C Cambridge University Press 2015
Expl Agric.: page 1 of 15 doi:10.1017/S0014479715000022
DY NA M I C S O F AC C U M U L AT I O N A N D PA RT I T I O N I N G O F
D RY M AT T E R A N D F RU C TO - O L I G O S AC C H A R I D E S I N
P L A N T F R AC T I O N S O F F O R AG E C E R E A L S
By A. IANNUCCI†¶, M. PIZZILLO‡, G. ANNICCHIARICO‡, M. FRAGASSO‡
and V. FEDELE‡
†Consiglio per la Ricerca e la Sperimentazione in Agricoltura – Cereal Research Centre
(CRA-CER), S.S. 673 Km 25, 71122 Foggia, Italy and ‡Consiglio per la Ricerca e la
Sperimentazione in Agricoltura – Research Unit for the Extensive Animal Husbandry
(CRA-ZOE), Via Appia, Bella Scalo, 85054 Muro Lucano (PZ), Italy
(Accepted 14 January 2015)
SUMMARY
During growth, several cereals store significant amounts of fructo-oligosaccharides (FOS), which have
important prebiotic properties. Cereal forage crops are also essential components of many Mediterranean
agricultural systems, although little information is available on their dynamics of accumulation and
partitioning of dry matter and FOS during growth. Oat (Avena sativa L., cv. ‘Flavia’ and cv. ‘Genziana’),
emmer wheat (Triticum dicoccum Schrank, cv. ‘Giovanni Paolo’), barley (Hordeum vulgare L., cv. ‘Diomede’)
and triticale (xTriticosecale Wittmack, cv. ‘Rigel’) were investigated for their synthesis of FOS, with a view
to development of management approaches for harvesting high-quality forage, and to determine whether
these species can be used as natural sources of FOS for commercial use. The study was conducted at
Foggia (Italy) and Bella (Potenza, Italy) over two growing seasons (2008–2009; 2009–2010). Dry-matter
accumulation and FOS contents were determined for plant fractions from heading to kernel-hard stages.
There were large variations across these species for dry-matter partitioning and dry-matter yield (greatest
for triticale: 1.24 kg m−2 ), and for FOS levels of total plants and plant fractions. Emmer wheat and triticale
showed greater FOS production (52.0, 41.1 g m−2 , respectively). Barley, emmer wheat and triticale showed
higher FOS levels in total plants (4.11%, 5.93%, 4.33% dry matter, respectively). Barley, emmer wheat
and triticale appear to be the most interesting species for production of forage biomass rich in FOS and as
natural FOS sources for industrial use.
I N T RO D U C T I O N
The Mediterranean environment is characterised by irregular rainfall and terminal
drought stress, and annual forage crops with autumn/ spring cycles can have important
roles in forage systems, to provide forage for grazing, hay or silage (Cazzato et al., 2012;
Francia et al., 2006). Annual cereals, such as oat (A. sativa L.), barley (H. vulgare L.),
emmer wheat (T. dicoccum Schrank) and triticale (xTriticosecale Wittmack), provide an
important portion of the livestock diet when these cereals are harvested prior to
maturity for their aerial total plant biomass, particularly for lactating dairy animals
(Khorasani et al., 1993). For the most effective use of this forage, the periods of highest
forage biomass and quality need to be identified and synchronised with the increased
¶Corresponding author. Email: [email protected]; http://www.cerealresearchcentre.it
2
ANNA IANNUCCI
et al.
livestock requirements during gestation and lactation. Many factors can affect cereal
feed quality and yield, including plant species, genotype and stage at harvest, as well
as environmental conditions and crop management. As reported by Lloveras and
Iglesias (2001), to optimise the use of forage in animal feed, knowledge is required of
the dynamics of dry-matter production and nutrient concentrations, and the nutrient
distribution within the plants. Indeed, plants can change their allocation patterns in
response to the environment, and such partitioning strategies are often considered to
be genetically determined; i.e., species-specific or genotype-specific (Weiner, 2004).
Growth analysis is a widely used analytical tool for the characterisation of plant
growth, and to compare growth differences due to environment and genotype (Tesar,
1984). Among the parameters typically calculated, the most important is the relative
growth rate (RGR). This integrates all of the environmental and physiological factors
that affect production. The leaf mass ratio (LMR), stem mass ratio (SMR) and relative
elongation rate (RER) are also important indices to define plant growth characteristics.
However, in most studies, plant growth is simply considered as the accumulation of
dry matter, without considering the chemical composition of the biomass.
Cereals have always been considered chiefly as dietary energy sources, because
of their high content of hydrolysable polysaccharides. However, they have recently
received attention as sources of compounds with added health benefits for humans and
animals, which include fructose polymers, such as fructans and FOS, and antioxidant
molecules, such as glutathione, ascorbic acid, tocopherols, carotenoids and flavonoids
(Adom et al., 2003). Indeed, temperate cereals, such as barley, wheat and oats, are
among the limited variety of plants that store fructans as a temporary carbohydrate
reserve (Hendry and Wallace, 1993; Ruuska et al., 2006).
Biochemically, fructans are oligosaccharides or polysaccharides that consist of a
single glucose residue that can be linked to varying numbers of fructose residues. One
way to classify fructans is according to their degree of polymerisation: fructans with
a degree of polymerisation >10 are polymeric fructans, and those with a degree of
polymerisation <10 are FOS.
These sugars are a constitutive part of the central carbohydrate metabolism that
supplies carbon for growth and respiratory processes in many fructan-storing species
(Lattanzi et al., 2012). Furthermore, fructans are involved in protective mechanisms
against abiotic stress, such as cold, salt and drought conditions, where they probably
contribute to osmotic homeostasis and prevention of membrane damage (Vereyken
et al., 2001).
From a nutritional point of view, fructans have important effects on health due
to their prebiotic activity. Indeed, increasing evidence suggests that fructans improve
gastrointestinal health in human and animal models (Roberfroid, 2007). Fructans
are non-digestible carbohydrates, and as such, they are exclusively fermented by
colonic microbiota. As a consequence, they can have several beneficial effects, such as
increased production of short-chain fatty acids, improved bioavailability of nutrients
and reduced levels of blood cholesterol (van den Ende et al., 2011). In ruminant
nutrition, a high fructan content leads to higher feed intake by animals, better weight
gain, and higher milk production (Gallagher et al., 2007). Furthermore, a new approach
Fructo-oligosaccharides in forage cereals
3
in the feed supply chain has suggested that milk composition can be influenced by the
availability and characteristics of the soluble carbohydrates in the animal diet (Leiva
et al., 2000). This evidence opens up the potential for using cereals as natural FOS
sources when fresh biomass is consumed by animals, as well as for FOS isolation to
obtain alternative products for adding to human foods, in terms of nutritional value
and health implications.
The aims of the present study were: (i) to determine the production and partitioning
of dry matter and FOS content in different plant organs, from heading to seed
maturation, of four cereal species grown in two environments; (ii) to define the growth
stage to obtain fresh forage rich in FOS; and (iii) to identify which cereals can be
recommended for commercial FOS production in the food industry.
M AT E R I A L S A N D M E T H O D S
Experimental sites
The study was carried out during the 2008–2009 and 2009–2010 growing seasons,
at the Cereal Research Centre (CRA-CER) in Foggia (Italy) (41°28 N, 15°34 E;
76 m a.s.l.) and at the Research Unit for Extensive Animal Husbandry (CRA-ZOE)
in Bella (Potenza, Italy) (40°46 N, 15°32 E; 662 m a.s.l.). Four graminaceous species
were evaluated at Foggia: oat (A. sativa L., cvs. ‘Flavia’ and ‘Genziana’), emmer wheat
(T. dicoccum Schrank, cv. ‘Giovanni Paolo’), barley (H. vulgare L., cv. ‘Diomede’) and
triticale (xTriticosecale Wittmack, cv. ‘Rigel’). Two of these were also evaluated at Bella:
oat (cv. ‘Genziana’) and triticale (cv. ‘Rigel’).
The trials at Foggia were performed in loam soils that were classified as Grumic
Calcic Vertisol (WRB 2007) with the following characteristics: 21% clay, 43% silt,
36% sand, pH 8 (in H2 O), 15 mg kg−1 available P (Olsen method), 800 mg kg−1
exchangeable K (NH4 Ac) and 21 g kg−1 organic matter (Walkey–Black method). The
trials at Bella were performed in clay loam soils classified as Cambisol Luvisol (WRB
2007) with the following characteristics: 39% clay, 28% silt, 33% sand, pH 7.6 (in
H2 O), 8 mg kg−1 available P (Olsen method), 208 mg kg−1 exchangeable K (NH4 Ac)
and 14 g kg−1 organic matter (Walkey–Black method).
The environmental data for the two growing seasons are shown in Table 1, with the
long term (10-year) averages for each location. All of the climatic data were obtained
from an on-site weather station. The maximum and minimum temperatures were
similar for the two years of the study for each site. The two years were cooler than
the long-term average at Foggia, and they were particularly rainy for both locations
(means above 10-year average, 54% for Foggia, 41% for Bella). The mean maximum
and minimum daily temperatures were used to calculate the growing degree days
(GDD; °Cd) with a 0 °C baseline temperature. Cumulative GDDs were calculated by
adding up the daily values, starting from the sowing date.
Field experiments and crop management
At each site, the experimental design was as randomised complete blocks with four
replications. Plots were 20 m long and consisted of 118 rows that were 0.17 m apart.
4
Table 1. Environmental data at Foggia and Bella during the growing seasons of four graminaceous species, as compared to the long-term (10-year) averages.
Location
Month
2008–09
2009–10
10-year average
2008–09
2009–10
10-year average
2008–09
2009–10
10-year average
2008–09
2009–10
16.2
11.5
10.0
10.6
14.3
18.4
26.4
28.4
17.0
16.5
12.5
9.9
12.1
14.8
17.9
23.2
28.2
16.9
18.3
14.0
12.4
14.4
18.0
21.2
27.3
31.9
19.7
7.1
4.2
4.1
1.2
3.9
8.4
11.8
15.1
7.0
6.3
4.7
2.8
3.6
3.7
6.7
11.3
14.6
6.7
8.5
5.8
4.8
4.6
6.5
8.7
12.9
16.7
8.6
119.5
116.3
153.5
24.8
154.3
98.5
16.8
65.2
46.8
73.0
69.8
75.3
48.3
52.3
41.3
29.3
51.1
74.3
57.4
33.2
39.4
53.7
28.6
48.1
348.4
590.5
810.0
976.7
1259.0
1660.9
2255.8
2907.3
342.4
610.1
805.9
1020.2
1310.4
1679.0
2214.9
2856.5
748.7
435.8
385.8
78.2
168.8
116.4
0.0
194.0
101.2
37.4
93.0
65.8
73.6
173.4
125.4
98.2
72.8
120.2
52.0
91.0
100.1
53.7
75.5
83.2
72.3
42.1
41.0
310.7
489.0
667.4
776.9
984.5
1323.6
1835.1
2389.9
307.4
555.3
681.4
833.4
1061.9
1388.6
1822.8
2369.3
789.0
781.4
558.9
15.1
9.2
8.9
6.1
11.2
16.5
22.2
24.4
14.2
14.8
11.4
7.1
8.9
12.3
16.1
19.3
24.0
14.2
13.6
9.3
8.1
9.1
12.5
15.7
20.2
25.3
14.2
7.5
3.0
3.9
-0.1
3.0
7.6
11.6
13.5
6.3
6.5
3.5
1.1
1.8
3.5
6.5
9.7
13.1
5.7
5.9
2.6
1.1
1.5
3.7
6.2
10.1
13.7
5.6
derivated from on-site weather stations at Foggia and Bella.
from 1 November, using the average daily temperature minus the base temperature of 0 °C.
∗∗ Calculated
Cumulative GDDs∗∗
Rainfall (mm)
et al.
∗ Data
Minimum temperature (°C)
ANNA IANNUCCI
Foggia
November
December
January
February
March
April
May
June
Mean
Total
Bella
November
December
January
February
March
April
May
June
Mean
Total
Maximum temperature∗ (°C)
Fructo-oligosaccharides in forage cereals
5
The genotypes were sown in the second half of November at Foggia, and in the first
half of December at Bella, for each year (2008 and 2009), at a seeding density of 400
viable seeds m−2 . Before sowing, chemical fertiliser was applied to all of the plots at
the following rates: 36 kg N ha−1 and 92 kg P ha−1 . During plant tillering, the plots
received in topdressing 52 kg N ha−1 . Weeds were controlled with hand weeding when
necessary.
Measurements and calculations
Different numbers of destructive harvests were carried out at weekly intervals (eight
at Foggia and five at Bella during 2009, and six at each location during 2010), starting
from the heading stage (from 22 April for oats, wheat and triticale, and from 14 April
for barley at Foggia, and from 11 May for oat and triticale at Bella, as the means of
the above years) up to the kernel-hard stage (Feekes scale, 10.1 and 11.3, respectively).
At each harvest, four random samples of 1 m2 from each plot (400 m2 ) were
hand clipped to a 5 cm stubble height. The forage was removed and weighed, and
a representative subsample of 50 shoots was weighed and used to assess the plant
fraction weights after oven-drying at 60 °C for 48 h (stems, leaves, heads; g shoot−l ).
Another subsample was taken, divided by hand into the plant fractions, and cut into
small pieces and immediately stored at −80 °C, for FOS determination.
Before the chemical analysis, the plant material was oven dried under vacuum at
40 °C for 48 h, and then ground using a cyclone mill with a 1-mm screen. Enzymatic
methods were used for the determination of FOS content (% dry matter; Megazyme,
according to AOAC International Method No. 999.03 (2005) and AACC International
Method No. 32.32). This analysis involves the hydrolyses of starch and sucrose by
specific enzymes (i.e., ß-amylase, pullulanase, maltase), removal of the reducing sugars
by treatment with alkaline borohydride and inulinase treatment to hydrolyse fructans
into glucose and fructose, which are then measured spectrophotometry at 410 nm.
At each harvest, the leaf to stem ratio (LSR, % by weight) was calculated for each
genotype, for both years and for both locations. Based on the biometric and plant
biomass parameters, LMR, SMR, RGR and RER were calculated for each genotype.
LMR (g g−1 ) and SMR (g g−1 ) indicate the biomass allocation to leaves and stems,
respectively, and these were calculated as the ratios of the leaves and stems, respectively,
to total dry weight, for each harvested sample, and they are reported as means over
the entire growing season. RGR (unit of dry mass increment per day, and per unit
of total dry mass of plant) and RER (increase in length of the main shoot per unit
shoot length per day) are measures of the efficiency of production and growth, and
they were calculated following the functional approach described by Hunt (1982).
Both of these indices were derived by fitting quadratic regressions of ln (total plant dry
matter or plant height) versus time for each genotype, year and location, using stepwise
multiple regression with the equation y = b0 + b1 T + b2 T2 , where y is the ln of the
variable under consideration, and T is time. The plant biomass and elongation were
ln-transformed to maintain the homogeneity of variance between sampling dates. Due
to the different timings of the plant growth stages for the different species, the RGR
6
ANNA IANNUCCI
et al.
Figure 1. Patterns of dry matter accumulation (a, b) and FOS content (c, d) through the growth cycle of total plants
of the cereal crops at Foggia (a, c) and Bella (b, d) for the experimental period (◦−◦, oat cv. ‘Flavia’; −, oat cv.
‘Genziana’; ∗−∗, emmer wheat; •–•, barley; –, triticale). Data are means ± SE across the two years.
and RER were calculated per GDD, to eliminate the effects of different temperatures
at the time of plant development. Means of four replicates from each genotype and
harvest were used for each year and location. The R2 values of the polynomial fits
varied from 0.90 to 1.00. The derivative of the function in relation to the time, allows
determination of the rates of dry-matter accumulation (mg g−1 °Cd−1 ) and plant
elongation (mm mm−1 °Cd−1 ) for the whole period comprised for each dataset.
An analysis of variance including the fixed factor genotype and the random factor
year was carried out for each character measured or calculated. When F-tests were
significant, the means were compared with the LSD values for p < 0.05. The RGR
and RER differences were evaluated as Treatment × Time interactions in an analysis
of variance, with ln (transformed data) as the dependent variable (Poorter and Lewis,
1986). According to Peng et al. (2011) and Gleason and Ares (2004), the regression
analyses were used to examine the relationships between ln (FOS content) and RGR
in the plant fractions. All of the statistical analyses were performed with STATISTICA
software (StatSoft version 7.1; StatSoft, Inc., Tulsa, OK, USA).
R E S U LT S
Dry-matter production
Figure 1a and Figure 1b shows the total aerial plant weights according to the
physiological stage. As the pattern of dry-weight accumulation for each genotype
did not vary significantly between years, the data presented in Figure 1 represent the
means over both of the years together. The total dry-matter accumulation showed a
linear increase for all species; however, the plant species showed different total amounts
Fructo-oligosaccharides in forage cereals
7
Table 2. Means over the years for dry-matter partitioning (% total) among the plant fractions during the spring
growth at Foggia and Bella.
Foggia
Development
stage
Heading
Flowering
Milky ripe
Mealy ripe
Kernel hard
Bella
Species
Leaf
(%)
Stem
(%)
Head
(%)
Leaf
(%)
Stem
(%)
Head
(%)
Oat ‘Flavia’
Oat ‘Genziana’
Emmer wheat
Barley
Triticale
Mean
Oat ‘Flavia’
Oat ‘Genziana’
Emmer wheat
Barley
Triticale
Mean
Oat ‘Flavia’
Oat ‘Genziana’
Emmer wheat
Barley
Triticale
Mean
Oat ‘Flavia’
Oat ‘Genziana’
Emmer wheat
Barley
Triticale
Mean
Oat ‘Flavia’
Oat ‘Genziana’
Emmer wheat
Barley
Triticale
Mean
30.4a
32.3a
33.2a
24.9b
26.0b
29.4
28.9a
25.8a
26.5a
22.2b
17.6c
24.2
20.3a
20.4a
21.4a
17.1b
14.0c
18.6
18.6a
18.9a
20.1a
11.4b
13.1b
16.4
17.7a
16.5a
16.8a
10.7c
13.8b
15.1
55.9b
46.2d
50.8c
54.4b
58.8a
53.2
51.4c
47.1d
54.4b
52.1bc
63.0a
53.6
51.4b
45.9c
51.2b
45.1c
56.9a
50.1
44.0a
43.8a
39.4ab
35.0b
44.9a
41.4
43.2a
43.8a
39.3ab
33.6b
43.3a
40.6
13.6b
21.5a
16.0b
20.6a
15.2b
17.4
19.7b
27.1a
19.1b
25.7a
19.4b
22.2
28.3bc
33.7ab
27.4c
37.8a
29.1bc
31.3
37.4b
37.3b
39.8b
53.6a
42.0b
42.0
39.1b
39.7b
44.0b
55.7a
42.9b
44.3
–
27.4a
–
–
31.1a
29.3
–
23.7a
–
–
25.8a
24.8
–
21.1a
–
–
20.0a
20.6
–
19.6a
–
–
15.2b
17.4
–
17.0a
–
–
13.1b
15.1
–
45.3a
–
–
53.9a
49.6
–
44.9b
–
–
55.2a
50.1
–
43.0b
–
–
53.9a
48.5
–
42.0a
–
–
44.5a
43.3
–
41.0a
–
–
42.0a
41.5
–
27.3a
–
–
15.0b
21.2
–
31.4a
–
–
19.0b
25.2
–
35.9a
–
–
26.1b
31.0
–
38.4a
–
–
40.3a
39.4
–
42.0a
–
–
44.9a
43.5
Within each developmental stage and plant fraction, means followed by the same letters are not significantly different,
according to LSD test at p ࣘ 0.05.
of dry matter produced, with more for triticale at both locations. With increasing total
plant mass, a greater proportion of the biomass was allocated to stems and heads
than to leaves. However, differences among the genotypes were also observed in the
patterns of biomass allocation among the plant species (Table 2). The oat and emmer
wheat at Foggia showed the highest leaf dry matter for all of the developmental stages
(from 32% at heading, to 17% at kernel-hard stage, on average over genotypes). Also,
at Bella, the oat cv. ‘Genziana’ showed the highest values for leaf dry matter (22%,
on average over stages). The stem dry matter increased to its maximum values at
the flowering stage, and then decreased. The highest values of stem dry matter were
recorded for triticale in both locations (53% at Foggia, 50% at Bella, on average over
stages). Furthermore, the highest contributions of the reproductive fractions to the
8
ANNA IANNUCCI
et al.
Table 3. Dry matter production and growth parameters of the five cereals at Foggia and Bella for the 2008–2009
and 2009–2010 growing seasons.
Location
parameter
Foggia
Year (Y)
2008–2009
2009–2010
Species (S)
Oat ‘Flavia’
Oat ‘Genziana’
Emmer wheat
Barley
Triticale
LSD(0.05)
Year
Species
Y×S
Bella
Year (Y)
2008–2009
2009–2010
Species (S)
Oat ‘Genziana’
Triticale
LSD(0.05)
Year
Species
Y×S
Dry
matter
(kg m−2 )
Leaf stem
ratio
(%)
Leaf mass
ratio
(g g−1 )
Stem mass
ratio
(g g−1 )
Relative
growth rate
(mg g−1 °Cd−1 )
Relative
elongation rate
(mm mm−1 °Cd−1 )
1.25a
1.02b
42.0
39.2
0.20b
0.22a
0.44b
0.51a
1.22
1.08
0.0068
0.0062
1.13b
1.20b
1.00c
1.02c
1.33a
42.0bc
43.5b
48.5a
37.5c
31.4d
0.23a
0.23a
0.24a
0.17b
0.17b
0.49b
0.45c
0.47bc
0.44c
0.53a
1.41
1.16
1.30
1.37
1.24
0.0086
0.0069
0.0058
0.0046
0.0062
0.06
0.10
1.37
NS
4.7
6.6
0.02
0.03
NS
0.02
0.03
NS
∗∗
∗∗
0.90b
1.16a
65.7a
49.1b
0.25a
0.19b
0.91b
1.15a
62.6a
52.2b
0.11
0.11
0.16
3.9
3.9
5.5
∗∗
∗∗
∗
∗∗
0.37b
0.52a
1.09
1.37
0.0055
0.0077
0.20b
0.24a
0.39b
0.50a
1.13
1.33
0.0071
0.0061
0.03
0.03
0.04
0.03
0.03
0.05
∗∗
∗∗
∗∗
NS
NS
∗∗
Values within a column for each principal factor not followed by the same letter are significantly different at p ࣘ 0.05.
NS, not significant.
∗ , p ࣘ 0.05; ∗∗ , p ࣘ 0.01.
total plant dry weights were recorded for barley at Foggia and oat cv. ‘Genziana’ at
Bella.
Crop growth characteristics
The years had significant effects on the total biomass accumulated at both locations.
The first growing season (2008–2009) was more productive at Foggia, whereas the
second season (2009–2010) was more productive at Bella (Table 3). Triticale showed
the highest total dry matter across both seasons for both locations (1.33 kg m−2
at Foggia, 1.15 kg m−2 at Bella). The data indicate that the leaf/stem ratios varied
considerably across species and environmental conditions: from 48.5% (emmer wheat)
to 31.4% (triticale) at Foggia, and from 62.6% (oat) to 52.2% (triticale) at Bella. The five
genotypes also differed markedly in both of the parameters for dry-matter distribution
and for growth rates. Indeed, the highest LMR in oat and emmer wheat indicated that
they had plants with more leaf mass (Table 3). The SMR indicated that the aboveground dry matter was partitioned preferentially into the stem tissue in all of the
Fructo-oligosaccharides in forage cereals
9
Table 4. FOS partitioning (% total) over the years among plant fractions during spring growth at Foggia and Bella.
Foggia
Development
stage
Heading
Flowering
Milky ripe
Mealy ripe
Bella
Species
Leaf
(%)
Stem
(%)
Head
(%)
Leaf
(%)
Stem
(%)
Head
(%)
Oat ‘Flavia’
Oat ‘Genziana’
Emmer wheat
Barley
Triticale
Mean
Oat ‘Flavia’
Oat ‘Genziana’
Emmer wheat
Barley
Triticale
Mean
Oat ‘Flavia’
Oat ‘Genziana’
Emmer wheat
Barley
Triticale
Mean
Oat ‘Flavia’
Oat ‘Genziana’
Emmer wheat
Barley
Triticale
Mean
19.1b
27.2a
16.4b
9.9c
15.1bc
17.5
17.9ab
22.4a
12.0b
2.1c
2.5c
11.4
13.5a
17.0a
6.5b
1.4c
1.4c
8.0
16.6b
21.6a
10.9c
1.7d
1.4d
10.4
55.6b
38.0c
77.7a
75.6a
70.5a
63.5
36.5b
31.2b
75.9a
67.2a
71.4a
56.4
39.5c
39.1c
68.5a
53.3b
60.6ab
52.2
44.0c
40.6c
65.4ab
56.0bc
79.3a
57.1
25.3ab
34.8a
5.9c
14.4bc
14.5bc
19.0
45.6a
46.4a
12.1c
30.7ab
26.1b
32.2
46.9a
43.9a
25.0b
45.3a
37.9ab
39.8
39.4ab
37.8ab
23.7bc
42.3a
19.2c
32.5
–
20.7a
–
–
12.3a
16.5
–
19.7a
–
–
8.4b
14.1
–
18.6a
–
–
2.2b
10.4
–
17.3a
–
–
2.2b
9.8
–
33.3b
–
–
73.4a
53.4
–
26.2b
–
–
71.9a
49.1
–
29.1b
–
–
60.4a
44.8
–
33.2b
–
–
71.5a
52.4
–
46.0a
–
–
14.3b
30.2
–
54.0a
–
–
19.7b
36.9
–
52.3a
–
–
37.4a
44.9
–
49.6a
–
–
26.3b
38.0
Within each developmental stage and plant fraction, means followed by the same letters are not significantly different
according to LSD test at p ࣘ 0.05.
genotypes, with triticale showing the highest SMR. The RGR varied from the lowest
of 1.13 mg g−1 °Cd−1 for oat cv. ‘Genziana’, to the highest of 1.41 mg g−1 °Cd−1
for oat cv. ‘Flavia’. Significant differences in the RER (p ࣘ 0.05) were seen among the
species only at Foggia, with the oats showing the greatest elongation of the internodes
of the plants.
FOS content
Our study demonstrates genotypic variation in the pattern of accumulation and
depletion of the FOS content of the total plants (Figure 1c and Figure 1d). In particular,
in emmer wheat and triticale, the FOS stored transiently in the total plant increased
until the milky ripe stage, after which it progressively decreased, to reach the minimum
at the end of the analysis period (mealy ripe stage). Oats and barley reached their
highest FOS levels at heading and flowering, respectively. The proportion of the FOS
content of the leaves and stems decreased from heading to milky ripe, whereas the
maximum percent proportion was recorded for the heads at the same stage in all of the
genotypes (Table 4). There were statistically significant differences in the partitioning
10
ANNA IANNUCCI
et al.
Table 5. Means of FOS production and FOS content in total plant and plant fractions of the five cereals at Foggia
and Bella for the 2008–2009 and 2009–2010 growing seasons.
FOS content (%)
Foggia
Year (Y)
2008–2009
2009–2010
Species (S)
Oat ‘Flavia’
Oat ‘Genziana’
Emmer wheat
Barley
Triticale
LSD(0.05)
Year
Species
Y×S
Bella
Year (Y)
2008–2009
2009–2010
Species (S)
Oat ‘Genziana’
Triticale
LSD(0.05)
Year
Species
Y×S
FOS production
(g m−2 )
Total plant
Leaf
Stem
Head
Forage
biomass†
27.8b
42.8a
2.71b
4.48a
0.65b
2.02a
3.04b
6.15a
3.45a
2.91a
2.36b
4.95a
19.5c
17.3c
52.0a
34.6b
53.1a
2.06c
1.55c
5.93a
4.11b
4.33b
1.54b
1.32b
2.57a
0.58c
0.69c
2.12c
1.46c
9.01a
4.84b
5.54b
2.57b
1.83b
2.83b
4.63a
4.04a
1.92d
1.40d
6.85a
3.61c
4.50b
5.6
8.9
12.5
0.52
0.83
1.17
0.19
0.30
0.43
0.70
1.11
1.56
NS
1.16
NS
0.51
0.81
1.15
9.7b
60.6a
1.35b
2.91a
0.55b
1.23a
1.08b
3.42a
2.49a
2.35a
0.87b
2.90a
11.3b
29.0a
1.55b
2.71a
1.40a
0.38b
1.20b
3.30a
2.18a
2.67a
1.26b
2.51a
6.2
6.2
8.8
0.52
0.52
0.73
0.20
0.20
0.28
0.70
0.70
0.99
NS
NS
NS
0.53
0.53
0.74
† Forage
biomass = leaf + stem.
Values within a column for each principal factor not followed by the same letter are significantly different at p ࣘ 0.05.
NS, not significant; ∗ , p ࣘ 0.05; ∗∗ , p ࣘ 0.01.
of the FOS contents (p ࣘ 0.05) in the different plant fractions of the five genotypes
at each growing stage. Oat accumulated more FOS (% of total) in the leaf and head
fractions than the other cereals for all of the developmental stages at both locations.
Both FOS content (g m−2 ) and FOS levels (%) in total plants and their fractions,
except for the head, were greatly influenced by the growing season (Table 5). Emmer
wheat and triticale showed greater FOS production (g m−2 ) at the two locations.
However, despite the same mean value for FOS production recorded for these two
species at Foggia, only emmer wheat had a greater FOS concentration in leaves and
stems (2.57%, 9.01%, respectively) and, as consequence, in forage biomass (6.85%).
Relationship between RGR and FOS content
The changes in the estimated RGR with respect to the FOS content in the total
plants, the forage biomass and the heads are shown in Figure 2. The RGR was
significantly and positively correlated with the FOS content for both of the oat cultivars
Fructo-oligosaccharides in forage cereals
11
Figure 2. Relationships between the relative growth rate (RGR) and fructo-oligosaccharides (FOS) content for total
plants, forage biomass (leaves plus stems), and heads of the cereal crops at Foggia and Bella for the experimental
period (◦−◦, oat cv. ‘Flavia’; −, oat cv. ‘Genziana’; ∗−∗, emmer wheat; •–•, barley; –, triticale). The trend lines
represent significant linear correlations (p < 0.05).
in all of the plant fractions (R2 > 0.43; n = 8–9; p < 0.05). However, no significant
correlations were seen for the other cereal species studied here.
DISCUSSION
The total above-ground dry weight of the cereal crops studied here increased
constantly after heading, and during this period the head dry matter increased
linearly with accumulated temperature. Thus, the partitioning ratios (reproductive/
total biomass) increased rapidly during seed setting. However, the genotypes showed
different patterns of accumulation and partitioning of the assimilates within the plants.
The final dry matter varied among genotypes, probably because it mainly results from
a combination of the duration of the growth period and the RGR, and both these
12
ANNA IANNUCCI
et al.
characteristics are specific for each genotype. Previously Schnyder (1993) indicated a
genotypic variation for the efficiency of reserve use in grain filling in wheat and barley,
and Juskiw et al. (2000) showed that the quantity and the dry-matter distribution among
leaves, stems and spikes were affected by genotype in different small-grain cereals. For
all of the species, the dry matter in the vegetative parts was always greater than that in
the reproductive parts. However, the differences in the partitioning of the accumulated
dry matter resulted in significant changes in the LSR, LMR and SMR indices. In
particular, the higher LSR and LMR in emmer wheat might positively influence
the forage quality in terms of palatability. According to Calvière and Duru (1999),
the proportion of leaves in the biomass depends on the environmental conditions,
although differences in morphology, phenology and reproductive behaviour of these
species might also affect the LSR of the plants. The high SMR for triticale confirms the
greater accumulation of stem dry matter in this species. Similarly, Ellen (1993) reported
that for barley, rye, triticale and wheat, the stems were the largest component of the
above-ground biomass until three weeks after heading, when this began to decline;
during this period, there was a rapid spike growth while the leaf weight decreased. The
high value of stem dry matter recorded in triticale might be related to the efficiency
in carbohydrate accumulation, particularly of fructans, as suggested by Schnyder
(1993).
The plant growth characteristics can also change according to the species, genotype
and environmental conditions. From a practical point of view, growth characteristics
like RGR and RER are useful as efficiency indices of the plant. In particular, the RGR
analyses how efficiently the existing crop produces additional biomass, regardless of the
plant density. There are still strong differences in RGR between species when these are
expressed per GDD. This suggests that other factors besides temperature determine
the differences in the growth rates of the cereal species. However, the data for the RGR
suggest that the amount of ‘initial capital’, that is the size of the assimilatory apparatus,
has an important role in determining the yield potential of the cereal genotypes studied
here. Indeed, a high RGR, as shown by the oat cv. ‘Flavia’, does not reflect on the
dry-matter yield obtained. The higher values for dry-matter accumulation recorded
for triticale were probably due to a greater initial biomass and a longer growing season,
rather than to the RGR. Bassu et al. (2011) reported that triticale often out-yields other
cereals in field experiments under different environmental conditions; this is probably
due to earlier onset of the elongation phase and greater early vigour, which contribute
to higher biomass accumulation.
Our study has demonstrated that the genotype, the developmental stage at harvest,
and even more so, the environmental conditions, have great influence on the total
FOS content and on their partitioning into all of the plant fractions. Furthermore,
FOS accumulation in the plants during the growth period examined was not parallel
to total dry-matter accumulation. We recorded marked differences for the patterns
of accumulation and depletion of FOS between oats and the other cereal species, at
all harvest times. Indeed, the maximum FOS content was reached at the early milky
stage, and a marked reduction during the later phase of kernel filling was seen only for
barley, emmer wheat and triticale. Similar results were reported by Dreccer et al. (2009),
Fructo-oligosaccharides in forage cereals
13
Yang et al. (2004) and Wardlaw and Willenbrink (2000), in stems of wheat genotypes.
Moreover, as observed by Takahashi et al. (2001) in winter wheat cultivars, during the
late and final phases of grain filling, the fructan content decreases, probably because
the prevailing photosynthate might not have been adequate to supply the requirement
of the grain for sucrose, and the stem reserves were used to maintain the rate of
grain filling. Furthermore, Schnyder (1993) and Shiomi et al. (2006) showed that low
molecular weight fructans, and mainly FOS, predominate in the stems of wheat and
barley during the grain-filling period, and that this can contribute significantly to the
final yield. We found high levels of FOS in both the stems and immature heads of
barley, emmer wheat and triticale. High FOS contents in immature wheat kernels
were also shown by D’Egidio et al. (1999) and Paradiso et al. (2008), with maximum
accumulation during the milky phase and a rapid decrease thereafter. This decrease
can be partially explained by the accumulation of starch, which is the most prominent
component of the mature wheat kernel (Xiong et al., 2014).
There was no unique relationship between RGR and FOS concentration among
these cereal species. These results possibly reflect differences in the capacity for
FOS accumulation and mobilisation and the rate of plant growth. Only in oats,
the coefficients of correlation between RGR and FOS are positive, which indicates
that the faster the plant grows, the faster the accumulation of FOS.
These results clearly indicate that during the growing cycle of the forage cereals
studied, the biomass FOS contents are a lot higher (from 1.3% to 6.9%, on average)
than those reported in other plants of nutritional interest, which were reported as
<1% in garlic, banana fruit, sugarcane, onion and tomato, by Spiegel et al. (1994).
However, Paradiso et al. (2008) reported maximum values for fructan contents of about
11% and 16% on average for stems and grain, respectively, of 45 cultivars of durum
wheat. Our experimental data suggest that these cereals, which are well adapted and
widely cultivated in the area of the study, can be used for the production of green
feed rich in FOS. The maturation stage in which the cereal plants have the highest
nutritional value in terms of FOS contents were different across these species. In
particular, oat and barley reached their highest FOS levels at heading and flowering,
respectively, whereas for emmer wheat and triticale this was at the milky ripe stage.
Generally, in the Mediterranean environment, the annual cereals used as green feed
are harvested at the heading stage, when the high content of protein and the highly
digestible fibre make them ideal forage for high milk production, rumen function, and
animal health (Aksland et al., 2010; Cazzato et al., 2013). However, Rosser et al. (2013)
recently suggested the need to reconsider the recommendations for when annual
cereal crops should be harvested for green feed. Their study showed that effectively
degradable dry matter (an indication of ruminal digestibility) increases when the whole
crop of barley, triticale and wheat are harvested at more advanced stages of maturity.
This information allows management approaches to be developed for harvesting
of high-quality forage that also takes into account the animal requirements under
alternative feeding regimens that are rich in functional compounds. In particular, with
its high yields of biomass and FOS, triticale harvested at the milky stage appears to be
particularly suitable to this purpose.
14
ANNA IANNUCCI
et al.
Furthermore, these results suggest the potential for using forage cereals for the
extraction of large amounts of FOS from vegetative tissue, to obtain alternative
products for adding as functional food ingredients. Indeed, there is a strong interest
in the application of fructans in the food industry, because of their dietary fibre
characteristics and their prebiotic effects. Jenkins et al. (2011) reported that FOS from
cereal sources, such as grain and stem of barley and wheat, show similar in vitro
fermentation characteristics as inulin and oligofructose; this suggests that these plant
fractions can be used as alternative sources of FOS in the diet. According to our data,
barley, emmer wheat and triticale can be recommended for such commercial use, due
to the high FOS levels in the total plant.
Acknowledgements. This study was supported by the Research Project OLLAT
(Improvement of the milk quality through the feeding of the ruminants with cereals
rich in fructo-oligosaccharides) funded by the Italian Ministry of Agricultural, Food
and Forestry Policies.
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