Resumen

SAHAGUN-CASTELLANOS, Jaime; RODRIGUEZ-PEREZ, J. Enrique  y  PENA-LOMELI, Aureliano. Combined sampling for regeneration of plant genetic resources of monoecious species with natural pollination. Agrociencia [online]. 2010, vol.44, n.3, pp.311-323. ISSN 2521-9766.

In the regeneration of plant genetic resources of monoecious species and those that are reproduced by random mating sampling procedures should be used to minimize cost and inbreeding, which in turn is related to the decrease of the effective population size, the increase of probability of extinction of genes, and so on. Two ways to take a random sample of individuals from one cycle to generate the next that does not require artificial pollination are: 1) completely random (MACA), as in the ideal population (IP), 2) as in the IP but in two stages (MADE), first n families of half-sibs are randomly selected and then from each one of them m individuals are randomly selected. In the latter case, the subsequent random mating will allow crosses between half-sibs. The objective of this study was to determine the effective population size in terms of inbreeding (N_e(f)) of MADE and its relation to that of MACA (N_e(f)CA). As for MADE, it was considered that the size of the completely random sample was mn. Based on the variance of the number of gametes of an individual forming progeny, for MADE it was found that N_e(f)= [4mn-2]/[m-(mn)^-1+2], which implies that for a sample of constant size mn MADE increases its N_e(f) as m is smaller (and, consequently, n is larger) and for any value of n reaches its maximum when m=1; and only in this case is larger than the effective size of MACA that is always equal to nm. When mn is large, the N_e(f) / N_e(f)CA. ratio is reduced to approximately 4/(m+2); this means that when m=1, the effective size of MADE exceeds that of MACA (approximately 33.33 %); and with m = 2 N_e(f)=N_e(f)CA. It was found that in MADE the composition of the sample is very important in the collection or regeneration of plant genetic resources. For example, with a sample size mn = 1000, N_e(f) can take values from 4 (with m = 1000 and n = 1) up to 1333.33 (with n= 1000 and m = 1).

Palabras llave : random mating; half-sib families; ideal population; effective population size.

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