Assessment of a stay-green mutant for variety improvement in Pakchoi (Brassica campestris L. ssp. chinensis)

Abstract

Stay-green refers to a trait whereby plants retain greenness during senescence. In our previous study, a stay-green mutant of Pakchoi nye was screened out from an open pollinated strain and we found that the stay-green was controlled by a single recessive gene Brnye1. Bra019346 was identified as the candidate for Brnye1. The aim of this study was to evaluate the application of the stay-green lines for variety improvement in Pakchoi. The leaves of nye maintained greenness during senescence and the pigment content of nye was higher than that of wild type. No significant excessive accumulation of chlorophyll catabolites was observed in the chlorophyll catabolic pathway in nye during leaf senescence, which indicated no presence of dangerous phototoxic molecules. The net photosynthetic rate and the photochemical efficiency of photosystem II remained the same level as the wild type, which suggested that the photosystem functioned normally. In order to create more stay-green lines, the nye and a good line ‘13A510’ were used as parents to create a hybrid. The stay-green plants from the F2 were used as donor materials to conduct isolated microspore cultures and a total of 687 stay-green doubled haploid lines were obtained. In order to utilize heterosis, a stay-green cytoplasmic male sterile line CMS-nye was created through backcrossing to a cytoplasmic male sterile line by using nye as recurrent parent. Storage experiment indicated that the stay-green Pakchoi could prolong shelf life and improve the quality of commodity. These results lay the foundation for application of the stay-green genetic resource for variety improvement in Pakchoi.