Control of fungal contamination in the accelerated ageing test of Brassica spp.

摘要

The high temperature and humidity used for the accelerated ageing (AA) vigour test procedure allows the growth of fungi on Brassica seeds, the presence of which may negatively affect the post-ageing germination. Two methods for control of this fungalcontamination were investigated. The first method involved substituting saturated salt solutions for the deionised water in the inner ageing chamber. Seeds from 27 seed lots of five Brassica spp. were aged at 41 deg C for 72h using 40 ml of deionised water (96%RH), or saturated salt solutions of NaBr (55% RH), NaCl (76% RH) or KC1 (83% RH) in the inner ageing chamber. The lower RH environments prevented fungal growth but did not allow seed ageing to occur, as post-ageing seed moisture contents (SMC) didnot exceed 12%. As neither increasing the ageing temperature (to 42 deg C and 45 deg C) or time (to 72h and 96h) at lower RH allowed ageing to occur, the use of saturated salts is not applicable for the AA testing of Brassica spp. For the second method,seeds from three seed lots each of a turnip x rape hybrid (B. rapa X B. campestris) and Asian kale (B. oleraceae var. alboglabra) were surface sterilised using a 1% sodium hypochlorite solution before being placed into the AA chamber. Their post-ageinggermination was then compared with that of seeds which had not been surface sterilised. Seed moisture content after ageing did not differ between the treatments, but post-ageing germination of five of the six surface sterilised seed lots was significantly increased because of a reduction in the number of abnormal seedlings. While surface sterilisation did not completely prevent fungal growth, the results indicate that this pre-treatment deserves further investigation for the AA testing of small-seeded species.