STUDIES ON NEW STRAIN SELECTED BY INTERGENERIC HYBRIDIZATION BETWEEN B.NAPUS AND C.BURSA-PASTORIS
YJ. Huang1 ,JW. Zhao2,HJ. Zhao1,FX. He2 and YC. Li1
1Oil Crops Research Institute of CAAS, Wuhan,430062,China
e-mail:ocgil @ public.wh.hb.cn
2Huazhong Agricultural University,Wuhan,430070,China
e-mail:brassica@ public.wh.hb.cn
ABSTRACT
Studies were made on new strain (YD16) selected from intergeneric hybridization between Brassica napus and Capsella bursa-pastoris. The anatomical observation showed that most inner structures of root, stem and leaf were between father and mother. While the size of pollen was superior to parents.YD16 has marked growth vigour .At seedling stage, the endogenous GA and IAA contents in YD16 leaves were much higher than that of the parents, but the endogenous ABA content was lower than that of the parents. After inoculated with Sclerotinia mycelia, the increases of peroxidase (POX) and polyphenoloxidase (PPO) activities in YD16 were more than that in susceptible variety S-89. YD16 has good resistance to Sclerotinia stem rot. In cultivar comparative test from 1995 to 1998 in different regions of Hubei, Hunan, Henan and Shanghai, the average incidence and index of stem rot inYD16 were 28.4% and 31.8% lower than that of the control variety .Three years yield test showed that the average yield of YD16 was 2705.2Kg/ha which was 10.5% higher than the c0ntrol .In 1998 autumn, the grown area of YD16 reached about 47,000 hectare.
KEYWORDS Anatomical structure, endogenous hormone, peroxidase and polyphenoloxidase, disease resistance, yield
INTRODUCTION
The genetic background of Chinese B.napus especially double low and single low varieties is believed to be very restricted ,which causes the weak resistance to disease and low seed yield. In order to enlarge the B.napus diversity and select resistant varieties, we have been carring out studies on intergeneric hybridization between B.napus and C.bursa-pastoris since 1970(HJ.Zhao,1993,1995,1996).And a new strain(YD16) was selected.YD16 not only has good resistance to Sclerotinia stem rot, but also has high yield. It is a promising new strain. Studies were carried our on this new strain to provide useful information for its popularization.
MATERIAL AND METHODS
Materials used were new strain YD16 and its parents. And Zhongyou 821 was used as the control variety. Root, leaf and stem anatomic structure of YD16 and its parents were observed with the method of microscope. Endogenous IAA,GA and ABA in leaves of YD16 and its parents were determined with method of enzyme linked immunosorbent assay (XY.Wu,1988).Peroxidase (POX) and polyphenoloxidase (PPO) activities were measured according to JS.Yang(1984).Disease resistance and yield were tested in different regions of different provinces from 1995 to 1998.
RESULTS
1.Anatomical observation
The obvious feature of YD16 was low branch, short stem and early maturity, which was similar to its father(C.bursa-pastoris).While the shape of stem and leaf was similar to its mother(B.napus).The inner structures of root, stem and leaf were mostly between mother and father. For root anatomic structure of YD16 ,the phloem/xylem had tendency to mother ,the generated number of vessel and tracheid was between its parents, but the vegetative substance stayed in phloem parenchyma cell was more than the mother and father .Table 1 and table 2 showed that the arrangement of vascular bundle of YD16 in stem was similar to mother, the leaf thickness was thinner than parents, other structures were between father and mother. The size of pollen grain was superior to parents. The diameter of pollen grain was 20µm in father,32µm in mother and 38µm in YD16.
Table 1 The comparison of stem anatomic structure
|
|
The size of |
|
Cortex |
|
Vascular |
bundle |
|
Material |
epidermal cell |
Thickness (mm) |
Number of cell` layer |
Arrange-ment of the cell |
Arrange-ment of V.B |
Phloeml xylem |
|
mother |
small |
495~1350 |
18-40 |
close |
close |
1:1 |
|
Father |
large |
240~966 |
6-11 |
looser |
rare |
1:2 |
|
YD16 |
larger |
450~990 |
11-21 |
loose |
closer |
1:1.5 |
Table 2 The comparison of leaf anatomic structure
|
|
Thickness |
Palisade |
|
Spongy |
tissue |
Distance |
|
Material |
of blade (mm) |
Number of cell layer |
Thickness (mm) |
Number of cell layer |
Thickness (mm) |
between V.B (mm) |
|
mother |
465~675 |
3~4 |
225~330 |
6~8 |
210~300 |
242 |
|
Father |
180~420 |
1~3 |
75~165 |
3~5 |
67.5~210 |
277.5 |
|
YD16 |
172~285 |
2~3 |
60~105 |
4~6 |
75~150 |
265.5 |
2.Endogenous hormones
Enzyme linked immunosorbent assay(ELISA) was used to determine the endogenous gibberellic acid(GA),indole-3-acetic acid(IAA) and abscissic acid(ABA) contents in leaves of YD16 and its parents(Table 3).At seedling stage, the GA content was 419.89% higher than that of mother and 232.99% higher than that of father; The IAA content was 99.13% higher than that of mother and 26.79% higher than that of father; While the ABA content was 37.15% lower than mother and 2.34% lower than father. The endogenous hormone contents indicated that YD16 had marked growth vigour.
.
Table 3. The comparison of endogenous hormones at seedling stage (nmol/g.F.W)
|
Material |
ABA |
GA |
IAA |
|
mother |
26.432 |
11.013 |
270.258 |
|
father |
17.010 |
17.194 |
171.928 |
|
YD16 |
16.612 |
57.256 |
342.666 |
3.Peroxidase and polyphenoloxidase
Figure 1 showed that PPO activity in YD16 leaf was increased significantly after inoculated with Selerotinia mycelia, while in the susceptible line S-89 was almost no increase. From Figure 2,we could see that POX activity in YD16 leaf was increased obviously, but in the susceptible line S-89 was decreased within 25 hours after inoculated. Close relationship was found between POX,PPO activities and resistance to Selerotinia stem rot in rapeseed. The measurement of POX and PPO activities could be used as a complementary method for resistant screening and breeding.
Figure 1 PPO activity of different resistant rapeseed at different time after inoculated
Figure 2 POX activity of different rapeseed at different time after inoculated
4.Disease resistance and yield
Studies showed that YD16 had resistance to Sclerotinia stem rot. Plants fed oxalic acid through roots indicated that the disease index in YD16 was 34.2% lower than that in the control variety Zhongyou 821. Detached leaves inoculated with Sclerotinia mycelia showed that 72 hours later the average diameter of lesion area in YD16 was 2.61cm, while in Zhongyou 821 was 3.44cm. YD16 expressed resistance to the spread of the disease. From 1995 to 1998,results of investigation on Sclerotinia disease of natural field infection in cultivar comparative test in different regions of Hubei,Huhan,Henan and Shanghai showed that the average incidence and index of stem rot in YD16 were 14.7% and 6.1%, which was 30.4% and 38.7% lower than that of the control variety.
Sclerotinia stem rot is a major constraint to rapeseed production in China. The improvement of disease resistance in YD16 is beneficial to rapeseed yield increase. Three years yield test trail in different regions showed that the average yield of YD16 was 2705.2kg/ha,which was 10.5% higher than the control variety. Therefore the increase of yield was notable. In addition,YD16 matured two days earlier than Zhongyou 821 .In 1998 autumn, the grown area of YD16 reached more than 47,000 hectares.
ACKNOWLEDGEMENTS
This work was supported by Hubei Province Natural Science Fund and Wuhan Key Project, by Wuhan Science and Technology Council.
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