Effect of the rhg1 gene on penetration, development and reproduction of Heterodera glycines race 3

Abstract

AbstractPenetration, development, and reproduction of Heterodera glycines (soybean cyst nematode, SCN) were compared in the roots of near-isogenic lines (NIL) differing at the rhg1 locus. Soybean seedlings were inoculated with newly hatched second-stage juveniles (J2) of an SCN race 3 inbred population. At an inoculum level of 2500 J2 per plant, similar numbers of J2 were detected in both NIL sampled daily up to 4 days after inoculation (DAI), although juvenile numbers in roots varied among experiments and over the sampling points. Samples were collected at 1, 4, 8, 12, 16 and 21 DAI to observe nematode development. All life stages of the nematode were detected in both NIL. No significant differences were observed between the NIL in the number of nematodes at juvenile stages or the adult male stage in the roots. By contrast, significant differences were detected in the number of mature females. Adult females were first seen at 12 DAI. A significantly lower number of females was consistently detected on the NIL-R line than on the NIL-S line at both 16 and 21 DAI. The number of females per plant on the NIL-R line was about 31 and 23% of those on the NIL-S line at 16 and 21 DAI, respectively. On average, the number of females at 21 DAI represented 7% of the number of J2 at 1 DAI on the NIL-R line, compared to 28% on the NIL-S line. Significantly fewer eggs were produced per female from the NIL-R line than from the NIL-S line at 21 DAI. At 28 DAI, the females on the NIL-R line were also significantly smaller than those from the NIL-S line. This study demonstrated that the presence of the rhg1 gene did not stop the nematode from penetrating. Instead, the effect of the rhg1 gene was to slowly suppress SCN growth, development and fecundity of females.