Iso-lines and inbred-lines confirmed loci that underlie resistance from cultivar ‘Hartwig’ to three soybean cyst nematode populations

Soybean [Glycine max (L.) Merr.] cultivars varied in their resistance to different populations of the soybean cyst nematode (SCN), Heterodera glycines, called HG Types. The rhg1 locus on linkage group G was necessary for resistance to all HG types. However, the loci for resistance to H. glycines HG Type 1.3- (race 14) and HG Type 1.2.5- (race 2) of the soybean cyst nematode have varied in their reported locations. The aims were to compare the inheritance of resistance to three nematode HG Types in a population segregating for resistance to SCN and to identify the underlying quantitative trait loci (QTL). ‘Hartwig’, a soybean cultivar resistant to most SCN HG Types, was crossed with the susceptible cultivar ‘Flyer’. A total of 92 F5-derived recombinant inbred lines (RILs; or inbred lines) and 144 molecular markers were used for map development. The rhg1 associated QTL found in earlier studies were confirmed and shown to underlie resistance to all three HG Types in RILs (Satt309; HG Type 0, P = 0.0001 R 2 = 22%; Satt275; HG Type 1.3, P = 0.001, R 2 = 14%) and near isogeneic lines (NILs; or iso-lines; Satt309; HG Type 1.2.5-, P = 0.001 R 2 = 24%). A new QTL underlying resistance to HG Type 1.2.5- was detected on LG D2 (Satt574; P = 0.001, R 2 = 11%) among 14 RILs resistant to the other HG types. The locus was confirmed in a small NIL population consisting of 60 plants of ten genotypes (P = 0.04). This QTL (cqSCN-005) is located in an interval previously associated with resistance to both SDS leaf scorch from ‘Pyramid’ and ‘Ripley’ (cqSDS-001) and SCN HG Type 1.3- from Hartwig and Pyramid. The QTL detected will allow marker assisted selection for multigenic resistance to complex nematode populations in combination with sudden death syndrome resistance (SDS) and other agronomic traits

Transgenic soybean overexpressing GmSAMT1 exhibits resistance to multiple-HG types of soybean cyst nematode Heterodera glycines

Soybean (Glycine max (L.) Merr.) salicylic acid methyl transferase (GmSAMT1) catalyses the conversion of salicylic acid to methyl salicylate. Prior results showed that when GmSAMT1 was overexpressed in transgenic soybean hairy roots, resistance is conferred against soybean cyst nematode (SCN), Heterodera glycines Ichinohe. In this study, we produced transgenic soybean overexpressing GmSAMT1 and characterized their response to various SCN races. Transgenic plants conferred a significant reduction in the development of SCN HG type 1.2.5.7 (race 2), HG type 0 (race 3) and HG type 2.5.7 (race 5). Among transgenic lines, GmSAMT1 expression in roots was positively associated with SCN resistance. In some transgenic lines, there was a significant decrease in salicylic acid titer relative to control plants. No significant seed yield differences were observed between transgenics and control soybean plants grown in one greenhouse with 22 °C day/night temperature, whereas transgenic soybean had higher yield than controls grown a warmer greenhouse (27 °C day/23 °C night) temperature. In a 1-year field experiment in Knoxville, TN, there was no significant difference in seed yield between the transgenic and nontransgenic soybean under conditions with negligible SCN infection. We hypothesize that GmSAMT1 expression affects salicylic acid biosynthesis, which, in turn, attenuates SCN development, without negative consequences to soybean yield or other morphological traits. Thus, we conclude that GmSAMT1 overexpression confers broad resistance to multiple SCN races, which would be potentially applicable to commercial production

An (E,E)-α-farnesene synthase gene of soybean has a role in defence against nematodes and is involved in synthesizing insect-induced volatiles

Plant terpene synthase genes (TPSs) have roles in diverse biological processes. Here, we report the functional characterization of one member of the soybean TPS gene family, which was designated GmAFS. Recombinant GmAFS produced in Escherichia coli catalysed the formation of a sesquiterpene (E,E)-a-farnesene. GmAFS is closely related to (E,E)-a-farnesene synthase gene from apple, both phylogenetically and structurally. GmAFS was further investigated for its biological role in defence against nematodes and insects. Soybean cyst nematode (SCN) is the most important pathogen of soybean. The expression of GmAFS in a SCN-resistant soybean was significantly induced by SCN infection compared with the control, whereas its expression in a SCN-susceptible soybean was not changed by SCN infection. Transgenic hairy roots overexpressing GmAFS under the control of the CaMV 35S promoter were generated in an SCN-susceptible soybean line. The transgenic lines showed significantly higher resistance to SCN, which indicates that GmAFS contributes to the resistance of soybean to SCN. In soybean leaves, the expression of GmAFS was found to be induced by Tetranychus urticate (two-spotted spider mites). Exogenous application of methyl jasmonate to soybean plants also induced the expression of GmAFS in leaves. Using headspace collection combined with gas chromatography–mass spectrometry analysis, soybean plants that were infested with T. urticae were shown to emit a mixture of volatiles with (E,E)-a-farnesene as one of the most abundant constituents. In summary, this study showed that GmAFS has defence roles in both below-ground and above-ground organs of soybean against nematodes and insects, respectively

A Standard Greenhouse Method for Assessing Soybean Cyst Nematode Resistance in Soybean: SCE08 (Standardized Cyst Evaluation 2008)

The soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is distributed throughout the soybean [Glycine max (L.) Merr.] production areas of the United States and Canada (Fig. 1) (26). SCN remains the most economically important pathogen of soybean in North America; the most recent estimate of soybean yield reduction in North America due to SCN totaled 34,659,000 metric tons during 2006 (34)

Quantitative Trait Loci (QTL) that Underlie SCN Resistance in Soybean [\u3ci\u3eGlycine max\u3c/i\u3e (L.) Merr.] PI438489B by ‘Hamilton’ Recombinant Inbred Line (RIL) Population

Soybean cyst nematode caused by Heterodera glycines Ichinohe is the most devastating pest in soybean [Glycine max (L.) Merr.]. Resistance to SCN is complex, polygenic, race and cultivar specific, and it is controlled by several quantitative trait loci (QTL). Our objective was to identify and map QTL for SCN resistance to races 3 (HG Type 0) and 5 (HG Type 2.5.7) using a high density SNP-based genetic linkage map based on the PI438489B by ‘Hamilton’ (PIxH, n=50) recombinant inbred line population. The PI438489B by Hamilton map contained 648 SNPs distributed on 31 LGs with coverage of 1,524.7 cM and an average distance of 2.35 cM between two markers (Kassem et al., 2011). Using interval mapping (IM) and composite interval mapping (CIM), eight QTL were identified for SCN resistance to races 3 and 5 on 7 different soybean chromosomes. Four QTL for resistance to SCN race 3 were identified and mapped on chromosomes 7, 13, 15, and 16. Similarly, four QTL for resistance to SCN race 5 were identified and mapped on chromosomes 5, 8, and 11. The QTL identified here will be highly beneficial in breeding programs to develop cultivars with resistance to both SCN races 3 and 5

Transgenic soybean overexpressing Gm SAMT

Soybean (Glycine max (L.) Merr.) salicylic acid methyl transferase (GmSAMT1) catalyses the conversion of salicylic acid to methyl salicylate. Prior results showed that when GmSAMT1 was overexpressed in transgenic soybean hairy roots, resistance is conferred against soybean cyst nematode (SCN), Heterodera glycines Ichinohe. In this study, we produced transgenic soybean overexpressing GmSAMT1 and characterized their response to various SCN races. Transgenic plants conferred a significant reduction in the development of SCN HG type 1.2.5.7 (race 2), HG type 0 (race 3) and HG type 2.5.7 (race 5). Among transgenic lines, GmSAMT1 expression in roots was positively associated with SCN resistance. In some transgenic lines, there was a significant decrease in salicylic acid titer relative to control plants. No significant seed yield differences were observed between transgenics and control soybean plants grown in one greenhouse with 22 °C day/night temperature, whereas transgenic soybean had higher yield than controls grown a warmer greenhouse (27 °C day/23 °C night) temperature. In a 1‐year field experiment in Knoxville, TN, there was no significant difference in seed yield between the transgenic and nontransgenic soybean under conditions with negligible SCN infection. We hypothesize that GmSAMT1 expression affects salicylic acid biosynthesis, which, in turn, attenuates SCN development, without negative consequences to soybean yield or other morphological traits. Thus, we conclude that GmSAMT1 overexpression confers broad resistance to multiple SCN races, which would be potentially applicable to commercial production

A Standard Greenhouse Method for Assessing Soybean Cyst Nematode Resistance in Soybean: SCE08 (Standardized Cyst Evaluation 2008)

The soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is distributed throughout the soybean [Glycine max (L.) Merr.] production areas of the United States and Canada (Fig. 1) (26). SCN remains the most economically important pathogen of soybean in North America; the most recent estimate of soybean yield reduction in North America due to SCN totaled 34,659,000 metric tons during 2006 (34).This article published as Niblack, T., Tylka, G. L., Arelli, P., Bond, J., Diers, B., Donald, P., Faghihi, J., Ferris, V. R., Gallo, K., Heinz, R. D., Lopez-Nicora, H., Von Qualen, R., Welacky, T., and Wilcox, J. 2009. A standard greenhouse method for assessing soybean cyst nematode resistance in soybean: SCE08 (standardized cyst evaluation 2008). Online. Plant Health Progress doi:10.1094/PHP-2009-0513-01-RV.</p