Desenvolveu-se uma série de pesquisas abordando os mais diversos ângulos relativos à propagação seminífera do marmeleiro, aspecto em que a literatura é extremamente escassa. Objetivou-se a coleta dos subsídios necessários, como ponto de partida ao seu melhoramento genético, e à obtenção de porta-enxertos de pereira, nespereira e do próprio marmeleiro. A presente dissertação e o relato dos trabalhos experimentais realizados na Seção de Fruticultura de Clima Temperado; do Instituto Agronômico de Campinas - IAC - com a colaboração de seções básicas do mesmo Instituto e do Centro de Energia Nuclear na Agricultura - CENA - USP, de Piracicaba, SP. Aos estudos utilizou-se principalmente o marmeleiro ‘Portugal’, o mais difundido nas regiões produtoras, e sete outras variedades menos comuns, atualmente disponíveis nas condições experimentais. Averiguaram-se os seguintes aspectos reprodutivos básicos e correlatos: meios e períodos de estratificação das sementes a frio-úmido; processos de preparo das sementes; capacidade de reprodução das variedades; processos de formação e rendimento de plantas; caracterização citogenética; meios e períodos de armazenamento; radiassensitividade das sementes; efeitos da radiação na composição mineral das plantas, e a radiossensitividade e o volume nuclear interfásico.

The present dissertation aims to expose a series of experimental works developed by the author over a period of five years at “Instituto Agronômico de Campinas” (IAC) with contributions of its basic sections and of the “Centro de Energia Nuclear na Agricultura” (CENA)-USP, Piracicaba, SP. Investigations were performed on quince (Cydonia oblonga Mill.) dealing with several aspects of seed propagation for breeding purposes and to obtain rootstocks for further studies with pear and loquat grafting. The quines culture in the State of São Paulo has nowadays a secondary importance. However, till the beginning of this century, it had been a promise one, showing various interesting aspects and expressive economic and social value. At the present time, otherwise, there is a great needing for informations concerning its technical problems, but the literature about this fruit tree is scarce and not easily found. So, as an effort to its reappearance, the quince culture history, based on the literature review, regarding ecological and some economic data from the main productive areas in the country, varieties under cultivation, plant growth habit, fruit characters, taxonomy and informations referring to the seed propagation, are also presented. The varieties employed experimentally were: ‘Portugal’, the main commercial one, and seven other available at Instituto Agronômico experimental conditions. Particularly, the following aspects of quince propagation were researched: media and periods to supply the seed chilling requirement in moist cold storage (5-10°C) to break the physiological dormancy; quince seeds viability prepared by several extraction processes; seed germination and seedling development of eight quines varieties; cytogenetic aspects of the varieties; seeds viability influenced by storage conditions and periods of time for storage; preliminary determination of seed radiosensitivity; concentrations of some macro and micronutrients in quince seedlings obtained from irradiated seeds, and radiosensitivity and interphasic nuclear volumes from three clonal materials.