Journal of Agricultural Science
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Developments in plant breeding for improved nutritional quality of soya beans I. Protein and amino acid content Soya beans, like other legumes, contain low concentrations of the nutritionally essential sulphur
amino acid, methionine. Cysteine, although not an essential amino acid because it can be synthesized
from methionine, also influences the nutritional quality of soya bean products when it is only present
in low levels. A low cysteine content will also aggravate a methionine deficiency. Soya bean lines
deficient in 7S protein subunits have been identified. The 7S proteins contain substantially less
methionine and cysteine than the 11S proteins. With the myriad of genetic null alleles for these
subunits it may be possible to tailor the 7S/11S storage protein ratio and their total composition in
seeds to include only those subunits with the richest sulphur amino acid composition. Cotyledon
feeding experiments, using isolated soya bean cotyledons, demonstrated that addition of methionine
to the culture media caused increased synthesis of both proteins and free amino acids but the
mechanism by which this takes place is not clear. Biotechnological approaches to improve nutritional
value of soya beans include elevated expression of genes that originate from other species which
encode high-sulphur proteins. High level expression of a 2S Brazil nut albumin gene in soya bean
resulted in raised methionine concentration although the Brazil nut gene is highly antigenic and
therefore will not be useful in production agriculture. Modification of glycinin to increase sulphur
amino acid content is possible, and these gene products are capable of normal assembly into trimers
in vitro although are rapidly degraded in vivo by the asparaginyl endopeptidase responsible for post-translational modification of proglycinin. Solutions to the methionine deficiency may be anticipated
from a combination of approaches followed in laboratories worldwide. Many of these approaches are
not without difficulty but, despite this, the likelihood is that soya beans with improved nutritional
quality (which may not be confined to sulphur-containing amino acids as other nutritionally essential
amino acids are also valuable) will be available in the near future. It will be essential to confirm that
the increased total methionine (or other amino acid) is digestible to the animal to at least the same
degree as conventional cultivars.
Journal of Agricultural Science - Tập 134 Số 2 - Trang 111-124 - 2000
Developments in plant breeding for improved nutritional quality of soya beans II. Anti-nutritional factors Nutritional value of most plant materials is limited by the presence of numerous naturally occurring
compounds which interfere with nutrient digestion and absorption. Although processing is employed
widely in removal of these factors, selection of cultivars of soya beans with inherently low levels
would have a considerable impact on efficiency of non-ruminant livestock production. The review
considers the role of plant breeding in achieving this objective. The most abundant trypsin inhibitors
are the Kunitz and the Bowman–Birk inhibitors, containing 181 and 71 amino acids respectively. The
Kunitz inhibitor is present at a concentration of 1·4 g/kg of total seed contents and the Bowman–Birk
inhibitor 1·6 g/kg. A large number of isoforms of the Bowman–Birk inhibitor have been described
in soya bean cultivars and it has been shown that the general properties of the inhibitor are, in fact,
attributable to different isoforms. Nulls for both Bowman–Birk and Kunitz trypsin inhibitors have
been identified, allowing new low trypsin inhibitor cultivars to be produced. However, research into
breeding for low trypsin inhibitor cultivars currently has limited application as trypsin inhibitors
contribute a major proportion of the methionine content of soya beans. Trypsin inhibitors are
thought to be involved in the regulation of and protection against unwanted proteolysis in plant
tissues and also act as a defence mechanism against attack from diseases, insects and animals. Hence,
in breeding programmes for low trypsin inhibitor cultivars, alternative protection for growing plants
must be considered. Use of soya beans in non-ruminant animal feeds is limited by the flatulence
associated with their consumption. The principal causes appear to be the low molecular weight
oligosaccharides containing α-galactosidic and β-fructosidic linkages; raffinose and stachyose. Non-ruminants do not have the α-galactosidase enzyme necessary for hydrolysing the α-galactosidic
linkages of raffinose and stachyose to yield readily absorbable sugars. Soya beans contain between
6·8 and 17·5 g of phytic acid/kg; a ring form of phosphorus (P) which chelates with proteins and
minerals to form phytates not readily digested within the gut of non-ruminants. One approach for
over-coming the effects of phytic acid is through synthesis of phytase in the seeds of transgenic plants.
Currently, recombinant phytase produced in soya beans is not able to withstand the processing
temperatures necessary to inactivate proteinaceous anti-nutritional factors present. Soya bean lectins
have the ability to bind with certain carbohydrate molecules (N-acetyl-D-galactosamine and
galactose) without altering the covalent structure. Lectins are present in raw soya bean at a
concentration of between 10 and 20 g/kg. Purified soya bean agglutinin is easily inactivated by
hydrothermal treatment but in complex diets binding with haptenic carbohydrates may confer
protection against denaturation. The majority of research into soya bean lectins is carried out using
laboratory animals so very limited information is available on their in vivo effects in farm animals.
This review is concerned specifically with breeding but there are other means of improving nutritive
value, for example processing which may alter protein structure and therefore functionality of
proteinaceous anti-nutritional factors present.
Journal of Agricultural Science - Tập 134 Số 2 - Trang 125-136 - 2000
The ‘teat order’ of suckling pigs: II. Fighting during suckling and the effects of clipping the eye teeth SUMMARY The development of stable suckling order, the incidence of fighting when suckling, weight gain during the suckling period, and the severity of facial wounding were studied with litters of piglets in which the canine and lateral incisor teeth were either clipped at birth or left intact. Facial wounding was largely confined to litters with unclipped teeth. Severity of wounding correlated with the observed incidence of fighting on the udder (P<0·01); and both wounding and fighting were more common among litters comprising a large number of piglets (P<0·05). When the effect of litter size was taken into account, there were no substantial differences in weight gain to 3 weeks between piglets with high and low scores for facial wounding, nor between clipped and unclipped litters. Piglets which habitually occupied the most anterior or most posterior teats had less facial wounding than middle-suckling piglets, and showed greater consistency in teat choice. No gross differences between clipped and unclipped litters were observed in the development of stable suckling order during the first week of life. It is concluded that the ‘eye’ teeth, although used in disputes over teat choice, have little influence on the frequency of such disputes or on the original development of stable suckling order.
Journal of Agricultural Science - Tập 84 Số 3 - Trang 393-399 - 1975
The effects of the genotype by environmental interaction on the fixation of heterosis in tomato Continuous honeycomb selection and testing in the absence of competition in a single environment, resulted in the isolation of recombinant inbreds in tomato that outperformed the hybrid only in that particular environment. Alternating selection and testing in two environments (open field v . glasshouse) reduced selection efficiency, by preventing exploitation of the whole constellation of genes contributing to heterosis. Selection in the F2 generation was most critical, as evidenced by the appearance of recombinant lines outperforming the hybrid as early as in the F3 generation. Exploitable genetic variation existed in advanced generations and even after the point of achieving theoretical homozygosity (F7 generation). In the future, and in order to fully exploit the unique possibilities offered by the honeycomb methodology (control of soil heterogeneity, high selection pressures, crop yield components), selection for reduced GE interaction should be practiced simultaneously over the target environments of adaptation.
Journal of Agricultural Science - Tập 139 Số 1 - Trang 55-60 - 2002
Variability within cotton cultivars for yield, fibre quality and physiological traits SUMMARY Selection within elite cotton cultivars is ineffective; it is believed that they are genetically homogeneous. Research in other crops, however, has verified significant intra-cultivar variation based either on phenotypic differentiation or molecular analysis techniques. The present study primarily investigated possible intra-cultivar variation for seedcotton yield. Honeycomb selection within three elite cotton cultivars, on the basis of single-plant seedcotton yield and under the ultra-low density of 1·2 plants/m2 , was performed. From each cultivar, six selfed (hand-pollinated) plants were selected and seed of each selected plant constituted a separate line. The 18 first generation lines were evaluated in three locations at a density of 1·2 plants/m2 . Within each line, the 10 selfed plants which yielded the highest were selected. Mixed seed from these selected plants constituted the respective second generation line. Offspring performance of the 18 second generation lines was also tested in three locations at a density of 1·2 plants/m2 . The results were indicative of intra-cultivar variation, since significant differentiation between lines of each cultivar was found for seedcotton yield per plant, averaged across two years and three locations. Additionally, significant intra-cultivar variation was found for fibre quality properties (length and micronaire, but not strength and uniformity) averaged across two years in a single location, as well as for physiological traits (leaf carbon isotope discrimination, ash content and K concentration) averaged across two years and three locations. In comparison with the original cultivars the second generation lines had higher seedcotton yields supporting the existence of exploitable genetic variation. The conclusion was that honeycomb selection in the absence of competition could be an effective technique in breeders' seed treatment in order to avoid gradual degeneration and beneficially exploit any latent or newly developed genetic variation.
Journal of Agricultural Science - Tập 146 Số 4 - Trang 483-490 - 2008
Intra-cultivar variation in cotton: response to single-plant yield selection at low density SUMMARY In a 5-year study (2004–2008), the possibility of exploiting intra-cultivar variation in cotton (Gossypium hirsutum L.) was investigated. Honeycomb single-plant selection for seedcotton yield was employed within three cultivars at a low density of 1·15 plants/m2 . First- and second-generation progeny lines (1GPLs and 2GPLs) were evaluated for seedcotton yield at low density at three sites, whereas third-generation progeny lines (3GPLs) were tested at the crop density of 10 plants/m2 across two sites and 2 years. Significant differentiation for seedcotton yield was discovered within cultivar (cvar)Christina and cvarCorona at both low and crop densities, and within cvarFlora at low density. In addition, significant intra-cultivar heterogeneity for fibre quality properties was found at crop density. The 1GPLs and 2GPLs grown at low density showed increases in seedcotton yield of 16 and 19%, respectively, in cvarChristina , and of 2·6 and 3·7%, respectively, in cvarCorona . In cvarFlora , the 1GPLs and 2GPLs yielded 10 and 3·3% lower than the mother cultivar, respectively. When grown at standard crop density, across sites and years, 12 and 5·2% higher yield was obtained by theChristina -derived 3GPLs and theCorona -derived 3GPLs, respectively, when compared with the original cultivars. These results provide evidence that elite cultivars are not homogeneous but rather heterogeneous material, within which selections can be made to maintain or improve uniformity and further improve desirable agronomic traits.
Journal of Agricultural Science - Tập 149 Số 2 - Trang 197-204 - 2011
The effect of improved potential yield per plant on crop yield potential and optimum plant density in maize hybrids Honeycomb selection in the F2 generation of maize (Zea mays L.) hybrid PR 3183, based on line performance per se in the absence of competition, led to recycled hybrids with improved potential yield per plant (mean yield per plant in the absence of competition). In the present study six S6 ×S6 recycled hybrids and two commercial single-cross hybrids (PR 3183 and B73×Mo17) were tested at three plant densities (25000, 41667 and 83333 plants/ha), in two locations (Technological Education Institute farm of Florina, Greece and University farm of Thessaloniki, Greece), for 2 years (1998, 1999). The study was undertaken to assess indirectly the potential yield per plant (p), the crop yield potential (Ymax ), and the optimum plant density (Dopt ) of the hybrids. Estimate of p and Ymax were obtained through linear regression analysis of yield per plant (Yp ) on plant density (D), expressed by the equation Yp = p−qD, with Ymax being equal to (1/4)p2 q−1 . Optimum plant density was assessed through linear regression analysis of natural logarithm of yield per plant on plant density, expressed by the equation ln(Yp ) = α−bD, with Dopt being equal to 1/b. The recycled hybrids had higher estimated potential yield per plant (p), than the two check hybrids, with p values being positively correlated with yield per plant of hybrids obtained experimentally in the absence of competition. Results indicated that the higher potential yield per plant decreases the optimum plant density, and renders the hybrids less density-dependent.
Journal of Agricultural Science - Tập 137 Số 3 - Trang 299-305 - 2001
Variation within maize lines and hybrids in the absence of competition and relation between hybrid potential yield per plant with line traits The objective of the study was to determine, in the absence of competition (0·74 plants/m2 ), the
existing variation within lines of maize (Zea mays L.) for plant and ear traits (yield per plant, number
of tillers, number of ears, plant height, number of nodes, ear length, and kernel row number), as well
as the relationship between hybrid potential yield per plant (i.e. yield per plant in the absence of
competition) with line traits. Two categories of material were tested in honeycomb trials, grown from
1989 to 1995 in the University farm of Thessaloniki, Greece. The first category were selections from
long-term inbreds B73 and Mo17, derived through honeycomb design in the absence of competition,
and their crosses. Inbred selections and their crosses were evaluated in different years. For the second
category two sets of S5 lines, A and B, derived through controlled selfing from the commercial single-
cross hybrid PR 3183, were used in random crosses between S5 plants of lines A and B and resulted
in 40 triplets; each triplet included each of the selfed parent, and their hybrid. Triplets of A and B
S6 lines and A × B S5 × S5 crosses were evaluated in the same experiment. Significant differentiation
among lines and hybrids was found for almost all traits; variation within lines for potential yield per
plant, even in case of B73 and Mo17, seemed to be transmissible to the hybrids. Although correlation
values were small in the case of B73 and Mo17 selections, there was a positive correlation between
hybrids and lines for their potential yield per plant. Selection for high yield within S lines gave
‘prolific’ plants, with line prolificacy being correlated with hybrid potential yield per plant.
Journal of Agricultural Science - Tập 134 Số 4 - Trang 391-398 - 2000
Comparative efficiency of three selection methods in <i>Dactylis glomerata</i> L. and <i>Agropyron cristatum</i> L. Two populations, one non-improved of Dactylis glomerata and one improved of Agropyron cristatum were selected in an isolated spaced plant environment (80 cm) by three selection procedures: (1) Mass honeycomb selection (MHS), (2) pedigree honeycomb selection (PHS) and (3) pedigree honeycomb selection-combined criterion (PHS-CC). The third procedure is a between-families selection based on increased family mean and reduced family coefficient of variation (CV). Response to selection assessed in sward trials in the first and second harvest year was effective for the three procedures, which ranked PHS-CC > PHS > MHS. Evaluation was based on consistent efficiency as measured by both cloned and half-sib families. The precision of assessing progeny performance under sward conditions on the basis of single plant evaluation in the isolation environment, increased with a reduction in competition among plants, the use of moving-ring selection, and the application of high selection pressures (1·6%). The efficiency of selection between unimproved families increased when families were selected concurrently for high family mean and reduced family coefficient of variation.
Journal of Agricultural Science - Tập 137 Số 2 - Trang 173-178 - 2001
Simulating the effects of grassland management and grass ensiling on methane emission from lactating cows SUMMARY A dynamic, mechanistic model of enteric fermentation was used to investigate the effect of type and quality of grass forage, dry matter intake (DMI) and proportion of concentrates in dietary dry matter (DM) on variation in methane (CH4 ) emission from enteric fermentation in dairy cows. The model represents substrate degradation and microbial fermentation processes in rumen and hindgut and, in particular, the effects of type of substrate fermented and of pH on the production of individual volatile fatty acids and CH4 as end-products of fermentation. Effects of type and quality of fresh and ensiled grass were evaluated by distinguishing two N fertilization rates of grassland and two stages of grass maturity. Simulation results indicated a strong impact of the amount and type of grass consumed on CH4 emission, with a maximum difference (across all forage types and all levels of DMI) of 49 and 77% in g CH4 /kg fat and protein corrected milk (FCM) for diets with a proportion of concentrates in dietary DM of 0·1 and 0·4, respectively (values ranging from 10·2 to 19·5 g CH4 /kg FCM). The lowest emission was established for early cut, high fertilized grass silage (GS) and high fertilized grass herbage (GH). The highest emission was found for late cut, low-fertilized GS. The N fertilization rate had the largest impact, followed by stage of grass maturity at harvesting and by the distinction between GH and GS. Emission expressed in g CH4 /kg FCM declined on average 14% with an increase of DMI from 14 to 18 kg/day for grass forage diets with a proportion of concentrates of 0·1, and on average 29% with an increase of DMI from 14 to 23 kg/day for diets with a proportion of concentrates of 0·4. Simulation results indicated that a high proportion of concentrates in dietary DM may lead to a further reduction of CH4 emission per kg FCM mainly as a result of a higher DMI and milk yield, in comparison to low concentrate diets. Simulation results were evaluated against independent data obtained at three different laboratories in indirect calorimetry trials with cows consuming GH mainly. The model predicted the average of observed values reasonably, but systematic deviations remained between individual laboratories and root mean squared prediction error was a proportion of 0·12 of the observed mean. Both observed and predicted emission expressed in g CH4 /kg DM intake decreased upon an increase in dietary N:organic matter (OM) ratio. The model reproduced reasonably well the variation in measured CH4 emission in cattle sheds on Dutch dairy farms and indicated that on average a fraction of 0·28 of the total emissions must have originated from manure under these circumstances.
Journal of Agricultural Science - Tập 148 Số 1 - Trang 55-72 - 2010
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