-Controlled crosses were done by using the mandarins Clementine and Sunki, the Rangpur lime and the Volkamer lemon as female parents with none, low, low to moderate and moderate polyembryony degrees, respectively, and Poncirus trifoliata and its hybrids as male parents for its easily recognizable trifoliate characteristic. The hybrid frequencies were 57.4%, 53.6%, 18.6% and 14.2% for Clementine, Sunki, Rangpur and Volkamer, respectively. It was also observed a negative association between polyembryony degree and hybrids frequency.A variabilidade genética presente em Citrus e gêneros afins é passível de ser explorada em hibridações visando ao desenvolvimento de novas 1 Aceito para publicação em 4 de junho de 1999.

Pesq. agropec. bras., Brasília, v.34, n.5, p.903-909, maio 1999 HYBRID VIGOUR ON SUNKI MANDARINABSTRACT -Controlled crosses of Sunki with Poncirus trifoliata and its hybrids were performed in order to estimate the zygotic seedlings frequency, by comparing its vigour with the ones from nucellar origin. A relatively high fruit set rate of 40% was achieved, which indicates a good compatibility within the parental crosses. The observed frequency of zygotic seedlings was 48% and certainly this was underestimated due to the presence of Poncirus hybrids in the pollinations. Epicotyl length and the true leaf number character estimates showed that 91% of the identified hybrids may be similar or even superior to the nucellar ones in relation to plant vigour.A obtenção de híbridos em citros é limitada por particularidades de natureza biológica, dentre as quais destacam-se a ocorrência da poliembrionia, comum em muitas variedades, o longo período pré-reprodutivo e a elevada heterozigosidade