AGRONOMIC PERFORMANCE AND SEED QUALITY OF A NEW SOURCE OF YELLOW SEEDED BRASSICA NAPUS
G. Rakow, J.P. Raney and J. Relf-Eckstein
Agriculture and Agri-Food Canada, Saskatoon Research Centre, 107 Science Place, Saskatoon, SK, Canada, S7N 0X2
A new source of yellow-seeded Brassica napus was developed from interspecific crosses between the black-seeded B. napus variety Westar and yellow-seeded B. juncea and B. carinata. The interspecific crosses had the objective to introgress genes for the yellow seed trait from the A genome of B. juncea and the C genome of B. carinata into the respective A and C genomes of B. napus. The two interspecific crosses were intercrossed and pedigree selected for yellow-seeded plants from the F2 to the F7 generations, and true breeding yellow-seeded lines identified. Sixteen F5 to F7 generation yellow-seeded lines were yield tested at three locations in 1996, and further pedigree selected for fatty acid composition and glucosinolate content and composition in 1997 and 1998. The yellow seed colour was affected by environmental conditions and varied among lines. High oil content lines were selected. Many yellow-seeded lines had low oleic acid and high linoleic and linolenic acid contents, typical of zero erucic acid forms of B. juncea and B. carinata. Through pedigree selection, yellow-seeded lines were identified that had fatty acid compositions typical of B. napus canola with greater than 60% oleic acid. Lines that were basically free of allyl glucosinolate and had a total alkenyl glucosinolate content of < 10 Fmoles per 1g of seed were also identified. This new yellow-seeded B. napus germplasm will provide much needed genetic diversity for the breeding of yellow-seeded B. napus varieties.
KEYWORDS: Interspecific crosses, fatty acid composition, glucosinolate composition and content.
In the past, the development of yellow-seeded Brassica napus (AC genome) has been attempted through interspecific crosses between its diploid ancestor species B. rapa (A genome) and B. oleracea (C genome). Bechyne (1987) crossed B. rapa yellow sarson with B. oleracea var. acephala followed by chromosome doubling of the resulting interspecific F1 plant. Only one B. napus plant with lighter coloured seed was produced, but the seed colour was not as bright and deep as that of the B. rapa parent. Also, Chen et al. (1998) used resynthesis for the creation of yellow-seeded B. napus. They crossed light brown-seeded B. alboglabra with yellow-seeded forms of B. rapa and used colchicine treatment for chromosome doubling. The resulting B. napus plants produced light brown seed. There was a range in seed colours, but it was difficult to obtain true breeding, yellow-seeded plants which was probably due to the lack of truly yellow-seeded B. oleracea as a parent for these crosses. They also found that the yellow-brown seed colour trait of resynthesized B. napus was controlled by multiple loci, making the breeding of yellow-seeded varieties difficult. Hou-Li et al. (1983) crossed B. napus with yellow-seeded B. rapa, pedigree selected this interspecific cross for seven generations and were able to isolate yellow-seeded B. napus plants (Hou-Li and Yong-Tong 1987, Hou-Li et al. 1991). The utilization of yellow seed colour genes from B. juncea and B. carinata in crosses with B. napus was first successfully accomplished by Rashid et al. (1994). These authors crossed the Canadian B. napus variety Westar with yellow-seeded B. juncea (as A genome donor of genes for yellow seed) and yellow-seeded B. carinata (as C genome donor of genes for yellow seed). They backcrossed the two interspecific F1 generations with B. napus Westar and produced backcross F2 generation plants from each backcross which they intercrossed in a diallel fashion. The F2 generation of the intercross segregated yellow seeded B. napus plants which were selected and pedigreed for four generations to develop genetically stable, true breeding yellow-seeded B. napus. The agronomic performance and seed quality of early generations of this new source of yellow-seeded B. napus has been reported at the last Rapeseed Congress in 1995 (Rashid and Rakow 1995, Rashid et al. 1995). This paper reports on the agronomic performance and seed quality (fatty acid composition and glucosinolate content) of a number of selected lines derived from the above crosses.
Sixteen F5 to F7 generation lines from the double interspecific cross described above were chosen for a first field test at three locations to evaluate the agronomic performance and seed quality of this new source of yellow-seededness in B. napus (Table 1). The lines were grown in 4-replicate yield tests at Saskatoon, Scott and Melfort in 1996. The official check varieties AC Excel, Legacy and Defender were used for comparison. In addition to yield (kg/ha), seed colour, and oil content (Table 1), observations were also made on days to flower and maturity, plant height and resistance to lodging; and on seed weight and protein content. The results of these additional observations are not presented.
Single plant selections made from most promising yellow-seeded lines, identified in the 1996 yield tests, were pedigree selected in 1997 and 1998, and the seed analyzed for fatty acid composition and glucosinolate content and composition. The analyses were conducted utilizing standard gas chromatographic separation and quantification techniques.
The seed yield of yellow-seeded B. napus lines varied, and none of the lines reached the seed yield of the check varieties (Table 1). The highest yielding lines were YN95-65 and YN95-13, and these
Table 1. Agronomic performance and seed quality of 16 selected yellow-seeded Brassica napus lines derived from interspecific crosses between yellow-seeded B. juncea and B. carinata, Saskatoon, Scott and Melfort, 1996.
|
|
Yield (kg/ha) |
|
Seed colour (WIE)1 |
|
Oil (% dw) |
||||||
|
Line |
Sask. |
Scott |
Melfort |
|
Sask. |
Scott |
Melfort |
|
Sask. |
Scott |
Melfort |
|
YN95-166 |
1699 |
1590 |
3068 |
|
-9.3 |
-25.9 |
-14.0 |
|
45.3 |
45.8 |
40.1 |
|
-159 |
1482 |
1185 |
2621 |
|
-17.9 |
-27.0 |
-18.9 |
|
39.9 |
42.0 |
37.2 |
|
-176 |
1973 |
1599 |
3049 |
|
-18.0 |
-17.0 |
-8.6 |
|
46.1 |
46.8 |
42.1 |
|
-178 |
1720 |
1487 |
3255 |
|
-21.3 |
-24.0 |
-11.6 |
|
43.1 |
44.2 |
40.1 |
|
-114 |
1315 |
923 |
2588 |
|
-9.4 |
-21.8 |
-9.0 |
|
44.1 |
43.7 |
39.6 |
|
- 65 |
2115 |
1623 |
3681 |
|
-8.7 |
-17.6 |
-6.9 |
|
48.9 |
49.2 |
44.6 |
|
- 71 |
1741 |
1714 |
3369 |
|
-12.5 |
-26.7 |
-9.6 |
|
48.5 |
48.2 |
42.9 |
|
- 68 |
2010 |
1539 |
3139 |
|
-6.4 |
-15.6 |
-5.4 |
|
47.0 |
48.3 |
42.3 |
|
- 45 |
1219 |
1276 |
2732 |
|
-13.8 |
-18.3 |
-9.4 |
|
44.9 |
44.6 |
40.2 |
|
- 40 |
1580 |
1061 |
2738 |
|
-10.1 |
-17.2 |
-9.4 |
|
42.9 |
43.5 |
40.1 |
|
- 13 |
2357 |
1599 |
3652 |
|
-10.4 |
-20.1 |
-6.8 |
|
49.8 |
50.2 |
45.0 |
|
- 19 |
2386 |
1464 |
3078 |
|
-11.4 |
-23.8 |
-11.3 |
|
47.8 |
48.4 |
41.8 |
|
- 28 |
2115 |
1297 |
3406 |
|
-14.1 |
-23.5 |
-11.0 |
|
47.2 |
46.7 |
41.4 |
|
-227 |
2288 |
1522 |
3167 |
|
-13.2 |
-30.6 |
-14.3 |
|
41.8 |
42.6 |
37.6 |
|
-212 |
1987 |
1615 |
3422 |
|
-18.3 |
-24.9 |
-11.6 |
|
43.6 |
44.2 |
40.0 |
|
-201 |
2029 |
1520 |
3332 |
|
-12.3 |
-24.4 |
-11.7 |
|
43.0 |
44.5 |
38.7 |
|
Checks2 |
2581 |
2063 |
3899 |
|
0 |
-0.9 |
-0.9 |
|
45.5 |
46.8 |
39.2 |
|
LSD (5%) |
306 |
140 |
490 |
|
|
|
|
|
1.1 |
1.0 |
1.5 |
1 HunterLab reflectance colour measurements, high negative values indicate light coloured seed.
2 Average of AC Excel, Legacy, Defender check varieties.
two lines had also high oil contents which were significantly higher than the oil contents of the check varieties at all three locations. Many other yellow-seeded lines also exceeded the oil contents of the check varieties. Seed colour ratings were also variable, and were highest at Scott and lowest at Melfort. Line YN95-178 had the highest score for the yellow seed colour, but seed colour varied greatly among locations. Best yellow colours were obtained at Scott under dry and hot conditions which in turn resulted in lower seed yields; while seed colour was poorest at Melfort under wet and cool conditions which in contrast produced the highest yields.
The target seed colour score is –25 to –30 which represents a good, bright yellow colour. This rating was achieved by some lines only under favourable dry and warm conditions. The environmental influences on seed colour expression in this material are undesirable and further breeding work is required to produce lines in which seed colour is less affected by environmental factors. It also appears that the highest yielding lines do not have the best yellow colour which is another concern.
The most positive and encouraging result of this study was that high yielding lines also had high oil contents which indicated that improved high yielding, high oil content B. napus lines can be developed for the western Canadian semi-arid prairie climate. To what extent the increased oil content of these lines is associated with their yellow seed colour remains to be determined.
Many yellow-seeded lines contained erucic acid in their seed oils which resulted from the high erucic acid B. carinata parent involved in the original crosses with zero erucic acid B. juncea and B. napus cv. Westar (data not shown). However, plant selections in 1997 and 1998 identified zero erucic acid segregates among yellow-seeded lines as expected. The zero erucic acid segregates had varying C18 fatty acid compositions with some progeny exhibiting reduced oleic acid and increased
linoleic and linolenic acid levels typical of those of zero erucic acid B. juncea and B. carinata (Getinet et al. 1994). This result was not unexpected because of the fact that B. juncea and B. carinata were used as donors for yellow seed colour genes in the original interspecific crosses. However, we were able to select yellow seeded plant progeny that had the typical B. napus C18 fatty acid profile of 60 to 65% oleic acid, 18 to 20% linoleic acid and 7 to 9% linolenic acid (data not shown). It is critical that we make these selections to ensure that the superior fatty acid composition of canola oil is retained in new yellow-seeded B. napus varieties.
The interspecific crosses of B. napus with B. juncea and B. carinata also introduced allyl (2-propenyl) glucosinolate into the progeny of these crosses. Allyl glucosinolate is the typical hot principle in mustard seed and is not present in B. napus. It is, in fact, unacceptable in canola meal. We therefore analyzed yellow-seeded progeny for glucosinolate content and composition and were able to identify, among the yellow seeded lines, progeny that were basically free (< 1 Fmoles per 1g of seed) of allyl glucosinolate and had a total alkenyl glucosinolate content of < 10 Fmoles per 1g of seed (data not shown). This is an important result which indicated that genes for allyl glucosinolate synthesis introgressed from B. juncea and/or B. carinata and present in selected yellow-seeded B. napus progeny from the interspecific double cross, can be eliminated from this population through selection.
Yellow-seeded forms of B. juncea and B. carinata can be utilized as sources for yellow seed colour genes in crosses with B. napus for the development of new yellow-seeded B. napus. Extensive pedigree breeding is required to obtain agronomically superior, high quality lines, and the fatty acid composition as well as glucosinolate content and composition must be selected to retain the favourable B. napus fatty acid profile, and to remove unwanted allyl glucosinolate from segregating yellow-seeded lines.
This material represents only one backcross to B. napus after the original interspecific cross and further backcrosses to B. napus are required to develop superior yellow-seeded B. napus varieties for production on the western Canadian prairie. This work is presently in progress.
This project was financially supported, in part, by a grant from Canodev Inc., a subsidiary of the Saskatchewan Canola Development Commission, Saskatoon, Canada and by the Matching Investment Initiative of the Government of Canada. The technical assistance of D. Rode,
D. Hennigan and G. Serblowski is greatly appreciated.
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