Cultivares de alho são sexualmente estéreis sob condições padrão de cultivo, com implicações diretas nos custos de produção comercial, bem como em programas de melhoramento. O alho é comercialmente propagado por meio de bulbilhos, o que facilita a transmissão de doenças e leva ao acúmulo de cargas virais ao longo das gerações. A cultura de tecidos produz clones livres de vírus que são mais produtivos, mantendo as características desejadas da cultivar. Consequentemente, esta técnica permite estudar a genética do alho, bem como garantir a conservação genética das variedades. Nosso objetivo foi analisar a regeneração in vitro de oito cultivares comerciais de alho usando segmentos de raiz como explante. Para cada genótipo, explantes derivados de bulbilho foram isolados e introduzidos em meio MS suplementado com 2,4-D e 2-iP. Calos foram transferidos para meio MS suplementado com 8,8 mM BAP e 0,1 mM NAA (meio de regeneração A), ou com 4,6 mM cinetina somente (meio de regeneração B). Os calos foram avaliados quanto à frequência de regeneração após sessenta dias de cultivo in vitro. A cultivar nobre 'Jonas' apresentou as maiores taxas de regeneração entre as cultivares testadas. O meio de cultura A, o qual continha auxina e citocinina, induziu as maiores taxas de regeneração em todas as cultivares. O processo aqui descrito é simples, reprodutível e pode ser usado potencialmente como uma ferramenta em estratégias de melhoramento para outras cultivares comerciais e genótipos de alho.

Garlic cultivars are sexually sterile under standard growth conditions, with direct implications for commercial production costs as well as breeding programs. Garlic is propagated commercially via bulblets, which facilitates disease transmission and virus load accumulation over vegetative generations. Tissue culture produces virus-free clones that are more productive, while keeping the desired traits of the cultivar. Consequently, this technique allows studies of garlic genetics as well as guarantees genetic conservation of varieties. We aimed at analyzing the in vitro regeneration of eight marketable cultivars of garlic using root segments as explants. For each genotype, bulblet-derived explants were isolated and introduced into MS medium supplemented with 2,4-D and 2-iP. Calli were transferred to MS medium supplemented with 8.8 mM BAP and 0.1 mM NAA (regeneration medium A), or with 4.6 mM kinetin alone (regeneration medium B). The calli were then evaluated for regeneration frequency after sixty days of in vitro cultivation. The noble cultivar 'Jonas' presented the highest rates of plant regeneration among the cultivars tested. The medium A, which contained auxin and cytokinin, induced the highest regeneration rates of all cultivars. The process described herein is simple, reproducible and can potentially be used as a tool in molecular breeding strategies for other marketable cultivars and genotypes of garlic.

Os hormônios vegetais são possíveis reguladores chave do desenvolvimento de micorrizas arbusculares (MAS). Contudo, seus papéis em MA são pouco conhecidos. No presente estudo, foram utilizados mutantes em cinco classes hormonais introgredidos em uma única cultivar (cv. Micro-Tom) de tomateiro (Lycopersicon esculentum Mill. Syn Solanum lycopersicum L.) para determinar seus efeitos no desenvolvimento de MA e expressão de genes relacionados à defesa (quitinases e b-1,3-glucanases) em raízes. Sob condição de baixo P, os mutantes epinastic (epi) e Never ripe (Nr), os quais são super produtores e pouco sensíveis a etileno, respectivamente, tiveram a colonização intra-radicular por Glomus clarum inibida quando comparada com o controle Micro-Tom (MT). Não se observou alterações significativas na colonização fúngica nos mutantes afetando outras classes hormonais. Sob condição de baixo P, o nível de transcritos codificando uma quitinase básica de classe I (chi9) foi mais elevado em raízes micorrizadas dos mutantes epi e Nr, quando comparado com o controle MT. Em contraste, o nível de transcritos de uma b-1,3-glucanase ácida da classe III (TomPR-Q'a) em raízes micorrizadas do mutante epi foi significativamente menor que em raízes micorrizadas de MT. A colonização de raízes no mutante epi foi acompanhada por várias alterações na morfologia fúngica, quando comparada com o controle MT. Os resultados sugerem que o etileno pode desempenhar um importante papel controlando o crescimento fúngico intra-radicular nas MAS.

Plant hormones are likely key regulators of arbuscular mycorrhizae (AM) development. However, their roles in AM are not well known. Here mutants in five hormone classes introgressed in a single tomato (Lycopersicon esculentum Mill. Syn Solanum lycopersicum L.) background (cv. Micro-Tom) were used to determine their effects on AM development and the expression of defense-related genes (chitinases and b-1,3-glucanases) in roots. Under low P conditions, mutant epinastic (epi) and Never ripe (Nr), ethylene overproducer and low sensitivity, respectively, had the intraradical colonization by Glomus clarum highly inhibited, as compared to the control Micro-Tom (MT). No significant alterations in fungal colonization were observed in mutants affecting other hormone classes. Under low P conditions, the steady state levels of transcripts encoding a class I basic chitinase (chi9) were higher in mycorrhizal epi and Nr mutant roots as compared to MT controls. In contrast the steady state levels of a class III acidic b-1,3-glucanase (TomPR-Q'a) transcripts in mycorrhizal epi mutant roots were significantly lower than in mycorrhizal MT roots. Root colonization in epi mutants was accompanied by several alterations in fungal morphology, as compared to root colonization in MT controls. The data suggest that ethylene may play an important role in controlling intraradical arbuscular mycorrhizal fungal growth.

Plant hormones play a crucial role in integrating endogenous and exogenous signals and in determining developmental responses to form the plant body throughout its life cycle. In citrus species, several economically important processes are controlled by phytohormones, including seed germination, secondary growth, fruit abscission and ripening. Integrative genomics is a powerful tool for linking newly researched organisms, such as tropical woody species, to functional studies already carried out on established model organisms. Based on gene orthology analyses and expression patterns, we searched the Citrus Genome Sequencing Consortium (CitEST) database for Expressed Sequence Tags (EST) consensus sequences sharing similarity to known components of hormone metabolism and signaling pathways in model species. More than 600 homologs of functionally characterized hormone metabolism and signal transduction members from model species were identified in citrus, allowing us to propose a framework for phytohormone signaling mechanisms in citrus. A number of components from hormone-related metabolic pathways were absent in citrus, suggesting the presence of distinct metabolic pathways. Our results demonstrated the power of comparative genomics between model systems and economically important crop species to elucidate several aspects of plant physiology and metabolism.

RNA silencing mechanisms are conserved throughout eukaryotic evolution, possibly due to their importance in viral resistance and other aspects of cell biology. Here, we explored the Citrus EST (CitEST) database in search of sequences related to the most important known genes involved in RNA silencing. Transcripts strongly matching Argonaute (AGO), Dicer-like (DCL), Hua enhancer (HEN), and RNA-dependent RNA Polymerase (RdRP) were found in many of the citrus libraries. The reads were clustered and quantified. This shows that post-transcriptional gene silencing apparatus is active in citrus. It seems plausible that a better understanding of the players of RNA silencing in Citrus spp. and related genera may help create new tools to defeat the viral diseases that affect the citrus industry. Functional analyses of these citrus genes would enable the pursuit of this hypothesis.

Com o objetivo de produzir calos embriogênicos de citros, óvulos abortados de frutos maduros de 6 variedades de laranja doce (Citrus sinensis L. Osbeck), ‘Bahia Cabula’, ‘Baianinha’, ‘Hamlin’, ‘Orvalho de Mel’, ‘Rubi’ e ‘Valência’ foram introduzidos em meio de cultivo MT modificado com adição de extrato de malte, com e sem adição de 5 mg L-1 benziladenina (BA). Os calos obtidos das variedades ‘Bahia Cabula’, ‘Orvalho de Mel’, ‘Rubi’ e ‘Valência’ foram cultivados em meio basal MT, contendo os carboidratos maltose, galactose, lactose, glicose ou sacarose nas concentrações de 18; 37; 75; 110 e 150 mM para a indução da embriogênese somática. Os calos destas mesmas variedades foram submetidos ao isolamento de protoplastos, com o uso de 3 soluções enzimáticas. Os resultados revelaram que há influência do genótipo sobre a calogênese. A embriogênese somática foi estimulada na presença de galactose, para a maioria das variedades. A solução enzimática composta de 1% de celulase, 1% de macerase e 0,2% de pectoliase foi a mais adequada para o isolamento de protoplastos a partir de calos das variedades de laranja doce estudadas.

Intending to produce embryogenic citrus calli (Citrus sinensis L. Osbeck), aborted ovules of ripe fruits from six sweet orange varieties (‘Bahia Cabula’, ‘Baianinha’, ‘Hamlin’, ‘Orvalho de Mel’, ‘Rubi’ and ‘Valencia’) were introduced onto modified MT medium with and without benzyladenine (BA). Calli obtained from ‘Bahia Cabula’, ‘Orvalho de Mel’, ‘Rubi’ and ‘Valencia’ varieties were grown on MT basal medium modified with the carbohydrates maltose, galactose, lactose, glucose and sucrose at 18; 37; 75; 110 and 150 mM. The effect on somatic embryogenesis was studied. Calli from the same genotypes were submitted to protoplast isolation, using three different enzymatic solutions. Results revealed the genotype effect in the callus induction. Somatic embryogenesis was stimulated in the presence of galactose, for most varieties. Enzymatic solution composed of 1% cellulase, 1% macerase and 0,2% pectolyase was the best for protoplast isolation from calli of all genotypes tested.