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The Disease-Resistance Mechanisms and Genetic Research of a New Brassica Napus Which is Resistant to the Sclerotinia Sclerotiorum

Author: ZhaoZuoZuo
Tutor: LiZaiYun
School: Huazhong Agricultural University
Course: Crop Genetics and Breeding
Keywords: Sclerotinia sclerotiorum Lignin Microspore culture Paraffin sections Determination of lignin content
CLC: S565.4
Type: Master's thesis
Year: 2013
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Abstract

The sclerotinia sclerotiorum is one of the three diseases of rapeseed in our country. It seriously affect the yield and quality of rape and has caused a loss about5%-30%every year. Therefore, researchers get more attention to the studies about the comprehensive control to the sclerotinia sclerotiorum and the disease-resistant breeding. At present, there are many studies about the disease-resistant mechanism of rape to the sclerotinia sclerotiorum, and lignin as a structural material has played a very important role when plants cope with the infection to the fungi. In this study, A hard stalk material(named689) is found in the hybrids of Capsella bursa-pastoris (L.) Medic (2n=4x=32) and Brassica napus (2n=38), it indicates that the lignin content in the stem of the material is20%higher than that of the contrast zhongyou821, and the fungal inoculation experiments confirmed that it has certain resistance to sclerotinia sclerotiorum. This study has purified the new material and has explored the anatomical differences in the tissue of the new material and the control zhongyou821at different developmental phase through the microspore culture, the determination of lignin content and the paraffin section et al.. At the same time, we hope to construct a mapping population to locate the gene involved in the lignin synthesis pathway in the new material via the hybridization between the new material and the Westar DH lines which is highly susceptible to the sclerotinia sclerotiorum, these are great significant to the disease-resistant breeding of rape. The main results were described below:1. We have obtained the DH lines of the hard stem material (689) through the microspore culture and we found the double effect of the new material was very poor when coped with colchicine.The reason may be that the high content of lignin in689can prevent the colchicine entering into the organizations of plant and then affect the chromosome reduplication.2. In the experiment of the determination of lignin content of the leaf and petiole of689、zhongyou821and Capsella bursa-pastoris et al., we found that the lignin content of the leaf and petiole of Capsella bursa-pastoris was the highest, the lignin content of leaf in689was15%higher than that of the control zhongyou821, but in the petiole, the results were contrary.3. Freehand sections of the stem of689and the control zhongyou821were excised at a defined distance25cm from the ground and stained with phloroglucinol-HCL to observe their anatomical differences. Results showed that the transverse distribution of lignin in the vascular system of the stem of689was wider than control, and in the same plant, the crosscutting structure of the stem from the root to the top also had significant differences that the distribution of lignin in the stem was less and less from root to top.4. Paraffin sections showed that the distribution of lignin in the transverse section of the hypocotyl of689was wider than zhongyou821, and the size and arrangement of vascular bundles in the two materials was significantly different. The diameter of the vascular bundles in689was longer than that of zhongyou821and vascular bundles in689were loosely arranged and those in zhongyou821were closely arranged. We got the opposite conclusion in the roots, the transverse distribution of lignin in the roots of zhongyou821was wider and the dyeing of lignin was deeper than that of689.5. In the seedling stage,the differences in the transverse distribution of lignin in the stalks of689and zhongyou821were consistent with the results of the freehand sections, and we have drawed the same conclusions in the leaf and petiole. In the florescence stage, we found the distribution of lignin in the anther wall of689, but no distribution in zhongyou821, and in the flower stalk and calyx, petal and ovary, the distribution of lignin in689was wider than that of zhongyou821. In the podding period, the distribution of lignin in the vascular bundle of peduncle in689was wider, and the cortex of zhongyou821was much thicker than that of689.

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