Micropropagation requires controlling contamination that might compromise the success of the process. Thermal sterilization is traditionally used; however, costs deriving from equipment acquisition and maintenance render this technique costly. With the purpose of finding an alternative to thermal sterilization, this research aimed at assessing the efficiency and ideal concentration of sodium hypochlorite for sterilization of culture media and glassware used during rooting of micropropagated Gerbera hybrida cv. Essandre. Two experiments were carried out. In the first one, treatments consisted of control I (no sterilization), control II (thermal sterilization), and total active chlorine concentrations of 0.0005, 0.001, 0.002 and 0.003%. In the second experiment, based on the results observed in the first experiment, treatments consisted of control I (thermal sterilization) and II (chemical sterilization), and total active chlorine concentrations of 0.002, 0.0025 and 0.003%. Plant behavior was assessed based on the length of aerial part and roots, number of roots, and dry biomass of plants. Results showed that the addition of an active chlorine concentration of 0.003% to culture media provided total control of contaminants, and there were no significant differences regarding the variables analyzed between plants obtained with thermal sterilization and with sodium hypochlorite sterilization. Thus, chemical sterilization can be used as a replacement for thermal sterilization of nutrition media for rooting of gerbera in vitro.
Ralstonia solanacearum is the causal agent of Moko disease in bananas, which in the state of Sergipe in northeastern Brazil causes "Sergipe facies". This disease induces atypical symptoms similar to those of Bugtok disease in the Philippines. This study was conducted to sequence, assemble, and annotate the genomes of the Sergipe faciescausing isolates SFC and IBSBF2570 (sequevar IIA-53) and compare their genomes with two representative isolates causing Bugtok disease. The genomes were sequenced and assembled, resulting in lengths of 5.58 Mb (SFC) and 5.46 Mb (IBSBF2570) in 185 and 174 contigs, respectively. The isolates of Sergipe facies and Bugtok disease showed similarities in their gene contents. We identified 5,668 information clusters, 3,752 of which were shared by all genomes (core genes). Moreover, 3,585 single-copy genes were identified. Isolates causing Bugtok disease exclusively shared 266 more information clusters than the isolates causing Sergipe facies. These results suggest that Sergipe facies and Bugtok disease isolates show high genomic similarity. However, the similarity is even greater between the Bugtok disease isolates. This may be because of their longer period of interaction compared to Sergipe facies isolates.
Banana vascular wilt or Moko is a disease caused by Ralstonia solanacearum . This study aimed to sequence, assemble, annotate, and compare the genomes of R. solanacearum Moko ecotypes of different sequevar strains from Brazil. Average nucleotide identity analyses demonstrated a high correlation (> 96%) between the genome sequences of strains CCRMRs277 (sequevar IIA-24), CCRMRs287 (IIB-4), CCRMRs304 (IIA-24), and CCRMRsB7 (IIB-25), which were grouped into phylotypes IIA and IIB. The number of coding sequences present in chromosomes and megaplasmids varied from 3,070 to 3,521 and 1,669 to 1,750, respectively. Pangenome analysis identified 3,378 clusters in the chromosomes, of which 2,604 were shared by all four analyzed genomes and 2,580 were single copies. In megaplasmids, 1,834 clusters were identified, of which 1,005 were shared by all four genomes and 992 were identified as single copies. Strains CCRMRsB7 and CCRMRs287 differed from the others by having unique clusters in both their chromosomes and megaplasmids, and CCRMRsB7 possessed the largest genome among all Moko ecotype strains sequenced to date. Therefore, the genomic information obtained in this study provides a theoretical basis for the identification, characterization, and phylogenetic analysis of R. solanacearum Moko ecotypes.
O Moko ou murcha bacteriana é uma doença que acomete a bananeira em países da América Latina, Filipinas e Malásia, provocando perdas de até 100% da produção. A doença é causada por Ralstonia solanacearum filotipo II (IIA e IIB), uma bactéria habitante do solo e nativa do Brasil, com isolados classificados nas sequevares IIA-6, IIA-24, IIA-41, IIA-53, IIB-3, IIB-4 e IIB-25, os quais são denominados de ecotipo Moko. No Brasil, R. solanacearum é uma praga quarentenária presente, restrita a estados das regiões Norte (Amapá, Amazonas, Pará, Rondônia e Roraima) e Nordeste (Alagoas e Sergipe), com ocorrência da maioria das sequevares assinaladas, o que indica a alta variabilidade da bactéria no país. Em Sergipe, foram observados sintomas atípicos da doença, causados pela sequevar IIA-53, exclusiva do nordeste brasileiro, sendo a variante sintomatológica denominada de síndrome Sergipe. Para a correta identificação do filotipo/sequevares do ecotipo Moko são empregados testes moleculares, tais como reação Filotipo Multiplex-PCR, sequenciamento parcial do gene egl e mutS e Moko Multiplex-PCR. Além disso, técnicas genômicas e de bioinformática têm possibilitado comparações entre genomas de isolados brasileiros de diferentes sequevares do ecotipo Moko, principalmente da sequevar IIA-53, visando entender aspectos relacionados à ecologia, epidemiologia e sintomatologia
As bactérias promotoras de crescimento de plantas (BPCP) são encontradas aderidas ao solo ou colonizando a superfície de raízes de muitas culturas, aumentando a sua produtividade. O objetivo deste trabalho foi caracterizar bactérias provenientes de solos cultivados com cucurbitáceas e avaliar o seu efeito no desenvolvimento de plântulas de melancia cv. Crimson Sweet. Após o isolamento das bactérias, procedeu-se a caracterização fenotípica e o agrupamento pelo método UPGMA com base no coeficiente de Bray-Curtis. Na avaliação da eficiência na promoção de crescimento, os tratamentos consistiram de 44 isolados bacterianos e a testemunha, utilizando-se o delineamento inteiramente casualizado com cinco repetições. Inoculou-se cada isolado bacteriano na concentração de 4,5 x 10-8 UFC.mL-1 nas sementes, durante 24 horas. As testemunhas foram imersas em água destilada e esterilizada pelo mesmo período de tempo. Decorridos 20 dias após a semeadura, avaliou-se o comprimento e a biomassa seca da parte aérea e radicular. Os dados foram submetidos à análise de variância e as médias comparadas pelo teste de Scott-Knott, a 5% de significância. Dos 44 isolados bacterianos, o dendrograma permitiu a formação de 29 grupos distintos a 80% de similaridade. O isolado UNEB 55 proporcionou aumento no comprimento e biomassa seca da parte aérea e radicular da melancia. Os isolados UNEB 05, UNEB 27, UNEB 53 e UNEB 57 induziram aumento no comprimento da parte aérea, sem efeito deletério nas demais variáveis. Esses resultados indicam que estes isolados poderão ser utilizados como promotores de crescimento em melancia.
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