Morphology and viability of castor bean genotypes pollen grains

ABSTRACT. The objective of this work was to characterize the morphology and viability of the pollen of 15 genotypes of castor bean (Ricinus communis L.) and to generate information that can assist in the selection of highly promising male parents for future use in genetic improvement programs aimed at producing seeds for oil extraction. Acetolysis and scanning electron microscopy was used to characterize the morphology of the pollen. The viability of the pollen grains was estimated by in vitro germination and colorimetric analysis (acetocarmine 2% and 2, 3, 5-triphenyltetrazolium chloride 1%). For the in vitro germination, pollen grains were grown in 10 types of solidified culture medium consisting of different concentrations of sucrose, boric acid, calcium nitrate, magnesium sulfate and potassium nitrate. The pollen grains had the following characteristics: medium size, isopolar and subspheroidal shape, radial symmetry, circular ambit, 3-colporate, elongated endoapertures, tectate exine and granulated sexine. The acetocarmine dye overestimated pollen viability. The media M5 and M8 were the most efficient at promoting the germination of pollen grains. The studied genotypes had high levels of viability and can therefore be used as male parents in genetic improvement programs.

摘要。本研究旨在表征15个蓖麻（Ricinus communis L.）基因型的花粉形态与活力，以期为筛选极具应用潜力的父本提供参考信息，助力未来以生产可用于榨油的种子为目标的遗传改良计划。本研究采用乙酰解（acetolysis）结合扫描电子显微镜（scanning electron microscopy）技术对花粉形态进行表征；花粉活力通过体外萌发（in vitro germination）实验与比色分析（colorimetric analysis）进行评估，所用试剂为2%醋酸洋红（acetocarmine）与1%的2,3,5-氯化三苯基四氮唑。体外萌发实验中，花粉被接种于10种固化培养基中，各培养基含有不同浓度的蔗糖、硼酸、硝酸钙、硫酸镁及硝酸钾。受试花粉具有如下特征：中等大小、等极（isopolar）、近球形（subspheroidal）形态，辐射对称，花粉轮廓呈圆形，具3孔沟（3-colporate）结构，内孔（endoapertures）狭长，外壁（exine）为覆盖层型，外壁外层（sexine）呈颗粒状纹饰。研究发现，醋酸洋红染色法会高估花粉活力；培养基M5与M8对花粉萌发的促进效果最优。本研究所涉及的15个蓖麻基因型均表现出较高的花粉活力，可作为遗传改良计划中的优质父本材料。