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.

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.

An investigation was made during 1988 to test the hypothesis that ‘Grasslands Huia’ white clover (Trifolium repens L.) could be eliminated under close sheep grazing. The effects of grazing management, topography and fertilizer on the contribution of Huia plants to the white clover population in an 85 ha experimental upland pasture ecosystem in the southern North Island, New Zealand (lat. 40° 20′ S, long. 175° 50′ E, 125–350 m altitude) were quantified 11 years after oversowing. Replicated sampling sites (108 in total) were located on nine combinations of slope and aspect within grazing management treatments comprising rotational grazing with cattle (RC), rotational grazing with sheep (RS) and continuous grazing with sheep (CS), with high and low fertilizer treatments in each case. White clover occurrence, leaf area, phosphoglucoisomerase-2 (PGI-2) allele frequencies and the proportion of Grasslands Huia plants in the white clover population were determined at each site. White clover frequency was lower on steeper slopes. Aspect, slope and grazing management affected area of individual clover leaves. The proportion of Huia plants in the white clover population averaged 54·9, 49·0 and 33·6% for RC, RS and CS, respectively (P < 0·039, 5 D.F.). Fertilizer and topography did not affect the proportion of Huia. It was concluded that although Huia did persist after 11 years of close sheep grazing, its contribution to the total white clover population was unsatisfactory in some cases, and use of better adapted cultivars is suggested.

Use of fertilizers and manures during 1994 were studied at the farm and catchment scale in the largely agricultural Ythan catchment, north-east Scotland, using farm level census data supplemented by questionnaire data. Grassland accounted for 40% of the agricultural land, and seven farm types represented 87% of the total land, having an average size of 90 ha. The average livestock density of 1·2 livestock units/ha was high compared to Scotland as a whole (0·5). Rates of inorganic fertilizer applied to individual crops in the area corresponded with the national average and current advisory recommendations. At the catchment scale, most fertilizer N was applied to grassland (47%), whereas spring crops received the greatest proportion of the fertilizer P (35%). The annual manure production equated to an average over the catchment of 63 and 16 kg/ha of N and P, respectively. When calculated for farm types these figures ranged from 27 and 6 kg/ha on ‘cereal’ farms to 384 and 163 kg/ha on ‘pig’ farms. The ratio of applied fertilizer N and P varied from 4[ratio ]1 for ‘general cropping’ to 10[ratio ]1 for ‘cattle and sheep (lowground)’ farms. There was no significant compensatory reduction in inorganic fertilizer applications on crops, which also had received manures.

Twenty slurries, 20 farmyard manures (FYM) and 10 poultry manures were chemically analysed to characterize their nitrogen (N) fractions and to assess their potential organic N supply. The organic N fraction varied between manure types and represented from 14% to 99% of the total N content. The readily mineralizable N fraction, measured by refluxing with KCl, was largest in the pig FYMs and broiler litters, but on average only represented 7–8% of the total N content. A pot experiment was undertaken to measure N mineralization from the organic N fraction of 17 of these manures. The ammonium-N content of the manures was removed and the remaining organic N mixed with a low mineral N status sandy soil, which was sown with perennial ryegrass (Lolium perenne L.). N offtake was used as a measure of mineralization throughout the 199 day experiment. The greatest N mineralization was measured from a layer manure and a pig slurry, where N offtake represented 56% and 37% of the organic N added, respectively. Lowest (%) N mineralization was measured from a dairy cow slurry (< 2%) and a beef FYM (6%). The mineralization rate was negatively related to the C[ratio ]organic N ratio of the ammonium-N stripped manures (P < 0·01, r = −0·63).

Fourteen field trials were conducted on farmers' fields in five villages of the Union Territory of Delhi, India during 1995–96 and 1996–97 to study the effect of introducing a crop of summer mungbean on the productivity of a rice–wheat cropping system. Timely sown summer mungbean yielded 0·4–1·3 t/ha protein-rich grain and, on average, increased rice yields by 0·5–0·9 t/ha and the yields of the succeeding wheat by 0·4–0·7 t/ha. The yield response of rice to the summer mungbean crop was greater when less urea-N fertilizer was applied, and N applied to the rice did not decrease the residual effect of the summer mungbean on the succeeding wheat. The increase in total productivity of rice–wheat cropping system due to summer mungbean ranged from 0·3 to 2·6 t/ha with an average of 1·6 t/ha.

In the last two decades, crop production models have been developed or modified for use in the semi-arid tropics. Although potential uses of crop models have been discussed in detail in the literature, examples of successful uptake and impact of those models is lacking. Four models developed specifically for the semi-arid tropics were used as a basis for evaluating uptake and impact of models in the semi-arid tropics. PARCH accounts for differences in water availability when predicting yield. PARCHED-THIRST covers water-harvesting, run-off and run-on. EMERGE identifies opportunities for successful crop establishment, and SWEAT calculates evapo-transpiration and estimates temperature and moisture throughout the soil profile. The models are dynamic, deterministic and mechanistic in nature. The equations and notations comprising them are generally well structured, meaningful and concise. The uptake and impact of these models on crop production in the semi-arid tropics was assessed using questionnaires and semi-structured interviews with the model developers. There was limited uptake. Low uptake resulted from lack of efficient dissemination and discontinuity in information transfer: from model developers to scientists in the national research institutions; and thereon to extension agents and so to farmers. Although this paper is based on a study of only four models, there are important lessons to be drawn in order to avoid similar mistakes being repeated. Guidelines for improving impact for future crop production modelling projects are proposed.

Pearl millet (Pennisetum glaucum (L.) R. Br.) is commonly grown at a wide range of plant population densities, both by design and as a consequence of stand establishment problems. High tillering genotypes are known to compensate effectively for lower plant population densities through their tillering capacity; less is known about the ability of naturally low tillering genotypes to adjust to low plant population densities. This is a particular concern in the case of the Iniadi landrace materials which are currently widely used in breeding programmes in both India and Africa. This research was done to determine how effectively the low tillering Iniadi types adjust to low plant population densities and how their mechanism(s) of adjustment compares to those of higher tillering materials. Two high and two low tillering genotypes were grown over a period of 5 years at plant population densities ranging from 12 to 2 plants/m2, under both high and low fertility regimes at the ICRISAT Centre, India. Both the high and low tillering types adjusted equally well to the reduced plant population densities, as judged by grain yield, but differed in their mechanism of adjustment. The high tillering genotypes adjusted, as expected, primarily by increasing productive tiller numbers, with only small changes in individual tiller productivity. The Iniadi genotypes increased productive tiller numbers in response to decreasing plant population densities to a limited degree, but increased panicle productivity to a much greater degree than the high tillering types. There was no differential effect on adjustment ability between the two types as a consequence of increased fertility, despite the stimulating effect of fertility on productive tiller numbers. The results are discussed in terms of generalized mechanisms of response to changing individual plant environmental resources (fertility and space), and in terms of the use of Iniadi germplasm in pearl millet breeding programmes.

Starting with the F2 generation of the single-cross commercial hybrid Lorena (PR3183), recombinant lines were developed combining half-sib/S1 evaluation on widely spaced plants in the direction of high yielding per se. Combining ability tests consisted of crosses between: (a) recombinant lines of common pedigree and (b) recombinant lines and freely available inbred lines. The highest-yielding crosses between recombinant lines reached 100% of the original F1 hybrid in a percentage of 14·2. Low heterosis was estimated owing to additive gene action of recombinant lines. Crosses between recombinant lines and freely available inbred lines outyielded significantly the commercial F1 hybrid in a percentage of 33·3. Heterosis was greater and the original F1 hybrid was outyielded significantly because of non-additive gene action. When the applied breeding procedure on a source population with high yield adaptability is adopted and where effects of intergenotypic competition masking the inherent genotypic value are controlled, population improvement may be substituted by combined half-sib/S1 selection for productivity of lines per se in low stress conditions during the very early stages.

The study was undertaken at Punjab Agricultural University, Ludhiana, in 1991–1992 to investigate the behaviour of the pollen tubes of four wild Pennisetum species in the stigmatic tract of P. typhoides and to identify stages of pre-fertilization impediments to interspecific hybridization. Pollen germination was normal in crosses with P. violaceum, P. squamulatum and P. orientale and slightly inhibited in a cross with P. setaceum. Fertilization was accomplished within 3 h of pollination in a control cross within P. typhoides. P. typhoides × P. violaceum was a compatible cross and the pollen tubes of P. violaceum reached the ovary within 4 h of pollination. The presence of P. squamulatum and P. orientale pollen tubes in the ovary 10–15 h after pollination indicated the possibility of normal fertilization, while in crosses with P. setaceum, pollen tubes did not penetrate the ovary even 15 h after pollination. The study indicated that there is no impediment at the pollen germination stage or in the stigmatic hairy region. Delayed/restricted growth of pollen tubes indicated that the barrier operates in the styllar hairless region for the crosses with P. squamulatum and P. orientale, and at the ovarian level for the P. typhoides × P. setaceum cross.

Eragrostis curvula (Schrad.) Nees s. lat., a highly polymorphic polyploid complex, can be considered as one of the most important warm season perennial grasses for the semi-arid regions of central Argentina. In apomictically propagated and perennial plants such as weeping lovegrass, where successive measurements can be done across time, repeatability estimates provide an indication of the degree of influence of permanent effects on the phenotypic variation and allow prediction of future performance from past records. Analysis of variance of the experiment showed highly significant variation (P < 0·01) for the main factors in all four traits. Although there was very high variability between cuts, hybrids of E. curvula exhibited considerable inter-entry variability, in particular for those traits determining forage yield. Repeatability calculated in this experiment was highest for the crown diameter (0·86), leaf length (0·84) and dry matter (0·84), while in panicle number (0·66) it was lowest. Repeatability estimates for the vegetative characteristics indicate small effects of temporal environment. The four traits studied, including panicle number with their moderate repeatability, do not require an essentially different number of observations to obtain measures at the same level of accuracy. For vegetative characters two harvests provided 98% of the accuracy of the total obtained with four cuts, and for panicle number the same percentage was obtained for three harvests. This stability of performance is a desirable characteristic for grass cultivars. Patterns of trait associations were also described. Because leaf length is closely associated with dry matter and has high repeatability, to use leaf length as an indirect evaluation criterion should be almost as efficient as direct evaluation for aerial biomass yield. Reliable estimates of parameters such as repeatability and phenotypic correlation are needed for prediction of production values and for the design of efficient improvement programmes. For genotype evaluation additional research is required to quantify the extent of genotype × environment interaction across years and localities of semi-arid regions.

During the introduction of a new crop, it is important to study and select for resistance to pests to ensure preservation of possible natural protection in the plant material. One accession of Barbarea verna (Mill.) Asch. and one of Barbarea vulgaris R. Br. was exposed to female pollen beetles, Meligethes aeneus Fab. (Coleoptera: Nitidulidae) in a greenhouse experiment. The experiment was initiated to reveal the extent to which the plant material is accepted as a host plant to this important Brassicaceae pest. The two species, B. verna and B. vulgaris, were used for oviposition by 26% and 21% of the females, respectively. The amount of oviposition and feeding injury on either of the two species throughout the experiment did not indicate any difference in acceptance of the species by the pollen beetle. For both species a majority of the egg-laying females oviposited only once during the 5-day period and laid less than 3 eggs per clutch. The females present on the Barbarea spp. were not more disposed to accept the species as the days passed and the mean clutch size did not increase with time since previous oviposition. Females laying eggs used large and small buds of B. verna to the same extent for feeding. On B. vulgaris there was a tendency for more frequent use of large buds for feeding than small. Acceptance for oviposition by the pollen beetle on the two accessions of Barbarea is low in this experiment. Injury caused was limited to a level probably tolerated by the plant material without causing economic damage. As the oogenesis of the pollen beetle is reduced by exposure to low-quality host plants the potential natural protection would endure despite an increasing occurrence of the species.

A method that allows the effect of temperature treatments on plant quality to be quantified is described. The proposed method is based on the analysis of temperature regions for plant quality characteristics and enables an easier and more precise analysis of the influence of day and night temperature on plant growth and development. Plant quality may be evaluated by the combination of any number of plant characteristics. The proposed method can assist growers in determining what temperature regimes are necessary to produce acceptable-quality crops on specified days.

A field experiment was conducted for two years (1994–96) to evaluate three nitrogen fixing bacteria (NFBs) namely Azotobacter, Azospirillum and Beijerinckia as foliar biofertilizers on mulberry (Morus spp.). Foliar application of these bacteria in their specific culture media with half of the recommended dose of N as a basal application of chemical fertilizer were compared with the recommended dose of N (300 kg/ha per year in four equal splits) but without biofertilizer. Other controls for comparison were respective culture media with half N. All the NFBs improved leaf yield over their respective controls (specific culture media). The addition of Azotobacter resulted in significantly greater yield than that given by the recommended dose of N. The Beijerinckia treatment resulted in a leaf yield equal to that from the recommended dose of N and Azospirillum reduced leaf yield in comparison to that from the recommended N treatment although the yield from Azospirillum treatment was more than that from the culture medium treatments. A combination of NFBs where Azotobacter was one of the components improved leaf yield over single NFB treatments. NFBs also resulted in improved leaf quality as indicated by their protein content and their impact on silkworm rearing and cocoon production when treated leaves were subjected to bioassay. The use of these NFBs, particularly the Azotobacter, as a foliar biofertilizer to increase mulberry leaf production has not been investigated before.