The present study estimates variances and genetic and phenotypic correlations for five traits in 27 progenies of cashew trees (Anacardium occidentale L.). Data were obtained from a trial conducted in 1992 at Pacajus, Ceará, experimental station of Embrapa Agroindústria Tropical. The characters studied were plant height (PH), North-South and East-West canopy spreads (NSS, EWS), and primary and secondary branch numbers (PBN, SBN). All genetic and phenotypic correlations presented positive and significant values. Selection to increase or decrease the average of any one of the five characteristics of cashew plants in the progenies studied affected the average of the others. The 16-month-old canopy spread can be predicted from NSS or EWS since correlations between them were high. Correlations between PH and SBN were low, indicating that there is a good possibility of obtaining smaller plants without causing drastic reductions in SBN. PH and SBN showed, respectively, the lowest and highest genetic variance estimates relative to the corresponding population means.
Neste trabalho são estimadas variâncias, correlações genéticas e fenotípicas e respostas correlacionadas, envolvendo cinco caracteres em 27 progênies de cajueiro (Anacardium occidentale L.). Os dados foram obtidos em Pacajus-CE, num ensaio conduzido no Campo Experimental da Embrapa Agroindústria Tropical, em l992. Os caracteres estudados foram altura de planta (PH), envergaduras norte-sul (NSS) e leste-oeste (EWS) e número de ramos primários (PBN) e secundários (SBN). Todas as correlacões genéticas e fenotípicas obtidas foram positivas e significativas. A seleção para aumentar ou reduzir a média de qualquer um dos cinco caracteres estudados nas progênies de cajueiro afetou indiretamente a média dos outros quatro caracteres. A envergadura da copa aos 16 meses pode ser representada por NSS ou EWS, tendo em vista que a correlação entre elas foi elevada. As correlações envolvendo PH e SBN foram baixas, indicando ser possível obter plantas de porte reduzido sem causar drástica redução no SBN. PH e SBN apresentaram, respectivamente, a menor e a maior estimativa da variância genética em relação à média do caráter

-Crop rotation and cover crop can be important means for enhancing crop yield in rainfed areas such as the lower Coastal Bend Region of Texas, USA. A trial was conducted in 1995 as part of a long-term cropping experiment (7 years) to investigate the effect of oat (Avena sativa L.) cover and rotation on soil water storage and yield of sorghum (Sorghum bicolor L.). The trial design was a RCB in a split-plot arrangement with four replicates. Rotation sequences were the main plots and oat cover crop the subplots. Cover crop reduced sorghum grain yield. This effect was attributed to a reduced concentration of available soil N and less soil water storage under this treatment. By delaying cover termination, the residue with a high C/N acted as an N sink through competition and/or immobilization instead of an N source to sorghum plants. Crop rotation had a significantly positive effect on sorghum yield and this effect was attributed to a significantly larger amount of N concentration under these rotation sequences.Index terms: rotation sequence, soybean, cotton. EFEITO DE CULTURA DE COBERTURA E DE ROTAÇÃO DE CULTURA NO ARMAZENAMENTO DE ÁGUA DO SOLO E NO RENDIMENTO DE SORGORESUMO -Rotação de cultura e cultura de cobertura constituem importantes meios para melhoria do rendimento de culturas em áreas de sequeiro como a região Coastal Bend do Estado do Texas. Um ensaio foi conduzido em 1995, como parte de um experimento de longa duração (7 anos), com o objetivo de investigar o efeito da aveia (Avena sativa L.) como cultura de cobertura, e da rotação de cultura, no armazenamento da água do solo e no rendimento do sorgo (Sorghum bicolor L.). O delineamento experimental adotado foi o de blocos ao acaso, em parcelas subdivididas, com quatro repetições. As rotações foram alocadas nas parcelas, e a cultura de cobertura, nas subparcelas. A cultura de cobertura reduziu o rendimento do sorgo. Este efeito foi atribuído à reduzida concentração de N disponível do solo. Por atraso no extermínio e incorporação da aveia, seu resíduo, com elevada relação C/N, atuou como dreno, pela imobilização, em lugar de ser fonte de N para o sorgo. As rotações sorgo/algodão e sorgo/soja proporcionaram efeito positivo no rendimento de sorgo. Este efeito foi atribuído à maior concentração de N nestas seqüências.Termos para indexação: seqüência de rotação, soja, algodão.

The oleaginous species Jatropha curcas (Euphorbiaceae) exhibits significant potential as a source of biodiesel, but the scarcity of information regarding genetic variability within the species limits its possible exploitation. We examined the genetic diversity and relationships among 97 accessions of J. curcas originating from the Brazilian states of Piauí, Maranhão, Ceará, Bahia, and Minas Gerais. One-hundred ISSR markers were tested and 11 selected for genotyping. Among 307 loci generated by these markers, 96 % were polymorphic. Genetic similarities between accessions were estimated from Jaccard coefficients and the corresponding similarity matrix, and genetic relationships were determined from the dendrogram constructed using the unweighted pair group method with arithmetic average (UPGMA) technique. Nei's genetic diversity indices varied between 0.0256and 0.1703, while Shannon's information indices ranged from 0.0374 to 0.1926. The number of alleles varied from 1.0619 to 1.3257 and the effective number of alleles ranged between 1.0438 and 1.1496. The ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 17 (4): gmr18208 S.O. Gomes et al. 2 inter-population genetic coefficient differentiation was 0.6306, while analysis of molecular variance revealed that genetic divergence among populations was highly significant (p< 0.001), expressed by a fixation index (Φ ST) of 0.4452. Pair-wise analysis of Φ ST confirmed an interpopulation diversity of 44.52% and an intra-population variation of 55.48%. UPGMA analysis allowed the separation of the accessions into four genotypic groups. We conclude that there is significant genetic diversity among the populations of J. curcas and that this variability is mainly due to intra-population genetic diversity.

Context Intercropping maize with tropical forages is known to provide multiple benefits for the agricultural sustainability in the Brazilian savanna. Despite that, more studies are needed to define strategies to improve soil quality and increase crop yield of subsequent crops. Aims This study aimed to evaluate the impacts of cultivating maize in monoculture or in double- and triple-intercropping with brachiaria and crotalaria on the chemical and microbiological attributes of soil, nutritional status of soybean, and the productivity of soybean and millet in succession in the cerrado of eastern Maranhão. Methods The intercropping systems implemented in 2017 were as follows: maize (Zea mays) + Urochloa ruzizienses (brachiaria); maize + Crotalaria juncea (crotalaria); maize + brachiaria + crotalaria; and monoculture maize as a control. In 2018 and 2019, soybean and millet were cultivated on the same plots. Key results The triple-intercropping promoted immediate improvement in the biological and chemical attributes of the soil, especially when compared with monoculture maize. Intercropping maize with brachiaria, with or without crotalaria, increased soybean productivity by 21% and millet by 44% in the subsequent year, compared with monoculture maize system. Intercropping maize with brachiaria, with or without crotalaria, increased the leaf concentrations of nitrogen, potassium, magnesium, and sulfur of the subsequent soybean crop, suggesting improved nutrient cycling with intercropped forages. Conclusions Intercropping maize + forage, especially brachiaria, can be recommended for crop rotation and succession systems in the Brazilian savanna. Implications These results quantified the benefits of crop rotation following intercropping with maize and forage, which can be an alternative for farmers in the Brazilian savanna.