Estimativa da produtividade de arroz irrigado por inundação em em função da temperatura do ar e da radiação solar

Foram desenvolvidas duas equações de estimativa da produtividade do arroz irrigado por inundação, para as variedades: IAC-242, IAC-100, IAC-101 e IAC-102, em função da temperatura do ar e da radiação solar, no período crítico de formação da produção, para a região de Pindamonhangaba (SP). Os valores de temperatura do ar e de radiação solar ótimos encontrados para as variedades foram, respectivamente, 25,0oC e 475 cal.cm-2.dia-1. O modelo agrometeorológico desenvolvido para previsão da produtividade da cultura que apresentou melhores resultados quando testado com dados independentes foi o que relacionou o menor desvio dos dois elementos climáticos em relação ao valor ótimo obtido através de uma equação de regressão linear múltipla. Os valores de produtividade estimados pelo modelo mostraram diferenças menores que 10% quando comparados com os valores obtidos no campo.Two regression equations were developed to estimate lowland rice yield as a function of air temperature and incoming solar radiation, during the crop yield production period in Pindamonhangaba, SP, Brazil. The following rice cultivars were used: IAC-242, IAC-100, IAC-101 and IAC-102. The value of optimum air temperature obtained was 25.0°C and of optimum global solar radiation was 475 cal.cm-2, day-1. The best agrometeorological model was the one that related least deviation of air temperature and solar radiation in relation to the optimum value obtained through a multiple linear regression. The yield values estimated by the model showed good fit to actual yields of lowland rice (less than 10%)

A comparative genetic diversity assessment of industrial and household Brazilian cassava varieties using SSR markers

This study was carried out in order to assess the genetic diversity of 20 cassava (Manihot esculenta Crantz) genotypes with high phenotypic performance using microsatellite markers. Two groups were considered for this study: eleven varieties for industrial uses and nine for household consumption. By using nine microsatellite primers, high polymorphism was identified in all the loci analyzed, with values reaching 100%. On average, 3.4 alleles per locus were found, with 0.371 the value estimated for the observed heterozygosity and 0.555 for gene diversity for the entire set of varieties. The genetic variability found in both varieties, cultivated on a large-scale in the South Center region of Brazil, is wide enough to allow the choice of divergent parental genotypes to be used in crosses to obtain new recombinant genotypes. Furthermore, the analyses indicated a high genetic variability within the two groups (I: varieties for industrial uses; II: varieties for household consumption). However, varieties for household consumption attain higher genetic variability, probably due to high priority placed on selection of different sensorial traits. In the cluster analysis, a tendency for separation of varieties for industrial use and household consumption was verified. Our results represent an important source of information to the cassava breeding program in Brazil