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Composition and quantity of oil and protein in the seed are influenced by the environment. Twenty seven cultivars, from the Maturity Groups III and IV, were tested in three contrasting environments of the southern pampeana region of Argentina.

Average of protein and oil contents was 39, 3% and 22,7%; 39,9% and 22,7%; 42,4% and 20,3% for Balcarce I, II and III respectively. The content of linolenic acid increased from 7,4% in Balcarce I to 9,1% in Balcarce III and that of oleic acid diminished from 27,3% in Balcarce I to 25,5% in Balcarce III. It is possible to modify the contents of oil, protein and fatty acids of soybean cultivars managing sowing dates, provided that water stress is avoided.

Soybean (Glycine max L. Merr.) is the most important oilseed crop in the world and in Argentina too. In this country, grain and byproducts are exported mainly. In the southern pampeana region, south of latitude 36º S, the crop is grown on proximately 100000 has with further expansion expected. Cultivars of maturity Groups III and IV are well adapted to this zone. Soybean grain is composed of proteins (40%), oils (20%), carbohydrates, fibers and aches.

The average protein and oil content in soybean, in Argentine, were 39,9% and 21% respectively (Cuniberti and Pérez, 1995). The objectives of soybean breeding programs in the world are geared towards the obtention of cultivars with specific contents of oil and protein according to the demand of the markets.

Soybean seed protein content and oil content and composition are influenced by environment during seed development (Gibson and Mullen, 1996). Oil and protein contents are negatively correlated (Burton, 1985) and the protein content shows more variability than oil content (Weilenmann and Lúquez, 1999). The objectives of this study were to observe 1) the effect of three different environments on oil, protein and fatty acids contents of 27 cultivars of maturity Groups III and IV sown in the southern pampeana region, and 2) the existence of variability for oil and protein contents among these cultivars.


MATERIALS AND METHODS

Cultivars were sown in three environments:

1) Balcarce I, normal sowing date (17/11/99) in dryland,
2) Balcarce II, normal sowing date (2/12/99) with 155 mm of irrigation, and
3) Balcarce III, late sowing (7/1/00) with 115 mm of irrigation.

At all sites, soils were Argiudoll typical. The trials included 27 cultivars supplied by different companies (Table 1).
Each trial was arranged as a randomised block design, with three replications. Plots were four rows wide at 0.7 or 0.35 m spacing and 5 m long and were sown at 23 seeds m-2 .

Weeds were controlled by chemical and mechanical methods according to the species present at each location. No insecticides or fungicides were used.

The two central rows of each plot were harvested in May 5 and June 20 and 29 at Balcarce I, II and III respectively.

Protein and oil contents were measured in two samples of 300g for each cultivar by near-infrared reflectance spectrophotometry.

Fatty acid contents (linolenic and oleic acids contents) were determined in a sample of the oil of 11 cultivars ( P9492, Tj 2046, DM 3800, Joketa 46, P 9396, DM 4300, A 4456, DM 440, A 3205, ACA 490, and P 94B01) with a High Performance Liquid Chromatograph.

Oil and protein means were separated using the least significant difference test for those effects having significant F-tests. Simple correlations (r) among means of oil and protein content were calculated.


RESULTS AND DISCUSSION

Oil and protein contents average accross environments are in Table 1. Average of protein content was 39, 3%, 39,9% and 42,4% for Balcarce I, II and III respectively in the combined analysis of variance, which showed significant differences between environments and cultivars and significant interaction genotype x environment (P< 0.05).

The percentage of proteins in Balcarce I ranged between 35,7 (HMS-41) and 41, 0% (P94B41), in Balcarce II between 36, 2 (A 3910) and 41,6% (P94B41), and in Balcarce III it was 40, 9 ( DM 4000RR) and 44, 6% (A3205).

Mean of oil percentage was similar for Balcarce I and II (22,7%) and it was of 20, 3% for Balcarce III in the combined analysis of the variance (cultivars with highest oil contents were DM 4000 RR, DM 43 and DM 48).

There were differences between environments and cultivares (P< 0.05), while the interaction genotype x environment was not significant.

The content of linolenic acid increased from 7,4% in Balcarce I (range between 4.66 for P 9396 and 8.67 for Joketa 46) to 9,1% in Balcarce III (range between 4.89 for DM 4300 and 11.02 for A 4456) and that of oleic acid diminished from 27,3% in Balcarce I ( range between 35,23 for P 9326 and 21,45 for Tj 2046) to 25,5% in Balcarce III (range between 22,27 for A 4456 and 29,38 for Joketa 46). Oil and proteins contents showed a negative correlation of -0.77 in the combined analysis.

In our experiment, temperature during seed fill would be the key environmental variable affecting grain quality characteristics, mainly oil content and fatty acid profiles.

This fact coincided with results of Kane et al. (1997). Increasing seed-fill temperature (Balcarce I and II) elevated oil content and level of oleic acid, but decreased protein content and level of linolenic acid. So, planting date influenced protein and oil contents and fatty acid profiles, and soybean breeders could target the development of lines with different protein and oil contents and oleic and linolenic acids levels, managing planting date, provided that water stress is avoided.



Table 1. Protein and oil contents in the grain of 27 soybean cultivars evaluated in three environments in the southern part of Buenos Aires province, Argentina.

Cultivars	Seed company	Protein content (%)	Oil content (%)
TJ 2046	BRETT S.A.	40.44	22.21
DM 48	DON MARIO S.A	39.89	22.38
FULGOR 33	JOSÉ BUCK S.A	39.99	21.77
P 9492	PIONEER S.A.	41.10	21.87
DM 4000 RR	DON MARIO S.A.	39.13	22.76
A 4100 RG	NIDERA S.A	40.73	22.03
TJ 2047 RR	BRETT S.A.	40.34	21.77
A 4657	NIDERA S.A.	41.24	21.80
P 94B01	PIONEER S.A.	41.93	21.91
A 4501 RG	NIDERA S.A.	40.93	21.91
DORADA 48	RELMÓ S.A.	40.99	21.79
JOKETA 46	NOVARTIS S.A.	40.61	22.21
P 94B41	PIONEER S.A.	42.06	21.26
A 4456 RG	NIDERA S.A	40.58	21.72
A 4423	NIDERA S.A.	40.67	21.83
DM 440	DON MARIO S.A.	39.66	22.20
A 3205	NIDERA S.A.	41.86	22.16
A 3205	NIDERA S.A.	41.86	22.16
N MITCHELL	PUBLIC	41.60	21.79
HMS-41	MONSANTO	39.48	21.80
P 9396 .	PIONEER S.A	39.86	22.23
DELIA 46	RELMÓ S.A.	39.21	22.23
DM 4700 RR	DON MARIO S.A.	41.64	21.59
DM 4300 RR	DON MARIO S.A.	41.13	21.69
A 3910	NIDERA S.A.	38.87	22.32
BONAERENSE	RELMÓ S.A.	41.22	21.34
DM 3800 RR	DON MARIO S.A.	40.42	22.29
DM 43	DON MARIO S.A.	39.83	22.38
Mean		40.57	21.97

REFERENCES

Burton, J.W. 1985. Breeding soybeans for improved protein quantity and quality. In: Shibles, R. (ed.). World Soybean Research III. Proceedings. Westview Press, Boulder and London.

Cuniberti, M. and Pérez, A. 1995. Calidad industrial de cultivares de soja de grupo de madurez V corto, V largo, VI, y VII. : 47-53. Primer Congreso Nacional de Soja. Segunda Reunión Nacional de Oleaginosos.

Gibson, L. and Mullen, R. 1996. Soybean seed composition under high day and night growth temperatures. JAOCS, vol. 73, # 6: 733-737.

Kane, M.; Steele, C.; Grabau, L.; MacKown, Ch. and Hildebrand, D. 1997. Early-maturing soybean cropping system: III. Protein and oil contents and oil composition. Agron. J. 89: 464-469.

Weilenmann de Tau, M.E. and Lúquez, J. 1999. Variability of oil and protein contents of commercial cultivars (group IV) in Argentina. Tests of Agrochemicals and Cultivars # 20: 62-63.

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