SOIL SUPPRESIVENES AGAINST HETERODERA SCHACHTII IN CALIFORNIA CROPPING AREAS

作者：Westphal A^*; Pyrowolakis A; Sikora R A; Becker J O

来源：Nematropica, 2011, 41(2): 161-171.

• biological control
• nematode egg-parasitic fungi
• Heterodera schachtii
• soil suppressiveness
• sugar beet
• sugar beet cyst nematode

A greenhouse bioassay was developed for determining the presence of biological suppressiveness against the beet cyst nematode, Heterodera schachtii, using eleven soils from southern California locations. Two soils exhibited H. schachtii-suppression of nematode population development in non-treated compared to methyl iodide-fumigated (500 kg/ha) equivalents. By counting nematode cysts and eggs, suppressiveness was detectable on Swiss chard after two generations of H. schachtii following infestation with second-stage juveniles (J2) of H. schachtii or on mustard-greens after infestation with nematode cysts. In another test, enumeration of nematode females visible through the transparent pot wall was a useful method for observing H. schachtii populations. In a survey with mustard-greens, two of 48 soils from southern California were suppressive against H. schachtii, indicated by reduced numbers of eggs or cysts of H. schachtii in non-treated portions compared to fumigated equivalents. The data suggested that various soil textures allow for suppressiveness against H. schachtii because of the four suppressive soils (of 59 total) two were loam soils, one a clay loam, and one a sandy loam. The number of nematode females visible through the transparent pot surface was correlated with the number of extractable cysts 100 g(-1) soil (R-2 = 0.45; P < 0.01). Thus, female counts provided estimates of the final H. schachtii population density. There was no relationship between the rates of fungal infection of the eggs and the numbers of eggs/cyst at harvest in the greenhouse tests, suggesting that such data are unsuitable predictors of soil suppressiveness for this nematode.

• 出版日期2011-12