背景:Daucus属(Apiaceae)包括约40种野生物种和栽培的胡萝卜,对经济和营养具有重要意义的作物。野生胡萝卜物种丰富的遗传多样性使其成为胡萝卜改良育种计划的宝贵基因库。因此,有足够的基因组结构的知识和野生酱之间的关系是至关重要的。为了扩大这种知识,在这项研究中,通过流式细胞术估算了14个Daucus种质和4个密切相关物种的核DNA含量,并通过光学和扫描电子显微镜(SEM)分析了它们的花粉形态。
结果:流式细胞术分析显示,Daucus分类群的平均2C值变化3.2倍,范围从0.999(D.卡罗塔亚科。sativus)至3.228pg(D.littoralis).在外群物种中,平均2C值为1.775-2.882pg.道果的花粉粒是三酚酸盐,主要是在形状上长成或长成(很少),主要是中等或小(很少)尺寸(21.19-40.38µm),而外群的物种有三甲,全扁圆形的,和中等大小(26.01-49.86µm)的花粉粒。在研究的分类单元中,SEM分析表明,壁饰呈条纹状,皱纹,穿孔,或者装饰图案是混合的。在脱落的时候,所有的花粉粒都是三细胞的,如DAPI染色所证明。我们还发现,极轴的长度(P)与花粉粒赤道直径的长度(E)之间存在高度正相关,以及P和P/E之间然而,当将细胞遗传学信息与孢粉学数据进行比较时,没有观察到显著的相关性。
结论:这项研究补充了有关Daucus中核DNA含量的信息,并提供了对其分类群花粉形态的全面了解。这些发现对于阐明Daucus物种之间的分类关系可能很重要,并且可以帮助正确识别基因库种质。从更广泛的角度来看,它们对于解释该属的进化趋势也有意义。
BACKGROUND: The genus Daucus (Apiaceae) comprises about 40 wild species and the cultivated carrot, a crop of great economic and nutritional importance. The rich genetic diversity of wild Daucus species makes them a valuable gene pool for carrot improvement breeding programs. Therefore, it is essential to have good knowledge of the genome structure and relationships among wild Daucus species. To broaden such knowledge, in this research, the nuclear DNA content for 14 Daucus accessions and four closely related species was estimated by flow cytometry and their pollen morphology was analyzed by light and scanning electron microscopy (SEM).
RESULTS: The flow cytometric analysis showed a 3.2-fold variation in the mean 2C values among Daucus taxa, ranging from 0.999 (D. carota subsp. sativus) to 3.228 pg (D. littoralis). Among the outgroup species, the mean 2C values were 1.775-2.882 pg. The pollen grains of Daucus were tricolporate, mainly prolate or perprolate (rarely) in shape, and mainly medium or small (rarely) in size (21.19-40.38 µm), whereas the outgroup species had tricolporate, perprolate-shaped, and medium-sized (26.01-49.86 µm) pollen grains. In the studied taxa, SEM analysis revealed that exine ornamentation was striate, rugulate, perforate, or the ornamentation pattern was mixed. At the time of shedding, all pollen grains were three-celled, as evidenced by DAPI staining. We also found high positive correlations between the length of the polar axis (P) and the length of the equatorial diameter (E) of pollen grains, as well as between P and P/E. However, when comparing cytogenetic information with palynological data, no significant correlations were observed.
CONCLUSIONS: This
study complements the information on the nuclear DNA content in Daucus and provides comprehensive knowledge of the pollen morphology of its taxa. These findings may be important in elucidating the taxonomic relationships among Daucus species and can help in the correct identification of gene bank accessions. In a broader view, they could also be meaningful for the interpretation of evolutionary trends in the genus.