Ideal harvesting point of ‘Limeira-IAC382’ trifoliate orange fruits for seed extraction

Abstract Trifoliate orange is one of the rootstocks most used worldwide mainly because it provides excellent quality fruit production. Harvest at the correct time is among factors that determine the physiological quality of seeds. The aim of this study was to identify physicochemical changes in ‘Limeira-IAC382’ trifoliate orange fruits, searching for the ideal harvest moment to obtain high quality seeds. Fruits were harvested at 180, 210 and 240 days after anthesis, stored in cold chamber and evaluated at 0, 15, 30 and 45 days of storage. The following variables were determined: mass loss, fruit color index, soluble solids, total titratable acidity and fruit juice ratio. Seeds were manually extracted and dried until reaching 30% water content. Seeds were used for the performance of germination, electrical conductivity and greenhouse seedling emergence tests. Seeds from fruits harvested at 240 DAA showed higher germination and greenhouse seedling emergence percentage compared to the other treatments until 30 and 45 days of storage in cold chamber, respectively. Storage for 45 days in cold chamber of fruits harvested at 210 DAA increases seed germination rate and the percentage of seedlings from seeds harvested at 180 DAA. It could be concluded that the harvesting of ‘Limeira-IAC382’ trifoliate orange fruits should be performed when fruits reached yellowish peel and low juice ratio, aiming at obtaining seeds with physiological quality.

摘要：枳是全球应用最为广泛的砧木之一，其核心优势在于可产出优质果品。适时采收是决定种子生理品质的关键因素之一。本研究旨在明确‘Limeira-IAC382’枳果实的理化变化，以探寻获取高品质种子的理想采收时机。试验分别于开花后180、210和240天（Days After Anthesis，缩写DAA）采收果实，置于冷藏库中贮藏，并分别于贮藏0、15、30和45天时开展相关测定。测定指标包括质量损失率、果实色泽指数、可溶性固形物含量、总可滴定酸度以及果实出汁率。通过人工方式提取种子并干燥至含水量30%，随后开展发芽试验、电导率测定及温室育苗出苗试验。结果显示，相较于其余处理组，开花后240天采收的果实所获种子，在冷藏贮藏30天时的发芽率及贮藏45天时的温室育苗出苗率均显著更高；对开花后210天采收的果实进行45天冷藏贮藏，可提升种子发芽率；而贮藏45天亦可提高开花后180天采收种子的育苗出苗率。综上，若要获取生理品质优良的种子，‘Limeira-IAC382’枳的采收时机应选择在果实果皮变黄且出汁率较低之时。