Biological Characteristics And Induced Resistance To Heterodera Glycines

Soybean cyst nematodes (Heterodera glycines Ichinohe)(SCN) is an important endoparasitic nematodes, has spread to all the countries and regions that growing soybean nowadays. SCN have been reported in14provinces and municipalities in China. The most suitable host of SCN is soybean (Glycine max), some crops including adzuki bean (Vigna angularis), snap bean(Phaseolus vulgaris), mung bean (Phaseolus aureus), green pea(Pisum sativum) and common lespedeza(Lespedeza striata) to name a few, and some kinds of weeds are also hosts. Parasitizing on soybean roots, SCN can depress root growth, reduce the amount of soybean root nodules, and cause soybean yield reduction or even totally yield lost under favorable conditions. This study has focused on biological characteristics of SCN parasitizing on soybean and tobacco, and induced resistance to SCN, the main research achievements are as follows:1. SCN were detected in14samples from55samples collected from Anhui, Jiangsu and Shanghai, the incidence was25.5%. SCN were not found in the only one sample from Jiading district in Shanghai. While the incidence of SCN in Jiangsu and Anhui Provience was26.7%and22.2%, respectively. The incidence was the highest in Nantong in Jiangsu, which was55.6%. However, SCN were not found in Kunshan, Dafeng, Yancheng and Sihong in Jiangsu, and Lingbi in Anhui. Among the samples collected from six crops, SCN only detected in soybean samples.2. Races of three SCN populations from Hangzhou in Zhejiang, Taigu in Shanxi and Haerbin in Heilongjiang were determined. It showed that Shanxi and Heilongjiang populations were race4, which were the same with the reports before. Hangzhou population was race3, and it can propagate for three generations during the whole growing season of spring soybean in Hangzhou.3. At18days post inoculation (dpi), competition between SCN and Rotylenchulus reniformis (Rr) showed that development of SCN in the early stage was not affected by Rr, and infectivity of SCN was stronger than Rr. Fresh root weight and shoot height were reduced by inoculation of nematodes. At30dpi, inoculation of Rr alone reduced freash root and shoot weight, while inoculation of SCN increased fresh root weight compared with control. Both Meloidogyne incognita (Mi) and SCN reduced fresh shoot weight and shoot height, stimulated root growth instead. Number of nematodes increased with the augment of inoculum amount, but at the same inoculum amount, the number of Mi was greater than SCN.4. The cyst nematodes parasitizing on tobacco (SCN-HN) in Xiang county, Xuchang city in Henan province was identified as H. glycines by means of morphological and molecular indentification. SCN-HN can infect all of soybean differentals, Peking, Pickett, PI90763, PI88988and Lee71, used in race determination. Some even developed into third stage juveniles (J3), but full development never occured until40dpi. SCN-HN and SCN-SX revealed a significant virulence difference. SCN-HN successfully invaded soybean roots, minimal development (to J3only) occurred at48dpi, but adult female never formed. Inoculation of SCN-SX to tobacco got similar results. Nematode can infect both Nicotiana tobacum and N. benthamiana, but only one J3developed on N. tobacum at12dpi, and one J3developed on N. benthamiana at30dpi. These results indicated soybean is non-host of SCN-HN, and tobacco is non-host of SCN-SX. We suggest that SCN population parasitizing on tobacco is a new pathotype of SCN.5. SCN-HN can infect all of Solanum melongena, Capsicum annuum and Lycopersicon esculentum studied at10dpi. However, adult female never formed on S. melongena (var. Hangjiaoyihao and Jizhuaxjilin), C. annuum (var. Hangzhouhongqie) and L. esculentum (var. Qiemen800) at33dpi, while female and male were developed on L. esculentum (var. Hangzayihao and Zhefen701). It seems that Hangzayihao and Zhefen701of L. esculentum are poor hosts of SCN-HN.9. Pathogenicity was compared between SCN-HN and Mi that parasitizing on the same tobacco in Xuchang. Tobacco growth was not affected, even stimulated by SCN-HN if inoculation level was less than1000, but fresh shoot and root weight were reduced when the inoculation level was higher. The suppression by Mi was stronger than SCN-HN. Fresh shoot weight was reduced at any inoculation level of Mi. Compared with inoculated one species alone, inoculating two species together at the same inoculum level resulted in less damage to tobacco, even compensated the damage caused by Mi. Number of SCN was gradually increased as the inoculum augment, but decreased as a result of intence competetion at level10000. Mi increased gradually at all of the level. When inoculated together, Mi increased more quickly than SCN-HN at lower level, but was inhibited by SCN-HN at higher level.7. Treatment of chemical elicitors salicylic acid (SA), jasmonic acid (JA) DL-β-amino butyric acid (BABA),2,6-dichloroisonicotinic acid (INA) and riboflavin to soybean, all reduced female number of SCN. BABA and INA were more effective, had suppression percentage of51%and53%, respectively. INA significantly reduced fresh root and shoot weight, and shoot height. BABA used as soil drench was more effective than used as foliar spray and root-drip. Root-drip decreased shoot height, soil drench caused reduction of fresh root weight, and foliar spray reduced fresh shoot weight.8. Phylogenetic analysis was conducted based on rDNA-ITS sequence of SCN populations from soybean and tobacco using PAUP4.0. The phylogenetic tree showed some genetic variation among SCN and other cyst nematodes, while it has certain stability in species level of SCN. SCN populations parasitizing on soybean and tobacco showed some but not specific variation. However, the Maximum parsimony tree did not differentiate the two pathotypes distinctly.