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

Abstract

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 segregant 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 phenotypic measure of 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 referred 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 aluminum tolerance on chromosome 8<br>O objetivo deste estudo foi identificar RFLPs (restriction fragment length polymorphisms) ligados a QTLs (locos de caracteres quantitativos) que controlam a tolerância ao Al tóxico em milho utilizando a estratégia de "bulked segregant analysis" (BSA). O material genético utilizado consistiu de uma população F2 proveniente do cruzamento entre a linhagem L53, suscetível ao Al, e a linhagem L1327, tolerante ao Al. Ambas foram desenvolvidas pelo programa de melhoramento do Centro Nacional de Pesquisa em Milho e Sorgo - CNPMS/EMBRAPA. Avaliaram-se 1554 indivíduos F2 em solução nutritiva contendo Al tóxico utilizando o índice comprimento relativo da raiz seminal (RSRL) como medidor fenotípico de tolerância. A distribuição de freqüência dos valores de RSRL foi contínua, unimodal com tendência para suscetibilidade. Plântulas F2 que apresentaram os maiores e menores valores de RSRL foram transplantadas para o campo e autopolinizadas para obtenção de famílias F3. Selecionaram-se 30 famílias F3 (15 suscetíveis e 15 tolerantes), as quais foram av...

Inheritance of aluminum tolerance in maize

“…In a study using RFLP in line L922, Sibov et al (1999) also found indications of the involvement of two loci (or two groups) located on chromosomes 6 and 10. The use of RFLP allowed Brondani and Paiva (1996) to associate aluminum tolerance with a gene or a block of genes on chromosome 2, and Torres et al (1997) associated chromosome 8 to aluminum tolerance.…”

Molecular studies for linkage analysis and determination of quantitative trait loci (QTL) for acid soil tolerance in maize (Zea mays L.)

“…For soil acidity combined across environments and for yield only one QTL was detected at chromosome 1 (at 116 cM) with a R" of 1%. Therefore, these results provided little evidence to support previous work with respect to aluminum tolerance related with a region on chromosome 8 (Reiter et al, 1991;Torres, et al, 1997). In this study, it was found in acid environments (single and combined) one QTL at 52 cM on the chromosome 8 in AYA65 for plant height (Table 27) with R~ of 7% and another at 21 cM in COM.…”

“…In South America (Brazil, Peru, Colombia, Venezuela, and Ecuador) about 80% of the agricultural activities occur in acidic areas. Brazil has the largest area with 205 million hectares (Cerrado Brasileiro) of which 112 million are suitable for agricultural production (Torres, et al, 1997).…”

“…One of more common techniques used in studies of the tolerance to soil acidity in maize is based on the effect of A1 on seminal root growth in nutrient solution. Although A1 toxicity is the most important factor in acid soils, there are other toxicities, deflciencies, and interactions with the organic matter content that constitute the complex responsible for lower maize yield (Evans and Kamprath, 1970;Adams and Moore, 1983;Torres, et al, 1997).…”

Avaliação de nove linhagens de milho em cruzamentos dialélicos quanto à tolerância ao alumínio

“…Para a maioria das espécies de plantas, a característica de tolerância ao Al é dominante, podendo ser controlada por um ou mais genes de ação maior, que atuam juntamente com genes modificadores (Kochian, 1995). Há uma grande variação nos relatos sobre herança da tolerância ao Al em milho, com resultados descrevendo desde herança monogênica (Rhue et al, 1978;Garcia Júnior & Silva, 1979), passando por característica controlada por dois genes complementares dominantes (Miranda et al, 1984), até herança poligênica (Magnavaca, 1982;Sawazaki & Furlani, 1987;Lima et al, 1992;Torres et al, 1997).…”