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Among the oilseed plants, physic nut stands out for its yield potential and for the quality of its oil for biodiesel and biokerosene production. Currently, low seed yield, uneven fruit maturation and the lack of high yielding genotypes limit the viability of this crop. Here we evaluated the yield performance of a population, structured in 16 half-sib families, in the 2nd, 3rd and 4th years after planting (2009-11). Seed yield showed variability. The families maintained their relative performance over time. Contrary to expectations, seed yield was lower in the 4th year, probably due the increased competition between plants and leafhopper (Empoasca spp) incidence. Temporal yield stability and adaptability estimates indicated a trend toward maintaining plant superiority over time, and families 7 (1059 kg ha-1) and 12 (984 kg ha-1) showed the best stability and yield performance. Physic nut has the potential for greater yield gains.

ResumoNo Brasil, o método mais comum de propagação de porta-enxertos de pessegueiro é através de sementes. Por se tratar de uma espécie que apresenta variabilidade no grau de dormência das sementes em função da cultivar, a estratificação em baixas temperaturas é requerida para uniformizar a germinação, emergência e aumentar o percentual de sementes germinadas. Com isso, o objetivo deste trabalho foi avaliar o efeito da estratificação em frio, a 7 ± 0,5 ºC, por 15; 30; 45 e 60 dias, sobre a emergência de plântulas obtidas de sementes com endocarpo dos porta-enxertos cvs. Capdeboscq, Nemaguard e Seleção 039-03-02. Avaliaram-se o índice de velocidade de emergência em campo, a percentagem total de plântulas emergidas, o diâmetro do caule, o número de brotações do caule até 25 cm acima do solo e a altura de plântula. Verificou-se que sementes das cultivares Capdeboscq e Seleção 039-03-02 estratificadas por 30 a 60 dias tiveram a emergência das plântulas antecipada e maior uniformidade no percentual de plântulas emergidas. Verificou-se que períodos de estratificação inferiores a 60 dias são insuficientes para promover rápida emergência e bom percentual de plântulas emergidas da cultivar Nemaguard. De maneira geral, a Seleção 039-03-02 apresentou os melhores parâmetros relacionados à emergência e ao crescimento inicial das plântulas em relação às cultivares Capdeboscq e Nemaguard.Palavras-chave adicionais: propagação por sementes; Prunus sp.; tratamento térmico; velocidade de emergência. AbstractIn Brazil, the most usual way of propagating peach rootstock is by means of the seed. Since peach seeds present a variable degree of dormancy, seed stratification under low temperatures is demanded to uniform germination and emergence and increase germination percentage. Having that in mind, the objective of this experiment was to evaluate the effects of submitting the seeds to a temperature of 7 ± 0.5 °C for periods of 15, 30, 45, and 60 days. Seeds with the endocarp of three rootstocks were used : Capdeboscq, Nemaguard, and Seleção 039-03-02. The speed of emergence in the field, total percentage of emerged seedlings, stem diameter, number of sproutings on the stem up to 25 cm above soil surface, and plant height. It was verified that the seeds of cultivars Capdeboscq and Seleção 039-03-02 stratified for 30 to 60 days had seedling emergence anticipated and higher seedling emergence percentage . It was verified for the Nemaguard cultivar that seed stratification periods lower than 60 days are not sufficient to promote quick emergence and high germination percentage. Cultivar Seleção 039-03-02 showed the best results as to seedling emergence and initial growth when compared to cultivars Capdeboscq and Nemaguard.Additional keywords: emergence speed; propagation by seeds; Prunus sp.; thermal treatment.