What are HG types?
SCN field populations vary in their ability to develop and reproduce on soybean lines that differ in their resistance to SCN. The variability of SCN virulence is described by HG Type schemes, in which the virulence phenotypes of SCN populations are determined by the number of females that develop on seven indicator lines as compared with susceptible Lee 74 or other suitable susceptible soybean varieties.
Table 1. Indicator lines for HG Type classification of soybean cyst nematode.
|Number||Indicator Line||Example: HG Type 2.5.7|
The soybean lines and varieties are inoculated with nematode eggs and maintained in the greenhouse under favorable conditions for about one month. The females formed on the soybean roots are collected and counted. Based on the number of females, Female Index (FI) is calculated: FI = (number of females on indicator line) × 100 / (number of females on Lee 74). If the FI is less than 10, the response of the soybean line is "–", and if = 10, the response is "+". The description of HG Type indicates the positive response of a population on the individual lines (Table 1). If no FI is more than 10 on any of the indicator lines, the population is described as HG Type 0.