Laboratory methods for studying non-preference resistance to cabbage root fly in cruciferous crops

A laboratory method for testing cruciferous plants for their non-preference resistance to cabbage root fly is described. Test plants were fully randomized on a turntable inside a large chamber containing cabbage root flies. The apparatus was housed in a controlled environment room. The root-fly eggs, laid in the sand surrounding test plants, were extracted using a flask flotation method which was quicker and more efficient than the stirring technique which it superseded. Two batches of plants were tested alternately, one being exposed to the flies, while the other was sampled for eggs. Each batch of test plants received three 1-day exposures to egg-laying, their positions within the test chamber being changed for each exposure to ensure complete randomization. This test method gave highly consistent results and indicated that there were differences in the flies' preference both between cultivars of radish and cauliflower and for individual plants within cultivars. Plants representing the extremes of preferences discovered in the two crops were saved for further study. It was not possible to correlate seed weight, time of seedling emergence, foliage surface area, or hypocotyl attitude in relation to soil level, with the egg-laying preference of the cabbage root flies.     

The development and yield of autumn- and spring-sown barley in south east Scotland

As part of a study of the relationship between plant development and grain yield, winter and spring barleys were sown in the autumn and spring. Apical development and leaf area development were monitored and the final yield was partitioned into grain weight and grain number. The photosynthetically active radiation (PAR) absorbed was calculated.
The main differences found were between sowings rather than between genotypes within sowings. The autumn sowing outyielded the spring sowing because the grains were heavier, although the autumn sowing tended to have fewer grains m^-2. In the autumn sowing the rate of initiation of spikelet primordia was slower, due to the lower temperatures encountered, but the initiation phase lasted longer and a larger proportion of primordia survived. However, the increased proportions of tillers to mainstem reduced the mean number of grains/ear.
The numbers of grains m^-2 and the yield were related to the PAR absorbed. In this analysis the earlier anthesis of the autumn-sown plants could be seen to be reducing the PAR absorbed and consequently the grains m^-2.     

Influence of cocksfoot streak virus on the growth of single cocksfoot plants

Healthy and streak-virus-infected cocksfoot plants of a single genotype were examined over a 2-year period. In the first year infection decreased tillering by about 40%, but in pot-grown plants individual tiller weights were 30% higher so dry-matter yield was decreased by only 10%. In the second year the larger tiller weights compensated completely for decreased tillering. No similar compensation was observed in field-grown plants. The virus had the largest effects when soil fertility was highest, healthy plants producing significantly greater responses to nitrogen effects, but potassium, at certain times of the year, produced larger tiller weights in infected than in healthy plants. Infection decreased dry-matter yield more in frequently than in infrequently cut plants. Infection greatly decreased the number of vegetative but not of fertile tillers. Infected plants tended to flower earlier and produced fewer, slightly smaller, viable seeds.     

The relationship between cabbage root fly egg laying and volatile hydrolysis products of radish

Radish populations selected from the cvs Asmer Tip Top and Sparkler on the basis of high or low preference by the cabbage root fly for egg laying were tested at different ages by exposing them to the pest in a laboratory test chamber. Results confirmed the existence of a cycle of changing attractiveness of radish for egg laying, the peak occurring as plants reached a marketable age. Selection within radish cvs for different levels of preference resulted in a shift in the cycle of attraction such that ‘high-preference’ plants reached a peak in attractiveness earlier than ‘low-preference’ ones. Egg laying was correlated with the total amounts of two volatile glucosinolate hydrolysis products (4–methylthio-3–butenyl isothiocyanate and 1–cyano-4–methyl-thio-3–butene) detected in ether extracts of macerated radishes. The relationship between chemicals and egg laying suggested a possible chemical assay to complement biological techniques for identifying cabbage root fly-resistant radish for breeding work.