Genetic variability of fruit characteristics in Kiyomi tangor progenies of citrus

[摘要] English: In a citrus breeding programme, information on the breeding value of available parents andthe heritability of specific characters can be an important aid to the breeder when planningcontrolled crosses for cultivar improvement. By quantifying the genetic variation in apopulation the breeder can study the relationships between the hybrids and parents andgain an understanding of how certain characteristics are inherited. Therefore a study wasundertaken to investigate the genetic variation in the progenies of six mandarin families,where female parent Kiyomi tangor was crossed with male parents Dancy, Hansen, Rishon,Roma, Shani and Sunburst mandarins. Data were collected over a two year period for thefruit quality characteristics of rind colour, fruit size, fruit shape and fruit internal quality.A significant level of variation was found between the families for all the fruit characteristicsstudied. The within family variation was larger than the between family variation andindicated a high level of genetic variation within the families, while the within tree variationwas found to be lower than the within family variation. Data collected over a two year periodshowed significant year and year x family variation for many of the fruit characteristics. Theintraclass correlation coefficient, relevant to selection within the families, was found to befairly low for all the fruit characteristics studied and indicated that the variation found withinthe families was only partly genetic and non-genetic factors contributed to the variation in thephenotype. Therefore only two years of testing will not be reliable and a mean performanceover multiple years data is recommended for effective selection.All the families showed an improvement in the population for rind colour, fruit shape and thefruit internal quality while half of the families showed an improvement for fruit size. All thefamilies showed heterosis with some individuals being superior to both parents. Familieswith male parents Hansen, Rishon, Shani and Sunburst had a rind colour superior to theother families, while the Kiyomi x Rishon family had larger fruit with a more round fruit shapeand the Kiyomi x Roma family had a superior internal quality. This study revealed the maleparent to have a large influence on the progeny and male parents with a deeper orange rindcolour, larger fruit size, better fruit shape and superior internal quality resulted in familieswith a greater improvement in the population. Therefore only male parents of the highestquality should be used as parents in breeding programmes in order to increase the chanceof obtaining a superior new cultivar.

[发布机构] University of the Free State