| Alfalfa(Medicago sativa) exists widely in the world, and is high quality pasture to domestic animal.With the expansion of the alfalfa acreage, the pests of alfalfa becoming one of the important threats to alfalfa production in China, especially since 2008, pea aphid(Acyrthosiphon pisum) has gradually become the predominant groups of insect pests of alfalfa field. This paper is based on the resistance evaluation of alfalfa, pea aphid fed on different varieties of alfalfa, measured the alfalfa phenolic substances and the contents of total saponins, main digestive enzymes activity and the contents of the protein and total carbohydrate of the haemolymph of pea aphid, to explore the influence of different alfalfa varieties to digestive enzymes and the absorption of nutrients of pea aphid. The results are as follows:1.The effect of resistance on phenolic substance and saponin contents of different alfalfa(Medicago staiva) varietiesThe contents of polyphenols,simple phenol, tannin, condensed tannin, total saponin is measured on 8 alfalfa varieties by the method of colorimetric in the laboratory. Results show that sandili the damaged alfalfa with highest contents of 121.04 ± 0.89 mg/g, the lowest contents on weinan, were 92.45 ± 1.56 mg/g; The contents of simple phenol of damaged alfalfa are highest on gold queen, were 39.81 ± 4.66 mg/g, the lowest on the weinan was13.27 ± 3.05 mg/g;The contents of tannin on damaged alfalfa about 8 varieties were higher than CK, the highest on sandili was 106.79 ± 1.72 mg/g, the lowest on golden queen was52.40 ± 5.61 mg/g;The contents of condensed tannin was highest on gannong no.5 was 18.44± 0.16 mg/g, the lowest on gannong no.3 was 12.46 ± 1.57 mg/g;The contents of total saponins was highest on gannong no.3 was 0.99 ± 0.06 mg/g, the lowest on tianshui was0.46 ± 0.16 mg/g. There was a significant difference between the two alfalfa varieties about the contents of polyphenols, simple phenol, tannin, condensed tannin, total saponin(P<0.05).In addition, the contents of condensed tannin of damaged alfalfa with resistance value of alfalfa was significantly negative linear correlation relationship, the regression equation was Y = 19.109-1.296 X(R=0.454), shows that the higher resistance of alfalfa varieties, the higher contents of condensed tannin in alfalfa.2.The effect of different alfalfa varieties on the midgut protease of pea aphidMeasured the digestive enzymes in midgut of the two biotypes of pea aphid that were fed on eight different alfalfa varieties by the methods of Folin-phenol and others.The results showed that the red biotype after they fed on weinan,the protease activity was 9.71 ± 0.63U/m L,and green biotype after they fed on the hunter river was 9.88 ± 0.56 U/m L, two biotypes after they fed on sandili were 0.33 ± 0.10 U/m L and 0.43 ± 0.02 U/m L; Lipase activity of red biotype after pea aphid fed on hunter river was 4.12 ± 0.30 U/m L,while thegreen biotype after they fed on weinan was 4.00 ± 0.29 U/m L, two biotypes after they fed on gannong no.5 the lipase activity were 1.63 ± 0.10 U/m L and 1.08 ± 0.13 U/m L; The amylase activity of two biotypes after they fed on hunter river were 2.30 ± 0.40 U/m L, 2.14 ± 0.29U/m L; The highest active alkaline trypsin-like enzyme activity of two biotypes of pea aphid after they fed on weinan, respectively were 2.94 ± 0.38 U/m L, 0.38 ± 0.10 U/m L,and were lowest after they fed on gannong no.5, respectively were 0.62 ± 0.10 U/m L, 0.97 ± 0.04U/m L;Weak alkaline trypsin-like enzyme activity of two biotypes were highest after they fed on weinan, were 1.04 ± 0.01 U/m L and 1.07 ± 0.04 U/m L, the lowest enzyme activity of two biotypes after they fed on gannong no.5 were 0.33 ± 0.05 U/m L and 0.46 ± 0.03 U/m L;Chymotrypsin activity of red biotype of pea aphid after they fed on weinan was 5.68 + 0.98U/m L, green biotype fed on hunter river was highest that was 5.46 ± 0.92 U/m L, activity of two biotypes were lowest after they fed on gannong no.3 that with resistence, respectively were 1.91 ± 0.37 U/m L and 0.37 ± 1.37 U/m L.The pea aphid after they infested 8 different resistance alfalfa varieties, it showed that the linear correlation between the resistance value of different alfalfa and the protease, lipase and amylase activity of the pea aphid, and the alfalfa aphid resistance is higher, which lower the enzyme activity. So the resistant alfalfa varieties will control the midgut digestive enzyme activity of the pea aphid.3.The effect of different alfalfa varieties on nutrient of hemolymph of pea aphidMeasurd the contents of protein and total carbohydrate of pea aphid haemolymph by the the method of bradford and anthrone after they fed on nine different alfalfa varieties.Results showed that the red biotype of pea aphid after they fed on weinan,the contents of protein was39.12 ± 4.07 mg/m L, green biotype up to 39.25 ± 4.98 mg/m L after they fed on low resistant variety of tianshui, both red and green biotype were lowest after they fed on longdong that were 26.80 ± 2.82 mg/m L and 23.77 ± 3.20 mg/m L;Red biotype of pea aphid after they fed on gannong no.3 the contents of total carbohydrate up to 86.13 ± 0.52 mg/m L, lowest on gold queen was 56.40 ± 5.06 mg/m L, total carbohydrate of green biotype infested tianshui was highest that up to 80.88 ± 2.86 mg/m L, lowest on sandili was 56.59 ± 7.62 mg/m L.The pea aphid after they infested nine different resistance alfalfa varieties, it showed that the linear correlation between the resistance value of different alfalfa and the contents of protein of the pea aphid, linear equation were Y = 30.408 + 1.486 X(R = 0.500), Y = 25.625+ 2.388 X(R = 0.577), the alfalfa aphid resistance is higher, which lower the contents of protein. And the contents of total carbohydrate had no significant linear correlation with the resistance value of different alfalfa.So the resistence of alfalfa varieties will control the contents of protein,and have no difference on absorption of total carbohydrate to pea aphid. |
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