Search

Cassava (Manihot esculenta Crantz) is an important food security crop in many parts of the developing world. The crop?s high yield potential and multitude of uses?both for nutrition and processing?render cassava a promising driver for the development of rural value chains. It is traditionally propagated from stem cuttings of up to 30 cm in length, giving a multiplication rate as low as 1:10. Propagating cassava traditionally is very inefficient, which leads to challenges in the production and distribution of quality planting material and improved cultivars, greatly limiting the impact of investments in crop breeding. The work described in the present study aimed to develop a seed treatment approach to facilitate the use of shorter seed pieces, increasing the multiplication rate of cassava and thus making the crop?s seed systems more efficient. After several tests, formulation was identified, consisting of thiamethoxam 21 g ha-1, mefenoxam 1.0 g ha-1, fludioxonil 1.3 g ha-1, thiabendazole 7.5 g ha-1 and Latex 2% as a binder. Plant growing from seed pieces treated with this formulation displayed increased crop establishment and early crop vigor, leading to an improved productivity throughout a full growing cycle. This allowed to reduce the cassava seed piece size to 8 cm with no negative effects on germination and crop establishment, leading to yields comparable to those from untreated 16 cm pieces. This, in turn, will allow to increase the multiplication ratio of cassava by a factor of up to 3. Notably, this was possible under regular field conditions and independently of any specialised treatment facilities. Compared with existing seed production protocols, the increased multiplication rates allowed for efficiency gains of between 1 to 1.9 years compared to conventional five-year cycles. We believe that the technology described here holds considerable promise for developing more reliable and remunerative delivery channels for quality cassava planting material and improved genetics. Made available in DSpace on 2020-05-13T04:40:58Z (GMT). No. of bitstreams: 1 Oliveira-et-al-PlosOne-2020.pdf: 2217574 bytes, checksum: 46f8ef3421bcdd79efbc4c128cf349e1 (MD5) Previous issue date: 2020

Modifications were made in the PCR conditions aiming to overcome the problem of non-amplification of the Xanthomonas phaseoli pv. manihotis (Xpm) fragment, using the primer pair XV / XK described in the literature. The objective of this study was to propose changes in the primers already described (XV / XK_MOD) and validate the use of these new primers in identifying Xpm. The validation procedure was carried out with the primer pair XV and XK_MOD, using different strains of Xpm, other plant pathogenic and endophytic bacteria genera and one isolate of X. phaseoli pv. passiflorae. As a control, additional reactions were conducted in multiplex with the universal primers for the 16S rRNA gene of the bacteria together with XV / XK and XV / XK_MOD. Using the forward primer (XV) described in the literature together with the modified reverse primer (XK_MOD), it was possible to achieve amplification from DNA extracted from in vitro cultures and from infected tissue, but no amplification was noticed for the primer pair described in the literature, confirming the effectiveness of the proposed modification. Made available in DSpace on 2019-10-15T18:08:32Z (GMT). No. of bitstreams: 1 ImprovementofthespecificdetectionofXanthomonas....pdf: 466638 bytes, checksum: 80e1d838621075228ead259a38babeab (MD5) Previous issue date: 2019

Over the last few years, considerable effort has been spent by Embrapa in the construction of a plant disease database representative enough for the development of effective methods for automatic plant disease detection and recognition. In October of 2016, this database, called PDDB, had 2326 images of 171 diseases and other disorders affecting 21 plant species. PDDB size, although considerable, is not enough to allow the use of powerful techniques such as deep learning. In order to increase its size, each image was subdivided according to certain criteria, increasing the number of images to 46,513. Both the original (PDDB) and subdivided (XDB)databases are now being made freely available for academic research purposes, thus supporting new studies and contributing to speed up the advances in the area. Both collections are expected to grow continuously in order to expand their reach. PDDB and XDB can be accessed in the link https://www.digipathos-rep.cnptia.embrapa.br/. Made available in DSpace on 2019-06-27T01:08:27Z (GMT). No. of bitstreams: 1 ID443892018v16n6p1749IEEELatinAmericaTransaction.pdf: 892792 bytes, checksum: fb724ff1aa6fdafc4f179b63ac2bd4c1 (MD5) Previous issue date: 2018 O título da revista foi grafado no artigo como IEEE LATIN AMERICA TRANSACTIONS, mas registro de título do periódico é REVISTA IEEE AMÉRICA LATINA.

Coffee leaf rust is the most limiting disease for coffee cultivation in Brazil. Despite its importance, relatively little is known about the genetic diversity of Hemileia vastatrix, the rust causal agent. In this work, the DNA from 112 monopustule isolates from different geographic locations and coffee genotypes were analysed by amplified fragment length polymorphisms (AFLP). The objectives were to assess the influence of the host and geographic origin on the diversity and population differentiation in H. vastatrix. The fungal population showed a low level of genotypic diversity. Gene diversity (h) was 0·027 and the hypothesis of random mating in the total population was rejected, but evidence for recombination was found for two subpopulations (Sao Paulo and Parana). The analysis of molecular variance revealed that 90% of the genetic distribution of the pathogen occurs among isolates within the subpopulation (states or host of origin). There was no correlation between geographic and genetic distance (r = −0·024, P = 0·74), which together with the high number of migrants and the low degree of differentiation in populations of H. vastatrix, is consistent with the fact that the inoculum is probably easily dispersed by wind over long distances, allowing dispersal of the pathogen among coffee growing areas in Brazil. Therefore, it is difficult to predict the durability of resistant sources to coffee rust. The recommendation for the breeding programmes is thus to incorporate multigenic resistance as a control strategy.

The objective of this work was to identify sources of resistance to dry root rot induced by Fusarium sp. in cassava accessions. A macroconidial suspension (20 µL) of 11 Fusarium sp. isolates was inoculated in cassava roots, from 353 acessions plus seven commercial varieties. Ten days after inoculation, the total area colonized by the pathogen on the root pulp was evaluated by digital image analysis. Cluster analysis revealed the presence of five groups regarding resistance. The root lesion areas ranged from 18.28 to 1,096.07 mm² for the accessions BGM 1518 and BGM 556, respectively. The genotypes BGM 1042, BGM 1552, BGM 1586, BGM 1598, and BGM 1692 present the best agronomical traits. O objetivo deste trabalho foi identificar fontes de resistência à podridão seca das raízes ocasionada por Fusarium sp. em acessos de mandioca. Inoculou-se uma suspensão (20 µL) de macroconídios de 11 isolados de Fusarium sp. em raízes de 353 acessos e sete variedades comerciais de mandioca. Dez dias após a inoculação, avaliou-se a área total colonizada pelo patógeno na polpa das raízes, por meio de análise de imagens digitais. A análise de agrupamento revelou a presença de cinco grupos quanto à resistência. As áreas lesionadas das raízes variaram de 18,28 a 1.096,07 mm² nos acessos BGM 1518 e BGM 556, respectivamente. Os genótipos BGM 1042, BGM 1552, BGM 1586, BGM 1598 e BGM 1692 apresentam as melhores características agronômicas.

Fusarium oxysporum f. sp. cubense, agente etiológico do mal-do-Panamá, vem provocando perdas elevadas na cultura da bananeira, sendo fator limitante ao cultivo de variedades apreciadas pelo mercado. O presente trabalho objetivou comparar dois métodos de inoculação deste fungo, utilizando a técnica de avaliação por imagens digitais.

The root rot complex is one of the most hazardous disease of cassava in the Brazilian Northeast region, and can be attributed to many pathogens, including oomycetes and fungus as Fusarium sp. The search for resistance to this disease is the main objective of the cassava development programs worldwide. T PDF. 1293.

A fusariose, causada porFusariumoxysporumf. sp. passiflorae (Fop), é uma das principais doenças do maracujazeiro. A principal estratégia para controle dessa doença é a utilização de resistência genética. PDF. 817

A produtividade do maracujazeiro é seriamente prejudicada por problemas fitossanitários, como a fusariose, causada porFusariumoxysporumf. sp.passiflorae. Neste estudo foram avaliados 25 acessos do Banco Ativo de Germoplasma de Maracujazeiro da Embrapa Mandioca e Fruticultura, quanto a resistência à fusariose em condições de campo infestado com o patógeno (sendo 14 acessos de maracujazeiro amarelo; três acessos de maracujazeiro roxo; três acessos de Passiflora alataCurtis; um acesso de Passiflora cincinnataMast.; e quatro híbridos de maracujazeiro amarelo). PDF. 818.

O objetivo deste trabalho foi avaliar, por meio de marcadores SSR, a diversidade genética de Xylella fastidiosa no Estado da Bahia. Foram estudadas duas das principais regiões produtoras de citros no Estado, o Litoral Norte e o Recôncavo Sul. Para fins comparativos, utilizaram-se dez amostras provenientes do Estado de São Paulo. Foram empregados os seguintes iniciadores: ASSR20, OSSR9, OSSR17, CSSR4, CSSR12 e CSSR20, dos quais os quatro últimos permitiram identificar 22 loci polimórficos. As populações de X. fastidiosa presentes em citros no Estado da Bahia apresentam elevada diversidade genética, com base nos marcadores SSR, com pools gênicos distintos e agrupamento geográfico. No Litoral Norte, as populações do isolado apresentam maior diversidade genética do que as da região do Recôncavo Sul da Bahia.