Biological Characteristics Of A Bud Sport From ‘Lane Late Navel Orange' And Evaluation Of Its Application

Bud mutation selection is a breeding method to improve the natural variation that is commonly found in the field.Some mutant plants have the potential to become good cultivars.In order to shorten the selection period and fasten the breeding process,bud mutation selection is an important way to innovate germplasm resources.At present,according to the market demand,a lot of navel orange breeders tend to choose new early-maturing cultivars with high sugar and low acidity characteristics.There is no report on the mutation in the appearance of navel orange yet.This study used a bud mutation from ‘Lane Late' navel orange as material,which was found in an orchard of Anxi Town,Xinfeng County.It was named as ‘pumpkin like navel orange' because it has the similar peel structure as pumpkin.The rind was irregularly arranged from the fruit pedicle to the top of the fruit.Biological characters of ‘Lane Late' navel orange and its bud mutation"pumpkin like navel orange" were studied in the aspects of ploidy detection,phenological phase observation,fruit growth,fruit quality changes in different periods,microscopic structure observation of fruit peel and ISSR molecular markers.The main results are as follows:1.Ploidy identification of "pumpkin like navel orange" and its parent ‘Lane late navel orange' was done using flow cytometry.The results showed that they were both diploid.2.Phenophase and fruit growth observation of "pumpkin like navel orange",‘Lane Late',the first generation of "pumpkin like navel orange" and ‘Newhall navel orange': the results showed that there was no difference in the timing of sprouting,flowering,fruit-falling,and shoot growth stages between "pumpkin like navel orange"and ‘Lane Late' navel orange but the fruit coloring period of the former was slightly later.Compared with ‘Newhall',the growth period and flowering period of the first generation of "pumpkin like navel orange" are delayed for 3-5 days;the fruit coloring period is delayed for one month;the coloring cycle is half a month longer than‘Newhall'.The fruit growth of the two materials is basically the same.In the same period,the fruit shape index of "pumpkin like navel orange" was smaller than that of‘Newhall'.3.Studies on the main quality changes in the development of "pumpkin like navel orange" and ‘Lane Late': results showed that the average fruit weight of"pumpkin like navel orange" was 200-270 g,diameter 70~85 mm,longitudinal diameter 66~78 mm,fruit shape index less than 1,thickness about 4.5 mm.Moreover,the fruit of "pumpkin like navel orange" is slightly flat and its peel is thinner.Edible rate and juice yield were high in both materials.In the same period,the content of Vc in "pumpkin like navel orange" was higher than in ‘Lane Late',with the highest content 59.76 mg/100 mL.Soluble solids content has been increasing during the test period.Titratable acid content has been decreasing,but the acid content in the same period was higher than that of ‘Lane Late'.The ratio of soluble solids to titratable acid showed an overall increasing trend.4.The microscopic structure of the pericarp was observed.In the young fruit stage,the epidermal cells in the pit of the "pumpkin like navel orange" peel were mostly elongated and concentrated.In the mature fruit stage,the epidermal cells were arranged in neat and tight rules.The oil vacuole arrangement was dense and mostly oval,with double layers.The thin-walled cells in the white cortex were densely arranged on the surface of the rib-like protrusions,while the thin-walled cells in the white cortex were loose and the density was small.5.Using ISSR molecular markers,PCR amplification was performed using the leaf genomic DNA of "pumpkin like navel orange" and ‘Lane Late'.We selected 17 primers out of 100 primers that could generate clear bands.was And further experiment revealed that primers UBC825,UBC827,UBC851,and UBC857 could distinguish "pumpkin like navel orange" and ‘Lane Late' on genetic level.In summary,"pumpkin like navel orange" has a novel appearance,uniformed fruit shape,high Vc content and high juice content.It tastes a little sour but has strong flavour.With the late-maturing characteristics and good genetic stability,the selection and breeding of this bud sport can enrich citrus germplasm resources and adjust the industrial structure,which has a good market prospect and application value.