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Adaptation and yielding ability of castor plant (
Ricinus
communis
L.) genotypes in a Mediterranean climate
S.D. Koutroubas
a
, D.K. Papakosta
a,
*, A. Doitsinis
b
aLaboratory of Agronomy (233), School of Agriculture, Aristotle University of Thessaloniki, Gr-54006 Thessaloniki, Greece
bNAGREF, Cotton and Industrial plants Institute, Sindos, 57400 Thessaloniki, Greece
Accepted 1 June 1999
Abstract
Successful castor (Ricinus communisL.) cropping in Greece depends on the yielding ability and yield stability of the cultivars (hybrids or inbreds) as well as the reliability of production systems. The adaptation and yielding ability of 19 modern castor oil genotypes were studied for 3 years in two sites of Northern Greece. Genotypes combining high seed and oil yield and desirable morphological characteristics were tested for 2 or 3 years, whereas the rest were tested for 1 year only. The growing period in both locations was long enough for ripening the first raceme and a number of secondary racemes depending on the genotypes. The plant height was dependent mainly on the genotypes but also was affected by the site and the year of the experimentation and ranged from 79 to 278 cm. The seed yield varied between 2.5 and 5.0 Mg ha−1, values that are among the highest reported in the literature. The seed yield was higher in the site where plants produced and ripened more secondary racemes. The seed oil content was dependent mainly on the genotype and ranged from 44.5 to 54.2%. The oil yield followed the changes in seed yield. The variation in seed yield between years was low and in most genotypes less than 20%. Results indicate that the castor oil crop was satisfactorily adapted in the area. © 1999 Elsevier Science B.V. All rights reserved.
Keywords:Mediterranean climate; Oil yield;Ricinus communis; Seed yield
1. Introduction countries are Brazil, China, India and the countries of the former Soviet Union. Yields in these coun-tries are generally low, between 400 and Castor plant (Ricinus communisL.) is an oilseed
900 kg ha−1 (Bonjean, 1991), mainly as a result plant with an oil content between 40 and 60% in
of growing unimproved cultivars and extensive commercial varieties ( Weiss, 1983). Castor oil has
cultivation. unique physical and chemical properties among
New castor plant genotypes (inbred lines or the vegetative oils and has found wide applications
hybrids) that combine a high seed and oil yield in modern technology. In spite of the increased
and desirable morphological characteristics for interest in castor oil, the world production of
mechanical harvesting have been developed over castor seeds remains relatively low compared to
the past few years in Europe. The yield of these the other oilseed crops. The major producing
genotypes reported in the literature varied from 2000 to 2620 kg ha−1 in France (Arnaud, 1990), * Corresponding author. Tel:+30-31-998633;
and 1500 to 2500 kg ha−1 in Italy (Laureti and fax:+30-31-998634.
E-mail address:quentin@agro.auth.gr (D.K. Papakosta) Marras, 1995). In Greece, with a Mediterranean
type of climate, castor plants could be adapted tions, cultural practices and time of harvesting. Hooks et al. (1971) found that the seed oil content satisfactorily taking into account their
environ-mental requirements. However, since castor plants is negatively correlated with days to flowering and with the number of nodes to the first and second have not been systematically cultivated in Greece,
information about the performance and the yield racemes and positively correlated with the number of racemes per plant and volume weight of seed. of the crop are lacking. Such data are necessary
in order to explore the feasibility of the castor oil High temperatures, above 35°C, and water stress during the flowering and oil formation can reduce as an alternative crop in Greek agriculture.
Seed yield depends on the number of racemes the seed oil content ( Weiss, 1983). Early harvesting of immature or still green capsules can also per plant, the number of capsules per raceme and
the thousand seed weight. Under natural condi- adversely affect the seed oil yield.
The purpose of this work was to study the tions, the castor plant has many racemes,
depend-ing on the number of branches, that develop adaptability of new castor plant genotypes in the environmental conditions of Northern Greece and progressively over the life of the plant. This is an
undesirable characteristic for commercial pro- to evaluate their yielding ability during the 3 years of experimentation.
duction since the high number of racemes results in an extended maturity period, thus making mechanical harvesting uneconomical. Low branched plants with one to three racemes resistant
to shattering are desirable in modern castor 2. Materials and methods varieties.
The number of capsules per raceme depends on The experiments were carried out at the farm of the Aristotle University of Thessaloniki, Greece, the number of female flowers on the raceme.
Castor plants are normally monoecius, with male and at the farm of the Cereal Institute in the village of Loudias, 50 km west of Thessaloniki in flowers on the upper portion of the raceme and
female on the lower. Flowers of both types can the years 1995, 1996 and 1997. The soil on the University farm was a sandy clay loam with a pH also be interspersed along the length of the raceme.
The proportion of male and female flowers on of 7.85, 0.85%organic matter, and a water-holding capacity of 0.34 cm3cm−3, and at Loudias, the each raceme varies and can be influenced by the
environment ( Weiss, 1983). The inflorescence can soil was a clay loam with a pH of 7.65, 3.48% organic matter, and a water-holding capacity of reach a length of 100 cm, but since there is a wide
variation in the distance between flowers, yield is 0.44 cm3cm−3. At Loudias, the underground water level was higher than on the University not necessarily correlated with length.
The plant height varies between 3 and 10 m in farm. Castor plants followed wheat on the University farm and corn at Loudias in 1995 and perennial types but is much lower in annual plants
(Bonjean, 1991). For mechanical harvesting, the 1997 and wheat in both locations in 1996. Nineteen castor plant genotypes were tested in plant height should be low. The node at which the
first raceme appears is also an important agro- both locations ( Table 1). The genotypes were hybrids, except Venda and Polluce, which were nomic characteristic, since it is associated with
early maturity. It is a varietal characteristic and, inbred lines. In order to study as many genotypes as possible and to examine their yield variation in dwarf-internode cultivars, usually occurs after
the sixth to twelfth node, but in a segregating over years, the genotypes that combined high seed and oil yield and morphological characteristics population can vary from six to 45 (Zimmerman,
1957). However, dwarf cultivars are at present less appropriate for mechanical harvesting were tested for 2 or 3 years, whereas the less promising geno-productive than normal-internode cultivars
(Laureti, 1981). types were tested for 1 year only. A randomized
complete block design with four replications was The seed oil content depends on the genotype
Table 1 Trifluralin applied at a rate of 1200 g ha−1 pre-Time from sowing to the beginning of female flowering on the sowing, and linuron applied at a rate of first raceme of 19 castor plant genotypesa
680 g ha−1 pre-emergence, together with hoeing using a hoe or rotovator at the three- to six-leaf Genotype Time (days)
stage, were used for weed control in both locations. 1995 1996 1997 At Loudias, fluazifop butyl was used forSorghum
halepensecontrol in 1996. The insecticide furadan
UF L UF L UF L
10 G was applied uniformly in the soil surface at Negus 65 63 57 44 65 53 a rate of 35 kg ha−1 before sowing and incorpo-Pronto 60 56 52 43 57 51 rated together with the fertilizers. At Loudias,
H530 62 48 68 55
deltamethrin at a rate of 18.75 g ha−1was used in
H526 55 44 58 49
1995 and 1996 forAgrotiscontrol.
HD912 54 44 64 53
Riscio 69 61 62 46 Irrigation was applied in both locations. A drip
B9 71 68 73 61 irrigation system was used, after emergence, on
H523 61 57 the University farm, and the total amount of water
Venda 68 60
used each year (280 mm in 1995 and 300 mm in Polluce 60 56
1996 and 1997) corresponded to about 70–75%of
114 68 65
929 62 57 the evapotranspiration in the area, measured by
H101 61 47 the pan evaporation method (Doorenbos and
125 61 42 Kassam, 1986 in Laureti and Marras, 1995). At
519 57 45
Loudias, the irrigation water (about 140 mm in
Castore 58 49
1995, 250 mm in 1996 and 200 mm in 1997) was
H531 65 56
H529 65 56 applied by sprinkler, and the time of irrigation
H913 67 58 was determined when temporary midday plant
wilting had occurred.
aUF: University farm; L: Loudias.
In 1996, the plants were sprayed with 20% diquat at a rate of 1000 g ha−1at Loudias in order to destroy any green leaves and to facilitate the rows, 0.6 m apart on the University farm and five
rows, 0.8 m apart, at Loudias. harvest.
Data regarding dates of emergence, female The experimental area on the University farm
was uniformly fertilized with 80 kg N ha−1 as flowering, first brown full capsule, first brown raceme, maturity for harvest and temperature sums ammonium sulphate, 48 kg P ha−1 as
superphos-phate, and 91 kg K ha−1 as potassium sulphate (base temperature 10°C, Arnaud, 1990) for each stage of development were collected each year. each year and at Loudias with the same amounts
in 1995, 100 kg N ha−1and 24 kg P ha−1 in 1996 Two seed harvests were carried out in 1995: the first when up to the three racemes were brown and and 80 kg N ha−1and 18 kg P ha−1in 1997 before
planting. the second when the rest of the racemes had
matured. One seed harvest was carried out in 1996 Seeds were hand-planted on 10, 26 and 18 April
on the University farm and 11, 25 and 23 April at and 1997, when almost all the capsules on the mature racemes became brown. At harvest, six Loudias in 1995, 1996 and 1997, respectively. The
row distance was 0.33 m on the University farm plants from the two central rows of each plot were cut at ground level, and the insertion height of the and 0.25 m at Loudias, in order to achieve yields
of approximately 50 000 plants ha−1in both loca- first raceme, the plant height and the number of secondary brown racemes with full capsules were tions. Three seeds were planted in each hill, and
the plots were hand thinned to one plant per hill measured. Then, the first raceme and the other racemes were separately collected from the four when the plants were at the four- to six-leaf stage.
of the first raceme and the others and the thousand andr=0.899, p<0.01 at Loudias) but not in the other years. The maturity of the first raceme was seed weight were calculated on a dry-seed basis.
The oil content was measured by the Soxhlet completed from the beginning to the middle of August in all genotypes in all three years (49– method (American Oil Chemists’ Society, 1983) in
1995 and 1996 and by nuclear magnetic resonance 62 days after the beginning of the flowering on the University farm and 48–64 days at Loudias), fol-(NMR) spectrometry in 1997. NMR estimates of
oil content were calibrated against Soxhlet lowed by a period of about 1.5 months with favourable environmental conditions for the matu-estimates.
A statistical analysis was performed according rity of secondary racemes. On the University farm, 122–137 days were needed for the maturity of the to Steel and Torrie (1980). The homogeneity of
the variances was checked, and all measured and reproductive racemes and at Loudias more time, 121–151 days, because the mean over genotypes derived data were subjected to analysis of variance
combined over locations separately for each year. number of secondary racemes was higher. The corresponding temperature sums (base temper-A combined analysis of variance over locations
and years was also performed for the data concern- ature 10°C ) varied from 1421 to 1792 d°C on the University farm and 1377 to 1895 d°C at Loudias, ing the genotypes used for more than one year.
LSD values were calculated and used to compare depending mainly on the genotype rather than on the years of experimentation.
treatment means. The relative contribution of the seed yield and the seed oil concentration to the sum of squares of the oil yield was determined by
linearizing the multiplicative relationships by 3.2. Morphological characteristics
taking logs according to the method of Moll et al.
(1982). According to this analysis, the sum of The plant height and the height of insertion of the first raceme differed between locations and cross products of each component trait by the
resultant trait (∑x
iyi) divided by the sums of among genotypes in all years. The locations× genotypes interaction was significant in 1995 and squares of the resultant trait (∑y2i) gives the relative
contribution of each component variable to the 1996 for the plant height and only in 1997 for the height of insertion of the first raceme ( Table 2). resultant variable.
The over genotypes mean values of both character-istics were higher at Loudias compared to those on the University farm, but the differences between 3. Results
the locations were greater for the plant height than for the height of insertion of the first raceme. The
3.1. Stages of development
plant height on the University farm varied from 79 cm (Negus in 1995) to 230 cm (H530 in 1996) Seedlings emerged after 19–26 days in 1995, 18–
26 days in 1997 and 11–14 days in 1996. The and at Loudias from 117 cm (HD912 in 1997) to 278 cm (Polluce in 1995), and the height of inser-flowering of the first raceme began 2–19 days
earlier at Loudias compared to the University tion of the first raceme from 23 cm (HD912 in 1997) to 111 cm (Castore in 1997) and from 34 cm farm, depending on the genotype and the year
( Table 1). The time from sowing to the beginning (Riscio in 1995) to 128 cm (Castore in 1997), on the University farm and Loudias, respectively. The of female flowering on the first raceme varied from
52 days (Pronto in 1996) to 73 days (B9 in 1997) plant height of most genotypes was less than 150 cm on the University farm and more than on the University farm and 42 days (125 in 1996)
to 68 days (B9 in 1995) at Loudias. The time of 150 cm at Loudias, and the height of insertion of the first raceme less than 70 cm in both locations. the beginning of the female flowering on the first
raceme was positively correlated with the time of Both the plant height and the height of insertion of the first raceme were affected by the year, but maturity of the first raceme in both locations in
Table 2
Height of insertion of the first raceme, plant height and number of secondary racemes of 19 castor plant genotypesa
Genotype Height of insertion of the first raceme (cm) Plant height (cm) Number of secondary racemes
1995 1996 1997 LSDb 1995 1996 1997 LSDb 1995 1996 1997 LSDb
UF L UF L UF L UF L UF L UF L UF L UF L UF L
Negus 26 36 25 38 26 37 6 79 176 106 182 93 125 16 2.3 4.1 1.9 3.8 3.3 3.3 0.6 Pronto 38 51 31 50 24 44 115 206 132 171 80 131 3.5 4.1 2.2 3.1 3.4 2.0
H530 102 104 55 101 9 230 245 176 222 23 1.7 2.1 2.2 2.6 0.5
H526 47 63 34 44 140 185 85 142 2.1 2.8 2.2 2.6
HD912 26 42 23 38 95 153 89 117 2.0 3.9 2.3 2.5
Riscio 34 34 38 42 12 96 190 125 218 38 2.3 6.2 1.3 4.3 1.7
B9 49 56 42 54 8 104 150 89 150 22 0.3 1.4 0.3 1.9 0.4
H523 47 58 137 255 3.2 3.6
Venda 79 89 159 256 1.6 2.7
Polluce 66 76 177 278 3.9 4.0
114 32 36 83 174 2.3 3.5
929 68 65 163 223 4.4 6.3
H101 33 38 119 187 1.5 2.1
125 27 36 119 164 2.6 5.4
519 33 42 118 146 1.8 5.2
Castore 111 128 229 270 2.0 2.8
H531 46 74 137 178 1.7 2.3
H529 40 60 101 149 2.0 2.3
H913 67 107 171 207 1.3 1.7
LSDc 12 10 9 21 23 22 1.0 0.7 0.5
Mean 48 56 47 58 40 62 124 212 141 192 113 158 2.6 4.0 1.9 3.6 2.1 2.2
Source of variationd
Location (L) * ** ** ** ** ** ** ** NS
Genotype (G) ** ** ** ** ** ** ** ** **
L×G NS NS ** ** ** NS ** ** **
CV (%) 16 14 12 9 10 11 22 19 15
aUF: University farm; L: Loudias.
bBetween genotypes common in the two or three years atp<0.05.
cBetween genotypes and locations for the same year atp<0.05.
dNS,p>0.05; *p<0.05; **p<0.01.
raceme was higher compared to the variation of The highest number of secondary racemes was observed in 929 (4.4 on the University farm and plant height.
All genotypes produced additional secondary 6.3 at Loudias) and the lowest in B9 (0.3 on the University farm and 1.4 at Loudias).
racemes, and the over genotypes mean number was higher at Loudias compared to the University
farm in 1995 and 1996 ( Table 2). In 1997, Pronto 3.3. Yield and yield components
and Negus produced significantly higher number
of secondary racemes on the University farm and The genotypes differed in total yield ( Table 3). The highest total yield was obtained with H531 in B9 and H531 at Loudias, whereas the other
geno-types produced the same in both locations. This 1997 (4.35 Mg ha−1), and the lowest total yield was with Negus in 1996 (2.46 Mg ha−1) on the resulted in the same over genotypes mean number
Table 3
Yield of the first and secondary racemes and total yield of 19 castor plant genotypesa
Genotype Yield of the first raceme (Mg ha−1) Yield of the secondary racemes (Mg ha−1) Total yield (Mg ha−1)
1995 1996 1997 LSDb 1995 1996 1997 LSDb 1995 1996 1997 LSDb
UF L UF L UF L UF L UF L UF L UF L UF L UF L
Negus 1.56 1.26 1.64 1.86 1.63 1.45 0.19 1.69 2.34 0.82 2.32 2.02 2.13 0.33 3.25 3.60 2.46 4.18 3.65 3.58 0.31 Pronto 1.97 2.08 2.22 1.70 1.60 1.91 1.26 2.54 1.13 2.88 2.32 1.45 3.23 4.62 3.35 4.58 3.92 3.36 H530 1.77 2.33 2.27 1.92 0.35 1.20 2.81 2.01 2.08 0.36 2.97 5.14 4.28 4.00 0.37 H526 2.29 2.15 2.26 2.10 0.87 2.72 1.63 1.99 3.16 4.87 3.89 4.09 HD912 2.06 1.93 1.98 1.89 0.93 3.02 1.62 2.14 2.99 4.95 3.60 4.03 Riscio 1.74 1.26 1.37 1.26 0.28 1.45 2.84 1.11 2.49 0.78 3.19 4.10 2.48 3.75 0.49 B9 2.87 2.99 3.43 2.86 0.56 1.12 1.16 0.32 2.22 0.57 3.99 4.15 3.75 5.08 0.57
H523 1.72 1.74 1.85 2.21 3.57 3.95
Venda 1.81 1.69 1.29 2.61 3.10 4.30
Polluce 1.36 1.29 1.75 1.96 3.11 3.25
114 1.87 1.36 1.18 2.33 3.05 3.69
929 1.49 1.06 1.56 1.93 3.05 2.99
H101 1.85 1.49 0.96 2.09 2.81 3.58
125 1.42 1.36 1.40 3.04 2.82 4.40
519 1.28 1.45 1.35 3.18 2.63 4.63
Castore 1.75 2.21 1.24 2.50 2.99 4.71
H531 2.65 2.51 1.70 1.42 4.35 3.93
H529 2.52 2.52 1.27 1.31 3.79 3.83
H913 2.82 2.48 1.24 1.55 4.06 4.03
LSDc 0.24 0.30 0.34 0.39 0.34 0.33 0.48 0.57 0.40
Mean 1.82 1.64 1.76 1.77 2.35 2.18 1.46 2.21 1.10 2.70 1.57 1.81 3.28 3.85 2.87 4.50 3.92 3.99
Source of variationd
Location (L) * NS * ** ** NS ** ** NS
Genotype (G) ** ** ** ** ** ** ** ** **
L×G ** ** * ** ** ** ** * **
CV (%) 10 12 11 15 13 14 10 11 7
aUF: University farm; L: Loudias.
bBetween genotypes common in the two or three years atp<0.05.
cBetween genotypes and locations for the same year atp<0.05.
dNS,p>0.05; *p<0.05; **p<0.01.
yield was obtained with H530 in 1996 on the University farm, whereas the others had a higher yield at Loudias. In 1997, the over geno-(5.14 Mg ha−1) and the lowest with 929 in 1995
(2.99 Mg ha−1). In 1995 and 1996, most of the types mean yield of secondary racemes was the same in both locations. The locations×genotypes genotypes tended to have a higher yield at Loudias
compared to the University farm, although the interaction in total yield in 1997 was due to the higher yield of B9 and HD912 at Loudias and of interaction locations×genotypes was significant.
The increased yield was mainly the result of the Pronto on the University farm.
The percentage of the total yield that was higher yield of secondary racemes ( Table 3). As
mentioned above, the over genotypes mean produced in the first raceme was affected by both locations and genotypes, and the locations× number of secondary racemes was also higher at
Loudias. The differences between locations in the genotypes interaction was also significant (Table 4). The over genotypes mean yield percen-yield of the first raceme were smaller, and some
Table 4
Yield of the first raceme to total yield and thousand seed weight of 19 castor plant genotypesa
Genotype Yield of the first raceme/total yield Thousand seed weight (g)
1995 1996 1997 LSDb 1995 1996 1997 LSDb
UF L UF L UF L UF L UF L UF L
Negus 0.48 0.35 0.67 0.44 0.45 0.41 0.05 359 342 365 312 358 351 34
Pronto 0.61 0.45 0.66 0.37 0.41 0.57 356 369 377 354 360 364
H530 0.60 0.45 0.53 0.48 0.07 390 375 370 377 27
H526 0.72 0.44 0.58 0.51 395 410 397 388
HD912 0.69 0.39 0.55 0.47 366 339 354 354
Riscio 0.55 0.31 0.55 0.34 0.11 325 307 318 299 25
B9 0.72 0.72 0.91 0.56 0.11 335 334 325 317 22
H523 0.48 0.44 364 371
Venda 0.58 0.39 297 314
Polluce 0.44 0.40 368 368
114 0.61 0.37 321 305
929 0.49 0.35 324 311
H101 0.66 0.42 364 308
125 0.50 0.31 341 328
519 0.49 0.31 363 326
Castore 0.59 0.47 349 368
H531 0.61 0.64 341 334
H529 0.66 0.66 350 382
H913 0.69 0.62 416 438
LSDc 0.06 0.06 0.06 20 30 21
Mean 0.55 0.42 0.61 0.39 0.60 0.55 339 336 363 342 363 367
Source of variationd
Location (L) ** ** ** NS ** NS
Genotype (G) ** ** ** ** ** **
L×G ** ** ** NS * NS
CV (%) 9 8 8 4 6 4
aUF: University farm; L: Loudias.
bBetween genotypes common in the two or three years atp<0.05.
cBetween genotypes and locations for the same year atp<0.05.
dNS,p>0.05; *p<0.05; **p<0.01.
University farm compared to Loudias. B9, which racemes, but in some genotypes, the year also affected the yields of the first raceme (Table 3). had the lowest number of secondary racemes
com-pared to all other genotypes, produced the 56– The weight of 1000 seeds was affected mainly by the genotypes ( Table 4). Differences between 91% of the seed yield in the first raceme. In the
other genotypes, this percentage ranged from 31 locations were observed only in 1996. Also, the genotypes behaved in the same way in the two to 72%.
From the over years analysis of genotypes used locations, except for that of Negus, H101 and 519 in 1996, which produced heavier seeds on the for more than 1 year, differences were found in
seed yield between years, which depended on the University farm compared to Loudias. The over locations mean heaviest seeds were produced by locations and genotypes. These differences mainly
H913 (427 g) in 1997 and the lightest by Venda compared to 1997. The over genotypes mean oil content was higher on the University farm com-(306 g), Riscio (309 g) and B9 (321 g) in 1995,
1996 and 1997, respectively. pared to Loudias. The oil content varied on the University farm from 46.3% (Pronto in 1997) to 54.2% (Castore in 1996) and 44.5% (Pronto in
3.4. Oil content and oil yield
1997) to 53% (Castore in 1996) at Loudias, but the differences among genotypes were larger at Oil content was affected by both locations and
genotypes in all years and the locations× Loudias compared to those at the University farm. The highest oil content was obtained in both genotypes interaction was significant in 1996 and
1997 but not in 1995 (Table 5). Differences in oil locations with Polluce in 1995, Castore in 1996 and H913 in 1997. The oil content was significantly content were also observed between years, and in
most genotypes, the oil content was higher in 1996 correlated with the seed yield only at Loudias in
Table 5
Oil content and oil yield of 19 castor plant genotypesa
Genotype Oil content (%) Oil yield (Mg ha−1)
1995 1996 1997 LSDb 1995 1996 1997 LSDb
UF L UF L UF L UF L UF L UF L
Negus 52.5 49.0 50.2 48.8 50.5 47.6 1.9 1.71 1.77 1.23 2.04 1.84 1.70 0.19 Pronto 49.0 47.3 49.9 47.5 46.3 44.5 1.58 2.19 1.67 2.18 1.81 1.50
H530 52.2 50.9 49.1 48.8 1.9 1.55 2.62 2.10 1.95 0.21
H526 53.5 52.3 50.6 49.1 1.69 2.55 1.97 2.01
HD912 53.2 50.0 51.4 50.0 1.59 2.47 1.85 2.02
Riscio 51.9 48.7 49.9 47.5 2.1 1.66 2.00 1.24 1.78 0.28
B9 52.1 49.6 48.8 48.6 1.3 2.08 2.06 1.83 2.47 0.34
H523 50.4 48.0 1.80 1.90
Venda 51.7 49.2 1.60 2.12
Polluce 53.0 51.2 1.65 1.66
114 52.6 48.5 1.60 1.79
929 53.1 50.8 1.62 1.52
H101 51.2 44.8 1.44 1.60
125 50.9 50.0 1.44 2.20
519 51.4 48.6 1.35 2.25
Castore 54.2 53.0 1.62 2.50
H531 49.3 47.7 2.15 1.88
H529 51.5 51.0 1.95 1.95
H913 52.5 51.9 2.13 2.09
LSDc 1.5 1.9 0.5 0.26 0.30 0.24
Mean 51.8 49.1 51.7 49.2 50.0 48.8 1.70 1.89 1.48 2.21 1.96 1.95
Source of variationd
Location (L) ** * ** ** ** NS
Genotype (G) ** ** ** ** ** **
L×G NS * ** ** ** **
CV (%) 2 3 1 10 11 9
aUF: University farm; L: Loudias.
bBetween genotypes common in the two or three years atp<0.05.
cBetween genotypes and locations for the same year atp<0.05.
Table 6
Contribution of the seed yield and the seed oil content to the sum of squares of the oil yield in castor plants
Resultant trait Component trait ∑x
iy/∑y2
Location
University farm Loudias
1995 1996 1997 1995 1996 1997
Ylog oil yield (g m−2) X
1log seed yield (g m−2) 0.985 0.838 0.818 1.145 0.724 0.783
X
2log seed oil content (g g−1) 0.015 0.162 0.182 −0.145 0.276 0.217
1995 and 1996 but not in 1997. The correlation tion of castor seeds, a soil temperature of 17°C is required ( Weiss, 1983). This means that the recom-was negative in 1995 (r=−0.773, p<0.05) and
positive in 1996 (r=0.769,p<0.01). mended time of sowing for the area is after the middle of April, when these soil temperatures are The oil yield followed the variations in seed
yield in all genotypes due to the remarkably low usually reached. Delayed sowing until the end of the April is not expected to have any serious variation of seed oil content (CV less that 3%,
Table 5). The over genotypes mean oil yield was consequences because the growing period in both locations was found to be long enough for the higher at Loudias compared to University farm in
1995 and 1996 and the same in both locations in ripening of the first raceme and a number of secondary racemes depending on the genotype. 1997. On the University farm, the highest oil yield
was obtained with H531 (2.15 Mg ha−1) in 1997 The proposed period for harvesting is between the end of September and the middle of October, and the lowest with Negus (1.23 Mg ha−1) in 1996
and at Loudias with H530 (2.62 Mg ha−1) in depending on the environmental conditions of the autumn. During this period, the first raceme and 1996 and Pronto (1.50 Mg ha−1) in 1997,
respectively. most of the secondary racemes reached maturity.
The increased number of mature secondary In Table 6 the analysis of the log of seed oil
yield (Y) as a function of the sum of logs of seed racemes is desirable since, in some genotypes, their contribution to total yield was more than 50%. yield (X
1) and seed oil content (X2) is given. The
contribution of the seed yield to the variation of The genotypes differed in plant height and height of insertion of the first raceme, and in most the oil yield among genotypes was the most
impor-tant and was higher than 70% in all years. It was cases, both characteristics had higher values at Loudias compared to University farm. At Loudias, more significant in 1995 compared to 1996 and
1997. In contrast, variation in seed oil content was the soil organic matter and the water table were higher than on the University farm. Also, the area small and accounted for less than 30% of the
variation of oil yield. at Loudias, where the experiments were estab-lished, has a microclimate with a high relative humidity (RH ), and many fields in the immediate neighbourhood are cultivated with rice. These con-4. Discussion
ditions favoured the vegetative growth and resulted in higher plants with a greater height of insertion The seedlings required a long period to emerge,
and the differences in time of emergence found of the first raceme. Since the greater plant height at Loudias was mainly due to increased internode between years are associated with the soil
temper-atures. Late sowing, after 20 April, resulted in length, compared to the University farm, rather than the greater number of nodes (data not higher soil temperatures at planting and, therefore,
greater for the plant height than for the height of of minor practical importance since the yield was high in all years. High yields with only small over insertion of the first raceme. Variations in these
characteristics found from year to year in geno- years variation are expected in this area because the environmental conditions are favourable for types tested for more than 1 year are difficult to
explain because the plants were grown in the same plant growth, and the growing period is long enough for a crop under irrigation.
fields with the same cultural practices.
The plant height is one of the most important Oil yield is the combination of seed yield and oil content. In the present study, the oil yield was morphological characteristics that affect the
mechanical harvest. Tall plants are not easily har- mainly determined by the seed yield because the seed oil content varied little. The negative contribu-vested by machines. For easy harvesting, the height
of the crop should be lower than 2 m (Laureti and tion of the seed oil content to the variation of the oil yield among genotypes observed at Loudias in Marras, 1995). According to this criterion, most
of the genotypes were found to be appropriate for 1995 was due to the negative correlation between the oil yield and the seed oil content (r=−0.68, mechanical harvest except for H530 and Castore
in both locations and Riscio, H523, Venda, p<0.05). The over genotypes mean seed oil content varied between 48.8 and 51.8%, values Polluce, 929 and H913 at Loudias. In order to
facilitate the mechanical harvest at Loudias, where that are similar to those reported in the literature ( Kittock et al., 1967; Arnaud, 1990; Laureti and the conditions favour the vegetative growth, a
defoliant is recommended. Marras, 1995). The very low oil content (44.8%) observed in H101 only at Loudias in 1996 probably The yield obtained during the 3 years of
experi-mentation by all genotypes in both locations was resulted from incomplete seed filling as indicated by the low thousand seed weight of this genotype. high and among the highest reported in the
litera-ture ( Vannozzi et al., 1983a, 1983b; Weiss, 1983; Although significant differences in oil content were found among genotypes, their ranking according Arnaud, 1990; Bonjean, 1991; Laureti and Marras,
1995). The seed yield is the sum of the first and to the oil yield was almost the same as that of the seed yield. Thus, the choice of a genotype should secondary racemes yield. The determination of
yield by the percentage of the above components be based on its yielding ability, and the aim of the growers should be to increase the seed yield. was not stable. The increased yield at Loudias,
compared to the University farm, was mainly due Taking into account the plant height and the yielding ability of the genotypes, the most promis-to the greater number of secondary racemes. As
mentioned above, the RH was higher at Loudias, ing for the University farm are B9, H526, Pronto, H531, H523, HD912, H101, H529 and Negus. For especially during the summer when the secondary
racemes were developed. This probably resulted in Loudias, where the environmental and soil condi-tions promote plant height, the recommended a higher degree of photosynthesis and consequently
a greater supply of assimilates compared to that genotypes are B9, HD912, H536, Pronto, Negus and H101.
at University farm. Castor plant, a tropical C3
plant, has a high photosynthetic capacity under The results have shown that the modern castor plant genotypes were satisfactorily adapted to the high humidity conditions but it is very sensitive to
low humidity. The inhibitory effect of low humidity environmental conditions of Northern Greece with yields ranging from 2.5 to 5.0 Mg ha−1and good on photosynthesis is mainly due to a lower CO
2
flux into the leaf, which is caused by stomatal quality with 47–53% oil content. Despite these high yields, the present international price of castor closure (Dai et al., 1992).
Except for the high yielding ability of the geno- oil does not allow the crop to compete with the major and subsidized crops in the area such as types, the yield stability is necessary for
commer-cial castor production. Although the differences in cotton, corn or sugarbeet. Castor-oil crop could be profitable only if it was equally subsidized with seed yield between years of the genotypes tested
Hooks, J.A., Williams, J.H., Gardner, C.O., 1971. Estimates of Acknowledgements
heterosis from a diallel cross of inbred lines of castors, Ricinus communisL. Crop Sci. 11, 651–655.
This work was funded by the Commission of Kittock, D.L., Williams, J.H., Hanway, D.G., 1967. Castorbean the European Communities project AIR3-CT94- yield and quality as influenced by irrigation schedules and
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Laureti, D., 1981. Prove di confronto fra cultivar di Ricino. We thank Mrs Francoise Labalette, the
coordi-Sementi elette 28 (3), 23–28. nator of the project, for her very efficient help in
Laureti, D., Marras, G., 1995. Irrigation of castor (Ricinus com-managing this work and the Cereal Institute of munisL.) in Italy. Eur. J. Agron. 4, 229–235.
Thessaloniki, for conceding the field at Loudias. Moll, R.H., Kamprath, E.J., Jackson, W.A., 1982. Analysis and interpretation of factors which contribute to efficiency of nitrogen utilization. Agron. J. 74, 562–564.
Steel, R.G.D., Torrie, J.H., 1980. Principles and Procedures of References Statistics: a Biometrical Approach. 2nd edition,
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