Up until the 1940s chemical disease control relied upon inorganic chemical preparations, frequently prepared by the user. Key areas of use were horticulture and vegetable production with key targets being diseases that caused easily recognized damage. After this era and as the damaging effects of more crop diseases became obvious by the use of chemical control, the crop protection industry expanded rapidly and research to discover new active materials began in earnest. As new areas of chemistry were introduced, each one aiming to offer advantages over the previous ones, chemical families were born with research-based companies frequently adopting patent-busting strategies in order to capitalize on the developing fungicides market. Systemic fungicides offered new opportunities in disease control. The rise in Research and Development (R & D) and the increase in the number and quantity of chemicals being applied led to the introduction of regulation in the 1950s, initially on a voluntary basis, but now strictly controlled by legal obligations. In the 1960s, the market switched from horticulture and vegetables to one in which the main agricultural crops dominated. The cereal market, initially based on barley, moved to the current dominant market of wheat. The costs of R & D have risen dramatically in recent years and have become dominated not by the discovery process per se but by the provision of all the extra data needed to obtain registration. These rising costs happened at a time when markets showed little growth and are currently showing some decline. This has resulted in an industry that is continually striving to cut costs, normally by mergers and take-overs. As a consequence, many plant disease problems are not now being targeted by the industry and special measures have been introduced to ensure adequate disease control is available for these minor markets. Plant disease control will remain a necessity and fungicides will remain as a key factor in such control, although it is predicted that integrated control using chemicals, biological controls and biotechnology approaches will begin to dominate.

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.

A study of the commercial growing of different varieties of Bacillus thuringiensis (Bt) cotton compares the performance of growing official and unofficial hybrid varieties of Bt cotton and conventional (non-Bt) hybrids in Gujarat by 622 farmers. Results suggest that the official Bt varieties (MECH 12 and MECH 162) significantly outperform the unofficial varieties. However, unofficial, locally produced Bt hybrids can also perform significantly better than non-Bt hybrids, although second generation (F2) Bt seed appears to have no yield advantage compared to non-Bt hybrids but can save on insecticide use. Although hybrid vigour is reduced, or even lost, with F2 seed the Bt gene still confers some advantage. The F2 seed is regarded as ‘GM’ by the farmers (and is sold as such), even though its yield performance is little better than the non-GM hybrids. The results help to explain why there is so much confusion arising from GM cotton release in India.

Changes in the seed coat morphology of 12 annual legumes were studied using environmental scanning electron microscopy (ESEM). The seeds of Biserrula pelecinus L. cv. Casbah, Ornithopus sativus cv. Cadiz, Trifolium clypeatum L., T. spumosum L., T. subterraneum L. cv. Bacchus Marsh, Trigonella balansae Boiss. & Reuter., Trigonella monspeliaca L. and Vicia sativa subsp. amphicarpa Dorthes (morthes.) were examined by ESEM after exposure to field conditions for 6 months, while those of Medicago polymorpha L. cv. Circle Valley, Trifolium clypeatum L., T. glanduliferum Boiss., T. lappaceum L., T. spumosum L., and T. subterraneum L. cv. Dalkeith, were examined after 2 years' exposure. The entry of water into seeds was followed by covering various parts of the seed coat with petroleum jelly and soaking the treated seeds in dyes.

As the seeds softened over time, more and larger fractures appeared on the seed coat. Water entered the seed either through fractures, over the seed coat as a whole or through the lens. It is hypothesized that the formation of fractures occurs after physicochemical changes in the seed coat, probably associated with changes in the amount and nature of seed coat lipids.

The newly matured whole seeds of M. polymorpha cv. Circle Valley, T. clypeatum, T. glanduliferum, T. lappaceum, T. spumosum, and T. subterraneum cv. Dalkeith were analysed for lipid content in 1997. The seed coats of T. subterraneum cv. Dalkeith and T. spumosum were separated from the cotyledons and examined in detail for lipid content.

The lipid content of whole seeds ranged from 48 (T. lappaceum) to 167 mg/g (T. subterraneum cv. Dalkeith). Total lipid of the whole seeds of T. subterraneum cv. Dalkeith and T. glanduliferum declined by about 9 mg/g over 2 years, while in T. spumosum it declined by about 17 mg/g.

In contrast, the major fatty acids in the seed coat declined by 0·67 mg/g over the 2 years. Change in seed coat lipids showed a marked similarity to changes in hardseededness for both T. subterraneum cv. Dalkeith and T. spumosum. The results strongly suggest that seed softening is associated with loss of lipids in the seed coat, because lipids have physical characteristics that are altered at temperatures experienced in the field.

In cereal-livestock farming systems of North Africa and West Asia the straw of durum wheat [Triticum turgidum (L.) Thell. ssp. turgidum conv. durum (Desf.) MacKey] is frequently used for feeding animals during the dry season and may enhance the sustainability and the flexibility of farming in various respects. In Algeria the average sale price per unit weight of the durum straw is around 30% of that of grain. Six tall and 18 semi-dwarf locally well-adapted cultivars were grown in the season 2000/01 at five Algerian locations representing the main durum wheat cropping areas to verify: (i) the impact of straw yield on the economic merit of cultivars for recommendation and (ii) the interest of tall v. semi-dwarf plant types for breeding. The tall material comprised four cultivars derived from local landraces and two old varieties. The semi-dwarf germplasm originated from CIMMYT, ICARDA or various Mediterranean countries. In the economic assessment the straw value was expressed in terms of grain-equivalent, defining an economic yield as: grain yield+(0·30×straw yield). The merit of individual cultivars was markedly affected by ignoring or taking into account the straw yield. On average, tall germplasm had a moderate (about 3%) but significant (P<0·02) economic advantage over semi-dwarf material as a result of much higher straw yield (+25%) and aerial biomass (+12%) and somewhat lower grain yield (−7%). However, three semi-dwarf varieties from CIMMYT were top-ranking for economic yield. They possessed outstanding aerial biomass and similar harvest index compared with the mean response of other semi-dwarf germplasm. On average, the tall germplasm showed higher grain yield stability (P<0·01), lower straw yield stability (P<0·01) and slightly higher stability of economic yield (P<0·11) than the semi-dwarf group as measured by Shukla's stability variance. Grain yield was negatively correlated with straw yield (r=−0·41, P<0·05), and was not correlated with aerial biomass, in the whole set of cultivars. However, it was not correlated with straw yield, and was positively correlated with aerial biomass (r=0·61, P<0·01), within the semi-dwarf germplasm. Information on straw yield can improve the targeting of cultivars for cereal-livestock farming systems. Breeding for these systems may target either a tall type within semi-dwarf material (i.e. a ‘tall dwarf’), or a truly tall plant type.

Glucosinolates and their hydrolysis products are of great concern because they are responsible for many of both the beneficial and harmful properties of glucosinolate-containing plants. Cabbage (Brassica oleracea L.) is a species highly consumed as a leaf vegetable in many countries showing high qualitative and quantitative differences in glucosinolate composition among cultivars. The standard analytical techniques for determining glucosinolate composition using conventional methods lead to high costs, labour input and delays, all of which affect both the availability of data and the taking of swift decisions. In contrast, near-infrared spectroscopy (NIRS) has emerged as a rapid and cost-effective technique of analysis for many agro-food products. In this work we test the potential of NIRS for screening the total glucosinolates (t-GSL), gluconapin (GNA), gluconasturtiin (GNAST) and neoglucobrassicin (NGBS) contents of cabbage leaf cultivars coming from Portugal and Spain. NIRS calibrations resulted in coefficients of determination and standard deviation to standard error of cross-validation ratio of 0·83 and 2·38 for t-GSL; 0·70 and 1·85 for GNA; 0·62 and 1·63 for GNAST; and 0·60 and 1·58 for NGBS, respectively. An examination of the loadings of the equation for t-GSL suggested that O-H groups of water, C-H combinations of the methylene group and also N-H groups of amides were the molecular associations most strongly used in modelling total glucosinolates. It was concluded that NIRS shows a high potential as an analytical method for total and individual glucosinolate routine analysis in cabbage.

Chemical-mutagen treatment of Ethiopian mustard (Brassica carinata A. Braun) line C-101 seeds (which contained about 441 g/kg C22[ratio ]1) led to isolation of a mutant, L-935, which contained about 190 g/kg erucic acid (intermediate C22[ratio ]1) in the seed oil. The objective was to determine the inheritance of the intermediate C22[ratio ]1 level in this mutant. The mutant L-935 was reciprocally crossed to C-101 and to the mutant line L-2890 (which contained 112 g/kg C22[ratio ]1; low). The F1, F2 and BC1F1 generations were obtained. Cytoplasmic effects were not observed in any of the crosses. The analysis of the fatty acid composition in the F2 populations from the crosses of L-935 with C-101 revealed a segregation pattern fitting a ratio 1[ratio ]2[ratio ]1 for intermediate, high and very high C22[ratio ]1 content. The segregation patterns fitted a one-locus (designated M2) model with two alleles (M2 and mi) and with partial dominance of high over intermediate C22[ratio ]1 content. The segregating generations of the crosses L-935×L-2890 showed a strong transgressive segregation with C22[ratio ]1 values ranged from 1·3–406·5 g/kg. The analyses of the F2, BC1F1 and F3 generations indicated that the combination of alleles at two loci, M1 and M2 controlled the transgressive segregation for C22[ratio ]1 content. The proposed genotypes (C22[ratio ]1 content) for each parent were as follows: L-935 (190 g/kg 22[ratio ]1)=MMmimiEEEE; L-2890 (112 g/kg C22[ratio ]1)=mmmmEEEE; and C-101 (441 g/kg C22[ratio ]1)=MMMMEEEE.

Few methods exist for estimating quantitatively the diet composition of free-ranging herbivores. The current study examined whether long-chain fatty alcohols (alcohols) or long-chain fatty acids (acids) could be used along with n-alkanes to allow reliable diet composition estimates to be made in herbivores consuming complex diets. Twelve Scottish Blackface wether sheep housed in metabolism crates were fed four different mixtures of three plant species (three animals per mixture) for a seven-period experiment. Concentrations of cuticular wax n-alkanes, alcohols and acids were estimated in samples of individual plant species, and the faeces from animals that consumed mixtures of these species. These concentrations were then used to calculate the dietary proportions of each species by a least-squares optimization procedure. To explore the differences between the estimation methods (individual markers and their combinations), the mean squares of errors (EMS) between the actual and predicted proportions of plant species were calculated.

In three out of the four mixtures, alcohols had the lowest discrepancies (lowest EMS values), followed by n-alkanes and then acids. Acids yielded the lowest discrepancy in one mixture and the highest in the others.

It is concluded that, for this particular set of mixtures, alcohols had great potential to estimate composition of complex diets. However, the estimation using acids was less good and n-alkanes were of intermediate potential. Estimation from the combination of the three marker classes was always better than using the poorest individual marker.

An experiment was conducted at the University of KwaZulu–Natal to assess the effect of constant photoperiods on sexual maturity and egg-laying performance in broiler breeders given two levels of control-feeding during the rearing phase. Cobb broiler breeder females were grown to reach 2·1 kg body weight at 17 or 21 weeks, and maintained on 10, 11, 12, 13, 14 or 16-h photoperiods from 2 days to 68 weeks of age. There were no significant interactions between photoperiod and growth rate for any production parameter. The time required reaching 2·1 kg increased proportionally with photoperiod but, because of delayed sexual development, birds on longer photoperiods consumed more feed to, and were heavier at, sexual maturity than shorter daylengths. The longer-photoperiod birds also had inferior rates of lay in the first half of the cycle, but superior in the second, which, together with the photoperiodic effects on maturity, resulted in birds on 11, 13 or 14 h producing most eggs to 68 weeks, and those on 16 h fewest. It is possible that the pattern of egg production was due to some of the birds on [ges ]13-h photoperiods becoming photorefractory, having a mid-cycle pause, and then spontaneously resuming egg production in the latter half of the cycle. However, a hinge-analysis of current and other data to the more usual depletion age of 60 weeks showed that the combined effects of photoperiod on sexual maturity and egg production resulted in constant 10-h birds producing the highest number of eggs, with numbers decreasing by 3·6 eggs/h of photoperiod above the hinge and 7·8 eggs/h of photoperiod below it. Mean egg weight increased by 0·4 g/h of photoperiod, but the proportion of abnormally large and floor eggs and the incidence of mortality were unaffected by daylength. For each photoperiod, accelerated growth resulted in body weights being heavier than controls at sexual maturity, despite the mean age at maturity being 10 days earlier for the faster-growing birds. Body weights for the two growth groups were not significantly different at 68 weeks. Faster-growth birds consumed 1 kg less feed to 2·1 kg body weight, but 1·3 kg more feed to sexual maturity and 2·7 kg more to 68 weeks, and produced 6 more eggs than, but had similar patterns of egg production to, the conventionally managed controls. Mean egg weight, the proportion of floor eggs and the incidence of mortality were similar for both groups. Notwithstanding that the overall production of abnormally large eggs was low (1·1 eggs per bird); the faster-growing birds produced significantly more than the controls. Egg weight was positively influenced by age at sexual maturity, body weight at sexual maturity and photoperiod, but was unaffected by rate of growth to 2·1 kg per se.

These findings show that there are differences between broiler breeders and egg-type pullets in their response to constant photoperiods. It is likely that the factors responsible for these differences, particularly in terms of sexual development, are the exhibition of photorefractoriness by, and the retardational effects of controlled feeding on, broiler breeders.