas partindo do cruzamento artificial entre os gen\uf3tipos "Fruto Verde Piloso" X "Fruto Vermelho Liso". Os alporques foram realizados em ramos de 1 a 2 cm de di\ue2metro, utilizando-se como substrato uma mistura de vermiculita e musgo. Foi avaliado o efeito (1) do tipo de anelamento da casca dos ramos (total ou parcial), com 1 cm de comprimento, (2) do AIB (\ue1cido indol-3-but\uedrico a 0 e 4,92 mM) aplicado em papel filtro e (3) do tipo de prote\ue7\ue3o dos alporques (filmes pl\ue1sticos transparente ou preto ou tecido tencel), no enraizamento de alporque dos dez gen\uf3tipos. A t\ue9cnica de alporquia proporcionou o enraizamento de ramos dos dez gen\uf3tipos avaliados, com efici\ueancia vari\ue1vel de 20 a 100%, havendo efeito do gen\uf3tipo sobre a frequ\ueancia de enraizamento. A sobreviv\ueancia desses alporques foi de 100% ap\uf3s o plantio quando estes foram produzidos com anelamento total, tratados com AIB e protegidos com pl\ue1stico transparente. Em casa de vegeta\ue7\ue3o os alporques desenvolveram ramos partindo da brota\ue7\ue3o de gemas caulinares constituindo estoques de explantes apropriados para serem utilizados como estacas ou como fontes de segmentos nodais para a propaga\ue7\ue3o in vitro desta esp\ue9cie.This study aimed to evaluate the usefulness of an air layering technique for vegetative rescue of annatto ( Bixa orellana L.) genotypes and obtainment of propagules for vegetative propagation. Ten 12 year-old annatto stock plants, whose genotypes are derived from artificial crossing between "Hairy-green capsule" X "Smooth-red capsule" were used in this study. Air layering adventitious roots were induced in branches (1-2 cm diameter) using as substrate a mixture of vermiculite and moss. The effects of (1) the type of girdling (total or partial), 1 cm in length, (2) IBA (indole-3-butyric acid at 0 and 4.92 mM) solution in paper filter and (3) the covering with either transparent or dark plastic films and tencel were evaluated. The technique of air layering provided rooted branches for the 10 genotypes evaluated, with efficiency ranging from 20 to 100%, and a genotype effect was observed on rooting frequency. Under greenhouse conditions, the survival of layers derived from totally girdled stems treated with IBA and protected with transparent plastic was 100%. Established layers provided vigorous branching from which shoot apexes or nodal segment explants were obtained for in vitro establishment and propagation of this species

Synergism and negative interference during co-infection of tomato and Nicotiana benthamiana with two bipartite begomoviruses

In Brazil, at least eight begomoviruses including Tomato rugose mosaic virus (ToRMV) and Tomato yellow spot virus (ToYSV) infect tomatoes. ToYSV symptoms in tomato and Nicotiana benthamiana appear earlier and are more severe compared to those of ToRMV. We investigated the role of several factors in this differential adaptation. To analyze infection kinetics, a single leaf was inoculated and subsequently detached after different periods of time. Viral DNA accumulation was quantified in plants, viral replication was analyzed in protoplasts, and tissue tropism was determined by in situ hybridization. Results indicate that ToYSV establishes a systemic infection and reaches a higher concentration earlier than ToRMV in both hosts. ToRMV negatively interferes with ToYSV during the initial stages of infection, but once systemic infection is established this interference ceases. In N. benthamiana, ToYSV invades the mesophyll, while ToRMV is phloem-restricted. During dual infection in this host, ToYSV releases ToRMV from the phloem

Leaf heteroblasty in Passiflora edulis as revealed by metabolic profiling and expression analyses of the microRNAs miR156 and miR172

Juvenile-to-adult phase transition is marked by changes in leaf morphology, mostly due to the temporal development of the shoot apical meristem, a phenomenon known as heteroblasty. Sugars and microRNA-controlled modules are components of the heteroblastic process in Arabidopsis thaliana leaves. However, our understanding about their roles during phase-changing in other species, such as Passiflora edulis, remains limited. Unlike Arabidopsis, P. edulis (a semi-woody perennial climbing vine) undergoes remarkable changes in leaf morphology throughout juvenile-to-adult transition. Nonetheless, the underlying molecular mechanisms are unknown.Here we evaluated the molecular mechanisms underlying the heteroblastic process by analysing the temporal expression of microRNAs and targets in leaves as well as the leaf metabolome during P. edulis development.Metabolic profiling revealed a unique composition of metabolites associated with leaf heteroblasty. Increasing levels of glucose and α-trehalose were observed during juvenile-to-adult phase transition. Accumulation of microRNA156 (miR156) correlated with juvenile leaf traits, whilst miR172 transcript accumulation was associated with leaf adult traits. Importantly, glucose may mediate adult leaf characteristics during de novo shoot organogenesis by modulating miR156-targeted PeSPL9 expression levels at early stages of shoot development.Altogether, our results suggest that specific sugars may act as co-regulators, along with two microRNAs, leading to leaf morphological modifications throughout juvenile-to-adult phase transition in P. edulis