Assessment of Activity Concentration of Radionuclides in Soil and Cassava Food Crop from Solid Mineral Mining Site in Ishiagu, Ivo L.G.A of Ebonyi State, Nigeria

The assessment of activity of concentration of radionuclides in soil and food crops from solid mineral mining sites at Ishiagu, in Ivo L.G.A of Ebonyi State was carried out using the necessary measuring instruments. Samples of soil and cassava crop collected from around the mining sites. The samples were analysed using gamma ray spectrometry. The average activity concentration of 226Ra, 232Th and 40K in soil samples were 12.37,16.08, and 144.29 Bqkg-1 while those for cassava were 2.81, 16.80, and 205.41 Bqkg-1. The soil/plant radionuclide transfer ratio estimated are 0.62, 2.43 and 2.51 for 226Ra, 232Th and 40K, respectively. All the radiological risk parameters estimated are relatively low. The result of this work showed that the obtained results for all samples were lower than the international accepted limit. Hence, from radiological health standpoint, the obtained values of effective doses may not pose significant threat to both human and the environment.

Plantio Direto na Cultura da Mandioca

A cultura da mandioca ocupa uma área plantada no Brasil de 1,4 milhões de ha. É a quarta cultura em volume de produção sendo cultivada em sua maioria em solos arenosos e de baixa fertilidade por pequenos agricultores e agricultores familiares. Na região Centro-sul do Brasil é cultivada em grandes áreas com alto nível tecnológico, onde se obtém elevadas produtividades. Por ser cultivada em largos espaçamentos e recobrir mal o solo é altamente susceptível aos processos erosivos. Comparada aos cereais sua produtividade é superior, podendo atingir valores acima 35 t.ha-1, e por isso extrai grandes quantidades de nutrientes, principalmente K. O plantio direto é considerado um sistema conservacionista que reduz as perdas por erosão e aumenta os teores de matéria orgânica reduzindo também as perdas de nutrientes por lixiviação principalmente em solos arenosos. Nos últimos anos avanços foram feitos no que se refere ao plantio direto da mandioca, refletindo no crescente aumento das áreas sob este sistema. Entretanto os resultados de pesquisa não são conclusivos devido ao pequeno número de experimentos conduzidos, e pela ausência de experimentos de longa duração, que melhor avaliam os efeitos dos diferentes sistemas de produção. Tradicionalmente, os efeitos do plantio direto nos primeiros anos são indiretos, refletindo em produtividade nos sistemas já estabilizados após 2 ou 3 anos de implantação. Contudo boa parte dos resultados relatados são promissores, e demonstram elevado potencial para a melhoria da competitividade da cultura e a sustentabilidade destes agroecossistemas. Palavras chave: sustentabilidade, sistemas de produção, conservação do solo. Abstract Cassava crop is cultivated on 1.4 million ha. It is the fourth crop in terms of production amount, mostly cultivated on sandy and low-fertility soils by small farmers. In the Center-South region of Brazil it is grown in large areas with high technological level, where high yields are obtained. Because it is cultivated in large spaces and covers the soil poorly, it is highly susceptible to erosive processes. Compared to cereals, its productivity is higher, reaching values ​​above 35 t.ha-1. With this it extracts large amounts of nutrients, mainly K. No-tillage is considered a conservation system that reduces losses by erosion, increases the contents of organic matter and also reduces the losses of nutrients by leaching mainly in sandy soils. Many advances have been made towards the development of no-tillage of cassava, culminating in the growing increase in areas under this system. However, the research results are not conclusive due to the small number of experiments, and the absence of long-term experiments. Traditionally, the effects of no-till in the first years are indirect, reflecting on productivity in systems already stabilized after 2 or 3 years. However, part of the reported results is promising, and demonstrate high potential for improving the competitiveness of culture and the sustainability of agro-ecosystems. Keywords: sustainability, production systems, soil conservation.

Edaphic invertebrate macrofauna associated with cassava crop in different soil coverages

This study aimed to identify and assess the edaphic invertebrate macrofauna associated with cassava crop in succession to different soil coverages. The experimental design was randomized blocks as 6 x 3 factorial design with four replications. The first factor was soil cover cultivated from December 2014 to April 2015 (fallow, pearl millet, forage sorghum, Crotalaria ochroleuca, Urochloa ruziziensis and Corn+Urochloa ruziziensis). The second factor was sampling periods (March/2015, October/2015 and June/2016). We sampled four blocks of 0.25 x 0.25 x 0.20 m in each system, following the TSBF (Tropical Soil Biology and Fertility) collection method. The taxonomic composition and abundance of organisms, richness of groups and the diversity indexes of Shannon, Pielou equitability and Simpson dominance were evaluated. There was no interaction between the factors (soil cover x season) for the variables studied. There was difference in the dominance of organisms according to the soil cover (isolated), being the highest index (0.44) obtained by previous cultivation of forage sorghum. The abundance of organisms, group richness and diversity index were influenced by sampling period, demonstrating the influence of seasonality on the invertebrate macrofauna community of the soil

Karakteristik Morfologi dan Kelimpahan Populasi Parasitoid (Hymenoptera) pada Hama Invasif Kutu Putih Ubi Kayu, Phenacoccus manihoti Matile-Fererro (Hemiptera: Pseudococcidae) di Bali

Morphological Characteristics and Populations Abundance of Parasitoid (Hymenoptera) on Invasive Pests Cassava Mealybug, Phenacoccus manihoti Matile-Fererro (Hemiptera: Pseudococcidae) in Bali. This study aims to know the morphological characteristics of parasitoid, population abundance and distribution patterns of parasitoid associated with P. manihoti on cassava crop in Bali. The study was conducted on all cassava crop in Bali with a field observation method that was determined by taking shoots of cassava plants attacked by cassava mealybug P. manihoti, then cassava mealybug P. manihoti were nurtured, then observation was carried out every day until parasitoid appeared and being identified. The results of the study showed that there were three dominant types of parsitoid that were found to be associated with invasive pest P. manihoti, namely Anagyrus lopezi, Acerophagus papayae and Blepyrus insularis. The abundance of parasitoid populations was dominated by parasitoid A. lopezi with a range of values 48.6–81.8%. Then followed by parasitoid A. papayae 7.7 - 37.1%, and B. insularis 3.4 - 14.3%. The distribution pattern of parasitoid varies in each species, parasitoid A. lopezi spreads in groups categories, Parasitoid A. papayae and B. insularis spread random-regulary on cassava crop throughout on each of the Regencies in Bali.

First report of Colletotrichum chrysophillum causing cassava anthracnose in Brazil

Cassava (Manihot esculenta Crantz) has significant socioeconomic relevance in Brazil and other developing countries, as one of the main sources of carbohydrates for human and animal consumption (De Oliviera et al., 2011). Among the cassava crop diseases, anthracnose is one of the main limiting factors for production and may be caused by species like Colletotrichum plurivorum, C. karstii, C. fructicola, and C. siamense (Bragança et al., 2016; Liu et al., 2019; Oliveira et al., 2016; Sangpueak; Phansak; Buensanteai, 2018). Severity in the field is variable, depending on the resistance of the variety used and is also highly influenced by the climate, being the most severe disease under high humidity and high temperature. Under these conditions, it can cause losses of up to 100%. In 2019, cassava leaves presenting dark brown necrotic injuries of different sizes and irregular borders—typical anthracnose symptoms— were collected from commercial plantations in the states of Pará and Tocantins, Brazil. Symptomatic tissue fragments were superficially disinfected, placed in plates with potato dextrose agar (PDA), and incubated under 25 ± 2 °C for seven days. In the 56 isolates used in the morphological identification, the colonies were white and gray at the top and dark gray in the bottom with sector formation. The conidia were hyaline, cylindrical, and aseptic, 10.04 to 17.83 μm long × 3.29 to 5.75 μm wide. These phenotypical characteristics were similar to those of C. gloeosporioides lato sensu species (Weir et al., 2012). Genomic DNA was extracted from two representative isolates (UFT/Coll69, collected in the municipality of Casa de Tábua-PA; UFT/Coll82, collected in Pau Darco-PA) and the APN2 / MAT-IGS, DNA lyase (Apn2), and glyceraldehyde-3-phosphate dehydrogenase-IGS (GAP2-IG) intergenic spacers were amplified and sequenced. The nucleotide sequences were deposited in the GenBank (accession numbers: MT409462, MT396231, MT759633, MT396239, MT396232, MT800846). The BLASTn (Basic Local Alignment Search Tool) showed a 99 to 100% similarity with Colletotrichum chrysophillum. The maximum likelihood phylogenetic analysis grouped the isolates in the C. chrysophillum clade, with a high bootstrap value (98%). Based on morphocultural characteristics and the phylogenetic analysis, the isolates associated with M. esculenta anthracnose were identified as C. chrysophillum, with a frequency of 6.67% among Colletotrichum colonies isolated from cassava leaves. The inoculation of three isolates was carried out in three plants, three leaves for each plant, by spraying spore solution with a concentration of 1×106 conidia / ml, without wounding the leaves and placed in a humid chamber at 25 ° C for ten days. Control plants were inoculated with sterile distilled water. From the 2nd day after inoculation, small irregular necrotic lesions appeared that increased in size over time, while control plants remained asymptomatic. Both were pathogenic and the symptoms caused after inoculation were similar to each other and to those observed in the field. In Brazil, anthracnose by C. chrysophillum was reported in cashew (Veloso et al., 2018) and banana trees (Vieira et al., 2017). To our knowledge, this is the first report of cassava anthracnose disease by C. chrysophillum.

A simple PCR-based method for the rapid and accurate identification of spider mites (Tetranychidae) on cassava

The morphological identification of mites entails great challenges. Characteristics such as dorsal setae and aedeagus are widely used, but they show variations between populations, and the technique is time consuming and demands specialized taxonomic expertise that is difficult to access. A successful alternative has been to exploit a region of the mitochondrial cytochrome oxidase I (COI) gene to classify specimens to the species level. We analyzed the COI sequences of four mite species associated with cassava and classified them definitively by detailed morphological examinations. We then developed an identification kit based on the restriction fragment length polymorphism–polymerase chain reaction of subunit I of the COI gene focused on the three restriction enzymes AseI, MboII, and ApoI. This set of enzymes permitted the simple, accurate identification of Mononychellus caribbeanae, M. tanajoa, M. mcgregori, and Tetranychus urticae, rapidly and with few resources. This kit could be a vital tool for the surveillance and monitoring of mite pests in cassava crop protection programs in Africa, Asia, and Latin America.