EFFECTS OF SOURCE-SINK VARIATION ON THE REPRODUCTIVE ASSIGNATION OF ANNUAL AND PERENNIAL SPECIES OF LESQUERELLA (BRASSICACEAE)

BAEZA, W Y RAVETTA, D.A.

Chillan, Chile

Congreso; AAIC 21st Annual Meeting. International Conference: The next generation of Industrial Crops, Processes and Products. Termas de Chillán, Chillán, Chile. 14-19 November 2009.; 2009

Association for the Advancement of Industrial Crops

The development of perennial oil-seed crops offers an interesting alternate to aliviate problems associated with agricultural practices needed to produce on fragile environments such as extra-andean Patagonia. Although the annual Lesquerella fendleri is the prime candidate for the development of a lesquerolic rich oil-seed crop, within this genus there are several perennial species available to breeders some of which are perennials when cultivated. Still the feasibility of a perennial crop of Lesquerella is not clear because seed-yield in perennials is usually limited by low harvest indexes resultant from a trade-off between reproductive output and biomass allocated to organs devoted to perpetuation. Increases in seed-yield tend to reduce perenniality. Assimilated carbon is assigned to different organs (leaves, stems, roots, reproductive organs, etc) as the result of a set of metabolic and transport processes that govern the flux of energy through a system of sources and sinks. Within this context, one of the strategies used to evaluate variations in reproductive allocation is to alter source-sink relations of the plant. The aim of the present study is to evaluate the effect of source-sink ratio on the reproductive allocation of four Lesquerella’s species with different life-cycles. A field experiment was carried-on in Chubut, Patagonia Argentina (43º 14’S, 65º 18’W). We used a completely randomized design with twelve treatments in which we varied source-sink relationships on two annuals (L. angustifolia, L. gracilis) and two perennials (L. pinetorum, L. mendocina). We used a combination of shading timing (reduction of source) and removal of flower-buds (reduction of sink) to develop a range of source-sink relationships. Reproductive allocation was evaluated as the number of fruits per plant. Data was analysed using two-way ANOVAand post-hoc Tukey’s Multiple Range test. All four species had a similar response to source/sink treatments (p<0.05).The number of fruits was lowest for plants shaded during the vegetative (rosette) stage and highest for plants which had half their flower-buds removed at flowering. Plants shaded during the reproductive stage and control plants had a similar, intermediate number of fruits/plant. Species differed in the total number of fruits/plant (p<0.05) L. pinetorum was the species with the highest number of fruits/plant and L. mendocina and L. angustifolia had the lowest. Our preliminary results show that carbon-gain during the rosette stage may be relatively more important than actual assimilation during reproduction, which means that carbon storage also plays a key role in reproduction both in annual and perennial Lesquerella. The increase in fruit-set found with bud removal (compensatory fruiting) could potentially reduce longevity in perennial species, although it may also come from an increase in carbon gain, induced by sink enlargement. The mechanisms behind these responses should be further evaluated, especially the understanding of the relative importance of carbon reserves, current photosynthesis and carbon partition in determining yield components, and future yield and plant longevity.