A three factor experiment with winter wheat (Triticum aestivum L.) was carried out during two years on a coarse sandy soil in Denmark. The factors comprised four irrigation strategies including no irrigation, three nitrogen levels providing 67, 83 or 100% of the recommended nitrogen rate, and two strategies for control of leaf diseases (with and without fungicides). Different varieties were used in the two years, Pepital in the first year and Hussar in the second year. Mildew dominated the trial in the first year, but was almost absent in the second year. Septoria occurred in both years, but most severely in the second year. Irrigation increased grain yield, but there were no significant differences between the three strategies, where irrigation was applied. The effect of irrigation on yield was almost solely via an effect of increased transpiration, whereas water use efficiency and harvest index was unaffected. There was a significant interaction for grain yield between irrigation and nitrogen strategies with higher irrigation effects at higher nitrogen rates. This interaction was absent at high disease levels. Increasing nitrogen rate increased grain yield in the second year, but not in the first year. This was attributed to an increasing mildew incidence with increasing nitrogen rate. Irrigation also increased mildew incidence. This caused significant interactions for grain yield between fungicide application and nitrogen rate and between fungicide application and irrigation strategy. Septoria was also significantly affected by both nitrogen and irrigation strategies, but to a lesser degree and not in a consistent manner. The main effect of disease on grain yield was through a reduction in harvest index and a reduction in grain weight. Increasing nitrogen rates slightly reduced harvest index both on a dry matter and on a nitrogen basis. The interaction effects were smaller than the effects of the main factors, and the effect of changes in irrigation or nitrogen strategy on disease incidence could not substitute for the effective disease control obtained by fungicides. The results do, however, indicate possibilities of improving the efficiency of current decision support systems for both fungicide control by better timing of application and irrigation scheduling by reducing water application.

Data from a three factor experiment carried out during two years were used to analyse the effects of drought, nitrogen and disease on light interception (IPAR) and radiation use efficiency (RUE) in winter wheat (Triticum aestivum L.). The factors in the experiment comprised four irrigation strategies including no irrigation, three nitrogen levels providing 67, 83 and 100% of the recommended nitrogen rate, and two strategies for control of leaf diseases (with and without fungicides). Light interception was estimated from weekly measurements of crop spectral reflectance. This method was compared with estimates derived from crop area index measured by plant samples or by using the LAI2000 instrument. There was a good correspondence between the different methods before anthesis, but an overestimation of light interception with the methods using crop area index after anthesis due to an increase in non-photosynthetic active leaf area. Irrigation increased both IPAR and RUE. The relative increase in IPAR for irrigation was greater than the relative increase in RUE in the first year, whereas they were of similar size in the second year. The differences between the years could be attributed to changes in timing of the drought relative to crop ontogenesis. Increasing nitrogen rate increased IPAR, but caused a small decrease in RUE in both years. This reduction in RUE with increasing nitrogen concentration in leaves was also found to be significant when disease levels and drought effects were included in a multiple linear regression. Fungicide application increased IPAR in both years, but RUE was only significantly reduced by disease in the first year, where mildew dominated the trial. The data were also used to estimate the coefficients of partitioning of dry matter to grains before and after anthesis. About 40% of dry matter produced before anthesis and about 60% after anthesis was estimated to contribute to grain yield. The low fraction after anthesis is probably due to the fact that it was not possible to estimate changes in RUE with time, which may lead to biases in the estimation of partitioning coefficients.

When crops of wheat (Triticum aestivum L.) are stressed, grain set in potentially fertile florets is reduced. Cold temperatures and boron (B) deficiency during reproductive development cause grain set failure in wheat. Patterns of grain set in cold-stressed and B-deficient wheat ears were studied under field conditions in Nepal and in controlled environments in the UK. In both B-deficient and cold-stressed circumstances, ear fertility was reduced by up to 98% but the pattern of grain set within an ear was similar. Under cold-stressed conditions, florets in the uppermost one-third of the ear were 41 to 53% less fertile than those located in the middle and basal regions. Even in the unstressed crops, the top one-third of the ear was less fertile than below by as much as 8–13%. Similarly, within a spikelet, the distal florets always had fewer grains than the proximal ones. Decreased grain set following stress markedly reduced yield per ear. We conclude that fertility should be assessed on the entire ear. The determination of competent florets should be based on the presence of well-developed ovaries, feathery stigmas and the structures of anthers (which can still be seen in the sterile florets at maturity) rather than on the length of the lemma or on judgements based on visual appearance or other subjective criteria.

The growth and yield of pinto beans (Phaseolus vulgaris L.) cv. Othello in response to a total of six sowing dates (from October to December) and irrigation was examined over two seasons in Canterbury, New Zealand. In 1994/95, two irrigation treatments (nil and full) were combined with two sowing dates (27 October and 24 November). In 1995/96, Othello was examined under two irrigation treatments (nil and full) and four sowing dates (1 November, 15 November, 29 November and 13 December). The total rainfall for the two seasons was 50% and 60% of the long-term average, respectively. The mean temperatures for the seasons were similar to the long-term average. Both irrigation and sowing date had a marked effect on growth and seed yield. Averaged over both seasons, seed yield for fully irrigated crops was 337 g/m2, c. 50% higher than the yield of unirrigated crops. The irrigated crops yielded more than the unirrigated crops because they attained greater canopy closure, intercepting 84–95% of incident radiation. They also had on the average 47% higher leaf area duration (LAD), 72% higher maximum leaf area index (LAI) and greater utilization coefficient. The mid- to late November-sown crops yielded more than the late October to early November and December-sown crops because the leaf area of the former increased most rapidly, achieved a higher maximum LAI and LAD and consequently intercepted more photosynthetically active radiation (PAR). They also had faster pod growth rates and 26% of stored assimilates contributed to pod growth compared with 13% in late October to early November and 5% in December-sown crops. The results showed that pinto beans can grow and yield well in Canterbury, and that a yield advantage could be obtained when sown in mid- to late November and with irrigation.

Seed loss from sesame capsules before harvest is a major economic problem for mechanized production. Capsule dehiscence and seed loss were investigated by examining capsule anatomy of 32 sesame varieties and relating anatomical features to a measure of seed retention. This survey of sesame capsule anatomy illustrated that differences between varieties were mostly quantitative, except for the presence of cell layers over the median vascular bundle. This feature, associated with the indehiscent (idid) genotype, prevented capsule-splitting and increased seed retention. None of the dehiscent sesame varieties had capsule anatomical features that were correlated with seed retention. During capsule senescence, mesocarp cells shrank more than endocarp cells creating tension in the drying capsule wall. The tension forced capsules open along a zone of weakness between locules.

The late-season period in the humid tropics is characterized by drought and the production of crops such as tomato (Lycopersicon esculentum L.), okra (Abelmoschus esculentum), pepper (Capsicum spp.) and leafy vegetables depends upon the utilization of stored soil water. The efficient use of stored soil moisture ensures maximum plant adaptation and yield stability. The growth, development and yield of tomato grown on mulched and unmulched hand-hoed, raised beds and ridged sandy loam soil during the late cropping seasons of 1994, 1995 and 1996 in Akure, Nigeria was investigated. Hand-hoeing reduced soil temperature and conserved more soil moisture than ridging or the raised bed while grass mulch improved soil temperature and soil moisture regime compared with bare ground. Root biomass and root/shoot ratio increased in the order ridging, raised bed and hand-hoeing while shoot biomass, leaf area/plant and percentage fruit set decreased in the order raised bed, ridging and hand-hoeing. Number of fruit and fruit yield/plant produced by raised beds were significantly higher than those produced by ridging and hand-hoeing. Mulch ameliorated the hydrothermal regime of the soil, improved the vegetative and flowering performance and significantly increased the fruit yield of tomato over bare ground.

Liriomyza huidobrensis, the pea leafminer, is a recently identified pest on vegetables in Lebanon. The objectives of this study were to survey the leafminer infestation, to study its dispersion and its development on cucumber, swisschard and bean. In general, the infestation level was found to be higher in the middle coastal sites than in the other sites during the period of the study 1994–95. In the former sites, the pest was found to thrive on swisschard in October and November, in presence of cucumber under greenhouses, while it was encountered in significantly higher numbers on cucumber during the spring season, in absence of swisschard. Pairwise comparisons of Taylor's and Iwao's regression slope for L. huidobrensis larval mines indicated a contagious dispersion on leaves of cucumber and bean, while the pattern was random to slightly aggregated on swisschard. There was a significantly higher number of larval mines on the lower plant stratum compared to the middle and upper strata of cucumber through the cropping season. There was a significant difference in the overall development duration (19·6–22·3 days) of the insect among the three hosts. The larval development duration was significantly shorter on bean compared to swisschard and cucumber consecutively. However, there was no significant difference in egg or pupa duration among the three hosts. Results of this study provide bases for appropriate management of the pest, taking into consideration its infestation level, spatial pattern, and development duration on the mentioned hosts.

Four near-isogenic lines of wheat were employed to compare the effects of endosperm texture (hard v. soft) and the presence or absence of the 1B/1R translocation on amino acid digestion as determined with young broilers. Wheat samples were incorporated into diets at rates of inclusion of 250, 500 and 750 g/kg, with wheat as the only protein source. Diets included a mineral/vitamin mixture (50 g), oil (50 g) and were made up to 1000 g with a 50[ratio ]50 starch[ratio ]glucose mixture. Titanium dioxide was included at 5 g/kg as an inert marker. Each of the 12 diets was fed to 6 pairs of growing male (Ross) chickens for 3 days. Samples of ileal digesta were obtained from the birds following slaughter at 21 or 22 days of age and analysed for amino acid and titanium dioxide content. True and apparent digestibility coefficients were determined by regressing the amount of dietary apparently digestible amino acid in the diet against the rate of wheat inclusion and extrapolating the response to 1000 g and 0 g wheat/kg. The ordinate intercept was assumed to represent endogenous losses. Both the presence of the translocation and hard endosperm texture were associated with decreases in the apparent digestibility of amino acids, although the latter characteristic was not as important. As examples, for methionine the translocation was associated with a decrease in the coefficient of digestibility from 0·872 to 0·802 and a change in endosperm texture from soft to hard was associated with a decrease from 0·845 to 0·829.

Total DNA was extracted and purified from luminal digesta samples (1 g) of 14-week-old (c. 43 kg bodyweight) pigs. Digoxigenin (DIG) labelled PCR products of the beta toxin gene of Clostridium perfringens type C were generated with DIG-11-UTP and chemoluminescent signals of DIG-labelled PCR products were detected on slot blots and recorded with a sensitive charge coupled densitometric camera. Detection limit and correlation of chemoluminescent signals to initial target DNA concentration were evaluated. Detection of the beta toxin gene could be achieved with 100 ag C. perfringens DNA in the presence of 1 μg unspecific DNA. The semiquantitative DIG-PCR assay was used to evaluate the relative abundance of the beta toxin gene of C. perfringens type C in purified DNA extracts from intestinal samples of pigs, which were fed a wheat/barley diet (controls), supplemented with the antibiotic avilamycin (40 mg/kg feed), a xylanase (4000 U/kg feed) or a combination of both feed additives. The antibiotic treatment significantly reduced the amount of PCR product in ileal and colon DNA extracts. Xylanase supplementation significantly reduced the amount of PCR product in colon samples, but led to an increase in jejunal samples. From the results it is concluded, that the antibiotic inhibited growth of C. perfringens type C in the ileum and colon of pigs. The semiquantitative DIG-PCR assay can be used to sensitively monitor the relative abundance of specific pathogens in the intestinal tract.

The aim of this study was to determine whether the inclusion of a condensed tannin (quebracho tannin, QT) and/or the elevation of dietary protein could reduce Trichostrongylus colubriformis establishment and existence in the small intestine of lambs. Thirty-six lambs (mean liveweight 32·6±3·9 kg) were randomly allocated to one of six experimental groups, groups 1–5 were parasitized with a trickle infection of 3000 infective Trichostrongylus colubriformis larvae daily, whilst group 6 remained as uninfected controls. Experimental diets were formulated to contain 222 g CP/kg (high protein) or 97 g CP/kg (low protein) with or without the inclusion of 50 g QT/kg. All six animal groups were fed the low protein diet, group 2 fed low protein diet+QT, for one month prior to infection (groups 1–5). Once nematode eggs were observed in the faeces, diets were abruptly changed in three experimental groups. Group 1 remained on the low protein diet, group 2 remained on the low protein+QT diet, group 3 changed to the high protein diet, group 4 changed to the high protein+QT diet, group 5 changed to the low protein+QT diet and group 6 remained uninfected and fed the low protein diet. Production, haematological and parasitological parameters were monitored at regular intervals. Results show that parasitized animals fed the high protein diet achieved growth rates similar to those of uninfected low protein-fed lambs. Inclusion of dietary QT did not depress liveweight gain. Total daily faecal egg counts declined after feeding the high protein diet. Inclusion of QT into the low protein diet also reduced faecal egg counts to similar levels observed in the high protein-fed lambs. The inclusion of QT into the high protein diet did not further reduce faecal egg counts. No significant differences in the haematological parameters measured were observed between infected animals (groups 1–5), suggesting that the beneficial effect of dietary QT in the low protein diet is unlikely to be mediated through an immune response. These data suggest that the inclusion of QT in low protein diets may be an alternative to feeding high protein diets to reduce nematode burden in lambs.

A study on the use of quebracho tannins as chemical additives was carried out at the Spanish Council for Scientific Research, León, Spain during 1998 by conducting two experiments. In the first experiment, three ruminally cannulated ewes were used to determine in situ degradability of soya bean meals (SBM) treated with different doses of quebracho tannin. Samples were prepared by spraying 100 g SBM with 100 ml distilled water containing 0, 1, 5, 10, 15 or 25 g of commercial quebracho powder (S0, SQ1, SQ2, SQ3, SQ4 and SQ5, respectively). Intestinal digestibility of non-degradable protein was estimated in vitro. The rapidly degradable protein fraction of all quebracho treated soya bean meals was different (P<0·05) from the non-treated SBM (S0: 0·154), with values ranging from 0·032 to 0·133. SQ4 and SQ5 showed lower fractional rates of degradation of the protein than S0 (0·042 and 0·046 v. 0·082, respectively). By contrast, in vitro digestibility of the non-degradable protein was not significantly affected by the treatments imposed, with the exception of treatment with the highest dose of quebracho tannin in which intestinal digestion was reduced (0·939 v. 0·826 for S0 and SQ5, respectively. P<0·05). In the second experiment, ten ruminally cannulated ewes were used to examine the effect of a daily dosing of quebracho tannin into the rumen on the degradation of the quebracho-treated SBM. Long-term dosing of quebracho tannin did not increase the ability of the rumen microbes to degrade tannin treated SBM. It was therefore concluded that quebracho tannins could be used as chemical additives for improving the digestive utilization of protein-rich feeds in sheep.