Life Cycle of Heterodera glycines in Resistant and Susceptible Soybean

The life cycle of the soybean cyst nematode lasts approximately 21-24 days at temperatures ranging from 23 °C to 25 °C. Mean temperatures above 25 °C are often found in Goiás State and in other Brazilian regions. Thus, the aim of the present study is to assess the penetration and cycle duration of Heterodera glycines Type 0- (race 3) in nematode-resistant and susceptible soybean cultivars grown in greenhouse under controlled conditions. The study was conducted at soil temperatures ranging from 23.9 °C to 31.1 °C using two soybean cultivars that were assessed in ten different periods; each assessment was conducted in six plants. The herein used soybean cultivars were BRS Valiosa RR and BRSGO 8860RR, which were, respectively, susceptible and resistant to the nematode. Root staining assessments were performed 2, 4, 6, 9, 12, 15, 18, 21, 24 and 30 days after inoculation (DAI). Besides the root staining assessments, the females and eggs were also assessed through extraction using the sieving and flotation method, at the 30th DAI. Heterodera glycines J2 penetration was similar in both the susceptible and the resistant cultivars throughout the assessment period. It indicates that the nematode penetration was not affected by resistance. The Heterodera glycines cycle at soil temperature ranging from 23.9 °C to 31.1 °C and at room temperature ranging from 27.0 °C to 36.3 °C was complete in 15 days, in both the susceptible and the resistant cultivars. A similar number of J2 has penetrated the roots of both cultivars and greater penetration intensity was found from the 6th to the 15th DAI. The peak J3, J4 and female formation period in the resistant cultivar was later than that observed in the susceptible cultivar.