Overexpression of the transcription factor MdWRKY115 improves drought and osmotic stress tolerance by directly binding to the MdRD22 promoter in apple

Abiotic stress reduces plant yield and quality.WRKY transcription factors play key roles in abiotic stress responses in plants,but the molecular mechanisms by which WRKY transcription factors mediate responses to drought and osmotic stresses in apple(Malus×domestica Borkh.)remain unclear.Here,we functionally characterized the apple GroupⅢWRKY gene MdWRKY115.qRT-PCR analysis showed that MdWRKY115 expression was up-regulated by drought and osmotic stresses.GUS activity analysis revealed that the promoter activity of MdWRKY115 was enhanced under osmotic stress.Subcellular localization and transactivation assays indicated that MdWRKY115 was localized to the nucleus and had a transcriptional activity domain at the N-terminal region.Transgenic analysis revealed that the overexpression of MdWRKY115 in Arabidopsis plants and in apple callus markedly enhanced their tolerance to drought and osmotic stresses.DNA affinity purification sequencing showed that MdWRKY115 binds to the promoter of the stress-related gene MdRD22.This binding was further verified by an electrophoretic mobility shift assay.Collectively,these findings suggest that MdWRKY115 is an important regulator of osmotic and drought stress tolerance in apple.

Comparative transcriptome analysis reveals key genes and pathways in response to Alternaria alternata apple pathotype infection

Apple leaf spot,caused by the Alternaria alternata apple pathotype(AAAP),is an important fungal disease of apple.To understand the molecular basis of resistance and pathogenesis in apple leaf spot,the transcriptomes of two apple cultivars‘Hanfu'(HF)(resistant)and‘Golden Delicious'(GD)(susceptible)were analyzed at 0,6,18,24 and 48 h after AAAP inoculation by RNA-Seq.At each time point,a large number of significantly differentially expressed genes(DEGs)were screened between AAAP-inoculated and uninoculated apple leaves.Analysis of the common DEGs at four time points revealed significant differences in the resistance of‘HF'and‘GD'apple to AAAP infection.RLP,RNL,and JA signal-related genes were upregulated in both cultivars to restrict AAAP development.However,genes encoding CNLs,TNLs,WRKYs,and AP2s were only activated in‘HF'as part of the resistance response,of which,some play major roles in the regulation of ET and SA signal transduction.Further analysis showed that many DEGs with opposite expression trends in the two hosts may play important regulatory roles in response to AAAP infection.Transient expression of one such gene MdERF110 in‘GD'apple leaves improved AAAP resistance.Collectively,this study highlights the reasons for differential resistance to AAAP infection between‘HF'and‘GD'apples which can theoretically assist the molecular breeding of disease-resistant apple crops.

Biochar alleviates apple replant disease by reducing the growth of Fusarium oxysporum and regulating microbial communities

Apple replant disease(ARD)negatively affects plant growth and reduces yields in replanted orchards.In this study,biochar was applied to apple replant soil with Fusarium oxysporum.Our aim was to investigate whether biochar could promote plant growth and alleviate apple replant disease by reducing the growth of harmful soil microorganisms,changing soil microbial community structure and improving the soil environment.This experiment included five treatments:apple replant soil(CK),methyl bromide fumigation apple replant soil(FM),replant soil with biochar addition(2%),replant soil with F.oxysporum spore solution(8×10^(7)spores·mL^(-1)),and replant soil with biochar and F.oxysporum spore solution addition.Seedling biomass,the activity of antioxidant enzymes in the leaves and roots,and soil environmental variables were measured.Microbial community composition and community structure were analyzed using 16SrDNA and ITS2 gene sequencing.Biochar significantly reduced the abundance of F.oxysporum and increased soil microbial diversity and richness.Biochar also increased the soil enzyme activities(urease,invertase,neutral phosphatase,and catalase),the biomass(plant height,fresh weight,dry weight)and the activity of antioxidant enzymes(superoxide dismutase,peroxidase,and catalase).The root indexes of apple seedlings was also increased in replant soil by biochar.In sum,biochar promoted the growth of plants,improved the replant soil environment,and alleviated apple replant disease.

The role of the auxin-response genes MdGH3.1 and MdSAUR36 in bitter pit formation in apple

Apples often exhibit bitter pits in response to metabolic disorders during ripening and storage;however, the mechanisms underlying the bitter pit(BP) development remain unclear. Here, metabolome and transcriptome analyses were performed to investigate BP pulp of 'Fuji'. Two auxin-response genes, MdGH3.1 and MdSAUR36, were screened. Their expression as well as the auxin content in BP pulp were found to be higher than those in healthy pulp(P < 0.01). In the field, excess CO(NH2)2increased the incidence of BP. Moreover, the auxin content and MdGH3.1 expression increased in apples after nitrogen fertilization. On Day 30 before harvest, the two genes were transiently transferred to the fruit, and 20.69% and 23.21% of BP fruits were harvested. After 10 μmol·L-1auxin was infiltrated at low pressure into postharvest fruit, the increase in MdGH3.1 expression occurred earlier than that in MdSAUR36. MdGH3.1 increased the expression of MdSAUR36, but MdSAUR36 did not increase expression of MdGH3.1. Therefore, we suggest that MdGH3.1 acts upstream of MdSAUR36 during BP formation and that these genes induce BP formation by regulating auxin and phenylpropanoid biosynthesis.

Silencing of early auxin responsive genes MdGH3-2/12 reduces the resistance to Fusarium solani in apple

Apple replant disease(ARD)has led to severe yield and quality reduction in the apple industry.Fusarium solani(F.solani)has been identified as one of the main microbial pathogens responsible for ARD.Auxin(indole-3-acetic acid,IAA),an endogenous hormone in plants,is involved in almost all plant growth and development processes and plays a role in plant immunity against pathogens.Gretchen Hagen3(GH3)is one of the early/primary auxin response genes.The aim of this study was to evaluate the function of MdGH3-2 and MdGH3-12 in the defense response of F.solani by treating MdGH3-2/12 RNAi plants with F.solani.The results show that under F.solani infection,RNAi of MdGH3-2/12 inhibited plant biomass accumulation and exacerbated root damage.After inoculation with F.solani,MdGH3-2/12 RNAi inhibited the biosynthesis of acid-amido synthetase.This led to the inhibition of free IAA combining with amino acids,resulting in excessive free IAA accumulation.This excessive free IAA altered plant tissue structure,accelerated fungal hyphal invasion,reduced the activity of antioxidant enzymes(SOD,POD and CAT),increased the reactive oxygen species(ROS)level,and reduced total chlorophyll content and photosynthetic ability,while regulating the expression of PR-related genes including PR1,PR4,PR5 and PR8.It also changed the contents of plant hormones and amino acids,and ultimately reduced the resistance to F.solani.In conclusion,these results demonstrate that MdGH3-2 and MdGH3-12 play an important role in apple tolerance to F.solani and ARD.

Transcriptional regulation of MdPIN7 by MdARF19 during gravityinduced formation of adventitious root GSA in self-rooted apple stock

Self-rooted apple stock is widely used for apple production.However,the shallowness of the adventitious roots in self-rooted apple stock leads to poor performance in the barren orchards of China.This is because of the considerable difference in the development of a gravitropic set-point angle(GSA)between self-rooted apple stock and seedling rootstock.Therefore,it is crucial to study the molecular mechanism of adventitious root GSA in self-rooted apple stock for breeding self-rooted and deep-rooted apple rootstock cultivars.An apple auxin response factor MdARF19 functioned to establish the adventitious root GSA of self-rooted apple stock in response to gravity and auxin signals.MdARF19 bound directly to the MdPIN7 promoter,activating its transcriptional expression and thus regulating the formation of the adventitious root GSA in 12-2 self-rooted apple stock.However,MdARF19 influenced the expression of auxin efflux carriers(MdPIN3 and MdPIN10)and the establishment of adventitious root GSA of self-rooted apple stock in response to gravity signals by direct activation of MdFLP.Our findings provide new information on the transcriptional regulation of MdPIN7 by auxin response factor MdARF19 in the regulation of the adventitious root GSA of self-rooted apple stock in response to gravity and auxin signals.

Improved multi-scale inverse bottleneck residual network based on triplet parallel attention for apple leaf disease identification

Accurate diagnosis of apple leaf diseases is crucial for improving the quality of apple production and promoting the development of the apple industry. However, apple leaf diseases do not differ significantly from image texture and structural information. The difficulties in disease feature extraction in complex backgrounds slow the related research progress. To address the problems, this paper proposes an improved multi-scale inverse bottleneck residual network model based on a triplet parallel attention mechanism, which is built upon ResNet-50, while improving and combining the inception module and ResNext inverse bottleneck blocks, to recognize seven types of apple leaf(including six diseases of alternaria leaf spot, brown spot, grey spot, mosaic, rust, scab, and one healthy). First, the 3×3 convolutions in some of the residual modules are replaced by multi-scale residual convolutions, the convolution kernels of different sizes contained in each branch of the multi-scale convolution are applied to extract feature maps of different sizes, and the outputs of these branches are multi-scale fused by summing to enrich the output features of the images. Second, the global layer-wise dynamic coordinated inverse bottleneck structure is used to reduce the network feature loss. The inverse bottleneck structure makes the image information less lossy when transforming from different dimensional feature spaces. The fusion of multi-scale and layer-wise dynamic coordinated inverse bottlenecks makes the model effectively balances computational efficiency and feature representation capability, and more robust with a combination of horizontal and vertical features in the fine identification of apple leaf diseases. Finally, after each improved module, a triplet parallel attention module is integrated with cross-dimensional interactions among channels through rotations and residual transformations, which improves the parallel search efficiency of important features and the recognition rate of the network with relatively small computational costs while the dimensional dependencies are improved. To verify the validity of the model in this paper, we uniformly enhance apple leaf disease images screened from the public data sets of Plant Village, Baidu Flying Paddle, and the Internet. The final processed image count is 14,000. The ablation study, pre-processing comparison, and method comparison are conducted on the processed datasets. The experimental results demonstrate that the proposed method reaches 98.73% accuracy on the adopted datasets, which is 1.82% higher than the classical ResNet-50 model, and 0.29% better than the apple leaf disease datasets before preprocessing. It also achieves competitive results in apple leaf disease identification compared to some state-ofthe-art methods.

Effect of Different Raw Material Processing Methods on the Quality of Apple Distilled Spirits

In this study,the effect of yeast strains(X16 and RMS2),fruit seed,and pectinase on the quality of apple distilled spirits were investigated with apple as material.The results showed that pectinase shortened the fermentation period.The strain X16,fruit seed remaining,and pectinase addition groups had higher yields of crude distilled spirits than the strain RMS2,fruit seed removal,and without pectinase groups,respectively.Regarding the first-grade distilled spirits quality,the X16 group had higher content of total acids,total esters,higher alcohols,and alcohol content than the RMS2 group;the group with fruit seeds had higher total acids but lower alcohol content and total esters than the group with fruit seed removal;the group with pectinase addition had higher total acids and alcohol content than the group without pectinase addition.Regarding the second-grade distilled spirits quality,the X16 group had higher total acids,total esters,and alcohol content than the RMS2 group;the group without fruit seeds had higher alcohol content than the group with fruit seeds;the group with pectinase addition showcased higher total acids but lower alcohol content than the group without pectinase addition.In summary,yeast strains and pectinase affected the quality of apple distilled spirits,and strain X16 was more suitable for brewing apple distilled spirits.Pectinase affected the quality of apple distilled spirits by affecting fermentation rate and temperature.

Overexpression of auxin/indole-3-acetic acid gene MdIAA24 enhances Glomerella leaf spot resistance in apple(Malus domestica)

Auxin is throughout the entire life process of plants and is involved in the crosstalk with other hormones,yet its role in apple disease resistance remains unclear.In this study,we investigated the function of auxin/indole-3-acetic acid(IAA)gene Md IAA24 overexpression in enhancing apple resistance to Glomerella leaf spot(GLS)caused by Colletotrichum fructicola(Cf).Analysis revealed that,upon Cf infection,35S::Md IAA24 plants exhibited enhanced superoxide dismutase(SOD)and peroxidase(POD)activity,as well as a greater amount of glutathione(reduced form)and ascorbic acid accumulation,resulting in less H_(2)O_(2)and superoxide anion(O_(2)^(-))in apple leaves.Furthermore,35S::Md IAA24 plants produced more protocatechuic acid,proanthocyanidins B1,proanthocyanidins B2 and chlorogenic acid when infected with Cf.Following Cf infection,35S::Md IAA24 plants presented lower levels of IAA and jasmonic acid(JA),but higher levels of salicylic acid(SA),along with the expression of related genes.The overexpression of Md IAA24 was observed to enhance the activity of chitinase andβ-1,3-glucanase in Cfinfected leaves.The results indicated the ability of Md IAA24 to regulate the crosstalk between IAA,JA and SA,and to improve reactive oxygen species(ROS)scavenging and defense-related enzymes activity.This jointly contributed to GLS resistance in apple.

Potassium alleviated high nitrogen-induced apple growth inhibition by regulating photosynthetic nitrogen allocation and enhancing nitrogen utilization capacity

There is a close relationship between potassium(K)and nitrogen(N).However,the roles of K under high N conditions remain unclear.Using a hydroponics approach,we monitored the morphological,physiological,and molecular changes in M9T337 apple(Malus domestica)rootstocks under different nitrate(10 and 30 mmol·L^(-1)NO_(3)^(-))and K supply(0.5,6,10,and 20 mmol·L_(-1)K^(+))conditions.Results revealed that high nitrate inhibited the root growth of M9T337 rootstocks,downregulated the expressions of K transporter genes(MdPT5,MdHKT1,and MdATK1),and reduced the net NO3-and K+influx at the surface of roots,thereby resulting in an N/K imbalance in rootstocks.Further investigation showed that 10 mmol·L^(-1)K increased the activity of N metabolic enzymes(NR,GS,NiR,and GOGAT),upregulated the expressions of genes related to nitrate uptake and transport(MdNRT1.1,MdNRT1.2,MdNRT1.5,and MdNRT2.4),promoted15N transport from the roots to the shoots,optimized leaf N distribution,and improved photosynthetic N utilization efficiency under high nitrate conditions.These results suggest that the negative effects of high nitrate may be related to the N/K imbalance and that reducing N/K in plants by increasing K supply level can effectively alleviate the inhibition of N assimilation by high nitrate stress.

Isolation of Trichoderma virens 6PS-2 and its effects on Fusarium proliferatum f. sp. Malus domestica MR5 related to apple replant disease in China

Apple replant disease(ARD) is primarily caused by biotic factors that seriously inhibits the development of apple industry. Therefore, the use of biological control measures to inhibit the main pathogens(such as Fusarium spp.) that cause ARD is of great significance to the sustainable development of the apple industry. Trichoderma virens 6PS-2, which exhibited antagonism toward a variety of pathogens, was screened from the rhizosphere soils of healthy apple trees(Malus robusta) in different replanted orchards in the Yantai and Zibo Cities, Shandong Province, China. Its fermentation extract inhibited the growth of pathogenic Fusarium proliferatum f. sp. Malus domestica MR5, which was proportional to the concentration. These substances also increased the hairy root volume and growth of Arabidopsis thaliana lateral roots. The phenotype of Malus hupehensis seedlings and microbial community structure in rhizosphere soils in greenhouse experiment using Highthroughput sequencing were analyzed, and the field experiment with grafted apple trees were used for further verification. Compared with the application of potato dextrose broth(PDB) medium, application of 6PS-2 spore suspension directly to replanted soils could improve the growth of M. hupehensis seedlings as well as the elongation of grafted apple trees. Concomitant decreases in the gene copy number of Fusarium and increases in the culturable bacteria/fungi were also observed in the greenhouse and field experiments. The abundance of Trichoderma,Bacillus, and Streptomyces increased significantly, but that of Fusarium, Pseudarthrobacter, and Humicola decreased. The content of esters, phenols,furans, and amino acids in root exudates of M. hupehensis seedlings increased, which significantly inhibited the multiplication of Fusarium, but was positively correlated with Bacillus and Trichoderma. In summary, T. virens 6PS-2 not only directly inhibits the activity of pathogenic Fusarium but also secrets secondary metabolites with antifungal and growth-promoting potential. In addition, 6PS-2 spore suspension can also promote the growth of plants to a certain extent, and change the soil microbial community structure of rhizosphere soils. It is believed that T. virens 6PS-2 has the potential for the alleviation of apple replant disease(ARD) in China.

ALL ABOUT APPLES!

Crunch!Apples are a sweet and delicious fruit.There are over 7,500 different kinds!The fruit is usually red,but it can be green or other colors.Applesaren't expensive.They make a great snack.You can eat a whole apple.You can slice it,too.They're also good with other foods.Do you like apples?

Effects of Trichosporon sp. in Combination with Calcium and Fungicide on Biocontrol of Postharvest Diseases in Apple Fruits

The capability of yeast Trichosporon sp., an antagonist isolated from peach fruit, in biological control was evaluated in apple ( Malus domestica Borkh. cv. Fuji) fruits, when inoculated with different concentrations of Botrytis cinerea Pers. and Penicillium expansum (Link) Thom, as well as in combination with calcium and fungicide. The concentrations of the yeast cells and pathogen spores obviously influenced disease incidence and lesion development in apples. There was a significant negative correlation between concentrations of the yeast cells and infectivity of the pathogens. When the yeast cell suspensions reached the concentration of 10 8 colony_forming units (CFU) /mL, there was no infection caused by B. cinerea and P. expansum with spore concentrations below 10 6 spores/mL in apple fruits. The yeast at concentrations of 10 6-10 7 CFU/mL in combination with fungicide (iprodione at 50 μL/L) provided control of decay caused by B. cinerea and P. expansum better than separate application. Effect of controlling gray mould and blue mould rots was enhanced when Trichosporon sp., even at low concentration of 10 5 CFU/mL, was applied in the presence of 1%-2% CaCl 2 in an aqueous suspension.

Occurrence Regularity and Control Research of Apple Early Defoliation Disease in West Sichuan Plateau

[ Objective ] The research aimed to discuss the occurrence regularity of apple early defoliation disease and control effects of fungicides in west Sichuan plateau. [ Method ] Apple early defoliation disease in west Sichuan plateau was systematically investigated during 2009 and 2011, and the control effects of different fungicides during different spraying periods were studied. [ Result] The species of pathogen mainly was Marssonina ma/i （ P. Henn）, accounting for 32.5%, Phyl-losticta Pirina Sa accounted for 29.9%, and Alternaria mali Roberts accounted for 25.7%. The field fluctuation regularity was as follows ： the disease generally be- gan in the mid-May and ended in early and middle October with only one damage peak during the whole year, the fluctuation had positive correlation with rainfall （ R2 =0.891 8 ＊ ＊ ）. Control test showed that 40% flusilazole had the best control effect （86.5%）, which was best to apply after anthesis. [ Conclusion ] The paper provided theoretical basis for the effective control against apple early defoliation disease.

Distribution of Calcium in Bagged Apple Fruit and Relationship between Antioxidant Enzyme Activity and Bitter Pit

[Objective]The aim was to study the distribution of Ca in bagged apple fruit and the relationship between antioxidant enzyme activity and bitter pit disease,which will provide a basis for resolving Ca metabolism disorder in apple cultivation. [Method]With Fuji Apple as the tested material,the changes of Ca2＋ content and antioxidant enzyme activity in different parts of apple fruit after picking bags and storage period were determined. [Result]The results showed that Ca contents in the light surface of fruits were higher than that in the backlight surface. The Ca contents of stalk cavity were higher than that of calyx-end. The activities of SOD,POD,CAT and APX in the light surface of fruits were higher than that in the backlight surface. The activities of SOD,POD,CAT and APX of stalk cavity were higher than that of calyx-end. The contents of MDA in the light surface of fruits were lower than that in the backlight surface. The contents of MDA of stalk cavity were lower than that of calyx-end. [Conclusion]The incidence rate of bitter pit in the light surface of fruits were lower than that in the backlight surface,and the incidence rate of bitter pit of stalk cavity were lower than that of calyx-end.

Effect of Metaxenia on Volatile Compounds in Bagged Apple Fruit of Fuji

In the present study, the effect of pollen grain sources on volatile com- pounds in bagged apple fruit of Yan Fuji 3, grown at two experiment sites and pol- linated by pollens of other five cultivars was evaluated, to select appropriate poll- enizer cultivars for Fuji, and to provide a theoretical basis for improving the flavor and aroma of bagged apple fruit of Fuji. The results proved the significant metaxe- nia effect of the five pollenizer cultivars on volatile compounds of bagged apple fruit of Fuji. The numbers of both volatile compounds and characteristic aroma com- pounds in bagged apple fruit pollinated by Golden Delicious were larger and those of the fruit pollinated by Gala were smaller at both experiment sites. However, there were differences in the numbers of volatile compounds and characteristic aroma compounds among the fruits pollinated by Starkrimson, Jinxiuhaitang and Ruby at both experimental sites. The differences were caused by 12 compounds that only existed at a low level in certain samples. All of them were not the aroma contribu- tors except ethyl 2-methylbutyrate. The content of alcohols in bagged Fuji fruit was largely increased by Starkrimson and Ruby pollination; the content of aldehydes was obviously increased by Golden Delicious, Starkrimson and Gala pollination; the con- tents of esters and terpenes were significantly increased by Golden Delicious, Starkrimson and Ruby pollination. Jinxiuhaitang pollination showed no significant ef- fects for improving the content of four categories of volatile compounds. The metax- enia of the pollenizer cultivars on volatile compounds in bagged Fuji fruit was stable at the two experimental sites.

A Record of the Invasive Golden Apple Snail Pomacea canaliculata (Lamarck 1819) at Black Dragon Spring,Dianchi Basin

The golden apple snail Pomacea canaliculata （Lamarck 1819） was first recorded at Black Dragon Spring, Dianchi Basin, Baiyi Township, Songming County, Kunming City, Yunnan Province, China, in October 2004. The water from the spring flows into the Songhuaba Reservoir, the major drinking water resource for Kunming City, and part of the Dianchi Lake basin. This is the first record of this invasive snail in the Dianchi Lake Basin. Pomacea canaliculata originates from Central and South America, and in Asia the snail has spread through deliberate and accidental introductions to the Philippines, Vietnam, Thailand, Laos, Cambodia, Malaysia, Indonesia, Papua New Guinea, Korea, Japan and South China. It has become a major pest in rice-growing areas, resulting in huge damage to crops. Strict prevention and control measures have to be implemented to prevent the spread of the snail in Yunnan, together with public awareness campaigns to inform the public of the dangers of this invasive snail.

Ultrastructure of Epidermis and Flesh of the Developing Apple Fruit

The ultrastructure of the epidermis and flesh of apple ( Malus domestica Borkh cv. Red Fuji) fruit was systematically observed during the fruit development via transmission electron microscopy. The results showed that, in spite of the ultrastructural changes in many aspects of the developing fruit epidermal cells, it remained almost unchanged throughout the whole developmental process that the cytoplasm was filled with numerous endoplasmic reticula (ER). Most of these endoplasmic reticula were tube_like and rough_ER with enlarged cisterna from which many vesicles were produced. Some of the vesicles were shown to merge into vacuole. Some dynamic Golgi bodies were also found. All the ultrastructural characteristics showed that the epidermal cells have the features of excretory cells. The ultrastructure of the fruit flesh cells at the young fruit stage were shown to be metabolically active, characterized by the presence of numerous clustered plasmodesmata, cisterna enlarged_ and rough_ER filling the cytoplasm, plenty of vesicles and Golgi bodies, indicating their dynamic cellular transport function. Some giant_circular rough_ERs were found. All the ultrastructural features at this early developmental stage should be closely associated with the enlargement of the young fruit. At the rapid growing phase of the fruit the main changes were characterized by: the starch grain_filled amyloplasts, furcating of the single orifice of plasmodesmata, and the cytoplasm enrichment of both the Golgi body_formed vesicles and other vesicles. These features correspond well with those of a photoassimilate sink_cell. An ultrastructural degeneration phenomenon was observed at the fruit ripening stage, but the mitochondria and plasmalemma still remained intact, which might be related to the continuous development of fruit quality during the fruit ripening.

Outbreak and the Reasons of Apple Valsa Canker in Yantai Apple Producing Area in 2011

[Objective] This study aimed to investigate an outbreak of apple valsa canker （Valsa ceratosperma） in Yantai apple producing area in 2011 and analyze the major causes of the disease. [Method] In May 2011, 21 commercial apple or-chards in Qixia, Haiyang and Laiyang were selected to investigate the outbreak of applevalsa canker. [Result]The results showed that apple canker occurred seriously in Yantai apple producing area in 2011. The ratio of diseased plants with new canker scars was 68.20% and the ratio of dead plants infected with Valsa cer-atosperma was 2.76%. The average ratios of diseased branches and one-year-old dead branches were 23.98% and 10.74%, respectively. The percentage of orchards with more than 50% diseased plants accounted for 25%-30% of the total number of orchards investigated, and the overal prevalence situation was more serious than normal years. In the investigation, 967 new canker scars were observed, with an average of 2.32 canker scars per plant. Specifical y, 80.04% canker scars were de-veloped from pruning wounds; 60.29% canker scars were developed from previous scars. [Conclusion] The long-period precipitation in the autumn of 2010, low temper-ature in the winter of 2010 and the severe drought in the spring of 2011 might be the major factors causing the outbreak of apple valsa canker in Yantai apple pro-ducing area in 2011. Pruning wounds were the main infection entrances of V. cer-atosperma, and the recurrence in previous scars was the main reason for the out-break of apple canker in spring.

Biocontrol Efficacy of Three Antagonistic Yeasts Against Penicillium expansum in Harvested Apple Fruits

Three antagonistic yeasts, Trichosporon pullulans (Lindner.) Diddens and Lodder, Cryptococcus laurentii (Kuffer.) Skinner and Rhodotorula glutinis (Fresen.) F. C. Harrison, selected from over 50 yeasts on apple fruits, were investigated of their biocontrol efficacy against blue mould rot caused by Penicillium expansum Link in apple fruits. T. pullulans was identified to be a new yeast antagonist and was the most effective at inhibiting blue mould rot in the three yeasts. The effects of different concentrations of the three yeasts and addition Of nutrients, as well as combination with calcium on controlling blue mould rot in apples were presented in the paper. The results indicated that the higher the yeast concentrations, the more effective the yeasts on biocontrol activity. Addition of nutrients reduced the biocontrol capacity of the yeasts. Combination of 0.18 mol/L CaCl2 with C. laurentii cell suspensions could significantly enhance its effect to P. expansum in apple fruits, while the efficacy of calcium on biocontrol activity of T. pullulans or R. glutinis was not remarkable.