HYBRID ASPARAGUS CULTIVARS - REGIONAL SUITABILITY AND PRODUCTIVITY FOR PROCESSING AND FRESH EXPORT IN WAIKATO, NEW-ZEALAND

The green spear production characteristics of 26 European and United S tates asparagus (Asparagus officinalis L.) hybrids were compared with those of the open-pollinated cultivar 'Mary Washington 500W'. The high er numbers, weights, and proportions of marketable grade spears produc ed by the United States hybrids 'Jersey Giant', 'Jersey King', and 'UC 157' and by the Dutch hybrids 'Limbras 10' and 'Limbras 26', increased processing and fresh export yields by 50-150% and 160-450% respective ly. 'Jersey Giant', with earlier production and higher Stemphylium dis ease resistance, was the most productive. 'Limbras 10' and 'Jersey Kin g' yielded 22% less processing and 30% less export product than 'Jerse y Giant.' For export, 'UC157' produced an equal yield of earlier, high er quality, less purple spears than 'Limbras 10' or 'Jersey King'. Cou ntry of origin rather than type provided the best indication of the ab ility of the hybrids to increase marketable yields. European and Unite d States double and single-cross, mixed-sex and all-male hybrids offer ed similar scope to improve total yield and early production. The supe rior spear quality of the United States hybrids offered better prospec ts for improving marketable yield. The United States 'New Jersey' hybr ids were the only group with improved Stemphylium disease resistance.