This study determined the concentrations of lead and cadmium in edible parts of Colocasia esculenta, Amaranthus spp.and Ipomoea batata cultivated on farms in industrially polluted sections of Nyabugogo Marsh in Kigali, Rwanda. The concentrations in all three crops exceeded European Union (EU) standards for metal concentration in food crops. C. esculenta roots (Taro) contained the highest concentration of lead (1.02 mg kg-1) and cadmium (0.56 mg kg-1), approximately ten and six times over the EU limits, respectively. Even though I. batata (sweet potato) contained the lowest concentrations of lead (0.75 mg kg-1), this is almost eight times the upper limit. The highest bioaccumulation factors (the ratio of plant metal concentration to that of the soil in which it is found growing) for both metals were observed in amaranth plants. The concentrations of lead and cadmium in the farm soils were all acceptable based on EU standards (300mg kg-1 for lead and 3mg kg-1 respectively. The average daily consumption by an adult in the community living around the Marsh and where some of the produce is sold is 50g of amaranth, 120g of taro and 180g of sweet potato. Based on the metal concentration and these rates of consumption, the daily dietary intake of lead by an adult in the community from amaranth, taro and sweet potato is 1 x 10-4, 3 x 10-4 and 4 x 10-4 mg kg-1 respectively. The daily intake of cadmium is 4 x 10-4, 1.7 x 10-4 and 1.2 x 10-4 mg kg-1 for amaranth, taro and sweet potato respectively. These metal intakes are well within the recommendations set forth by the World Health Organisation. The community also has access to multiple sources of dietary and non dietary zinc such as beans, milk and rain water collected from zinc coated roofing sheets, which serves to ameliorate the effects of cadmium. It is however worth noting that survey data may have yielded overestimates of these zinc sources, due to the conditions under which the surveys were conducted i.e. in the hearing of neighbors due to the cramped nature of housing, which may have prompted respondents to inflate consumption quantities of expensive food items. The calculated maximum recommended quantities for daily intake of the crops are very large and are unlikely to be consumed by the population i.e. >2kg of amaranth, >2 kg of taro and 3 kg of sweet potato per day for an adult. Additionally, because this is a poor community, access to such quantities of food on a daily basis is not likely. The community is therefore not exposed to health risks from consuming metal contaminated crops, largely because of the small quantities consumed. The local population is therefore at no immediate risk to exceeding metal consumption limits by consuming vegetables grown in the Nyabugogo Marsh, but the threats will likely increase if the pollution of the Marsh is not addressed.

Aiming to characterize morphologically the genotypes of sweet potato, to estimate the genetic divergence and to evaluate the yield performance in the edaphoclimatics conditions in the municipality of Junqueiro, Alagoas, Brazil, an experiment was developed, consisting of two varieties and nine clones, in the randomized blocks design with three replications. For morphological characterization, were used 21 descriptors, being fourteen of the shoot and seven of the storage roots. To evaluate the genetic divergence, were used two methodologies: principal components and the generalized Mahalanobis distance, being the genotypes grouped by Tocher method. For the evaluation of the yield performance of the genotypes, were conducted variance analysis, with the averages confronted by Scott-Knott test (P < 0.05). The results indicate there phenotypic variability between the traits of shoot and storage root of the genotypes of sweet potato evaluated. In the estimation of the genetic divergence from principal components analysis, the general form of the mature leaf, the immature leaf color and secondary color of the stem were the traits that most contributed to the divergence of the shoot, explaining 77.08% of the variability existing in the first three principal components. In storage roots, the format, the defect of the surface and the intensity of the predominant color, were the traits that most contributed to the divergence, achieving explain 86.79% of the variability existing in the first three principal components. The acquisition of six groups among the eleven genotypes studied, showed a significant divergence between the genotypes of sweet potato based on the morphological descriptors. When used the generalized Mahalanobis distance methodology, the clone 6 and the variety Sergipana, by their distances of high magnitude, were the most dissimilar (D2 = 244.3). The traits that contributed mostly to the genetic dissimilarity were the marketable root yield (30.79%), the shoot phytomass yield (16.56%) and the internode length (12.84%). The taking of five groups among the eleven genotypes studied showed a significant genetic divergence between the genotypes of sweet potato. The clones 6 and 11 showed the highest marketable roots yield, with 12.08 and 9.08 t ha-1, respectively. The clones 8, 14 and the variety Rainha Prata had the highest shoot phytomass yield, with 5.42, 5.17 and 5.83 t ha-1. These results suggest new prospects for the cultivation of sweet potato in the region of Junqueiro, Alagoas. It was concluded that there is genetic and phenotypic variation among genotypes of sweet potato, explained by morphological characterization and the two techniques to estimate the genetic divergence. According to the results presented in this paper, the Breeding Program of CECA - UFAL may to adopt three measures: the first is the assessment of clones 6 and 11, most yields, in field testing in the municipality of Junqueiro, aiming stability tests, to launch them as varieties. The second will be realization of artificial crosses aiming based in the genetic distances and the per se yields of parents (clones 6 and 8). And the third measure will be the formation of a population with large genetic basis, thereby increasing the probability of obtaining superior genotypes in the segregating generations. / Com o objetivo de caracterizar morfologicamente os genótipos de batata-doce, estimar a divergência genética e avaliar o desempenho produtivo nas condições edafoclimáticas do município de Junqueiro, Estado de Alagoas, foi desenvolvido um experimento, composto por duas variedades e nove clones, no delineamento em blocos casualizados com três repetições. Para a caracterização morfológica, foram utilizados 21 descritores, sendo quatorze da parte aérea e sete das raízes. Para estimar a divergência genética, foram utilizadas duas metodologias: componentes principais e distância generalizada de Mahalanobis, sendo os genótipos agrupados pelo método de Tocher. Para a avaliação do desempenho produtivo dos genótipos, foram realizadas análises de variância, sendo as médias confrontadas pelo teste Scott-Knott (P < 0,05). Os resultados indicam haver variabilidade fenotípica entre os caracteres da parte aérea e os da raiz dos genótipos de batata-doce avaliados. Na estimativa da divergência genética a partir da metodologia dos componentes principais, a forma geral da folha madura, a cor da folha imatura e a cor secundária da haste foram às características que mais contribuíram para a divergência da parte aérea, explicando 77,08% da variabilidade existente nos três primeiros componentes principais. Nas raízes, o formato, o defeito da superfície e a intensidade da cor predominante, foram os caracteres que mais contribuíram para a divergência, conseguindo explicar 86,79% da variabilidade existente nos três primeiros componentes principais. A obtenção de seis grupos entre os onze genótipos analisados evidenciam uma significativa divergência entre os genótipos de batata-doce com base nos descritores morfológicos. Quando utilizado a metodologia da distância generalizada de Mahalanobis, o clone 6 e a variedade Sergipana, por suas distâncias de alta magnitude, foram as mais dissimilares (D2 = 244,3). As variáveis que mais contribuíram para a dissimilaridade genética foram a produtividade de raízes comerciais (30,79%), a produtividade de fitomassa da parte aérea (16,56%) e o comprimento do entrenó (12,84%). A obtenção de cinco grupos entre os onze genótipos analisados evidenciam uma significativa divergência genética entre os genótipos de batata-doce. Os clones 6 e 11 apresentaram as maiores produtividades de raízes comerciais, com 12,08 e 9,08 t ha- 1, respectivamente. Os clones 8, 14 e a variedade local Rainha Prata apresentaram as maiores produtividades de fitomassa da parte aérea, com 5,42; 5,17 e 5,83 t ha-1. Estes resultados apontam novas perspectivas para o cultivo de batata-doce na região de Junqueiro, Estado de Alagoas. Diante do exposto, pode-se concluir que existe variabilidade fenotípica e genética entre os genótipos de batata-doce, explicado pela caracterização morfológica e pelas duas técnicas para estimar a divergência genética. De acordo com os resultados apresentados nesta pesquisa, o Programa de Melhoramento do CECA UFAL poderá adotar três medidas: a primeira será a avaliação dos clones 6 e 11, mais produtivos, em ensaios de campo no município de Junqueiro, Estado de Alagoas, visando testes de estabilidade, para lançá-los como variedades. A segunda será a realização de cruzamentos direcionados com base nas distâncias genéticas e nos rendimentos per se dos genitores (clones 6 e 8). E a terceira medida será a formação de uma população de ampla base genética, aumentando assim, a probabilidade de obtenção de genótipos superiores nas gerações segregantes.