The Agricultural Research Service, U.S. Dept. of Agriculture, stonefruit breeding program in Fresno, Calif., is developing freshmarket Japanese-type plums (Prunus salicina Lindl.). The fruit crosses among plums were made in 1955. Since then, >62,000 seedlings have been grown and five cultivars released: 'Queen Rosa', 'Frontier', 'Friar' (Weinberger, 1975), 'Calita', and 'Blackamber' (Ramming and Tanner, 198 1). Currently, 'Friar' and 'Blackamher', both black plums, make up 25% of the 222,000 tons of fresh plums produced in California [California Tree Fruit Agreement (CTFA), 1990]. As a result, black plum prices usually are depressed during midseason, when 'Blackamber' and 'Friar' are ripe. Therefore, growers have been looking for red plum cultivars that command a higher market price. 'Fortune' plum (Fig. 1), a large, red, Japanese-type plum hybrid, has been released to provide an attractive, shiny, bright-red plum for the midseason market to complement the abundant supply of black plums.

We study a class of generalisations of Thompson's group V arising naturally as topological full groups of purely infinite, minimal groupoids. In the process, we show that the derived subgroup of such a group is 2-generated whenever it is finitely generated and has no proper characters in full generality. We characterise this class of groupoids through a number of group-theoretic conditions on their full groups including vigor, the existence of suitable embeddings of V , and compressibility. We moreover give a complete abstract characterisation of those groups that arise as either topological full groups or derived subgroups of purely infinite, minimal groupoids. As an application, we describe all proper characters of the Brin-Higman-Thompson groups.

‘Nemared’ is a new peach rootstock [Prunus persica (L.). Batsch] that combines vigorous growth in the nursery to permit early budding, root-knot nematode resistance, and red leaves to facilitate identification (Fig. 1).

‘Castlebrite’ is an early-maturing apricot (Prunus armeniaca L.) for the fresh market with exceptional color and firmness. The fruit ripens toward the end of May, with ‘Pinkerton’ and about 4 weeks before ‘Blenheim’.