Njoroge Samuel M C, Kabir Zahangir, Martin Frank N, Koike Steven T, Subbarao Krishna V
Department of Plant Pathology, University of California, Davis, c/o U.S. Agricultural Research Station, 1636 E. Alisal Street, Salinas, CA 93905.
USDA-ARS, 1636 E. Alisal Street, Salinas, CA 93905.
Plant Dis. 2009 May;93(5):519-527. doi: 10.1094/PDIS-93-5-0519.
The effects of broccoli and lettuce rotations on population densities of Verticillium dahliae and Pythium spp. in soil and on strawberry (Fragaria × ananassa) growth, yield, and Verticillium wilt were evaluated in conventional and organic production systems in California for 2 years. Under both management systems, strawberry was planted after two successive crops of broccoli or lettuce. The control treatment in the conventional field was strawberry planted in soils fumigated with methyl bromide + chloropicrin. Preplant densities of V. dahliae and Pythium sp. did not differ in these fields. At the end of the second broccoli crop, V. dahliae densities in conventional plots had declined by 44% in both years. In contrast, after the second broccoli crop, densities in organic fields decreased 47% in 2000 and 25% in 2001. In general, there were no differences in V. dahliae inoculum densities in organic and conventional plots following lettuce rotations. After the second vegetable production cycle, population densities of V. dahliae in broccoli rotated organic (24 CFU/g of soil in 2000 and 27 CFU/g of soil in 2001) or conventional (23 CFU/g of soil in 2000 and 19 CFU/g of soil in 2001) fields were significantly lower than those in lettuce rotated organic (40 CFU/g of soil in 2000 and 42 CFU/g of soil in 2001) or conventional (39 CFU/g of soil in 2000 and 35 CFU/g of soil in 2001) fields. However, crop rotation treatments had no consistent effect on the inoculum densities of Pythium spp. Canopy diameters of strawberry plants grown in rotation with broccoli were not different from those in fumigated control plots, whereas those from lettuce plots were 10% smaller. Strawberry plant nutrient analysis showed that fertilizer inputs into organic or conventional production were not responsible for the observed differences in plant size. Increases in strawberry yields were not consistent between years. Verticillium wilt incidence on strawberry was 12 to 24% lower in fields rotated with broccoli compared with fields rotated with lettuce. Wilt severity on strawberry was 22 to 36% lower in fields rotated with broccoli compared with those rotated with lettuce. The strategy of using broccoli rotation coupled with postharvest incorporation of broccoli residue continues to show promise as a tool in the management of Verticillium wilt in both conventional and organic strawberry production systems.
在加利福尼亚州的传统和有机生产系统中，对西兰花和生菜轮作对土壤中大丽轮枝菌和腐霉菌种群密度以及草莓（凤梨草莓）生长、产量和黄萎病的影响进行了为期两年的评估。在两种管理系统下，连续种植两季西兰花或生菜后种植草莓。传统田地的对照处理是在经溴甲烷+氯化苦熏蒸的土壤中种植草莓。这些田地中大丽轮枝菌和腐霉菌的种植前密度没有差异。在第二季西兰花作物结束时，传统地块中大丽轮枝菌的密度在两年中均下降了44%。相比之下，在第二季西兰花作物之后，有机田地中的密度在2000年下降了47%，在2001年下降了25%。一般来说，生菜轮作后有机和传统地块中大丽轮枝菌接种体密度没有差异。在第二季蔬菜生产周期后，西兰花轮作的有机（2000年为24 CFU/g土壤，2001年为27 CFU/g土壤）或传统（2000年为23 CFU/g土壤，2001年为19 CFU/g土壤）田地中大丽轮枝菌的种群密度显著低于生菜轮作的有机（2000年为40 CFU/g土壤，2001年为42 CFU/g土壤）或传统（2000年为39 CFU/g土壤，2001年为35 CFU/g土壤）田地。然而，作物轮作处理对腐霉菌接种体密度没有一致的影响。与西兰花轮作种植的草莓植株冠幅直径与熏蒸对照地块的没有差异，而生菜地块的则小10%。草莓植株养分分析表明，有机或传统生产中的肥料投入与观察到的植株大小差异无关。草莓产量的增加在不同年份并不一致。与生菜轮作的田地相比，与西兰花轮作的田地中草莓黄萎病发病率低12%至24%。与生菜轮作的田地相比，与西兰花轮作的田地中草莓黄萎病严重程度低22%至36%。在传统和有机草莓生产系统中，采用西兰花轮作并在收获后掺入西兰花残茬的策略，作为一种管理草莓黄萎病的工具，仍然显示出前景。
