Pollinator effectiveness, breeding system, and tests for inbreeding depression in the biofuel seed crop,<i>Jatropha curcas</i>

Abstract

SummaryExperiments were conducted to determine factors that could influence seed production in the potential biofuel seed crop, Jatropha curcas. Controlled pollination experiments in a South African plantation of J. curcas showed that plants required pollinator visits for seed production and were genetically self-compatible. Pollen-supplementation did not lead to increased fruit set, suggesting that seed production in the study population was not pollen-limited. Both male and female flowers produced nectar and were highly attractive to honeybees. These insects were effective pollinators of J. curcas, as shown by experiments in which flowers exposed to single or multiple visits by honeybees set significantly more fruit than those from which visits had been prevented. Self-pollination led to marginally lower levels of fruit set relative to cross-pollination. However, fruits arising from self-pollination were almost as numerous and as large as those arising from cross-pollination. Progeny from selfed plants had significantly shorter roots than the progeny of out-crossed plants. However, in general, there was little evidence of inbreeding depression. These results provide empirical evidence that honeybees are effective pollinators of J. curcas and indicate that promotion of cross-pollination does not have to be a priority in orchard management for fruit yield.