Embryonic Callus Induction From Leaves And Veins And Endogenoushormonecontent Inloquat(Eriobotrya Japonica Lindl.)

Aiming at further broadening the explant types of loquat culture in vitro and exploring a more suitable regeneration system,the research was carried out with leaves and veins as explants,comparing the performance of the two types of explants,including callus induction,embryogenic callus occurrence,proliferation and differentiation.Some factors influencing the response of leaf and vein culture weresystematically investigated.Finally well-growing embryogenic calluses and heart-shape embryowere obtained from leaf explants.Besides,the endogenous hormones of leaves and calluses in subculture were analyzed by High Performance Liquid Chromatography(HPLC)and established the relation between endogenous hormones and embryogeniccallusoccurrence,accumulating data for in vitro regeneration system of loquat and transgenic receptor system and laying the foundation for developing genetic transformation and preserving germplasm resources.The main results were as follows:1.Selectionofexplants and inoculation ways:Loquat leaves picked from March to May,the light green leaves that had spread out for 12d with the leaf length of about 14 cm and little lightbrown tomentum covering the surfacewere appropriate.Thebasalandmiddle leaf and vein sections were betterforin vitro culture and callus induction.In vein culture,fewer explants were browing and the rate of callus induction was higher.Calluses of leaf explants occurred later but the quality was better and had great potential of differentiation.The response of leaves and veins to inoculation ways were different.Laying on the medium in abaxial side down was better for leaf culture and growth of calluses,in whichcallus induction rate was 60.3%,significantly higher than the other inoculation way,while the culture of veins responsed in the opposite manner and calluses formed more quickly and callusinductionrate was 35.4%higher when laid in adaxial side down.2.Callus induction,embryonic callus appearanceand differentiation:1/8MS +1.0 mg/L 2,4-D +1.0 mg/L 6-BA was suitable for the primary culture of leaf explants,in which the rate of callus induction was 64.6%.Callus initiation of vein explants was earlier.1/4MS +2.0 mg/L 2,4-D +1.0 mg/L 6-BA was suitable for the primary culture of vein explants,in which the rate of callus induction was 65.6%.Both leaf and vein callus multiplication were better in the medium of 1/2MS + 0.5 mg/L 2,4-D + 0.25 mg/L 6-BA +0.2 mg/L NAA + 1.0 g/L AC.The multiplication rate of leaf callus was 4.39.Embryonic callus grew well in the medium and the rate of embryonic callus formation was 31.1%.The multiplication rate of vein callus was 4.73 and the rate of embryonic callus induction was 17.9%.Calluses of leaf explants grew well in the differentiation medium of MS + KT 0.2 mg/L + 6-BA 0.4 mg/L + NAA 0.1 mg/L + CH 600 mg/L.Heart-shape embryos were obtained from the embryonic calluses.Most of vein calluses were dark-green and tuberculate.Some protrusionsappeared on the surface of the calluses butno differentiation.3.The effect oflight spectrumto the callus multiplication:Red,blue and the mixture of red&blue(1:1)had positive effect on the callus growth,and the effect of blue light was the most obvious.Although had slower growth,calluses under the red light had great potential of differentiation.4.Relation between embryonic callus induction from leaves and endogenous hormonecontent:IAA/ZT in leaves had positive effect on the embryonic callus induction rate,while GA3/IAA had negative effect.Higher content of IAA,ABA,ZT and lower content of GA3 was observed in the embryonic calluses.Yellow-green and granularcalluses were similar to the embryonic calluses in the level of endogenous hormones.Theyhad great potential of differentiation,and they were also the favorable materials for differentiation culture.