Abstract
The aim of the study is to assess Crotalaria ochroleuca susceptibility to six Heterodera glycines races. To this, C. ochroleuca seedlings and two soybean cultivars were transplanted and individually inoculated with nematode races 1, 2, 3, 5, 6 and 14. Plants were collected and assessed 30 and 60 days after inoculation. Crotalaria ochroleuca reduced the number of females and the total number of eggs of the races 1, 2, 5 and 6. The reproduction of race 3 in crotalaria was equal to that of soybean cultivars in both assessment periods, whereas race 14 only reduced the reproduction in crotalaria to 60 days. Races 1 and 6 (30th day) and races 6 and 14 (60th day) showed number of eggs female-1 smaller than the controls. According to female index (FI), C. ochroleuca was resistant to races 1, 2 and 5, susceptible to race 3, and showed varying reactions to races 6 and 14.
Highlights
The soybean cyst nematode or SCN (Heterodera glycines Ichinohe) stands out among the main pests affecting soybean yield in Brazil
Heterodera glycines females show lemon-like shape and contain approximately 300 eggs; they remain attached to the root system in the form of small white spots (Schmitt & Riggs 1989; Dias et al, 2010)
The 60-mesh sieve was coupled to a 500 mesh one; the cysts and females were macerated in the first sieve to release eggs and juveniles, which were retained in the second sieve, in order to prepare the inoculum
Summary
The soybean cyst nematode or SCN (Heterodera glycines Ichinohe) stands out among the main pests affecting soybean yield in Brazil. It is estimated that such yield may be totally compromised in case of severe infestations (Dias et al, 2009). Dead females detach from the root, acquire dark-brown coriaceous appearance, and are named cysts (Dias et al, 2010). The function of this survival structure lies on protecting the eggs from desiccation, heat and deterioration-fact that keeps them viable for up to eight years, as well as on promoting their dissemination (Schmitt & Noel, 1984; Andrade & Asmus, 1997)
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