Evaluation And Exploitation Of Heterosis In Cytoplasmic Male Sterile Line Of Leaf Mustard0912A

Leaf mustard (Brassica juncea Coss.) is an important raw materials for processing of pickled vegetables. The market demand of leaf mustard is gradually increasing with the rapid development of the pickled vegetable processing industry. However, the cultivars of leaf mustard in production are all conventional because of lacking perfect male sterile line of leaf mustard. A novel type of cytoplasmic male sterility line of Brassica juncea, hau CMS, was taken as a sterile source. The cytoplasmic male sterile line of leaf mustard0912A was obtained by hybriding and10generations of backcrossing with the leaf mustard. The infertility, flowering seed traits, cytoplasmic effection and heterosis were investigated in order to evaluate the prospects of its production and application in this study. Ctytological observations of the anther sterility and molecular identification of the cytoplasmic male sterile type were also performed. The mainly results are as follows.1. The botanical characteristics of the cytoplasmic male sterile line0912A and the maintainer line0912B were observed and measured. The t-test analysis of variance between the male sterile line and the maintainer line showed no significant difference in most of the botanical characteristics except for plant height, of which the male sterile line was lower than the maintainer line. This indicated that the male sterile line of leaf mustard has been transferred successfully.2. Morphology and fertility of flowers were observed in two different places, Wuhan Hubei and Linxia Gansu, for two years. The results showed that the degree of pollen sterility and the ratio of sterile plants were both100%; the sterility was stable without the effects of temperature and the duration of sunshine; the development of floral nectary was normal, no dead buds were observed; the pistil developed completely; and fruits and seeds were produced normally.3. Cytological observations of anther in leaf mustard cytoplasmic male sterile line0912A was made by means of paraffin section in order to determine the period, methods and characteristics of anther abortion. The results showed that the stage of abortion in male sterile line was different, but mainly occurred at the stage of differentiation of archesporial cells, which had no pollen sac formation. Some anthers occurred at the stage of pollen mother cell to the mono-nuclear microspore. Some pollen mother cells were concentrated and disintegrated gradually after vacuolization; some pollen mother cells disintegrated due to the hypertrophy of tapetal cells in the radial direction; while some pollen mother cells could develop to tetrad, but then disintegrated; and part of the pollen mother cells could develop to mono-nucleus microspore, and then highly vacuolated and broken. We also found that the stamens of0912A were degenerated as filament through observing the morphology of the flower, which totally aborted.4. Three pairs of specific primers for PCR amplification were designed from the conserved sequences of mitochondrial sterility genes that were previously reported. PCR amplification, cloning and sequencing analysis were employed to identify the cytoplasmic male sterile type of leaf mustard0912A. A single fragment was amplified only with the orf288primers. The sequencing results showed that this fragment was identical to the orf288of hau cytoplasmic male sterile line.5. Incomplete diallel cross method was used, with0912A and its maintainer line0912B as maternal parents, five typical inbred lines as male parents, which of sources were different. Five F1hybrids carrying sterile cytoplasm hau and five F1hybrids of normal cytoplasm were produced. The analysis of cytoplasmic effect showed that male cytoplasm had distinct negative effect on the weight of plant, reaching10.12%, but the negative effects on the other traits were relatively weak, almost under10%. And the male cytoplasmic effect on hybrid traits varied with different nuclear genetic background. The negative effect of cytoplasm could be reduced or even eliminated by choosing suitable male parents.6. The heterosis analysis of hau cytoplasmic hybrid F1plants showed that the heterosis of leaf mustard in several agronomic traits were obvious. The combination of (0912A×X4)was higher than other combinations in most of the agronomic traits, and the heterobeltiosis of weight per plant was also the largest, reaching41.55%, which had great yield potential. But the heterosis of quality was little, the average of super-parent advantage in protein content was only1.06%; and the average heterosis of soluble sugar content was negative.