Survey of aflatoxins and ochratoxin A in stored tubers ofCyperus esculentus L.

The mold incidence, moisture contents, pH and levels of mycotoxins (aflatoxins B₁, G₁ and ochratoxin A) on/of/in rootstock snack (tubers ofCyperus esculentus L.) samples were monitored during a 150-day storage period. Whereas the mold incidence, moisture and mycotoxin levels increased with storage time, the pH declined during the same period. Altogether, 12 fungal species, mostly toxigenic, includingAspergillus flavus, A. parasiticus andA. ochraceus were isolated. At collection period only 3 of the 9 snack samples analysed contained trace amounts of aflatoxins. By 120th day, all the 9 samples were contaminated and the average levels were 454 and 80 ppb for aflatoxin B₁ and aflatoxin G₁ respectively on the 150th day. Ochratoxin A was not detected before 120th day and then only at low levels, occuring in a maximum of four samples and ranging between 10 and 80 ppb.     

两类柑桔杂种砧木对脐橙(Citrus sinensis Osbeck)幼树生长和叶片糖营养含量年变化的影响

以体细胞杂种红桔＋枳和红桔＋粗柠檬、有性杂种Troyer枳橙和Swingle枳柚作砧木的耐湿脐橙(Citrus sinensis Osbeck)2年生嫁接苗为试材,通过盆栽试验研究了砧木对苗木生长和叶片糖营养含量年变化动态的影响。结果表明：红桔＋枳的生长势和花量明显地强于和大于其它砧木,红桔＋粗柠檬的生长和花量表现介于2种有性杂种之间。叶绿素a／b和类胡萝卜素含量在不同砧木间无显著差异,而不同砧木显著或极显著地影响叶绿素含量各指标。砧木影响叶片可溶性糖和淀粉含量年变化动态的基本特征。在休眠期,红桔＋枳的可溶性糖和淀粉含量都高于2种有性杂种砧木,而红桔＋粗柠檬则反之;在生长期,红桔＋粗柠檬的可溶性糖和淀粉含量表现出高于有性杂种砧木的趋势,而红桔＋枳则介于2种有性杂种砧木之间。同时还重点讨论了2种体细胞杂种砧木的利用价值。     

Roots play a vital role in flood-tolerance of poplar demonstrated by reciprocal grafting

Poplar is one of the most important multipurpose afforestation trees in river floodplains and arable farmland which are subject to frequent flooding. To determine the relative roles that the roots and shoots have in responses to waterlogging, six root-shoot grafting combinations of full-sib poplar clones LS1 (flood-tolerant) and LS2 (flood-susceptible) were compared for waterlogging effects on them, using reciprocal and self-grafts. Plants of the six combinations comprised non-grafted (LS1) and (LS2), self-grafted (LS1/LS1) and (LS2/LS2), LS1 grafted onto LS2 (LS1/LS2), and LS2 grafted onto LS1 (LS2/LS1) experimental plants. The two clones LS1 and LS2 originated from Populus deltoides cv. Lux ex. I-69/55 (flood-tolerant) × P. simonii (flood-susceptible). Growth, morphological and ecophysiological parameters of plants belonging to the six grafting combinations were subjected for 21 days to flooding, followed by a six-day drainage and recovery stage. Results showed that flooding stress affected adversely growth, biomass accumulation, morphological and ecophysiological characteristics in all flooded plants. The more severe influences were found in the plants with LS2 roots (LS1/LS2, LS2/LS2, LS2), whereas plants having roots of LS1 (LS2/LS1, LS1/LS1, LS1) were less negatively affected. At the end of the study, 100%, 100%, 93.3%, 26.7%, 6.7% and 20% survival rates, respectively, were observed in flooded plants of LS1, LS1/LS1, LS2/LS1, LS1/LS2, LS2/LS2 and LS2. In conformity with the results for growth, biomass accumulation and morphology, responses to flooding of gas exchange, chlorophyll fluorescence, relative membrane permeability of leaves, the overall root metabolism parameter dehydrogenase activity (TTC assay), as well as malonaldehyde contents of leaves and roots also indicated that flood injury was significantly more pronounced in plants having LS2 roots than in those with LS1 roots. Plants with roots of LS1 displayed clearly faster recovery after flooding than the plants with LS2 roots. The results indicate that flooding-tolerance of poplar is based more on influences from the rootstock than on those of the scion. It is thus the root genotype that plays the decisive role in flood-tolerance of poplar.