ABSTRACT

Seed of selected plants tolerant to salinity from the two cultivators of spring rapeseed (Brassica napus ) Fido and Tower were grown in a soil affected by salinity (ds/m = 4 to 8 ) at El-Serw Agricultural Research Station, North Delta of Egypt during 1993/1994 and 1994/1995 seasons . Natural haploid plants were selected (2n=19) over the two seasons and 14 homozygous diploid lines (HDL) were produced They were evaluated in field trails in 1996/97 and 1997/98 seasons compared with the parental lines and Pactol cultivar under two levels of salinity ( ds /m = 2 to2.5 and 5.5 to 6.5 ).The results indicated that the high level of salinity was significantly reduced seed yield , oil content and total dry matter Two HDL were more tolerant to salinity and over yielded their parents by 35 to 55 % ,1.5 to 2.3 % and 13 to 38 % in seed yield kg /ha, oil content and total dry matter kg/ha respectively.

INTRODUCTION

Oilseed rape became a new oil crop in Egypt which may reduce the gap between the local production and consumption of the edible oil . But this new crop face difficulties to compete with the main crops in the Nile valley land during winter seasons. The new reclaimed land outside the valley is the target for rapeseed growing. The most of these land is characterized with high levels of salinity, specially in the North area of the country. Therefore new genotypes adapted and tolerant to salinity is very essential for the success of rapeseed growing (Keshta 1998).

A crop improvement program must be based on adequate variability for the desired trait , and indeed considerable variability for tolerance of salinity has been observed among and within species (Epstein et al 1980) Various screening procedures have been devised for identifying salt tolerant lines or even individual plants within species (Norlyn and Emanuel 1989, Epstein 1977, Kingsbury and Epstein 1984 and Shanon 1979 )

One of the rapid breeding method for the development of new improved rapeseed cultivars is producing homozygous diploid lines derived from the natural occurring haploid plants ( Thompson 1979 ) . He illustrated that trails results from spring and winter rape showed that occasional homozygous diploid lines yielded consistently more oil per/ha than the parental varieties. Loof (1975) considered that comparatively homozygous lines would not include all the desirable characteristics of winter rapeseed e.g. extremes winter-hardiness and resistant to diseases, necessary to give variety sufficient adaptability to different soil and climatic condition in Sweden.

The purpose of this study is to evaluate some homozygous diploid lines of spring rape produced from the natural occurrence haploid plants with their parental varieties and the cultivated variety Pactol under saline condition to find lines more salinity tolerance.

MATERIALS AND METHODS

The two cultivars of spring rapeseed ( B.napus ) eg. Fido and Tower were grown in soil affected by salinity ( ds/m =4 to 7) for salinity hardiness in the experimental farm of El Serw Agricultural Research Station The natural haploid plants (2n=19) were taken and treated for producing homozygous diploid lines (2n=38) as described by Tompson (1979) . Successive 8 and 6 homozygous diploid lines (HDL) were produced from Fido and Tower cultivars respectively during 1993 / 94 and 1994/95 seasons .The seed of each line were propagated by bagging the plants to avoid pollen contamination The 14 HDL were evaluated with the parental lines and the cultivated variety Pactol in two field experiments under surface irrigation ( 5 irrigation/ season). Samples of the soil were collected at 20 and 40 cm depth to determine electric conductivity (EC_e) on the soil saturation extract (1:5) and reported as average mmhos /cm The soil electrical conductivity are presented as an average of the two depth. Two levels of salinity were chosen i.e. S₁ ( EC_e = 2.0-2.5 ds/m) and S₂ ( Ec_e=5.5-6.5 ds/m)

Two field experiments (for each salinity level) were carried out during 1996/97 and 1997/98 seasons in the experimental farm of El Serw Agricultural Research Station The randomized complete blocks design in factorial arrangements was used with four replications .The area of each plot was 10 m2 ( 5 rows x 0.5 m width x 4 m long )

Seed were sown in hills during the first week of November ( 5gm / plot ) in both seasons .The fertilizers of P and K(40 kg P₂O₅ + 30kg K₂O/ha) were applied during land preparation and the nitrogen fertilizer (120 kg N /ha) was applied in two equal doses, half during land preparation and the other half at the time of the second irrigation.. Plants were hand thinned three weeks after sowing leaving one plant/hill . Observations were recorded on five plants selected from the inner rows for the following characters; number of racemes and number of sillqua per plant . Plants of the three inner rows from each plot were harvested at the end of the season and air-dried to determined thousand seed weight ,seed yield /ha, total dry matter /ha ( converting the yield kg/ plot to yield kg/ ha) . Oil content were estimated according to the procedures of A.O.A.C (1975).Harvest index was also calculated as seed yield / biological yield.

The relative value:The value of any character studied of each genotype at the low salinity level (S1) considered to be 100 and the value of the same character of each genotype at the high level of salinity is considered as a percentage of S1 level . It was calculated as the following formula :

Relative value = ( S₂ / S1)x100

The data were statistically analyzed according to Gomez and Gomez (1984).

RESULTS AND DISCUSSION

Low salinity effect (S1) :

Data presented in Tables (1,2) showed variations among the homozygous diploid lines and their parental lines in all of the studied characters , Some HDLs were significantly earlier than their parent (T₃,T₅ and T₈), while T₆ and F₄ were significantly later . Number of racemes per plant has recorded varying among the lines and their parents, but only three of F lines (F₃ F₅ and F₆ ) were significantly decreased .Number of silliqua per plant were also recorded significant increases in 4 lines (T₅, T₈, F₂ and F₆) and three significant decreases in 4 lines (T₅,T₈ and F₆).The 1000-seed weight did not record any significant increases among the lines and their parents, but T₄, F₁ and F₄ were significantly decreased. Oil content recorded little varying , some lines showed little increases in oil content (only T₅ were significantly increased) and others were significantly decreased (F₁, F₄ and F₆). Total dry matter showed great variation among the lines and their parents, but there is non of them increased more than any parent . Harvest index showed significant increases in 7 out of 8 lines derived from Tower cultivator , while F lines showed 3 increases and 3 decreases compared with Fido.

Data presented in Table (2 ) showed that seed yield of HDLs was varying from 1675 to 2870 kg / ha compared with the control c.v. Pact . This result appeared that the HDLs F₂ ,T₂, T₈ and T₅ outyielded the cultivated cultivar pactol by 48 , 35,34 , and 27% respectively. and outyielded their parents by 7, 14 , 13 and 8% respectively .The results also showed that the increases due to the increases in number of racemes /plant , number of silliqua /plant and 1000-seed weight.

The significant differences in the mean performance of the studied traits among the homozygous lines and their parents probably due to the differences in their genetical constitution since they represent varied ecological regions. The natural occurrence haploid lines appeared significant divers among themselves proved that the natural mutations results great diversity among lines derived from the same parent. These results are in agreement with those obtained by Thompson (1979 ) and Loof (1975 ).

Table 1) : Average values of some characters of the rapeseed HDLs , their parental lines and the pactol cultivar under two levels of salinity (S₁.&S₂) over 1996/97 and 1997/98 seasons

Genotyps	Days to 50% flowering.			N.of racemes /plant			N.of silliqua / plant			1000-seed wt. gm
(G)	S1	S2	Mean	S1	S2	Mean	S1	S2	Mean	S1	S2	Mean
Pactol	105	104	105	7.3	4.2	5.8	269	128	199	4.1	2.8	3.5
Tower	108	107	108	8.1	5.7	7.8	341	205	273	4.6	3.1	3.9
Fido	110	108	109	9.4	5.3	7.4	327	198	266	4.5	3.0	3.8
T1	111	108	110	7.6	4.2	5.9	269	173	221	4.8	3.1	3.9
T2	111	109	110	8.3	4.0	6.2	311	210	261	4.5	3.2	3.9
T3	107	104	105	8.0	4.3	6.2	307	195	251	4.7	3.6	4.2
T4	108	106	107	8.1	5.1	6.6	315	187	251	4.1	3.0	3.6
T5	104	101	102	9.2	7.3	8.3	388	240	314	4.9	3.4	4.2
T6	113	109	111	7.0	4.1	5.6	321	207	264	4.5	3.1	3.8
T7	109	106	107	6.9	4.3	5.6	275	187	231	4.3	2.9	3.6
T8	101	99	100	8.8	7.0	7.9	376	252	314	4.7	3.5	4.1
F1	110	108	109	8.4	5.3	6.9	289	157	223	3.9	3.1	3.5
F2	112	109	110	9.0	5.4	7.2	381	210	296	4.7	2.9	3.8
F3	109	105	107	7.6	4.5	6.1	279	169	450	4.2	3.0	3.6
F4	113	108	110	8.1	5.6	6.9	326	198	262	3.9	2.8	3.4
F5	111	105	108	6.8	4.3	5.6	298	177	236	4.7	3.3	4.0
F6	109	103	106	8.0	5.1	6.6	365	205	285	4.5	3.4	3.9
Mean	109	106		8.1	5.0		319	200		4.4	3.1
LSD at5% for : S	1.6			1.6			36			0.3
G	2.1			1.4			30			0.4
GxS	2.4			1.9			65			0.6

*T=HDL derived from Tower cultivar & *F = DHL derived from Fido cultivar.

Effect of high salinity (S₂ ),

Results presented in Tables (1,2) show that average of days to 50% flowering ,number of racemes per plant , number of silliqua per plant ,1000-seed weight , seed yield per hectare , oil content , total dry matter and harvest index were significantly decreased by increasing the soil salinity from 2.5 to 6 mmohs by 2.8 ,38.3 ,37.3 ,29.5 , 57.6 ,14.5 ,44.0 %, and 25.0 % respectively. Therefore number of silliqa/ plant , 1000- seed weight , seed yield kg/ha and total dry matter characters were more injurious than the other traits Days to flowering were reduced from 1 to 6 days and the reductions were greater in the late flowering lines.The highest two yielded lines (T₅ and T₈ ) showed the highest values of number of racemes / plant and number of silliqua / plant The weight of 1000-seed were also affected by increasing salinity levels and the range was between 2.8 to 3.6 gm

The two homozygous lines T₈ and T₅ exceed all the other lines and outyielded their parents in seed yield kg/ha by 35% and 23 % respectively and they exceed cv. Pactol by 75.0 and 59.5 %. These results were true since they gave the highest values of the studied trait under the high salinity level. On the other hand, although F₆ produced the highest yield under the normal condition , it was not the best under the high salinity level .

Oil content revealed difference reductions among the lines, the highest oil content obtained from T ₅ T ₈ and their parent Tower although they were not the best under low salinity condition. Total dry matter is the result of the previous studied characters and it was reduced about 44% . The reduction in these characters caused by salinity could be attributed to increasing osmatic pressure of the soil solution to a point which retarted or reduced the intake of water resulting in water stress in the plant and decreasing cell devision, cell elongation and cell initiation

The data also presented in Tables 1&2 showed significant interaction among genotypes and salinity in all studied traits, but it was varing from character to another and from line to another.

(Table 2): Average values of some characters of rapeseed HDL , their parental lines and the pactol cultivar under two levels of salinity (S₁.&S₂) over 1996/97 and 1997/98 seasons

Genotypes	Seed yield kg/ha.			Oil content			Total dry matter kg/ha			Harvest index
(G)	S1	S2	Mean	S1	S2	Mean	S1	S2	Mean	S1	S2	Mean
Pactol	1965	810	1373	46.7	38.3	42.3	5688	3240	1620	0.34	0.25	0.30
Tower	2280	1050	1665	45.3	46.3	42.8	7670	3890	5780	0.30	0.27	0.28
Fido	2664	1160	1912	45.9	39.3	42.6	8195	3915	6055	0.33	0.29	0.31
T1	2360	920	1640	45.8	39.1	42.5	5950	3833	4892	0.40	0.24	0.32
T2	2610	1030	1820	45.1	38.2	41.2	7080	3960	5520	0.37	0.26	0.32
T3	2390	675	1533	45.7	37.1	41.4	6230	2812	4521	0.38	0.24	0.31
T4	2385	870	1627	46.2	36.3	41.3	6745	3480	5113	0.35	0.25	0.30
T5	2465	1292	1879	45.9	40.8	43.4	6070	3747	4908	0.41	0.34	0.38
T6	2010	940	1475	45.2	38.2	47.1	5636	3480	4558	0.38	0.27	0.33
T7	1675	830	1253	46.1	38.3	42.2	6310	3190	4750	0.32	0.26	0.29
T8	2590	1418	2004	45.5	41.1	43.3	7220	4137	5678	0.36	0.34	0.35
F1	2215	835	1525	44.3	38.3	41.3	6375	3100	4738	0.34	0.27	0.31
F2	2870	786	1828	45.6	37.1	41.4	7280	3030	5155	0.39	0.26	0.34
F3	1855	795	1325	46.6	36.6	41.6	6340	3180	4760	0.29	0.25	0.27
F4	1935	805	1370	44.1	37.3	40.7	6655	3220	4937	0.29	0.25	0.27
F5	1865	935	1400	45.2	38.9	42.1	6345	3395	5120	0.29	0.27	0.26
F6	2340	1160	1750	44.6	38.3	41.5	7285	3560	5423	0.37	033	0.35
mean	2261	959		44.9	38.4		6140	3463		0.36	0.27
LSD at 5% for : S	.	187.		0.9			341			0.03
G		224		1.1			415			0.04
GxS		308		1.8			621			0.06

*T=HDL derived from Tower cultivar & *F = HDL derived from Fido cultivar.

Table : (3) Relative values of some characters of some rapeseed cultivars and some homozygous diploid lines .

Genotypes	n.of racemes/pl.	n. of sillqua/pl.	oil content	1000-seed wt/gm	seed yield kg/ ha	total dry matter /ha	harvest index
Pactol	58	48	82	42	41	70	74
Tower	70	60	89	46	46	55	90
Fido	56	61	86	43	44	35	88
T1	55	64	85	39	40	54	60
T2	48	68	85	39	39	47	70
T3	54	64	82	28	28	38	64
T4	63	60	79	31	37	52	71
T5	79	62	89	52	52	62	83
T6	59	64	85	47	47	45	71
T7	63	68	83	50	49	47	70
T8	80	67	90	53	54	66	62
F1	65	55	86	38	38	47	79
F2	60	55	81	26	27	33	62
F3	59	61	72	43	43	51	86
F4	69	61	85	42	42	49	86
F5	63	59	86	51	50	62	86
F6	64	66	86	50	50	49	69

Relative values: Relative value in this study express salt tolerance of any character. In another ward, the highest relative value is the highest salt tolerance . Data presented in Table (3) showed difference values among lines and among characters . For number of racemes /pl, the highest values obtained from T₅ and T₈ followed by Tower parent. Number of silliqua per plant showed that the lowest value obtained form cv Pactol (48%) while the highest values were obtained from T₈ and T₅. Oil content was also affected but less than the other characters, and the highest values obtained from T₅ ,T₈ and Tower. Relative 1000- seed weight is not acting similar because the highest seed yielding lines were not record the highest values . Relative seed yield presented in this study showed that the highest seed yielding lines under high salinity (T₈ and T₅ ) recorded the highest relative values ( 53 and 52% ).Harvest index did not act the same ,while the highest seed yielding genotype did not record the highest relative seed yield, the parental lines Tower and Fido recorded the highest relative values (90 and 88%). Relative seed yield expressed salt tolerance for all traits , while the highest seed yielding line under the normal condition (F₆}did not gave the same result under the salinity level.

In general the two homozygous diploid lines T₅ and T₈ recorded the highest relative values of number of silliqua /pl , number of racemes /pl, seed yield kg/ ha . These results proved that there are genitical variation among the lines derived from the same parent in agronomic characters and salt tolerance These results were also correspondent with that obtained by Keshta (1998), Thompson (1979), Epstein (1975) and Loof (1975).

CONCLUSIONS

This study provides , an evidence that natural occurring haploid plants could be a rapid source for genitical diversity which could be useful to find genotypes with high salinity tolerance in rapeseed. Some homozygous diploid lines tested in this study were similar to their parents and others were more salinity tolerance and outyielded their parents under the high salinity level in yield and yield component . The two homozygous diploid lines derived from Tower cultivar (F5 and F8) characterized with high salinity tolerance and early mature , therefore they could be successfully grown better in land affected by salinity.

REFERENCES

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