Research Of Frost Injury Mechanism And Control Techniques In 'Skiranui Tangerine' Hybrid Citrus Fruit

Citrus was one of the important fruit trees.Citrus were cultivated by more than 80 countries in the world.And the area and output of citrus was premier in the world.China was the primary to plant the citrus,mainly distributed in the Changjiang River and the southern area.There were 19 provinces to plant it,and concentrated in the gentle slope and the foothill which was the north latitude 20°～30°and the elevation 700～1000m.In Recent years,the cultivated areas were stabilized in 120～130 hm² ten thousand,and the outputs were the third in the world.From currently the citrus industry development,it had become the development trend which was" peel easily,aspermous(little pit),had the thick flavor,taste".The hybrid citrus(orange and orange,orange and pomelo) would cater to this development trend,and could develop quickly in recent years.The Skiranui tangerine(C.unshiu×C sinensis cv.Skiranui tangerine) was one of the superior hybrid citrus cultivars that were introduced and extended by the Citrus Institute in Institute of Agricultural Science in china from Japan.It was seen as citrus cultivars popularly in the 21 st century.The cultivars had more characteristics that the fruit was big and aspermous,average each weight was about 250 grams,dissoluble solid content was up to 16～18%,flesh was tender and crisp,the taste was thick,and the quality was very excellent.And its mature period was the annual February-March that was off-season in the fresh fruit market.In sichuan,hybrid citrus cultivars developed quickly because of its quality,output and so on.The cultivated area of hybrid citrus cultivars was 6667hm² at present,and the Skiranui tangerine was above 60%.In the south of our country,especially Sichuan Basin,in recent years because of the climatic change,the low temperature of the annual winter and the early spring next year were more and more frequent.However the mature time of the Skiranui tangerine was February to March.When nearly ripe,the fruits in the Sichuan Basin were often subjected to the threat of frost in the coldest months(from December to January next year).The frost resulted in the great quantities of fruits going down and the yield down sharply.In the production,the widespread method was overlaied the ex-tree before the coldest month coming,and through this method could ease the fruit frost in some extent and hide the ray seriously.Thus it caused the crown of a tree to deteriorate badly in the light condition,and the fruit quality descended seriously.Currently,researchs on the citrus frost injury had focused on the leaves and branches, but researchs on the citrus fruit frost injury had not been reported,which was that the' Skiranui tangerine' fruit frost caused by the INA,and controlled method.In this study,'Skiranui tangerine' hybrid citrus fruit was used,through separation and purification,it may be found to have INA bacteria of this fruit,and the INA were identificated.With the use of chemical reagents and the antagonistic bacterias which were isolated from Valencia Orange,blood orange and trifoliate orange,grapefruit and other fruit,the INA bacteria on the 'Skiranui tangerine' fruit were prevented and cured in the room and in the field.We looked forward to find a way that may keep the quality of 'Skiranui tangerine',and it was also safe and effective to control frost,and offered a reliable guarantee for high-quality' Skiranui tangerine' fruit.The main findings were as follows:(1) Separated by plate dilution and Vali small droplets freeze,9 strains of INA bacteria are isolated and identified from the surface of 'Skiranui tangerine' fruit in the first time.INA 110(Erwinia ananas) and INA3023(Pseudomonas syringae pv.syringae) which are supplied by the molecule pathology group of key laboratory of plant diseases and insect pests biology of plant protection research institute of Institute of Agricultural Science in china is become standand strains.According to the bacteriology identification,4 isolatess arc Erwinia ananas and 5 isolates are Pseudomonas syringae pvs,respectively for 44.44% and 55.56%.(2) The activity of INA bacteria from 'Skiranui tangerine 'fruit is affected by temperature,bacteria mixture concentration and pH value.If the density of INA bacteria is 5×10²ï½ž5×10⁸ml^-1 and temperature is -2～-7℃,the density of INA bacteria is more higher and ice-nucleation activity is more better.When the density of INA bacteria is to some extent,temperature is more lower and ice-nucleation activity is more better.PH value of INA bacteria growth is 5.0～9.0,and the best pH value is 7.0,acidic solution(pH2～4)and alkaline solution(pH10) can destroy ice-nucleation activity of INA bacteria.Among three experimental medicaments as NO.1 frost-resistant medicament,lime-sulphate medicament and macozeb have good effect on controlling experiments,above 90%.NO.1 frost-resistant medicament(2000 times) shows the best effects on the INA bacteria.(3) In a simulated natural frost artificial box,ten kinds of chemical medicaments as NO.1 frost-resistant medicament(1000 times,1500 times,2000 times),80%Macozeb(500 times),72%Streptomycin(1000 times),99.5%boric acid(200 times),98%CuPFerron (1000 times),98%ZNCl₂(1000 times),and other chemical medicament that pH value of mixture which used Lime-sulphate medicament and boric acid is 4 and 10 are used to prevent and cure the INA bacteria.2000 times mixture of NO.1 frost-resistant medicament shows the best effects on controlling the INA bacteria in' Skiranui tangerine' fruit,and its killing rate is 99.80%.(4) 16 isolates of antagonistic bacteria of INA bacteria are isolated from 'Valencia Orange' fruit and other four citrus fruits on the same ecological condition.Thereinto,D₁ bacteria isolated from 'Valencia Orange' shows the best effects on controlling the INA bacteria indoor.(5) Under the low temperature condition(≤0℃,14d;frost day,Sd;snowy day,5d;the absolute minimum temperature is -5℃),ten kinds of chemical medicaments as NO.1 frost-resistant medicament(1000 times,1500 times,2000 times),80%Macozeb(500 times),72%Streptomycin(1000 times),99.5%Boric Acid(200 times),98%CuPFerron(1000 times),98%ZNCl₂(1000 times),and other chemical medicament that pH value of mixture which used Lime-sulphate medicament and boric acid is 4 and 10 are used to prevent and cure in the field.NO.1 frost-resistant medicament(2000 times) and boric acid(200 times) show the better results,with both frostbite rates respectively are 8.90%and 10.00%.The effects on frost preventing in the field for 'Skiranui tangerine' fruit of six antagonistic bacteria(D₁,D₂,D₅,D₇,D₉,D₁₂) which were isolated from 'Valencia Orange' fruit and other four citrus fruits were not very ideal.But the effect of D₁,D₂ antagonistic bacterias from the 'Valencia Orange'(C.sinensis cv.Valencia orange) was better relatively.In six different approachs of physical frost preventing,as big house plastic sheeting, little house plastic sheeting,crown shallow coverage of plastic sheeting,fruit bagging (white),fruit bagging(black inside and grey outside) and fruit bagging(brown paper),big house plastic sheeting showed the best effect on preventing in the field,the frostbite rate is 5.57%,but the cost of big house plastic sheeting is high,so it is difficult to promote in the production.Above mentioned 22 different frost-resistant treatments as medicaments,biocontrol bacteriums,fruit baggings and equipment treatments and so on in the field,the equipment treatments had higher effect on the flower bud differentiation and the fruit quality,the single flower rate of having leaf is only 5.03%with crown shallow coverage of plastic sheeting.Synthetically considering the combination of factors,such as fruit quality,cost, operation and the output next year,the treatment of frost-resistant that used NO.1 frost-resistant medicament(2000 times),boric acid(200 times) and fruit bagging(white) is good,and it can be widely used in the production.