The 2011 ASHS Annual Conference

Commercial annona varieties, such as cherimoya (Annona cherimola Mill.), sugar apple (A.  squamosa) and atemoya (A. squamosa × A. cherimola), are generally grown on seedling rootstocks and very susceptible to water-logging, even for short periods. Annona atemoya Hort cv. African Pride (AP) was introduced to China in 1980s, and became popular due to its high quality and unique flavor. Prevalence of root diseases in wet soils is the main problem in AP production, which restricts the development of AP in south China, where rainfall is plenty and flooding frequently occurs. It has been found that some annona species like A. Montana (M), A. glabra (G) and A. muricata are relatively flood-tolerant and can survive continuous flooding and periodic water logging conditions. There is potential increase flood tolerance of commercial annona varieties by the use of flood-tolerant rootstocks. As reported before, the incompatibility between these water-logging tolerant species and commercial species could be overcome by interstocks, such as hybrid of 'AP' atemoya × A. reticulate (AR). In this study, an experiment was conducted with the aim to study the effects of continuous and cyclic soil flooding on four different annona scion/rootstock combinations: AP/AR/G (scion/interstock/rootstock, AR/G (scion/rootstock), AP/AR/M and AR/M, and to identity the suitable ones that may tolerate flooding environment and maintain crop growth. Plant growth, leaf gas exchange and chlorophyll fluorescence parameters were measured regularly after flooding treatment. Both continuous and cyclic soil flooding significantly reduced photosynthesis and shoot extension and leaf production in plantlets of AP/AR/M and AR/M, some of which showed wilting within 2 weeks. Flooding slightly enhanced the growth and photosynthesis rate in the plantlets of AP/AR/G and AR/G, which produced vigorous adventitious roots. Thus, we recommend A. glabra instead of A. montana as a rootstock, AR as an interstock to increase flood-tolerance for commercial annona varieties.