Roberto Luis Weiler

TESTE DE PATERNIDADE E AVALIAÇÕES AGRONÔMICAS DE POSSÍVEIS HÍBRIDOS DE TANGERINEIRA 'SUNKI'

Citrus production is spread all over the world. In Brazil citrus represent the major volume of fruit production. The rootstock is extremely important to establish a good-quality orchard. At the Estacao Experimental Agronomica of the Universidade Federal do Rio Grande do Sul was established placed a hybrid citrus plants orchard, originated from openpollination with ‘Lee’ tangelo [Citrus clementina Hort. ex Tan. x (C. tangerina Hort. ex Tan. x C. paradisi Macf.)] as female parent. Amongst those hybrids, fourteen plants were selected with characteristics alike to those of the rootstock ‘Sunki’ tangerine (Citrus sunki Hort. ex. Tan.) In order to confirm hybrids paternity, single sequence repeat (SSR) markers were used. The molecular analysis allowed to identify eleven hybrids that did not have ‘Sunki’ tangerine as male parent. The hybrids 49, 77 and 92, potencialy hybrids of ‘Sunki’, stood out for higher poliembriony, higher number of emerged seedling per seed and higher number of seeds per fruit in comparison to ‘Sunki’.

Caracterização morfológica, determinação do número de embriões e taxa de poliembrionia em três porta-enxertos híbridos de citros

Abstract Due to several phytosanitary problems that affect Brazilian citriculture, diversification of rootstocks is a priority. Hybrid root-stocks are being developed by citrus genetic breeding programs, and those hybrids must be evaluated regarding mor-phological characteristics and yield. Therefore, the objective of the present paper was to characterize leaves and fruits, to determine embryo number per seed and to evaluate polyembriony rates of three hybrid rootstocks: citranges ‘Fepagro C 13’, ‘Fepagro C 37’ and ‘Fepagro C 41’, comparing then to three other rootstocks currently used in citrus orchards Trifoliata, citru-melo ‘Swingle’ and citrange ‘Troyer’. Little morphological variation was found in leaves but, for fruits, some differences were observed, especially in citranges ‘Fepagro C 13’ and ‘Fepagro C 37’ that produced, in average, many seeds per fruit 24.2 and 35.0, many of them viable, 19.2 and 21.2 and with a good number of embryos 5.0 and 3.1, respectively, besides presenting high polyembriony taxes, 84% and 92%, respectively. The results show that these two hybrids have a good potential to be used as seed donor plants to citrus rootstocks.Key words: citriculture, alternative rootstocks, leaves and fruits morphology.

Ploidia e fertilidade de pólen em progênies de citros

PLOIDY AND POLLEN FERTILITY IN CITRUS HYBRIDS This work was performed to estimate pollen fertility and determinate the ploidy level of 11 to 12 years old progenies of crosses of ‘Montenegrina ’ mandarin (Citrus deliciosa Ten.) with ‘King’ mandarin (C. nobilis Lour.) and with ‘Caipira’ sweet orange (C. sinensis (L.) Osb.) maintained at Estacao Experimental Agronomica of UFRGS, in Eldorado do Sul, Brazil. The ploidy level was determined by chromosome countings in meiosis cells and pollen fertility evaluated by staining pollen grains with propionic carmine. All evaluated hybrids are diploid and pollen fertility varied from zero to 98%. C27, a hybrid ‘Montenegrina’ x ‘Caipira’, was found is sterile, and C21, from the same cross, showed 10 % fertility. The lowest observed fertility in the progeny ‘Montenegrina’ x ‘King’ was 42 %.