An improved method to obtain novel mutants in Cucurbita pepo by pollen viability

Abstract

A new genetic resource for Cucurbita pepo has been developed with chemically induced mutagenesis. The seeds of the zucchini cultivar MU-CU16 were treated with 40mM–80mM ethyl methanesulfonate (EMS), reaching high germination rates between 70 and 85%. However, most plants of those M1 populations did not produce offspring, and the fertility rates were lower in plants treated with higher concentrations of EMS. Once we established that visual flower abnormality rates were not sufficient to explain low fruit yield, pollen viability was analysed with fluorochromatic reaction. Compared with untreated plants, treatment with EMS produced a substantial decrease in pollen viability, and only the group of plants with pollen viability rates higher than 45% yielded nearly 70% of fruits with seeds. Therefore, the main issues to be addressed for developing mutant lines in this species are to increase the number of mutations in the genome and to increase the number of mutant lines with sufficient fertility. In this case, the early plantlet selection for high pollen viability carried out as part of this work represents a useful tool for use in future breeding programs by mutagenesis, allowing an increase of up to 40% in the production of mutant lines for a dosage of 65mM EMS.