A Preliminary Study On The Effect Of Grafting Between Wild And Cultivated Cassava On Growth And Development Of Shoots

There are significant differences in the photosynthetic efficiency and the accumulation efficiency of the tuber starch between wild ancestors and cultivars of cassava.The essence is that there are genetic differences in response to tropical environment factors such as light,temperature,soil moisture,nutrient absorption and utilization.In this study,the wild species W14,which have completed genome sequencing,and cultivars KU50 and SC205,were grafted with each other.Grafting methods and environmental conditions were optimized to obtain grafted genotype chimeras.Through the analysis of the starch synthesis,physiology,phenotypic and the expression level of key photosynthetic genes systematically,the interaction between sink and source was explored in cassava,which provided the theoretical basis for the growth and breeding of cassava.1.The seeds were soaked in solution with difference concentrations of hormones for 24 h,and the optimal solution was 100 mg/L NAA and 100 mg/L GA3.The germination rate was 52%.2.This study selected cassava germplasm resources,wild ancestor W14,cultivated varieties KU50 and SC205 planted in pots,which are very different in source and sink.Through the grafting between wild and cultivated type,suitable grafting methods and management scheme were screened out.The grafting technique was scion grafting by splicings.The temperature was 27-29℃,and the light was gradually increased after stay in dark for 24 hours.Humidity was above 90%in the first three days after grafting,and the humidity was gradually reduced to normal.3.Through phenotypic statistics,determining plant height and stem diameter of grafted and ungrafted plants,it was found that the change of phenotypic characteristics was not obvious between the others.But the plant height of the grafted plants was generally higher than that of the ungrafted plants.The growth rate of stem diameter was just the opposite.The growth contribution of the plant height was most in the scion.4.At 60 d,90 d,180 d and 210 d,the photosynthetic rate and chlorophyll content of the grafted and ungrafted plants were measured.The results showed that Wild-type rootstocks inhibit the photosynthetic efficiency of the cultivated scions,while the opposite,the cultivated rootstocks promote the photosynthetic efficiency of wild-type scions.It aslo shows that the growth and development of the aerial parts are related to the selection of rootstocks.The increase in the strong stock of rootstocks is conducive to the growth and development of the plants,and the decrease of the sink strength will play an opposite role.5.Select three representative genes of the photosynthetic pathway MeRibulose,MePEPC and MechlPPDK,use the database of GenBank and JGI to download the relevant information,and analyze the expression level by Realtime fluorescence quantitative PCR.It find out the significantly difference in the expression level of MechlPPDK between grafted and ungrafted varieties.The expression of MeRibulose and MePEPC was not greatly different among the varieties,indicating that the inter-specific grafting can affect the expression of some genes and then affect the physiological characteristics of the plants.The purpose of this study was to obtain the grafting plants,to further elucidate the effect on photosynthetic efficiency and starch synthesis after the change of sink and source by grafting.The preliminary work has been done to explore the internal coordination mechanism of the source,flow,and sink of cassava.It also provides reference for the following breeding and production of cassava.