Utilização de marcadores SSR como ferramenta auxiliar na análise de fatores associados a dureza do grão em milho.

xSuplemento. Edição dos resumos do 46º Congresso Nacional de Genética, Águas de Lindóia, SP, 2000

A search for RFLP markers to identify genes for aluminum tolerance in maize.

The objective of this study was to identify restriction fragment length polymorphism (RFLP) markers linked to QTLs that control aluminum (Al) tolerance in maize. The strategy used was bulked segregation analysis (BSA) and the genetic material utilized was an F2 population derived from a cross between the Al-susceptible inbred line L53 and Al-tolerant inbred line L1327. Both lines were developed at the National Maize and Sorghum Research Center - CNPMS/EMBRAPA. The F2 population of 1554 individuals was evaluated in a nutrient solution containing a toxic concentration of Al and relative seminal root length (RSRL) was used as a phenotype measured tolerance. The RSRL frequency distribution was continuous, but skewed towards Al-susceptible individuals. Seedlings of the F2 population which scored the highest and the lowest RSRL values were transplanted to the field and subsequently selfed to obtain F3 families. Thirty F3 families (15 Al-susceptible and 15 Al-tolerant) were evaluated in nutrient solution, using an incomplete block design, to identify those with the smallest variances for aluminum tolerance and susceptibility. Six Al-susceptible and five Al-tolerant F3 families were chosen to construct one pool of Al-susceptible individuals, and another of Al-tolerant, herein refered as "bulks", based on average values of RSRL and genetic variance. One hundred and thirteen probes were selected, with an average interval of 30 cM, covering the 10 maize chromosomes. These were tested for their ability to discriminate the parental lines. Fifty-four of these probes were polymorphic, with 46 showing codominance. These probes were hybridized with DNA from the two contrasting bulks. Three RFLPs on chromosome 8 distinguished the bulks on the basis of band intensity. DNA of individuals from the bulks was hybridized with these probes and showed the presence of heterozygous individuals in each bulk. These results suggest that in maize there is a region related to aliminum tolerance on chromosome 8

Eficiência do comprimento relativo de raiz seminal (CRRS) na avaliação de plantas individuais para tolerância ao alumínio em milho.

xSuplemento. Edição dos resumos do 43º Congresso Nacional de Genética

Uso de marcadores de RFLP na identificação de QTLs para tolerância ao alumínio em milho utilizando populações segregantes F2 e F4.

Suplemento. Edição dos resumos do 43º Congresso Nacional de Genetica, Goiânia, 1997

Use of RFLPs to identify genes for aluminium tolerance in maize.

The objective of this study was to identify restriction fragment length polymorphism (RFLP) markers linked to quantitative trait loci that control. Al tolerance in maize. The strategy used was bulked segregant analysis, which is based on selecting for bulk bred true F2 individuals. The genetic material used consisted of an F2 population derived from a cross between Al susceptible (L53) and Al tolerant (L1327) maize inbred lines, Both lines were developed in the maize breeding programme of the Centro Nacional de Pesquisa de Milho e Sorgo. The relative seminal root length (RSRL) index was used as the phenotypic measure of tolerance. The frequency distribution of RSRL showed continuous distribution, which is typical of a quantitatively inherited character, with a tendency towards Al susceptible individuals. The estimated heritability was found to be 60%. This moderately high heritability value suggests that, although the caracter has a quantitative nature, it may be controlled by a small number of genes, Those seedlings of the F2 population that stored the highest and lowest values for RSRL were subsequently selfed to obtain the F3 families. These falmilies were evaluated in nutrient solution to identify those that were not segregating. On the basis of the results, five individuals were chosen for each bulk. Sixty-five probes were selected at an average interval 0f 30 cM, covering all ten maize chromosomes. For the hybridization work, a non-radioctive labelling system, using dig-dUTP and alkaline phosphatase, proved to be quite efficient and reliable, resulting in Southern blots with good resolution and allowing the menbranes to be stripped and reprobed as least three times. Twenty-three markers showed a co-dominant effect, identifying 40 RFLP loci that could distinguish the parental inbred lines. These 23 probes are now being hybridized with DNA from the two contrasting bulks. Also, a search for other informative markers is being carried out to increase genome coverage