Abstract: 【Aim】 The objective of this study is to clarify the dissimilarities of feeding behaviors of biotype E of the greenbug, Schizaphis graminum on oat (Avena sativa) lines with different phenotypic resistance so as to ascertain aphid-resistant factors. 【Methods】 The frequencies and duration of eight basic waveforms of A, B, C, Pd, E, F, G and np for probing and penetrating behaviors of apterous adults of biotype E greenbug were recorded by using direct current-electrical penetration potentiometer (DC-EPG Giga-4) on ten MN hulled oat lines with varied phenotypic resistance. 【Results】 The electrical penetration graph showed that recognition time of biotype E greenbug ranged from 1.03 to 2.62 min on ten MN hulled oat lines with varied phenotypic resistance. Non-penetrating time was longer and the time to the first penetration from initiation of electrical penetration graph was the longest on MN10253 hulled oat line with moderate-level phenotypic resistance, which were 117.77 min and 13.80 min, respectively, suggesting that interference factors adverse to host locating and recognizing of biotype E greenbug possibly exist in host surface. Total duration of penetrating into mesophyll and xylem by stylet and the duration of penetrating into xylem by stylet from initiation to the first penetration were all the shortest on MN08252 hulled oat line with moderate-level phenotypic resistance, which were 78.01, 6273 and 32.29 min, respectively, and the frequency of np waves was up to 28.57 times, suggesting that aphid-resistant factors are likely present in mesophyll and xylem. Total and mean duration of F waves were the longest on MN06203 hulled oat line with low-level phenotypic resistance, which were 4.96 min and 5.81 s, respectively, suggesting that the line has fair physical resistance. Total duration of E₁ waves was the shortest while duration of penetrating into phloem by stylet from initiation to the first was the longest on MN11213 hulled oat line with low-level phenotypic susceptibility, which were 1.94 min and 246.05 min, respectively, suggesting that aphid-resistant factors might be present in phloem. 【Conclusion】 Aphid-resistant factors are most possibly seated on the leaf surface of MN10253 hulled oat line with moderate-level phenotypic resistance, in the mesophyll and xylem of MN08252 hulled oat line with moderate-level phenotypic resistance, in the phloem of MN11213 hulled oat line with low-level phenotypic susceptibility, while the MN06203 hulled oat line with low-level phenotypic resistance has stronger physical resistance.

Key words: Schizaphis graminum; Avena sativa, phenotypic resistance, feeding behavior, electrical penetration graph (EPG)