Review of recent research on navy beans (Phaseolus vulgaris) in the United Kingdom

Navy beans are the raw material for ‘baked beans’. Since the 1960's a number of workers have attempted to introduce the crop to the United Kingdom. The paper reviews the results of research to date. In favoured areas of the United Kingdom yields of 300 g seed/m² may be expected in small-plot trials. The optimum plant spacing is between 20 and 30 plants/m² and dressings of about 150 kg/ha of N fertiliser are required for maximal yield. The nitrogen fertiliser may be dispensed with, at the cost of a small reduction in yield, if the seed is inoculated with an elite strain of Rhizobium phaseoli. In the United Kingdom the potential diseases of the crop include halo-blight (Pseudomonas syringae pV. phaseolicola), bean common mosaic virus, and anthracnose (Colletotrichum lindemuthianum). Genetic sources of resistance have been identified, and they are incorporated in some of the UK-bred material. It seems likely that the varieties with improved adaptation and disease resistance that are now available from the UK work will be useful to farmers in continental Europe. For the UK itself, some improvements in cold-tolerance and yield stability may still be required. The paper concludes with a discussion of the lessons to be learned from the project.     

Spatial and temporal distribution patterns of drifting pupal exuviae of Chironomidae (Diptera) in streams of tropical northern Australia

1. Periodic collecting of floating cast pupal cuticles of chironomids (exuviae) in two tropical northern Australian streams demonstrates (i) spatial heterogeneity in species composition across a wide stream, (ii) temporal heterogeneity in the maximum abundance of each species, and that (iii) species accumulate as a function of sample size and duration of sampling, 2. Spatial heterogeneity is ascribed to variation in larval microhabitat across the wide stream, combined with short exuvial drift duration and restricted upstream mixing. 3. Temporal heterogeneity is ascribed to diel periodicity in adult emergence and, as with spatial heterogeneity, to the short floating life. 4. The consequences of spatial and temporal variation for the sampling of exuvial drift are discussed in relation to the objectives of particular programmes. Thus, if the objective is assessment of chironomid species composition for inventory purposes such as faunistics or conservation, the large sample sizes attained by 24-h sampling are necessary and appropriate. However, for rapid assessment that requires comparable samples at different sites, species numbers may be optimized by temporally and spatially restricted sampling of the maximal emergence period, which in this study is at dusk, or by subsampling from a 24-h sample.     

An analysis of the seasonal variation in the dry seed yields of eleven cultivars of Phaseolus vulgaris

Nine determinate and two indeterminate-bush dry seed cultivars of P. vulgaris were grown in trials for four successive years. Mean annual yield of air dry seed (15% moisture content) varied between 222 and 398 g/m². Most of the annual variation in yield was accounted for by differences in the quantity of nitrogen fertiliser applied and in the duration of bright sunshine during August. The annual mean harvest date varied between 20 September and 9 October. There was a significant negative correlation between the mean harvest date and the number of Ontario heat units accumulated between 20 May and 20 July. There were significant interactions between genotype and environment for both yield and harvest date; joint regression analysis of the interactions showed that five of the cultivars, which had previously been identified as cold tolerant in laboratory tests, all showed greater stability of yield and of maturity date than standard navy bean types. Environmental variation in the yield components of the cold tolerant selections tended to be compensatory, while that of the standard navy beans was additive in its effects on yield.     

Genotypic and environmental correlations between leaf growth and bulb size in onions

Populations of onion breeding lines were grown in five field trials over 2 years. Measurements were made of leaf length, number of leaves produced during July and August, date of foliage collapse, plant density and bulb yield. Correlations and partial correlations between these attributes, separated where possible into genetic and environmental components, gave similar results from all trials. The genetic and environmental components of leaf length and earliness of foliage collapse were positively associated with yield. Partial correlations showed that short-leaved plants were lower yielding and later maturing than long-leaved selections, but that the effects were not attributable to correlations with plant density.     

Tropical acid streams – the chironomid (Diptera) response in northern Australia

1. Chironomidae, sampled by interception of drifting cast pupal exuviae, responded to inputs of acid, heavy metal-rich waters in a seasonally flowing tropical stream in northern Australia.
2. Responses included gain of distinctive (indicative) taxa, loss of some species typical of pristine conditions, and increase in species richness.
3. Experimental manipulation (upstream diversion) of a mine adit entry showed that these responses were the result of change in water quality.
4. The higher species richness at low pH, which is contrary to temperate studies, may be explained by the large tropical (Australian and south-east Asian) pool of species tolerant of naturally occurring acidic aquatic habitats.
5. The structure and responses of the exuvial-assessed chironomid community matched long-term larval data.     

Evidence of a latitudinal gradient in spider diversity in Australian cotton

The most common explanation for species diversity increasing towards the tropics is the corresponding increase in habitats (spatial heterogeneity). Consequently, a monoculture (like cotton in Australia) which is grown along a latitudinal gradient, should have the same degree of species diversity throughout its range. We tested to see if diversity in a dominant cotton community (spiders) changed with latitude, and if the community was structurally identical in different parts of Australia. We sampled seven sites extending over 20° of latitude. At each site we sampled 1–3 fields 3–5 times during the cotton growing season using pitfall traps and beatsheets, recording all the spiders collected to family. We found that spider communities in cotton are diverse, including a large range of foraging guilds, making them suitable for a conservation biological control programme. We also found that spider diversity increased from high to low latitudes, and the communities were different, even though the spiders were in the same monocultural habitat. Spider beatsheet communities around Australia were dominated by different families, and responded differently to seasonal changes, indicating that different pest groups would be targeted at different locations. These results show that diversity can increase from high to low latitudes, even if spatial heterogeneity is held constant, and that other factors external to the cotton crop are influencing spider species composition. Other models which may account for the latitudinal gradient, such as non‐equilibrium regional processes, are discussed.     

Selection for cold tolerance in Phaseolus vulgaris— yields of selected lines grown in warm and cool environments

Forty-eight F₄ families of a cross between two cultivars of Phaseolus vulgaris were grown in ‘warm’ and ‘cool’ environments in the field. The F₂ and F₃ generations had been assessed for cold tolerance using the test described by Hardwick & Andrews (1980). The mean seed yields of the F₄'s were 333 and 167 g m^-2 in the ‘warm’ environment (blackened soil surface, clear polyethylene mulch, windbreaks) and ‘cool’ environment (whitened soil surface, no mulch or windbreaks) respectively. The ratio of yields in the two environments was larger in families selected for cold sensitivity than in those selected for cold tolerance (values of ratio 2.28 to 1 and 1.76 to 1 respectively). The ‘warm’ treatment decreased the number of days between sowing and emergence from 15.6 to 8.6, increased the estimated weight per seedling axis at emergence from 544 to 904 mg/plant, and increased the weight/plant at flowering from 3.75 to 4.7 g. Plants from the ‘warm’ treatment had bigger leaf weights, smaller stem weights, more branches and bigger specific leaf areas than plants of the same weight from the ‘cool’ treatment. Differences in yield were due mainly to differences in the number of seeds produced/plant. Eleven F, families were grown in a simple yield trial the following year. The season was cooler and yields were reduced. The reduction in yield was greater in the cold sensitive than in the cold tolerant families.     

The Nitrogen Content of Plants and the Self-thinning Rule of Plant Ecology: A Test of the Core-skin Hypothesis

The ‘core-skin’ hypothesis postulates that secondarilythickened plants behave energetically as an inert ‘core’covered by an active ‘skin’, the ‘skin’being two-imensional, the ‘core’ three-dimensional.This would explain the ‘self-thinning ‘or‘–3/2’ rule of plant ecology, that is, the tendencyfor log (dry weight per plant) and log (number of plants perunit area) to progress along a straight line relationship, withslope = – 3/2’. The hypothesis was tested as follows. Plant nitrogen contentwas used as an estimate of the mass of ‘skin’ perplant, and dry weight as an estimate of the mass of the ‘core’.As plants mature the slope of the relationship between y = log(mass of nitrogen per plant) and x = log (mass of dry matterper plant) is expected to decline from an initial value of 1.0towards a final value of 0.66. The intercept of the relationshipis expected to reflect the intrinsic content of ‘skin’per unit of ‘core’. Genotypic variation in thisparameter should cause genotypic differences in the maximumattainable yield of biomass per unit area. The expectations were investigated by fitting the function y= p+qx+r exp – x to 30 sets of data on plant nitrogencontent, plant weight and time in 18 different vegetables. Simplelinear regressions of y on x were fitted to more limited setsof data on weights and nitrogen contents of mature trees. Theexpectations were, with some minor exceptions, confirmed. Nitrogen, yield, plant competition, self-thinning