Cassava root rot (CRR) disease associated with a complex of soil pathogens has caused great yield losses in the crop. The objective of the current work was to obtain insights about the genetic architecture of CRR resistance caused by Fusarium (dry root rot – DRR), Phytophthora (soft root rot – SRR) and Botryosphaeriaceae (black root rot – BRR) species, using genome-wide association studies (GWAS). Phenotyping data of 263 accessions (artificial inoculation) and 14 094 single-nucleotide polymorphisms (SNP) (missing data <0·10 and minor allele frequency >0·05) were used. The severity of CRR in peel and pulp was variable among accessions, but the pathogens that caused DRR were more aggressive. Broad-sense heritability ($h_g^2 $) was of medium magnitude for all groups of resistances for pathogens, with variation from 0·16 ± 0·019 (Fspp Pulp) to 0·31 ± 0·028 (Fspp Peel). The kinship matrix was used to correct for stratification as well as for clustering the accessions. Overall, this analysis showed that there was no relationship between agronomic traits and resistance to CRR and the four clusters obtained from kinship matrix. The GWAS identified 38 significant SNPs, of which eight and 22 are related to the severity of DRR in the pulp and peel, respectively. The other eight SNPs were associated with SRR-peel (1), SRR-pulp (1), BRR-peel (3) and BRR-pulp (3). Half of the SNPs associated with CRR resistance have functional annotations related to defence and response to pathogen attack as well as general cellular processes. The current study revealed that resistance to CRR is controlled by multiple loci with small effects, and significant SNPs can be used to identify putative genes that control these traits.

Between 1989 and 1993, 17 experiments tested the effect of cover crop species, sowing date and destruction date on cover crop dry matter (DM) yield, N uptake and on soil mineral nitrogen (SMN) content. All the experiments were carried out in Suffolk, Norfolk, Lincolnshire and Yorkshire on sandy-loam textured soils after crops of cereals or oilseed rape had been harvested. The largest DM yields were obtained with early sowings and averaged 1·6 t/ha. Cover crop N uptake was less dependent upon sowing date and averaged 35 kg N/ha. The average reduction in SMN was from 46 to 32 kg N/ha. Differences between cover crop species were small when compared with season/site variations.

Cereal cover crop DM yields were closely related to the thermal time accumulated from the first significant rainfall after sowing, whilst the yields of non-cereal cover crops were more affected by the moisture content of the soil at sowing. The amount of SMN in the soil at sowing had little or no effect on cover crop yield. The yields of cereal cover crops were much more predictable than those of non-cereal cover crops. Water usage by cover crops was estimated to be 20 mm/t DM and large cover crops delayed the onset of leaching and reduced the amount of water leached. However, even in dry autumns and winters, soils are likely to reach field capacity before the following beet crop is sown. Due to their large C[ratio ]N ratio (20[ratio ]1) little N would be mineralized after cover crop destruction. Cover crops comprising volunteer cereals and weeds often performed as well as the other cover crops and in most cases will be the most cost-effective cover crops.

A comparison is made, under similar cultural conditions in pot experiments, of the behaviour of a number of varieties of wheat, barley, rye and oats on two soils on which oats had previously displayed pronounced symptoms of manganese deficiency.

All of these cereals were found to develop disease symptoms on these soils, rapid recovery from which invariably took place after the plants had been sprayed with 1% manganese sulphate solution. Variations in deficiency symptoms in the different cereals are indicated and observations on the course of the disease throughout the season are recorded for some thirty-two varieties.

A review of papers on the statistical design and analysis of experiments published in the Journal of Agricultural Science, Cambridge, over the last 100 years is presented. The development of significant ideas in the practical design of field experiments is reviewed. Some possible future developments in the design of spatial field trials and computer-aided design of experiments are discussed.

The present study compared slug, earthworm and carabid beetle abundance and slug damage to plants in minimum tillage (MT) and conventional tillage (CT) autumn-sown cereals. Winter barley was sown by CT and MT for 3 years followed by winter wheat for 6 years on a light-textured soil (Trial 1). Each cultivation was split so that straw was incorporated into the soil during cultivation in one split while the other did not receive straw. A similar investigation with winter wheat, over the same period, was undertaken on a nearby heavy-textured soil (Trial 2). The effects of method of cultivation and soil incorporation of straw on slug abundance and damage, and on earthworm populations were measured. Additionally, at Trial 1, the effects of cultivation and straw treatments on carabid beetle occurrence were measured in years 5–9. Over the 9 years, the method of cultivation had a significant effect on slug numbers in each trial. Slugs were more numerous in MT than CT plots, significantly so in 3 of the 9 years in Trial 1 and in 5 years in Trial 2. In Trial 1, slug numbers were significantly greater on no-straw than straw plots in 3 years as well as for the 9 years combined. Slug numbers did not differ between straw and no-straw plots in Trial 2. Slug numbers varied significantly between years and were influenced by factors other than the method of cultivation and straw application. Slug damage to seed and seedlings was quite low in each year (1–2%). Slug damage to cereal leaves at GS 23 was widespread in both trials, and severe in some years. MT had more leaf damage than CT in 5 of the 9 years in each trial, significantly so in 3 years in Trial 1 and in 4 years in Trial 2. Straw did not affect leaf damage in either MT or CT. Slug damage was not related to, nor did it affect either ear density or grain yield. The dominant slug species was Deroceras reticulatum. Earthworm numbers were significantly greater in MT than CT, for combined years, in each trial. Annually, these differences were significant for 5 years in Trial 1 and 2 years in Trial 2. Straw plots had significantly more earthworms than no-straw, for combined years, in each trial. The latter differences were significant for 5 years in Trial 1 and 3 years in Trial 2. In MT, the positive effect of straw on earthworm numbers was significant in Trial 2 but not in Trial 1. In CT, the latter effect was significant in each trial. Lumbricus species were more numerous in MT than CT and in straw than no-straw treatments. The impact of cultivation on numbers of carabid beetles was species-specific. The large beetle, Pterostichus melanarius, was significantly more numerous in MT than CT in 2 of the 5 years and for the aggregate of 5 years. Small carabids (Bembidion species and Trechus quadristriatus) were significantly more abundant in CT than MT in 3 of the 5 years as well as for the aggregate of 5 years. Straw did not affect the number of any or all carabid species either for combined cultivations (MT + CT) or within either MT or CT. It is concluded that MT increases slug numbers, slug damage and earthworm numbers relative to CT cultivations. MT favours large carabid beetles and CT favours small beetles. Straw incorporation increases earthworm numbers but not slugs, slug damage or carabid beetles. Slug damage to cereal leaves does not affect ear density or grain yield in either MT or CT crops when sown to a depth of 40 mm and before 18 September.

A model of reproductive performance was developed to study the influences of breeding management decisions and animal characteristics on the reproductive performance and the calving distribution in a beef herd. In the model, reproductive performance is formalized as a sequence of events (parturition, ovulation, conception), each of which modifies the reproductive status of the simulated cow. With respect to reproduction, a cow can be in one of three possible states: open-not-cycling, open-cycling or pregnant. The length of the different intervals that are included between two successive reproductive events (calving to first cycle interval, length of oestrous cycles, calving–conception and calving intervals) is formalized using stochastic or empirical laws that may be influenced by numerous animal or environmental factors or by management decisions (feeding strategy, breeding season and length of the breeding period). Within the herd, cows are considered to differ from each other by their parity, calving date, body condition at calving and their bull exposure.

Calving to first oestrous interval (postpartum anoestrous interval (PPAI)) is expressed as the sum of three equations which formalize the respective effects of calving date, body condition score at calving (BCScalving) and the response to early bull exposure in interaction with BCScalving. The influences of these variables on reproductive performance were quantified by analysing data sets (three bibliographical and two experimental) or by expertise. Special attention was paid to the influence of calving date on PPAI and a biological interpretation of this effect is proposed. Probabilities of natural insemination success were estimated according to the number of oestrus and the number of matings.

The model was fitted to data from primiparous Charolais cows (n=139) bred at the experimental station Laqueuille (French National Institute for Agricultural Research (INRA)). Its ability to simulate PPAI was tested using an independent data set of primiparous Charolais cows (n=188) from the experimental farm Le Pin. The model only accounts for 39% of the observed inter-individual variability. However, the analysis of the mean square deviation components led to validation of the structure of the model. In particular, the assumption that the influence of calving date on PPAI can be attributed to a sensitivity of the reproductive function to the variation of the photoperiod during the month preceding parturition was confirmed. Simulations also revealed that fat cows could have similar anoestrus to thin cows when they are exposed early to a bull. Such a result emphasized the necessity to investigate further and better calibrate the combined effects of BCS at calving and bull exposure on PPAI.

During the last sixty years numerous percolation and evaporation experiments have been made in this country and elsewhere. The method employed has been that originally used by Dalton, which has the advantage that the chemical and physical properties of the soil may, if desired, be thoroughly investigated. In addition to these experiments in which the evaporation from the soil, or from the soil with vegetation, is estimated by deducting the amount of drainage from the rainfall of the same period, numerous determinations of soil moisture have been made in the United States, from which evaporation may be directly determined. The difference between the estimated evaporation and the rainfall gives of course the amount of percolation.

In field experiments carried out over a period of three years studies were made of the effects on soil moisture characteristics and crop yields of incorporating pulverized fuel ash into the surface 30 cm of a sandy loam and a coarse sand. Ash from two different sources was used at rates equivalent to 0, 125, 251, 502 and 753 t/ha and crops of carrots, lettuce, radish and red beet were grown.

On every occasion when determinations were made the available-water capacities of the soils treated with 251 t/ha or more of ash were greater than the untreated soils; the largest increase (93%) was obtained with the highest rate of ash. Moisture release characteristics indicated that the increased amount of available water was retained in the soils at matric suctions between 0·05 and 1·0 atmospheres.

Despite the increased amount of available water retained in these soils there was generally no beneficial effect on crop growth and yields.

Weekly blood samples were collected from 42 Friesian cows between 5 weeks before and 10 weeks after calving, and analysed for serum cholesterol, albumin, total protein, glutamate-dehydrogenase, sorbitol-dehydrogenase and ornithine-carbamyl-transferase and blood glucose.

Cholesterol concentrations increased 2½-fold during the first 8 weeks of lactation. There was also a transient decrease in glucose concentration at calving, but there was no relationship between conception rate and the concentrations of these two constituents.

Albumin concentrations decreased at calving in some but not all cows and remained low for up to 2 weeks. Average concentrations of albumin determined by two analytical methods, a HABA dye-binding and a single radial diffusion assay method, were significantly lower (P < 0·05) between 0 and 2 weeks post-partum in eight cows which required four or more services than in 32 cows which conceived after fewer services. Similarly, the average decrease in concentration over calving was greater in those cows which conceived only after four or more services (P < 0·01).

Globulin concentrations (total protein minus albumin) decreased during the 5 weeks before, and increased in the 3 weeks following calving. The net change over calving was significantly related to conception rate, and the albumin/globulin ratio was reduced (P < 0·001) in the eight cows requiring four or more services.

Activities of all three enzymes doubled after calving, but there was no correlation between these increases and the decreases in albumin concentration, suggesting that, if liver insufficiency is a factor, it is probably due to malfunction rather than tissue damage.

The withdrawal of food from Clun Forest ewes pregnant with twins produced signs of pregnancy toxaemia accompanied by a significant decrease in the concentration of glucose, a significant increase in the concentration of ketones, non-esterified fatty acids (NEFA) and 3-hydroxybutyrate in plasma and a significant decrease in total entry rate and irreversible loss of glucose. A single intramuscular injection of 0·05 or 0·2 mg/kg of triamcinolone acetonide had no significant effect on the concentration of glucose, ketones or 3-hydroxybutyrate in plasma or on the total entry, irreversible loss or recycling of glucose in ketotic or in normal pregnant sheep. The low dose had a significant effect on the concentration of NEFA in plasma. Recovery from the clinical signs was slow after either dose of steroid but appeared to be hastened by the onset of parturition which was more rapid after the higher dose.

Assuming a uniform heavy soil, without tilth, the water movement in which obeys diffusion laws, expressions have been deduced for four quantities, starting with a known moisture profile.

(a) The moisture profile at any subsequent time in the absence of rainfall or irrigation (neglecting evaporation, transpiration, and any other source of loss of moisture).

(b) The moisture profile at any subsequent time during such rainfall as causes flushing of the drains.

(c) The minimum rainfall necessary to cause flushing of the drains (maximum acceptable rainfall).

(d) The acceptable rainfall after a period of recovery following the previous drainage period.

A screenhouse study in Haryana in 1986/87 evaluated the effect of boron on the wheat cultivar WH147 grown in pots in a sandy soil at three salinities. Before sowing, 0–9 mg B/kg soil was added. Without added B the crop produced significantly more grain at electrical conductivity of the saturation extract (ECe) 6 dS/m than at other salinities, but at ECe 8 dS/m yields were similar to those in nonsaline (ECe 0·8) soil. Grain yield in nonsaline soil was not affected significantly even at the highest concentration of added B, even though at the boot stage the shoots had accumulated as much as 307 mg B/kg. At ECe 6 and 8 dS/m, grain yield was significantly less with 3 and 1 mg added B/kg, respectively, than without added B, even though the B concentration in the shoots was only 72 and 31 mg/kg, respectively. The results indicated that B tolerance decreased with increasing salinity of the soil, even though B absorption by plants was 24–62% less in saline than in nonsaline soil at similar B concentrations. As B and salinity often occur together, threshold values of B in soil and plants for optimum growth of wheat will differ with the ECe of the soil. The results suggested that Ca:B ratio in wheat straw is not a reliable indicator of B toxicity in the soil.

Genetically modified (GM) plants expressing Bt toxin provide protection against lepidopteran pests. The only GM crop in Pakistan is Bt cotton, which was illegally imported and adopted rapidly by cotton producers. Farmers gained access to the seed of many unapproved Bt genotypes before the matter was picked up and formal approval granted by the relevant governmental agencies. The present study was conducted to evaluate the samples of Bt cotton, collected from farmers and seed dealer, for transgene integration and expression. Seeds of 52 cotton genotypes, labelled as Bt, were collected from various farmers and seed dealers. An immunoblot strip test was carried out, which showed that only 0·86 of the samples collected were synthesizing Cry1Ac toxin. According to multiplexed polymerase chain reaction (PCR) results, 0·86 of the genotypes tested were positive for the Mon531 event (an ‘event’ is a specific genetic modification in a specific species) and 0·14 were negative for any transgene. Transcript analysis of transgenes in positive genotypes by real-time Rt-PCR confirmed the synthesis of mRNA in all genotypes but with significant variation. The concentration of Bt toxin revealed by enzyme linked immunosorbent assay (ELISA) showed that only 0·02 genotypes had the reported optimum level. The real-time PCR and ELISA results further confirmed the attenuation of transgene expression at transcriptional and translational level by various internal and external factors. The same type of event was found in all genotypes, with significant variation in toxin level, revealing the impact of genetic background on transgene expression. The findings support the recommendation to improve the existing quality criteria for transgenic cotton variety approval and certification in Pakistan, with the inclusion of toxin concentration in the list of parameters to be considered.

Selection for specific adaptation in a breeding programme may be required when significant genotype×environment (G×E) interaction occurs within a target production region. Knowledge of the key stress factors underlying the G×E interaction permits delineating a production region into homogeneous zones for the purpose of recommending specific varieties. Twenty-eight cowpea genotypes were evaluated in 2002 and 2003 at four locations in the Guinea and Sudan savannah zones of Ghana, to assess grain yield stability and its relationship with intensity of stress in each production environment. Data were analysed in a year-location cross-classification, producing eight environments. Significant variations were observed between the genotypes for grain yield and grain yield components, biomass production, days to maturity, and resistance to Striga, pod-sucking bugs, and bacterial blight severity. Across environments, stress intensity (in terms of grain yield) was negatively correlated with the genotypic and error variances but positively correlated with the phenotypic, genotypic and experimental coefficients of variation. Stress intensity was also negatively correlated with heritability for grain yield. Genotypic correlations for grain yield between locations were moderate to high. The b-value as a measure of yield stability showed positive correlations with mean yield over all environments, and also with average yield in each of the three most favourable locations. In the least favourable location, the b-value showed a weak inverse relationship (P=0·10) with grain yield. Although direct selection for grain yield was considered superior in the target environments, simultaneous selection for grain yield and tolerance to stress in the less favourable environments will identify genotypes broadly adapted to the major cowpea growing regions.

The graphical and statistical analyses of competition diallels devised by Durrant were applied to an experiment investigating competition between four spring-wheat varieties. The results indicated that at low seed rates mixtures between varieties having a wide phenotypic difference between them in competitive characters, such as height and early maturity, could significantly outyield pure-stands of the component varieties. However, the results of a second experiment, in which these mixtures were grown at a range of seed rates, indicated that the yield advantage of mixtures over pure-stands was unlikely to occur at normal seed rates.

It is suggested that, at the low seed rates likely to be used in growing F1 hybrid wheat crops, mixtures of F1 hybrids and male parental lines might achieve very nearly the same yield as the pure F1 hybrid variety with a seed bulk that was cheaper to produce.

Four varieties of rice straw, MRl, MR71, MR84 and MR27, were separated into the following botanical fractions; inflorescence, stem, leaf blade and leaf sheath. The relative proportion of each fraction in whole straw was estimated and analysed for its chemical composition and in vitro digestibility (IVD). The composition and IVD of whole straw was then calculated. Cluster analysis showed that MRl was distinct from the other varieties. This could be attributed to a high proportion of stem (32·3%), high IVD (36·9%), low insoluble ash (4·0%) and a low silica content (2·7%) in the whole straw. The genetic distance between any two varieties ranged from 5·4 × 10-3 to 47·8 × 10-3 and was largest between MRl and the other varieties. Cluster analysis also showed that within a variety, the chemical composition and IVD of the stem, leaf blade and leaf sheath were similar, suggesting that sampling errors may be reduced if the inflorescence, which comprises 7–13% of the whole straw, is excluded when the material is analysed. Stepwise and canonical discriminant analyses indicated that the important variables to be measured when comparing straw varieties were IVD, crude protein and insoluble ash.

1. Follicular fluid was collected by aspiration from the ovaries of cows which had been treated with pregnant mare serum, and were killed 3–4 days after heat.

2. Various chemical determinations have been carried out with samples of follicular fluid which, amongst others, was found to contain 39–43 mg./ 100 ml. of glucose, between 13 and 95 mg./100 ml. of lactic acid, and 0·8–3·0 mg./100 ml. of ascorbic acid.

3. The effect of follicular fluid upon sperm fructolysis was examined; however, no effect other than that due to the glucose content of the follicular fluid, could be observed.

Tomato leaf curl virus (TLCV) is a major viral disease in tomato that causes quantitative and qualitative losses to the crop. One hundred and fifty three tomato genotypes were screened for three consecutive years (2006–09) under glasshouse and field conditions for TLCV resistance. The incidence of disease was higher during the Rabi season as compared to the Kharif season trials. The reactions of different genotypes were studied by artificial inoculation. Based on the coefficient of infection, nine genotypes (viz. EC-520049 (Solanum chmielewskii), EC-520058, EC-520060 and EC-520061 (S. habrochaites), EC-520070, EC-520071, EC-520077, EC-520079 (S. pimpinellifolium) and H-88-78-1(S. lycopersicum; a derivative of S. habrochaites f. glabratum) were found to be highly resistant in both environments. H-88-78-1 was used for inheritance studies during 2008–10. Using F2 Mendelian segregation, populations showed a 3 (resistant):1 (susceptible) ratio for TLCV disease and were proposed to have both additive and dominant non-allelic gene interactions for various traits.

The problem of sheep grazing in the deserts of Rajasthan is that animals do not get drinking water for 2–3 days at a time. Studies carried out at this Institute, on water deprivation in sheep, have indicated that sheep deprived of water for 72 h did not show any adverse effect on wool yield, in spite of the fact that water deprivation reduced feed intake (More & Sahni, 1972). The present experiment is a part of extensive studies carried out on water deprivation with particular reference to sheep production. The paper describes the influence of water deprivation on nutrient digestibility and nitrogen retention in sheep.

The feasibility of measuring lysine and protein nitrogen in barley using an infra-red reflectance analyser was examined. This is a very rapid technique, requiring no manipulative skills, and measuring several components simultaneously using milled grains. The results show that this instrument is sensitive to changes in lysine and protein nitrogen and can be calibrated to measure these components to a high degree of accuracy. It is shown that the gross morphological and biochemical abnormalities of high lysine mutants do not affect these measurements, indicating that this method is suitable for the rapid screening of material from breeding programmes designed to improve the lysine content of barley proteins.