Flowering And Fruiting Characteristics And Nectar Secretion Regulation Mechanism Of Male Sterile Lines In Broccoli(Brassica Oleracea Var. Italica)

Broccoli(Brassica oleracea var. italica) is an important vegetable crop, using male sterile lines to cultivate new varieties and produce hybrids is an important approach for its heterosis utilization. Broccoli genetic breeding started late in China, introduction of foreign resources is the main way to look for excellent cytoplasmic male sterility(CMS) sources at present. However, the genetic backgrounds of the introduced CMS sources are not always clear, which usually lead to repeatedly transfer of the same CMS source. Some CMS sources existed serious bud abortion, carpelloid stamen, late flowering, small flower, low amount of nectar and seed yield in practical applications. Therefore, it is very important for the development of broccoli industry to solve the problems mentioned above.In this study, broccoli maintainer lines, CMS materials and dominant genic male sterility(DGMS) lines were used to systematically and deeply study the flowering and fruiting characteristics, origin of CMS sources, carpelloid stamen, gene expression characteristics of abortive bud, genetic mode of flowering time and floral organ size, nectary development and nectar secretion regulation mechanism. The objectives were: to determine the effect of different origin of CMS sources on flowering and fruiting characteristics in broccoli; to develop molecular marker that can distinguish carpelloid stamen and normal CMS sources; to discover genes involved in the regulation of abortive bud; to obtain the genetic pattern of flowering time and floral organ size; to parse the regulation mechanisms of nectar secretion. The results are as follows:1. The flowering and fruiting characteristics and bees visiting flowers were significantly different among the CMS lines, which were transferred from different origins of CMS sources. Four excellent CMS materials CMS738, CMSGD, CMS1169 and CMS1183 were screened out.2. A mitochondrial marker mtSSR2 that can differentiate between the cytoplasm of carpelloid and normal stamens was discovered for the first time. The polymorphic product of carpelloid stamen had the highest similarity with Raphanus sativus and Brassica carinata, which had a deletion of 51 bases compared with normal stamen materials.3. The 39 different origins of CMS accessions all contained ogu orf138 fragment and belonged to ogu CMS type. When coefficient was larger than 0.89, the 39 CMS accessions were divided into five groups and ogu CMS R3 constituted 79.49%.4. Bud abortion was related to polygalacturonase metabolism, glycosyl hydrolases, redox processes, phenylalanine metabolism and phenylpropanoid biosynthesis. Twelve genes and two transcription factors ERF 115 and bHLH 137 that probably involved in regulation bud abortion were discovered for the first time.5. Corolla and petal width and stamen and anther length were controlled by polygene; flowering time, petal and stigma length were governed by two major genes plus polygene; style length was controlled by one major gene plus polygene. The major QTLs controlled flowering time, petal width and style length were obtained on chromosome 2(0.9-2.9 Mb), recorded as ft2.1、pw2.1 and sl2.1, respectively. The candidate region of ft2.1 was 228 Kb and contained 29 genes, which 14-3-3 protein could promote flowering in Arabidopsis thaliana. pw2.1 and sl2.1were colocalized, the candidate region was 191.66 Kb and contained 21 genes, which E3 ubiquitin-protein ligase could control flower organ size in Arabidopsis thaliana.6. The differences and similarities of nectar amount and sugar content, occurrence and development process of nectaries were first determined among the maintainer, DGMS and CMS lines. The cytological pathways of nectar secretion were defined: the raw honey generated by screen pipe, transported by pore and vesicular structure and plasmodesmata, stored in the form of starch grains, processed in Golgi apparatus and endoplasmic reticulum, and secreted by honey hole. The related genes that led to the differences of above materials were analyzed, and a specific gene with high expressed in DGMS lines was obtained.