Morphological, pedigree, and molecular distances and their association with hybrid wheat performance

Abstract

-The objectives of this work were to estimate the genetic distance among wheat genotypes using morphological, pedigree, molecular, and combined morphological and molecular measures, to determine the correlations between these measures, and to evaluate the combining ability of the genotypes. Three generations and two planting designs were studied. Six wheat genotypes were crossed using a diallel design. The F 1 , F 2 and F 3 generations were evaluated in the fi eld, in the crop seasons of 2003, 2004 and 2005, under spaced plant and full-row planting designs. The estimated general and specifi c combining abilities of tested hybrids were infl uenced both by the generation and the planting design. The correlation coeffi cients among the distance measures and between these measures and genotype performances of different generations for the two planting designs were low to moderate. In order to obtain a more precise estimate of the genetic distance among cultivars and its association with the hybrid performance, more than one generation, planting design, and genetic distance estimation technique should be employed.Index terms: Triticum aestivum, combining ability, genetic variability, parental selection. Distâncias morfológicas, genealógicas e moleculares e suas associações com o desempenho de híbridos em trigoResumo -O objetivo deste trabalho foi estimar a distância genética entre genótipos de trigo, por meio de dados morfológicos, genealógicos, marcadores moleculares AFLP ("amplifi ed fragment length polymorphism"), usados individualmente ou simultaneamente, e calcular a correlação entre essas medidas de distância e a capacidade de combinação dos genótipos. Foram estudadas três gerações e dois sistemas de semeadura. Seis genótipos de trigo foram cruzados de forma dialélica. Os híbridos F 1 e as populações F 2 e F 3 foram avaliados em campo, nos anos agrícolas de 2003, 2004 e 2005, com os esquemas de semeadura de planta espaçada e em linha cheia. As capacidades gerais e específi cas de combinação dos híbridos testados foram infl uenciadas tanto pela geração quanto pelo esquema de semeadura. Os coefi cientes de correlação foram de baixo a moderado entre as medidas de distância e entre estas e o desempenho dos genótipos, nos dois esquemas de semeadura. Para a obtenção de uma estimativa fi el da distância genética entre cultivares e da sua associação com o desempenho dos híbridos, devem ser empregados mais de uma geração, sistema de semeadura e técnica de estimativa da distância genética.Termos para indexação: Triticum aestivum, capacidade de combinação, variabilidade genética, seleção de genitores.

Relationships between four measures of genetic distance and breeding behavior in spring wheat

“…This confirmed that the selected parents and their respective hybrid combinations were contrasting. No significant differences were detected for generations, as has been reported by Bertan et al (2009). However, the generation effect showed interactions with treatment and with GCA and SCA.…”

Multivariate analysis to determine the genetic distance among backcross papaya (Carica papaya) progenies

“…Besides providing a better understanding of the organization of germplasm and improving the efficiency in the sampling of genotypes, knowledge of the genetic distance also allows the selection of biologically oriented crossings (Vieira et al, 2007;Bertan et al, 2009), resulting in obtaining the segregating progenies with high genetic variability for selection (Marić et al, 2004). This genetic variability available in segregating populations is essential for breeding programs, because besides increasing the chance of identifying superior genotypes it is directly related to the genetic gain obtained by artificial selection.…”

“…Examples can be found in studies conducted with tomato (Gonçalves et al, 2008) and wheat (Marić et al, 2004;Vieira et al, 2007;Bertan et al, 2009), where the highest correlation coefficient was found between combined analysis and molecular data. However, when conducting a comparative analysis between the degree of polymorphism revealed by molecular markers in different studies, it is verified that the values ranged from 68 to 93.2% in the studies mentioned above, while in the present study this level of polymorphism was significantly lower (27.5%), resulting in a low correlation.…”

Use of morpho-agronomic traits and DNA profiling for classification of genetic diversity in papaya

“…The strong influence of the descriptors, which were the most abundant in the dissimilarity matrix, was also observed by Bertan et al (2009), while studying genetic diversity in wheat. These authors observed a low correlation (r = 0.05) between the morphological and molecular data (AFLP) but a high correlation (r = 0.65) between combined (morpho-agronomic and molecular) and molecular data.…”

“…Exploitation of this genetic variability may strengthen the genetic basis of this crop through the development of new lines and hybrids, given that the reproductive system of papaya enables crosses and that the absence of inbreeding depression makes it possible to obtain lines with high vigor (Oliveira et al, 2010a). Knowledge of genetic variability is very useful for identifying the best combinations between genotypes with the potential to maximize the genetic gains made by hybridization (Máric et al, 2004;Bertan et al, 2009).…”