Abstract The objective of the present work was to use MAS in self-pollinated cassava populations for obtaining individuals with high inbreeding (f) aimed at rapid development of partial inbred lines. Three progenies (F0222, F1378 and F1662) were self-pollinated, generating a total of 233 S1 individuals. The progenies and the S1 individuals were evaluated in the seedlings and clonal evaluation trials (CETs). In the CET, plants were evaluated for the following traits: plant height (PH), root dry matter content (DMC), above ground yield (AGY), root (RY) and starch yield (SY). Twenty-seven microsatellites and five minisatellites were used to determine the level of inbreeding of the S1 individuals. Inbreeding (f) values varied from 0.15 to 0.89 within progenies, whereas most of the S1 individuals presented f values above 0.50. In average, 25% of the S1 individuals were selected, which resulted in a 38% inbreeding increase in the cassava progenies. In contrast, phenotypic selection showed no differences in inbreeding increase. Furthermore, there was no correlation between the level of inbreeding and agronomic traits. MAS was efficient for the identification and selection of cassava S1 individuals, with higher inbreeding values contributing to the decrease in the breeding cycles necessary to obtain new cassava inbred lines.

Não há disponibilidade de cultivares comerciais de feijoeiro (Phaseolus vulgaris) com alto nível de resistência à Xanthomonas axonopodis pv. phaseoli (Xap) no Brasil. Isto se deve à complexa herança de resistência que, apesar dos diversos estudos efetuados, ainda não foi completamente elucidada. Os objetivos deste trabalho foram complementar um mapa genético do feijoeiro, construído com base no cruzamento entre um genótipo susceptível 'HAB-52' e um genótipo resistente 'BAC-6' e mapear e analisar regiões genômicas (QTLs) relacionadas com a resistência à Xap. Onze grupos de ligação foram identificados, por meio de 143 marcadores RAPD, cobrindo 1234,5 cM do genoma. Este mapa foi usado para detectar QTLs associados à resistência em folhas e em vagens a Xap. As médias de severidade de doenças em folhas e em vagens, representadas pelo índice de doença transformado (IDT) e pelo diâmetro de lesão em vagens (DLV), respectivamente, foram adicionados aos dados do mapa de ligação. Detectaram-se cinco QTLs para IDT e um para DLV. Os QTLs para IDT localizaram-se nos grupos de ligação A, B, G e J, com variância fenotípica variando de 12,7 a 71,6%. O QTL identificado para DLV, com variância fenotípica de 12,9%, localizou-se num grupo de ligação distinto, indicando que a reação de resistência em folhas e vagens é controlada por diferentes genes.

Common bean (Phaseolus vulgaris) cultivars with a high degree of resistance to Xanthomonas axonopodis pv. phaseoli (Xap) are not available in Brazil. Despite many studies, a low degree of resistance to Xap continues to exist due to its complex genetic inheritance, which is not well known. The objectives of this research were to complement a common bean genetic map based on the cross between a susceptible genotype 'HAB-52' and a resistant genotype 'BAC-6', and to map and analyze genomic regions (quantitative trait loci – QTLs) related to Xap resistance. Eleven linkage groups were determined using 143 RAPD markers, covering 1,234.5 cM of the genome. This map was used to detect QTLs associated with Xap resistance on leaves and pods. The averages of disease severity on leaves (represented by the transformed disease index – TDI) and pods (represented by the diameter of lesion on pods – DLP) were added to the data of the linkage map. Five TDI QTLs and only one LDP QTL were detected. The TDI QTLs were placed in the A, B, G and J linkage groups, with phenotypic variations ranging from 12.7 to 71.6%. The DLP QTL explained 12.9% of the phenotypic variation and was mapped in a distinct linkage group. These results indicate that there are different genes involved in the control of resistance on leaves and pods.