Biological Characteristics And Molecular Assisted Identification Of Early Maturing Bud Mutan ’Tian Gong Mo Yu’ From ’Summer Black’ Grape

The Summer Black grape is a triploid seedless grape variety from Japan,bred from ‘Kyoho’ and ‘Thompson’.Due to its excellent quality,seedless and high yield,it has been planted in most grape producing areas in China.In 2008,we found a precocious mutant in the grapevines of the Summer Black from Jinhua Zhaichun Agricultural Development Co.,LTD.The mutant grape possesses many advantageous horticultural traits,including beautiful spike shape,easy colouring,7-10 days earlier than Summer Black,uniform fruit color and good quality,so it has higher commodity value,market competitiveness and greater promotion value.In this experiment,the mutant of Summer Black(TianGong MoYu)was used as material to compare the biological characteristics with Summer Black grape,conduct molecular assisted identification,and explore the formation rules of fruit development and quality,and use the high throughput RNA-seq technique to identify the difference between Tiangong Moyu and Summer Black in transcriptome level,so as to provide scientific basis for grape breeding and new variety identification.The results of the study are as following: 1.Comparison of botanical and biological characters(1)The morphological characteristics of the mutant grape and Summer Black grape were different in the color of tender tip leaves and young leaf villi.The mutant of Summer Black grape tender tip leaves were light reddish brown(Summer Black reddish brown),and the villi on the back of young leaves were sparse(Summer Black medium density).(2)In terms of fruit economic properties,during the same period,the soluble solids content of Tiangong Moyu increased and it was higher than Summer Black.When it was fully ripe,it could reach 18-23%.There was no significant difference in fruit quality between the two cultivars at full ripening stage.(3)In terms of phenological phase,the mutant strain matured 7-10 days earlier than the Summer Black grape(4)In terms of growth and fruiting habits,the flower bud differentiation of the mutant strain was better,and the germination rate and fruit-bearing branch rate were higher than those of Summer Black grapes.(5)In terms of disease resistance,the mutant strain had stronger resistance to acid rot,gray mildew,downy mildew and branch canker than Summer Black grape.2.Formation rules of fruit development and qualityThe dynamic changes of single fruit quality,longitudinal and transverse diameter,anthocyanin,sugars,organic acids,total sugars,titratable acid,total phenols and flavonoids were measured at different developmental stages of Summer Black and the mutant.According to the law of fruit growth and development,the trends of growth and fruit quality are basically the same,but there are also differences.The contents of sucrose,fructose,glucose and total sugar in the mutant were higher than Summer Black grape in the whole development period;the contents of malic acid,tartaric acid and titratable acid in the mutant decreased rapidly after fruit color changed,and the content of titratable acid was lower than Summer Black.The content of titratable acid began to decrease one week earlier than Summer Black.The content of anthocyanin in the mutant was lower than that in Summer Black grape,lower at the early stage of development and slightly higher at maturity than that in Summer Black grape.The color transformation period of Summer Black bud mutant grape was 7-10 days earlier than Summer Black grape,and the difference of anthocyanin content in Summer Black bud mutant grape was very significant during the same period.3.Molecular assisted identificationIn the identification of ISSR molecular markers,using ISSR primers to amplify DNA of Tiangong Moyu and Summer Black,26 ISSR primers and 7 pairs of primer combinations with stable amplification were screened according to polymorphism.The results showed that the allele bands amplified by the two materials were identical,indicating that genetic background of the mutant was very similar to Summer Black.In SSR molecular marker identification,40 pairs of SSR primers with good stability and polymorphism were screened on 19 chromosomes.The results showed that the bands amplified by primer E10 were inconsistent,suggesting that there were different bands between them,indicating that they existed at genomic DNA level.4.RNA-seqThe gene expression profiles at 5 different developmental stages from fruit set to ripe berries(2,4,5,8 and 10 weeks after anthesis)were compared between Summer Black and bud mutant using RNA-seq.The results showed that there was a certain amount of differentially related genes due to different developmental stages.