Monday, November 13, 2006

Inheritance of Resistance in Soybean PI494182 to Cyst Nematode Populations.

Prakash Arelli, USDA-ARS, 605 Airways Blvd., Jackson, TN 38301, United States of America and Dechun Wang, Michigan State Univ, A384-E Plant & Soil Bldg, East Lansing, MI 48824-1325.

Soybean [ Glycine max (L.) Merr] Plant Introduction 494182 is a newly found source of resistance to multiple cyst nematode (SCN: Heterodera glycines Ichinohe) populations. It is yellow-seeded, maturity group ‘0’ soybean , resistant to SCN Races 1, 3, 5 and, moderately resistant to  Race 2 ( corresponding to HG Types 2.7, 0, 2.5.7, 1.2.7, respectively). PI 494182 may be a potential source for diversifying SCN resistance genes in the soybean cultivars  and  provide durable resistance . We have determined inheritance of resistance in PI 494182 to SCN Races 3 and 5. A segregating population was produced by crossing PI line with a susceptible cultivar Skylla. We used established greenhouse methods to evaluate 162 F3:4 progenies for nematode reaction. A female index of  10% was used to determine 20 resistant and 142 susceptible/segregating and three resistant and 159 susceptible/segregating  plants for SCN Races 3 and 5, respectively. Based on chi-square values ( 0.394, 90%<P>80% ; 0.085, 80%<P>70% for SCN Races 3 and 5, respectively) a three-gene model is proposed  for conditioning resistance to SCN Races 3 and 5. These genes are confirmed in a mapping study and the  results will be useful to soybean breeders for developing  cultivars  for broad resistance.