SUMMARYThe effects of two levels of irradiance and of water supply on grain development in two cultivars of winter wheat were studied by imposing treatments during the phases of cell production and cell expansion in the endosperm. The storage capacity of the grain was determined by cell number in the endosperm, which was reduced by both treatments during the cell production phase. Changes in cell number caused by the treatments were due to changes in the rate of production of cells; the duration of the cell production phase was constant. Weight per grain at maturity was proportional, both within and between cultivars, to the number of endosperm cells, except when treatments altered the supply of assimilate to the grain during the cell expansion phase.Reducing irradiance and water during the cell expansion phase decreased the rate of accumulation of dry matter in the grain and reduced weight per grain at maturity, with no effect on the duration of grain filling. Shrivelled grain resulted from a failure of the endosperm cells to fill completely, and was characterised by a reduction in the number of ‘B’‐type starch granules.

A preliminary screening was made of many lines of white clover to find a line suited to New Zealand conditions, with resistance to the stem nematode (Ditylenchus dipsaci).A rapid screening technique developed for seedlings by Scandinavian workers was modified to give results which related to field resistance studies.The effects of inoculation varied with age of seedling, unsatisfactory results being obtained if plants were inoculated too soon after germination. Varieties differed in their relative susceptibilities to the white clover and red clover races of nematodes.Screening has revealed several lines relatively resistant to stem nematodes. and these have now to be tested for agronomic type. INTRODUCTIONThe varieties of Trifolium repens L. (white clover) in general use in New Zealand pastures have been found to be susceptible to infestation by the Ditylenchus dipsaci (Kuhn) Filipjev. stem nematode (Barclay and Williams, unpublished). In a spaced plant study a Ladino white clover and a variety of Moroccan origin possessed high resistance to such infestations, but both were considered to be too open in habit to be useful in New Zealand pastures. Furthermore, crosses made between these resistant types and those in general use produced hybrids which were often resistant to stem nematode but relatively open in habit (Barclay and Williams, unpublished).To make rapid progress in breeding agronomically desirable, nematode-resistant white clovers, many plants may need to be screened for resistance. The present study describes further suitable modifications to a laboratory screening technique devised and modified by Frandsen (1951), Bingefors (1957), Dijkstra (1956), Grundbacher (1962), and Hanna and Hawn (1956. Results of screening a wide range of white clover varieties and ecotypes with the modified technique are described.

INDEX WORDSLupinus albus, alkaloid, mutants, genetic control. SUMMARYThe pattern and concentration of component alkaloids in wildtype and mutant genotypes homozygous for the alleles pauper, exiguus and nutricius in L. albus have been determined. Alkaloid production in genotypes homozygous for identical and complementary alleles have been determined. The study has revealed at least two alleles possessing different effectiveness in reducing alkaloid levels at the pauper locus, and the frequency distribution of alkaloid concentration in F2 indicates dominance of the high-alkaloid allele is incomplete. Seven alkaloids were identified in the wild-type genotype, of which four were found in all homozygous mutant genotypes in approximately similar proportions. The mutatiol3s identified by means of the Dragendorff reaction appear to affect a common substrate without affecting the amount of the different component alkaloids that are produced.

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Data on the level and composition of protein and oil in L. albus, L. angustifolius, L. luteus and L. mutabilis are presented. Correlations between a range of physiological characters and seed yield are given and the results of selected hybridisations are discussed.