Functional Analysis Of Resistance Gene To Soybean Aphid From P746 And Induced Resistance To Soybean Aphid

Aphis glycines Matsumura（Hemiptera: Aphididae）, named as soybean aphid（SBA）, is an important pest of soybean [Glycine max（L.） Merr.] in China and North America. Summer host of soybean aphid is cultivated and wild soybeans. The main method to control this pest is using traditional insecticides, but multiple sprayings and increasing use of insecticides pose a direct concern for potential environmental pollution and insecticide resistance in soybean aphids.China is one of the original birthplaces of soybean aphid, four biotypes have been discovered in America, but biotype determination has not been conducted in China. It is necessary to identify biotype differentiation of soybean aphid along with aphid-resistance breeding. To further clarify application value of soybean resource P746 in aphidresistance breeding, which had antibiosis resistance to Shanghai aphid isolate, we analyzed the biotypes of soybean aphids collected from four different soybean-growing areas in China. Responses of four soybean aphid isolates from Changchun（Jilin province）, Jinan（Shandong province）, Shanghai, and Guiyang（Guizhou province） were assessed by infesting 11 soybean genotypes in noncaged and caged tests. We distinguished four isolates on their abilities to infest a set of host plants with known resistance genes Rag1 through Rag6（Rag: resistance to Aphis glycines）. Results showed biotype profiles of four isolates were different from each other, and that there were at least four biotypes of soybean aphid in China. We named them as CB1 to CB4（CB: China Biotype）. Meanwhile, we found P746 was resistant to Changchun and Jinan isolates, and P746 was a promising genotype to breed resistant variety which was appropriately growed in northern soybean belt of China.Based on previous study of molecular marker, we has located the resistance loci between marker BARCSOYSSR₁3₁278 and BARCSOYSSR₁3₁363 in antibiosis soybean germplasm P746. This section is on chromosome 13 of soybean genome, and has three Serine/Threonine protein kinase genes. Through analyzing their expressions attacked by aphids, we found one gene, Glyma13g40530, was upregulated more than 50 folds than control, and named this gene as GmSTPK1 temporarily. This gene belonged to NBS-LRR gene family and had three important domains: Concanavalin A-like lectin/glucanase domain, Serine-threonine/tyrosine-protein kinase catalytic domain and ATP binding site. GmSTPK1 protein was located in membrane system. Numbers of soybean aphid and tabacco aphid（Myzus persicae Sulzer） were significantly reduced on transgenic soybean hairy roots or T3 and T4 generations of Arabidopsis thaliana respectively. These results showed great prospect of GmSTPK1 gene in plant breeding of resistance to aphids in future.Induced systemic resistance（ISR） is getting more and more attention in controlling agricultural pests. We selected β-aminobutyric acid（3-aminobutyric acid or DL-β-aminobutyric acid, BABA） as plant elicitor to activate resistance against soybean aphid. In both choice and non-choice tests, soybean aphid numbers were significantly decreased on seedlings drenched with 25 mM BABA compared to controls. Mechanisms of BABA induced resistance against soybean aphid included: enhancing activities of defense enzyme, such as phenylalanine ammonia-lyase（PAL）, peroxidase（POX）, polyphenol oxidase（PPO）, chitinase（CHI）, and β-1, 3-glucanase（GLU）; activating genes expressions of phenylpropanoid pathway, consistent with increased contents of isoflavones and lignin; augmenting callose deposition in aphids infected seedlings. Moreover, foliar application of 1 g/L BABA also inhibited the reproduction and growth of soybean aphid, and BABA induced resistance was broad-spectrum to four soybean aphid biotypes which were identified in this study. These results showed BABA application was a promising way in Integrated Pest Management（IPM）.In summary, four aphid isolates belonged to different biotypes and this was the first study of Chinese biotype variation of soybean aphid. GmSTPK1 gene controlled soybean aphid resistance in P746, and this gene also enhanced resistance against tabacco aphid in Arabidopsis thaliana. Throuth BABA application, we found the resistance mechanisms of BABA induced resistance against soybean aphid and this resistance inducer had broad spectrum resistance to different soybean aphid biotypes.