ISHS Acta Horticulturae 510: VII Eucarpia Meeting on Cucurbit Genetics and Breeding
OUTCROSSING RATE AND IMPLICATIONS FOR THE IMPROVEMENT OF A SEGREGATING POPULATION OF WATERMELON |
| Authors: | M.A.J.d. Ferreira, R. Vencovsky, M.L.C. Vieira, M.A. de Queiróz |
| Keywords: | Citrullus lanatus, inbreeding, mating system, outcrossing, plant breeding, RAPD |
| Abstract:
This study was aimed at estimating the natural outcrossing rate (t=l-s) of a partially andromonoecius segregating population (with 53.3% monoecious and 46.7% andromonoecious plants) of watermelon, the results being discussed from the perspective of the plant breeder. Twelve maternal families, each composed of 23 individuals plus the corresponding seed parents, were genotyped with RAPD markers. The MLDT (Multilocus Estimation of Outcrossing with Dominant Markers) procedure was used, considering a mixed mating system model. The following estimates were obtained with reasonable consistency over families: average coefficient of inbreeding, F = 0.091; multilocus outcrossing rate, tm= 0.765. The results indicated that this population practices a mixture of selfing and outcrossing for reproduction, and this has several implications on breeding strategies, such as: for recurrent selection, more than one generation is required for attaining a condition close to equilibrium; even without epistasis progress from recurrent selection is no longer a function of additive variance alone, depending also on D1 (which may be negative) and D2; and immediate and permanent progress tend to be different and are not easily estimatable. The need for estimating the outcrossing rate is stressed for populations that are not typically allogamic or autogamic. | |
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