Development and quality of pollen in Lachenalia cultivars with determination of genome size and chromosome number

Abstract The genus Lachenalia J. Jacq. ex Js. Murray (Asparagaceae) comprises 136 species endemic to South Africa and Namibia. These bulbous geophytes are considered to have excellent horticultural potential due to their morphological and genetic diversity, and thus have been chosen for the initiation of a breeding program to develop new cultivars that suitable for commercial use. From breeding perspective, studies on pollen viability and morphology are of great importance, since pollen quality represents an essential factor that influences crossbreeding processes. Therefore, to comprehensively characterize the pollen of selected Lachenalia cultivars, we conducted a multi-level analysis in which we investigated the processes of microsporogenesis and pollen grain development, as well as evaluated pollen morphology and viability. We also performed somatic chromosome counts and flow cytometry, thereby providing, for the first time, valuable cytogenetic data on the chromosome numbers and nuclear DNA contents of these cultivars. Morphologically, all the pollen grains were classified as medium-sized, subspheroidal in shape, and monosulcate with a single elongated aperture. Their exine ornamentation was categorized as reticulate with a heterobrochate reticulum. The pollen viability analysis revealed one of the cultivars to be nearly completely sterile, however, we were able to explain this phenomenon and found that this cultivar was affected by meiotic abnormalities associated with its triploid nature. Based on the obtained results, three of the studied cultivars may be considered as suitable pollinizers. From the perspective of applied research, the findings of our research offer important information for selecting appropriate donors for cross-pollination in the development of new Lachenalia cultivars.