S.C. JUTZI and J. NÖSBERGER

Institut für Pflanzenbau, Eidgenössische Technische Hochschule, CH-8092 Zürich Switzerland .

Abstract

Seed production and growth of the tropical pasture legume, Zornia latifolia accession CIAT 728, were studied. Effects of daylength, temperature, soil moisture and plant density on flowering, seeding and growth were analysed; breeding system and seed quality were investigated. The experimental work was conducted in eastern Bolivia and central Brazil (field and glasshouse) and in Zürich (growth chambers).
Zornia latifolia showed a short day response in flowering. The critical photoperiod was about 12.5 hours. Low temperatures promoted less vigorous flowering under longer photoperiods. Optimum mean temperature for seed set ranged from 20°C to 27°C. Higher temperatures were necessary for vigorous vegetative growth. Relatively high plant densities improved the seeding performance of the accession. Fertilisation was mainly autogamous with a very low potential of insect-dependent cross-pollination. The percentage of hard seeds was higher than 90% at harvest. Seed yields between 400 and 700 kg/ha were recorded (1000 grain weight: 1.3 g). More than half of the total seed yield was lost due to pod segment shattering before the seeds had reached maturity. Field studies with Zornia latifolia confirmed that the central Brazilian savanna (Cerrado) is generally suitable for seed production.