Evaluation Techniques Of Transgenic Wheat Resistance Effect To Sitobion Avenae (Fabricius)

According to current two strategies of transgenic wheat to aphid, the antibiosis effect of lectins andrepellent effect of EβF to wheat aphid, several investigations of aphid resistant evalution of two kinds oftransgenic wheat to wheat aphid, Sitobion avenae (Fabricius), were conducted in laboratory andgreenhouse. First, at the seedling stage of transgenic wheat lines, the target genes, Arisaemaheterophyllum agglutinin (AHA) or Pinellia ternate agglutinin (PTA) was detected by PCR. Second,resistance evaluation of transgenic wheat with lectin gene and EβF synthase gene was studied. Then,commercial lectin and EβF were used to investigated the impact of lectin and EβF on aphids' biologyand behavior. The major results are as follows:The feeding behaviors of S. avenae using electrical penetration graph technique (Giga-8DC-EPG)on the seedling stage of transgenic wheat lines with and without lectin gene were compared. Then,multi-objective comprehensive discrimination was used to identify the resistant level of different wheatvarieties (or lines) to aphid. The results showed that duration proportion of E waveform among Lines117with PTA gene,48,54,278and406with AHA gene was significantly shorter than the transgenicreceptor cv.KN199. By the cluster analysis,10wheat varieties (lines) were clustered into three groupsaccording to the average duration of each waveform: Groupâ…  w as resistant lines including JPâ‘ andLines278,54,48,406with AHA gene; Group â…¡ was intermediate type including Line117with PTAgene; Group â…¢ was susceptible lines including Xinong2595, Beijing837, KN199and Line151withAHA gene. The duration of np waveform were significantly different among three groups, Groupâ…¡ wasthe longest one, but Group â…¢ was the shortest one; the duration of E₂in Group â…  and â…¡wassignificantly shorter than that of Group â…¢. The results based on multi-objective comprehensivediscrimination revealed that among the whole transgenic lines, except Line151being lowly susceptibleto aphid, Lines117,48,54,278and406were all lowly resistant to aphid. Duration of one generationand fecundity of S. avenae on transgenic lines406,151,48,117and278also decreased significantly. Asthe aphid-resistance identification among the lines, clustering analysis of EPG parameters wasconsistent with multi-objective comprehensive discrimination. When the proportion of E₂waveform>10min less than13%, and E duration ratio less than23%, the wheat line was resistant one, otherwisewas susceptible.The results of life parameters showed that there were lower net reproduction rate (R0), meangeneration time (T), intrinsic rate of increase (rm), finite rate of increase (λ), longer double populationtime (t) of S. avenae on trans-lectin wheats than control. Taking five parameters into consideration,Lines406and278with lectin gene were better than other lines to control aphid. Decrease of netreproduction rate (R0) and finite rate of increase (λ), increase of double population time (t) indicated thattransgenic wheat with EβF synthase gene had potential to inhibit aphid population growth.The result of host selection experiment showed that S. avenae had bad preference to transgenicwheat with EβF synthase gene, and Lines W1, W2, W3, W4, W8, W9, W10, W12, W17repelled aphidssingnificantly. Y-tube olfactory response test supported the above result except Line W4.Bioassay of two different sugar-specific binding lectins to S. avenae showed that, LC₅₀(48h)of mannose-binding specificity ConA was1.45mg/mL. LC₅₀(48h)of galactose binding specificity PHAwas1.88mg/mL. These two lectins were lethal to aphid at2mg/mL, aphids were dead totally afterfeeding ConA for5days and PHA for6days respectively. Feeding behavior result showed that durationof E₁followed by E₂was decreased significantly at all concentrations. The appearance number of E₁followed by E₂was decreased when ConA was more than0.5mg/mL. Passive ingestion was totallyinhibited when ConA was more than1.0mg/mL.Effect of different EβF concentrations on aphid was tested by short-range effect, long-distanceolfactory behavior, winged morphs formation and population growth. The numers of aphid treating with≥200ng/μL escaping from feeding site were significantly more than control. At concentrations≥400ng/μL, EβF inhibited population growth significantly. At the concentration≥600ng/μL, EβFinduced more wing morphs and Y-tube olfactory response showed significantly repellent effect. Basedon the above results, it can be deduced the EβF600ng/μL to be threshold concentrations as repellant tocontrol the aphid.