Breeding of hybrid varieties of winter oilseed rape based on the MSL-system

Martin Frauen and Werner Paulmann

Norddeutsche Pflanzenzucht (NPZ) Hans-Georg Lembke KG, Hohenlieth, D-24363 Holtsee, Germany; NPZ_Lembke@t-online.de

ABSTRACT

The MSL-system (Male Sterility Lembke) is based on a spontanous mutant selected in the NPZ nursery 1982. With MSL it is possible to produce fully restored rapeseed hybrids without any penalty in yield and quality. First winter oilseed rape hybrid varieties were registered in 1995 and are now covering about 250.000 hectares commercial rapeseed production in Europe. Also spring oilseed rape hybrids were developed based on the MSL-system. Besides yield also agronomic characters like plant length, disease resistance, straw stiffness and oil content have been improved.

KEYWORDS

Brassica napus, hybrid breeding, male sterility system, seed production

INTRODUCTION

Considerable heterosis for seed yield in F1 hybrids of oilseed rape (Brassica napus L.) has been reported by various authors at the beginning of hybrid breeding in rapeseed (Schuster, 1969; Röbbelen, 1985; Grant and Beversdorf, 1985; Lefort-Buson, 1987; Brandle and McVetty, 1989; Paulmann and Frauen, 1991). These results encouraged for the development of pollination control systems, i.e. male sterility, self incompatibility or gametocide application. First oilseed rape hybrid varieties are worldwide on the market using male sterility or self incompatibility. In winter oilseed rape the first hybrid varieties that were registered in Europe are hybrid-line-associations using the INRA ogura system and fully restored hybrids using the MSL system.

DEVELOPMENT OF HYBRID VARIETIES

The MSL-system

The MSL-system (Male Sterility Lembke) is a private system owned by NPZ/Lembke. All known conventional rapeseed cultivars and lines are restorer lines for this male sterility system. Therefore it is very easy to create experimental hybrids and test the combining ability of unlimited numbers of pollinators. The resulting hybrids are fully restored and there are no negative effects on quality and agronomic characters in the final hybrid variety due to the male sterility system.

Performance of hybrids

The first breeding lines were converted into the male sterility system by repeated backcrossing. The parental lines of the first hybrid varieties originate from breeding programmes of open pollinated cultivars with known combining ability. The yield increase of these first hybrids is between 5% and 15% compared to the best checks. Using parental lines with better agronomic characters resulted in hybrid varieties of the second generation which are in official trials. Additional to the yield other important traits are improved (Table 1).

Table 1:

New hybrid combinations in winter oilseed rape with higher yield and better agronomic characters compared to the check varieties EXPRESS, WOTAN and LIRAJET

	relative seed yield 1998					plant	straw	winter
variety	loc 1	loc 2	loc 3	mean	%oil	length	stiffness	hardiness
EXPRESS	99	98	100	99	44,6	161	8,6	7,2
WOTAN	102	102	92	99	43,6	176	6,6	7,2
LIRAJET	100	100	108	103	44,1	175	6,3	7,3
Lin 96685	136	123	119	126	44,9	174	8,4	8,2
Lin 96691	137	124	117	126	45,5	175	8,2	7,5

LSD 0,05: 10% (for yield)

Use of marker techniques

Molecular markers i.e. RFLP and SSR are used in the hybrid breding programme to estimate genetic distances of selected breeding lines. Parental lines with a genetic distance lower than a fixed minimum are not worthwhile to be tested in the field. This reduces the work of yield trials. A second application of molecular markers in the hybrid breeding programme is the marker assisted backcrossing of selected lines into the MSL-system. This can reduce the backcrossing steps from five to three backcross generations.

Creating distinct gene pools

The narrow genetic basis of oilseed rape is a limiting factor of increasing hybrid performance on the long run. By introducing resynthesized genotypes and using reciprocal recurrent selection procedures the genetic basis has to be extended step by step.

Seed production of hybrid varieties

Today the multiplication of rapeseed hybrid varieties is carried out in alternating strips where the pollinator is discarded after pollination. Our experience show that good pollination conditions are neccessary for a sufficient yield on the motherline. The relation of mother and pollinator should be 3:1 and 3 to 5 bee hives per hectare are useful.

The seed production in alternating strips is the only possibility to get high hybridity levels. Nevertheless it is also possible, but not yet accepted in Europe, to produce hybrid seed after mixing motherline and pollinator. The advantage of mixed production is a reduction of production costs. Our results of two years with different mechanical mixtures of a hybrid and its pollinator show that even 25% of pollinator in the hybrid did not reduce the seed yield significantly (Table 2).

Table 2:

Relative seed yields of pure hybrid variety PRONTO and different mixtures with pollinator

Mixture Pronto/pollinator	loc 1  1997	loc 2 1997	loc 3 1997	loc 4 1997	loc 5 1997	loc 1 1996	loc 2 1996	loc 3 1996	loc 4 1996	loc 5 1996	loct 6 1996	mean
100/0	100	100	100	100	100	100	100	100	100	100	100	100
95/5	103	99	97	101	95	98	101	97	93	99	95	98
90/10	100	100	99	101	100	102	98	92	99	94	96	99
85/15	96	92	97	100	98	103	102	100	102	97	96	98
80/20	100	95	103	102	104	98	101	95	97	91	99	99
75/25	99	92	95	99	101	101	99	94	94	105	93	98

LSD 0,05: 2%

Market situation

The acreage of hybrid varieties based on the MSL-system has increased in Europe from 30.000 hectares in 1997 to around 250.000 hectares in 1999 (Table 3). Several winter oilseed rape hybrid varieties are listed and marketed in Europe. Springtype hybrids are just starting in the market in North America (Table 4).

Table 3: Acreage of MSL-Hybrids 1999 in Europe

Germany	92.000 hectares	8% market share
United Kingdom	60.000 hectares	15% market share
France	53.000 hectares	4% market share
Denmark	7.500 hectares
Switzerland	7.500 hectares
Austria	5.000 hectares
Sweden	4.500 hectares
other: CZ, NL, IRL	6.000 hectares

Table 4: MSL hybrid varieties listed and/or marketed in Europe and North America

	Variety	listed/marketed in
Winter oilseedrape	JOKER	D
	PRONTO	D, UK, F, A, CZ
	PANTHER	D, UK, CH
	ARTUS	UK, DK, D, S, A
	KASIMIR	S, PL, LV
	BUFFALO	PL
Spring oilseedrape	ORAKEL	DK
	CL 2070	USA
	220	CAN
	HyPer Star 100	CAN
	PF 7528/95	CAN

CONCLUSION

The development of oilseed rape hybrids is highly competitive worldwide. A prerequisit of successful hybrid breeding work is germplasm, the knowledge of combining ability and a functional pollination control system. The MSL-system is one part to develop successful hybrid varieties.

REFERENCES

Brandle, J.E. and McVetty, P.B.E. (1989): Heterosis and combining ability in hybrids derived from

oilseed rape cultivars and inbred lines. Crop Science, 29: 1191-1195.

Grant, I. and Beversdorf, W.D. (1985): Heterosis and combining ability estimates in spring-planted

oilseed rape (Brassica napus L.). Canadian Journal of Genetics and Cytology, 27: 472-478.

Lefort-Buson, M., Guillot-Lemoine, B. and Dattee Y. (1987): Heterosis and genetic distance in

rapeseed : crosses between European and Asiatic selfed lines. Genome, 29: 413-418

Paulmann, W. and Frauen, M. (1991): Einsatz von biotechnologischen Verfahren in der praktischen

Rapszüchtung. Bericht der Arbeitstagung Saatzuchtleiter, Gumpenstein, 173-182

Röbbelen, G. (1985): Züchtung von Hybridraps. Bericht der Arbeitstagung Saatzuchtleiter,

Gumpenstein, 173-185

Schuster, W. (1969): Vergleich von zwei Zuchtverfahren in der Erhaltungszüchtung von Winterraps.

Zeitschrift für Pflanzenzüchtung 62: 47-62