Abstract The aim of this study was to develop a methodology that uses water deficit induction to increase the frequency of hybrids in Citrus varieties that have a high and an intermediate level of polyembryony, respectively. The experiment examined the ‘Sunki Tropical’ mandarin and ‘Rangpur Santa Cruz’ lime genotypes at three water stress intensities: 20, 40 and 100% of the pot capacity (PC). The generated fruits were harvested, and the seeds were counted. After germination, the number of nucellar and hybrid seedlings was determined. For ‘Rangpur Santa Cruz’ lime genotype, the highest hybrid frequency generated was 64.2%, which occurred at a PC of 40% and exceeded by 12% that occurring at a PC of 100%. For ‘Sunki Tropical’ mandarin, the highest observed hybrid frequency was 21.75%, which occurred at a PC of 20% and was more than double the hybrid frequency of 8.57% observed at 100% of the PC.

A diversificação de uso de porta-enxertos de citros é importante no Brasil devido à presença de diversos estresses abióticos e bióticos, além da busca por atributos horticulturais desejáveis como nanismo, alta eficiência de produção e indução de boa qualidade aos frutos. Para a seleção de um genótipo com potencial de uso como porta-enxerto, porém, o desempenho na fase de propagação também é relevante. Assim, caracterizaram-se os frutos e avaliou-se a propagação em ambiente protegido de porta-enxertos híbridos de citros obtidos ou selecionados pelo Programa de Melhoramento Genético de Citros da Embrapa: citrandarins ‘Indio’, ‘Riverside’ e ‘San Diego’, híbridos HTR-051, TSKC x (LCR x TR)-040 e 059, LVK x LCR-010 e 038, TSKC x CTTR-002, TSKC x CTSW-041 e LCR x TR-001, além das variedades comerciais citrumelo ‘Swingle 4475’, trifoliata ‘Flying Dragon’, limoeiro ‘Cravo Santa Cruz’ e tangerineira ‘Sunki Tropical’. Foram avaliados variáveis biométricas, fisiológicas e coeficientes técnicos. O delineamento experimental foi em blocos ao acaso, com quatro repetições e 50 plantas na parcela ou 20 frutos por genótipo, conforme a avaliação. Citrumelo ‘Swingle’ e LVK x LCR-010 apresentaram alta produção de sementes por fruto, enquanto HTR-051 e LCR x TR-001 produziram as menores quantidades. A poliembrionia foi superior para TSKC x CTTR-002, TSKC x (LCR x TR)–040, LCR x TR-001, citrandarins ‘Indio’, ‘Riverside’ e ‘San Diego’ e tangerineira ‘Sunki Tropical’, tendo trifoliata ‘Flying Dragon’ e LVK x LCR-010 apenas 45% de poliembrionia média. A emergência de citrandarin ‘Riverside’ foi mais rápida e uniforme em relação aos demais genótipos. O crescimento vegetativo da parte aérea e do sistema radicular foi superior para citrandarin ‘Riverside’, TSKC x (LCR x TR)-059, tangerineira ‘Sunki Tropical’, citrumelo ‘Swingle’ e limoeiro ‘Cravo’ e seus híbridos. Todos os híbridos de citros avaliados apresentam potencial de uso como porta-enxertos.

The diversification of citrus rootstocks in Brazil is important in order to adjust to the diversification of abiotic and biotic stresses the trees are confronted, besides the need for horticultural traits of interest as dwarfism and high production efficiency and fruit quality. The performance of the genotype during the propagation stage is also relevant for rootstock selection. Therefore, fruits of hybrid rootstocks obtained or selected by Embrapa Citrus Breeding Program and commercial varieties were characterized and their propagation evaluated in a protected environment. The hybrids were ‘Indio’, ‘Riverside’ and ‘San Diego’ citrandarins, the hybrids HTR-051, TSKC x (LCR x TR)-040 and 059, LVK x LCR-010 and 038, TSKC x CTTR-002, TSKC x CTSW-041 and LCR x TR-001, and the commercial varieties ‘Swingle 4475’ citrumelo, ‘Flying Dragon’ trifoliate, ‘Rangpur’ lime selection Santa Cruz, and ‘Sunki’ mandarin selection Tropical. Collected data included biometric and physiological variables and technical coefficients. The experimental design was randomized blocks with four replications with 50 plants in the unit or 20 fruits per genotype, according to the evaluation procedure. ‘Swingle’ citrumelo and LVK x LCR-010 presented high seed production per fruit (23 to 26), while HTR-051 and LCR x TR-001 produced the least amounts (2 to 3). Polyembryony varied from 97,5% to 100% for TSKC x CTTR-002, TSKC x (LCR x TR)–040, LCR x TR-001, ‘Indio’, ‘Riverside’ and ‘San Diego’ citrandarins and ‘Sunki Tropical’ mandarin, and from 40% to 50% for ‘Flying Dragon’ trifoliate and LVK x LCR-010. Emergence of ‘Riverside’ citrandarin was faster (27 days) and more uniform in relation to the other genotypes (29 to 43 days). ‘Riverside’ citrandarin, TSKC x (LCR x TR)-059, ‘Sunki Tropical’ mandarin, ‘Swingle’ citrumelo and ‘Rangpur’ lime and its hybrids had the highest canopy and root system vegetative growth. All evaluated hybrid citrus genotypes could potentially be used as rootstocks.