Effect of insect pollinator species deployment and interactions with parental inbred lines in hybrid carrot seed production.

Abstract

Insect pollinator species are highly valued for their contribution towards cross-pollination in many vegetable crops for food and seed production. Honeybees (Apis mellifera) are a significant main pollinator not only in entomophilous crop, but for many other plants in their natural habitats. Moreover, attempts to increase seed production through the introduction of an alternative pollinator species (such as Calliphorides flies) throughout the world have encouraged growers and breeders to think more precisely about the management of these pollinators for the future. However, several constraints, including climate, have resulted in low success of pollinators, thereby failing to meet pollination demand for hybrid carrot seed production, both nationally and internationally. The goal of this study was to identify alternative non-bee insect species that can be used as agents of pollination in commercial hybrid carrot seed production. The research experiment was conducted in Matjiesrivier farm (33o23'31.86" S and 22o05'14.91" E) that is situated under the Oudtshoorn district municipality, which is a Cango valley of Western Cape Province. Carrot parents were three cytoplasmic male sterile (CMS) lines, which were pollinated by two pollen donor-male inbred lines. Two insect species, honeybees (Apis mellifera) and Calliphorid flies (Chrysomya chloropyga), were used as agents of pollination. The experiment was arranged in a 2x2x3 factorial with two replications. The weight of umbels, seed weight and germination percentage data were collected to achieve research study objectives. Statistical analysis for all data was done using SAS (SAS Institute Inc, 2018) and R (R Core Team, 2019) statistical computation software. The data were subjected to analysis of variance (ANOVA) for individual umbel level (order) harvests. The TUKEY post hoc test was done at a 5% level of probability to compare the treatments. From the results, flies were comparably effective as honeybees during pollination, while analysis of variance for quantitative traits (germination percentage, seed weight, and umbels weight) was highly significant implying that the traits differed among the advanced lines and the deployment of the two species during pollination. The trait variability was influenced by the umbel stages of different CMS lines and their interaction with pollinator by male fertile and male sterile lines. This information will be useful in a breeding program that focuses on hybrid seed production in carrots and a combination of the two insect pollinators’ deployments to improve cross breeding for future management would be essential