Fusarium oxysporum f. sp. cubense (FOC) is the causal agent of banana Fusarium wilt and has become one of the most destructive pathogens threatening the banana production worldwide. However, few genes related to morphogenesis and pathogenicity of this fungal pathogen have been functionally characterized. In this study, we identified and characterized the disrupted gene in a T-DNA insertional mutant (L953) of FOC with significantly reduced virulence on banana plants. The gene disrupted by T-DNA insertion in L953 harbors an open reading frame, which encodes a protein with homology to α-1,6-mannosyltransferase (OCH1) in fungi. The deletion mutants (ΔFoOCH1) of the OCH1 orthologue (FoOCH1) in FOC were impaired in fungal growth, exhibited brighter staining with fluorescein isothiocyanate (FITC)-Concanavalin A, had less cell wall proteins and secreted more proteins into liquid media than the wild type. Furthermore, the mutation or deletion of FoOCH1 led to loss of ability to penetrate cellophane membrane and decline in hyphal attachment and colonization as well as virulence to the banana host. The mutant phenotypes were fully restored by complementation with the wild type FoOCH1 gene. Our data provide a first evidence for the critical role of FoOCH1 in maintenance of cell wall integrity and virulence of F. oxysporum f. sp. cubense.

This paper reports a plate assay to detect activities of polygalacturonase and cellulase secreted by Fusarium oxysporum f.sp.cubense(FOC),which is the most destructive pathogen of banana.The optimum cultural conditions for the polygalacturonase production were using pectin as induced substrate to inoculate with 1 × 104 mL-1 conidia of FOC and after being cultured for 3 days.The optimal temperature of polygalacturonase activity was 37 ℃.The optimum cultural conditions for cellulase production were using carboxymethyl cellulose(CMC) as induced substrate to inoculate with 1 × 105 mL-1 conidia of FOC in inducing medium after being cultured for 3 days.The optimal temperature of cellulase activity was 37 ℃.Based on the method,two mutants with impaired polygalacturonase and cellulose activity were attained through screening virulence-reduced mutants of FOC.

In order to study the status of soil degradation in the tobacco-planting fields in Nanxiong of Guangdong province, 54 farmers from 8 villages, whom totally planted 431.2 km2 tobacco, were investigated, which involved 103.4 km2 Purple soil, 109.4 km2 Niugantutian soil and 75.4 km2 Shanitian soil, and the average yield was 244.4 kg/km2. The results indicated that the tobacco output and quality were relatively higher in the Niugantutian and Purple soils. The tobaccoes planted in the continuous planting Shanitian soils were easy to be infected by Ralstonia solanacearum (bacterial wilt), meanwhile, the fertilization was more in the high-yield fields, but the relationship between them was not significantly correlated.In addition, soil samples were collected for studying the soil microbes.The figures indicated that the amounts and populations of bacteria, fungi and nitrogen-fixing bacteria were obviously different, namely the community diversity of the culture-dependent microbes is different. The bacteria and nitrogen-fixing bacteria amount were the most in the soybean and tobacco rotation field, and most for the fungi in the fields of slightly-infected by Ralstonia solanacearum, however, the fungi was less in the rhizosphere of tobaccos infected by Ralstonia solanacearum.Nitrobacteria amounts were more in rhizophere soil than in non-rhizophere soil.The abilities of dissolving CaCO3 were also different for the nitrogen-fixing bacteria form different soils.

A cost-benefit analysis and comparisons of tobacco and competitive-economic crops were drawn in this article, which was based on the raw data inquired in the investigation of Nanxiong in Guangdong province. And we discovered that the local competitive-economic crops had absolutely economic-benefit predominance comparing with tobacco. The rice, which holds the preponderant cost, had the lowest cost-benefit (116.9%). Meanwhile, the capsicum was in possession of the highest costbenefit, which up to 358.2%. Compare with tobacco (90.0%), the four competitive-economic crops are having the predominance in growth. Besides, based upon the analysis of the current low benefit in the production of tobacco, had with the development of modern tobacco agriculture in Nanxiong, several proposals had been put forward in the article, which would be significant for promoting the development of modern tobacco agriculture in Guangdong province.

概述了发达国家和我国农产品包装的现状,分析了我国农产品包装设计存在的问题和原因及未来我国农产品包装设计的发展趋势,提出了改进我哦过农产品包装设计的思路和对策.