TRANSFER OF DOUBLE LOW CHARACTERISTICS IN EARLY MATURING INDAN RAPESEED MUSTARD

GENETIC ENHANCEMENT FOR DOUBLE LOW CHARACTERISTICS IN INDIAN RAPESEED MUSTARD

Abha Agnihotri and Nutan Kaushik

Bioresources and Biotechnology Division

TERI, Habitat Place, Lodhi Road

New Delhi 110 003

Email: abhagni@teri.res.in

ABSTRACT

The rapeseed mustard cultivars being grown in India have high amounts of erucic acid (40-50%) in the seed oil and high glucosinolate (80-160Fm/g) in the oil free meal. Earlier attempts to introduce `canola' quality rapeseed varieties in India failed due to non-adaptability of these exotic cultivars under Indian agro-climatic conditions. The popularly grown high yielding B.juncea var. Varuna was crossed with low glucosinolate B.juncea line BJ-1058 for transfer of low glucosinolate. Simultaneously, a unique three way cross; B.juncea (var. Varuna x Zem-1) x BJ-1058 was made for transfer of double low characteristics. The fatty acids and glucosinolates were analysed through improved methods of GC and HPLC respectively. The double low B.juncea var. Varuna, developed through the three way cross, is late in maturity and have robust plant type. The low glucosinolate strains of B.juncea var. Varuna have been established having early maturity and slender plant type. The work is in progress for the agronomic improvement in the plant type of double low B.juncea by backcrossing with the low glucosinolate strains of B.juncea var. Varuna. The zero erucic acid strains of B.napus were developed at TERI from the advanced generation transgressive segregants of intergeneric crosses of Brassica. Some of these strains selected for early maturity were used for transfer of double low characteristics from exotic B.napus var. Regent and Cyclone. The newly developed double low strains of B.napus i.e TERI(OO)R985 and TERI(OO)R986 having zero erucic acid in the seed oil and low glucosinolate (12-15Fm/g) in the oil free meal have compact plant type and shorter maturity period (125-140 days) as compared to the widely grown national check B.napus var. GSL-1 having maturity period of 153 days. These double low B.napus strains are being tested for multilocation adaptation and possible commercialization.

KEYWORDS: B.juncea, B.napus, erucic acid, glucosinolate, double low, Rapeseed Mustard

INTRODUCTION

The plant species belonging to the genus Brassicas (Rapeseed mustard) are used as vegetables, condiments and oilseeds. In India, the oilseed Brassica is the second most important oilseed crop next only to groundnut and account for about 30% of the total oilseeds produced in the country. The rapeseed mustard oil has lowest amounts of saturated fatty acids as compared to any other vegetable oils. It also contains adequate amounts of the two essential fatty acids linoleic and linolenic that are not synthesized by man and need to be supplied to the human diet from external sources.

The oil free meal is a good source of proteins, well balanced in amino acids and minerals. The presently cultivated Indian varieties of rapeseed mustard, however, have high amounts (40-50%) of long carbon chain fatty acids, in particular erucic acid (22:1), in their seed oil and high amounts of sulphur containing compounds, i.e. glucosinolates (80-160Fm/g), in their oil free meal, as against the internationally accepted levels of less than 2% erucic acid in the seed oil and less than 30Fm glucosinolate/g oil free meal (`Canola' quality; Downey 1990).

Studies conducted on birds and animals had indicated adverse effects of diets rich in erucic acid and glucosinolates (Gopalan et. al. 1974, Kumar and Tsunoda 1980, Bille et. al. 1983, Bell 1984), leading to research efforts for breeding rapeseed mustard with low levels of these two nutritionally undesired components. As a result, several rapeseed cultivars with `Canola' quality (commonly known as double low or `00') were developed (Scarth 1995) and during the early eighties a complete changeover to `Canola' quality rapeseed took place in Canada, Germany, and other European countries. But in the major rapeseed mustard growing countries of Asia, China and India, this changeover is just now beginning and may take another 5 to 10 years to be completed (Downey and Chopra 1996).

EXPERIMENTAL

Transfer of low glucosinolate/double low characteristics in B.juncea

The high yielding B.juncea var. `Varuna', was selected for transfer of low glucosinolate/double low characteristics and used as a female parent. The exotic low erucic acid B.juncea var. `Zem-1' and the low glucosinolate line `BJ-1058' were used as pollen donors. For the transfer of low glucosinolate, reciprocal crosses of B.juncea var. `Varuna' and `BJ-1058' were attempted. For the transfer of double low characteristics in B.juncea var. `Varuna', a three way cross (`Varuna' x `Zem-1') x `BJ-1058' was attempted.

Transfer of double low characteristics in B.napus

The early maturing B. napus lines TBN-1 and TBN-5, derived from an advanced generation of a backcross progeny of (B. napus x Raphanobrassica) x B. napus (Agnihotri et. al. 1990) and selected for zero erucic acid via half seed technique (Agnihotri et. al. 1995) were used as the female parent. The exotic double low B. napus var. `Regent' and `Cyclone' were used as pollen donors for transfer of the double low characteristics.

Pollinations, quality analysis and selections

Flower buds on selected inflorescences of the female parent of B.juncea and B.napus were emasculated manually with the help of forceps and pollinated with pollen from freshly opened flowers of the respective male parent (as above). The F₁ seeds were harvested and F₂ single plant progenies were grown in experimental plots following standard agricultural practices. Plants were bagged and selfed; and in addition open pollinated (OP) F₃ seeds were collected from a large number of individual plants.

The F₃ OP seeds were analyzed for their glucosinolate content by an improved HPLC method (Kaushik and Agnihotri 1999). The selfed seeds of the plants, showing less than 30Fm glucosinolate/g oil free meal, were utilized to grow single plant progenies. During the next three subsequent generations again single plant progenies were grown and selfed; and in addition OP seeds were harvested from individual plants. The glucosinolate content was analyzed from OP seeds in each generation to select plants having glucosinolate less than 30Fm/g oil free meal. Simultaneously the plants were selected for early maturity in each generation.

The F₆ selfed seeds of the plants, from the crosses B.juncea var. (Varuna x Zem-1) x `BJ-1058'; `TBN-1' x `Regent'; and `TBN-5' x `Cyclone'; having less than 30Fm glucosinolate/g oil free meal, were analyzed for their fatty acids content by an improved GC method (Kaushik and Agnihotri, 1997). The plants having less than 2% erucic acid in the seed oil and less than 30Fm aliphatic glucosinolate/g oil free meal were identified for further progeny advancement. The F₇ single plant progenies of the double low B.juncea and B.napus plants thus derived, and of the low glucosinolate selections derived from the reciprocal crosses of B.juncea var. `Varuna' and `BJ-1058', were grown in the field during Rabi 1997-98 for collection of selfed and OP seeds, and agronomical data were recorded.

CONCLUSIONS

The glucosinolate content of the F₃ seeds, in the crosses B.juncea var. Varuna x BJ-1058; BJ-1058 x Varuna; and B.juncea var. (Varuna x Zem-1) x BJ-1058, ranged from 24-128 Fm, 25-130Fm and 16-134Fm/g oil free meal respectively. Plants identified for having less than 30Fm glucosinolate/g oil free meal synthesized glucosinolates in the range of 10-84Fm from the reciprocal crosses of Varuna and BJ-1058 and 10-55Fm from the crosses (Varuna x Zem-1) x BJ-1058 in F₄ to F₆ generations. In the F₇ generation, some plants were selected showing stability to their glucosinolate contents, and all plants in the single plant progeny synthesized less than 30Fm/g oil free meal. In general, the plants derived from the reciprocal crosses of B.juncea var. Varuna and BJ-1058 are early in maturity (132-135 days) as compared to those derived from B.juncea (var. Varuna x Zem-1) x BJ-1058 (145-152 days). The F₈ single plant progenies of the low glucosinolate/double low B.juncea lines have been grown in the field during Rabi 1998-99 for recording of agronomical data and evaluation of their yield potential. Once the low glucosinolate/double low lines having stable low/double low characteristics are derived, work will be undertaken to derive early maturing double low B.juncea strains through the biparental mating programme of double low and low glucosinolate lines of B.juncea var. `Varuna'.

The glucosinolate content of the F₃ seeds in the B.napus crosses made with `Regent' and `Cyclone' ranged from 16-120 and 11-80Fm/g oil free meal, respectively. While some of the plant progenies segregated for their glucosinolate content (showing plants having more than 30Fm glucosinolate/g oil free meal), others showed stability to their glucosinolate content and all plants synthesized less than 30Fm glucosinolate/g oil free meal in the subsequent generations (F₄ to F₆). In general, the plants derived from crosses with `Regent' are early in maturity (120-130 days) as compared to those derived from crosses made with `Cyclone' (125-145 days). These double low strains are 15-28 days early in maturity as compared to the B.napus var. `GSL-1' (national check), a desired characteristic to secure timely harvest of the crop. The selected lines have low erucic acid (<2%) and low glucosinolate (12-15 Fm) as compared to about 36% erucic acid and 77 Fm glucosinolate/g oil free meal in the national check B. napus var. `GSL-1'. In addition, they have a higher oleic acid content (48-57%) as against only about 25% in GSL-1. High oleic acid is regarded beneficial in human diets for nutritional and health reasons. The quality and agronomical characteristics (based on average of ten randomly selected plants) of the selected low erucic acid, low glucosinolate strains TERI(OO)R985 and TERI(OO)R986, derived from crosses B. napus line TBN-1 x `Regent' and B. napus line TBN-5 x `Cyclone', respectively, are given in Table 1. Further work is in progress to evaluate these double low rapeseed strains for multilocation adaptation and possible commercialization.

Table 1. The agronomical and quality characteristics of double low B. napus strains developed at TERI

Strains	TERI(OO)R985	TERI(OO)R986	GSL-1^*
Pedigree	B. napus line TBN-1 x B. napus var. Regent	B. napus line TBN-5 x B. napus var. Cyclone
Agronomical Characteristics
Plant height (cm)	121	174	176
No. of primary branches	6	10	8
No. of secondary branches	4	5	4
Seed yield/plant (g)	13.08	15.21	8.72
Days to maturity	125	143	153
Quality Characteristics
Oleic acid (%)	48.0	57.2	21.6
Linoleic acid (%)	32.7	22.3	14.8
Linolenic acid (%)	12.9	10.5	20.5
Erucic acid (%)	0.0	0.0	36.7
Glucosinolate (Fm/g oil free meal)	15.3	12.2	77.2

* B. napus national check variety.

ACKNOWLEDGEMENT

The authors are grateful to Dr. R.K. Downey, Emeritus Scientist, Agriculture and Agri-Food Canada Research Station, Saskatoon, Canada for kind gift of the double low pollen donors and constructive suggestions. Thanks are also due to Dr. N.B. Singh, ADG (OP), ICAR; Dr. J.P. Singh, Secretary, NOVODB and Dr. A.K. Singh, IARI, for useful discussions. The technical assistance by Mr. Gautam Sarkar and Mr. Bir Singh is highly appreciated. The work was advanced through the financial assistance from National Oilseeds and Vegetable Oils Development Board (Ministry of Agriculture), Government of India.

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