Acta Agriculturae Zhejiangensis

Potassium alleviates inhibition of ammonium stress on wheat root

WANG Feng, YE Jing, GAO Jingwen, WANG Qiang, YU Qiaogang, HE Xinhua, MA Junwei

2020, 32(11): 1923-1933. DOI: 10.3969/j.issn.1004-1524.2020.11.01

Abstract ( 1186 )

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To explore the effects of potassium on ammonium stress, wheat seedlings cultivated with nitrate (

$\text{NO}_{3}^{-}-\text{N}$ ) or ammonium (

$\text{NH}_{4}^{+}-\text{N}$ ) nitrogen were treated with different potassium levels (low, 1 mmol·L^-1; normal, 3 mmol·L^-1; high, 6 mmol·L^-1). It was shown that compared with

$\text{NO}_{3}^{-}-\text{N}$ ,

$\text{NH}_{4}^{+}-\text{N}$ significantly (P<0.05) increased

$\text{NH}_{4}^{+}$ concentration in the plants (including root and leaf), and root growth was inhibited as the total root length, root surface area and root volume were significantly (P<0.05) reduced under the same potassium level. With the increasing K dose, the root inhibition was relieved. Under

$\text{NH}_{4}^{+}-\text{N}$ conditions, leaf area, stomatal conductance, and net photosynthetic rate were increased with the increasing K dose, which resulted in the significantly (P<0.05) increased soluble sugar content in leaf and root, and thus could provide more carbon skeleton for

$\text{NH}_{4}^{+}$ assimilation. Meanwhile, higher potassium siginificantly (P<0.05) increased the activity of sucrose phosphate synthetase (SPS) activity in leaves. In addition, the indole-3-acetic (IAA) concentration and the ratio of IAA to cytokinin (CTK) in root increased with the increasing K dose. It was inferred that, under

$\text{NH}_{4}^{+}-\text{N}$ condition, the exogenous application of potassium enhanced the capability of wheat photosynthesis, provided more carbon skeleton for

$\text{NH}_{4}^{+}$ assimilation, promoted the hormone balance in roots, thus reduced the accumulation of

$\text{NH}_{4}^{+}$ in plant and alleviated root inhibition.

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Determination and difference analysis of soluble sugar content in 11 sweetpotato germplasm resources

SHEN Shengfa, XIANG Chao, WU Liehong, LI Bing, LUO Zhigao

2020, 32(11): 1934-1940. DOI: 10.3969/j.issn.1004-1524.2020.11.02

Abstract ( 939 )

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The determination method of plant soluble sugar by HPLC-ELSD has the advantages of high sensitivity, low detection limit and large linear range. In order to understand the soluble sugar components and saccharification characteristics of sweetpotato varieties, the soluble sugar content of 11 important sweetpotato germplasm resources had been measured and analyzed. The results showed that fructose, glucose, sucrose and maltose were all contained in the soluble sugars of both raw root and cooked root,and the average content of the tested group were 58.41 mg·g^-1 and 123.05 mg·g^-1, respectively. Among the soluble sugars in raw root, sucrose content was the highest, accounting for about 45% of the soluble sugars, while maltose was the least, only accounting for about 10% of the soluble sugars. Among the soluble sugars in cooked root, maltose was the highest, about 90% of which came from the conversion of starch during steaming, and the increment accounted for more than 50% of the soluble sugars in cooked root. Fructose, glucose and sucrose in cooked root mainly came from soluble sugars in raw root, while their changes were small during steaming. Therefore, soluble sugar content in cooked root of sweetpotato was determined by maltose content. Zheshu 13 had a good effect of saccharification after steaming, in which the content of soluble sugar and maltose were 179.64 mg·g^-1 and 138.44 mg·g^-1, respectively, significantly higher than the other 10 varieties. Hongpibaixin was a variety with high sugar in raw root, and the content of soluble sugar and fructose in raw root ranked first among the varieties tested.

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Association analysis of four spike traits in barley

HU Qianwen, XU Yanhao, WANG Rong, ZHANG Wenying, HUA Wei, LYU Chao

2020, 32(11): 1941-1953. DOI: 10.3969/j.issn.1004-1524.2020.11.03

Abstract ( 1169 )

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Spike traits are important determinants of barley yield and quality. A good spike structure should have a certain spike length, suitable spikelet density and spikelet number per spike. In this study, 137 barley materials from a wide range were used as the population for association analysis. A total of 224 pairs of SSR markers were used to analyze the genotype of the population. Under two environmental experiments, grain number per spike, spikelet density, spikelet number per spike and spike length were recorded. General linear model (GLM) and mixed linear model (MLM) models were used to analyze the association between four spike traits and SSR markers. The results showed that there were significant differences among the four spike traits of the tested barley population. Grain number per spike was significantly related to spikelet number per spike, and spike length was significantly related to spikelet density. A total of 479 alleles were detected for SSR markers. The average effective allele number, Shannon's index and PIC were 1.765, 0.612 and 0.327, respectively. The genetic similarity coefficient (GS) of the tested materials ranged from 0.486 to 0.891. The barley materials were divided into two groups at GS value level of 0.580. Population structure analysis also divided the materials into two subgroups. The results of GLM analysis showed that there were 33, 13, 34 and 6 loci associated with grain number per spike, spikelet density, spikelet number per spike and spike length, respectively, and the phenotypic variation explained by a single marker ranged from 8.65% to 50.08% (P<0.001). These markers were located on seven chromosomes of barley. The results of MLM analysis showed that there were 4, 3, 4 and 1 marker sites associated with the four spike traits described above, respectively. The phenotypic variation explained by a single marker ranged from 3.12% to 16.95% (P<0.001). These markers were located on the chromosome 1H, 2H and 4H of barley. The four markers Ind1003, Ind2030, Ind2055 and Ind4012, which associated to both grain number per spike and spikelet number per spike, could be detected by two models in two tests.

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Effect of sertoli cells apoptosis in piglets induced by single or combined administration of zearalenone and deoxynivalenol

ZHU Lei, JIA Beiping, CAO Li, XU Jingru, ZHAO Jie, FENG Shibin, LI Yu, WU Jinjie, WANG Xichun

2020, 32(11): 1954-1962. DOI: 10.3969/j.issn.1004-1524.2020.11.04

Abstract ( 957 )

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The aim of this study was to investigate the mechanism of apoptosis of sertoli cells in piglets induced by single or combined administration of zearalenone and deoxynivalenol. Sertoli cells were treated with 10 μg·mL^-1 ZEA and 0.2 μg·mL^-1 DON for 24 h. Cell viability was detected by CCK-8 method, ultrastructural changes were observed by electron microscope, apoptosis rate and mitochondrial membrane potential were detected by flow cytometry and immunofluorescence. The expression of apoptosis related genes was detected by fluorescence quantitative PCR. The results showed that single or combined administration of ZEA and DON could decrease the viability of sertoli cells, damage the ultrastructure of sertoli cells and increase the apoptosis rate. In addition, ZEA and DON could down regulate the mRNA expression of Bcl-2, Bax, Bid, Caspase-3 and Caspase-9. Moreover, the combined effect of ZEA and DON was stronger than single effect. These results showed that ZEA and DON could induce apoptosis of sertoli cells of piglets through mitochondrial pathway, and the combined toxicity was greater than that of single toxicity, showing additive effect.

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Growth characteristics and cross utilization of Tibetan pig in subtropical area

WANG Sutian, MENG Fanming, HU Bin, XIN Haiyun, LI Baohong, DU Zongliang, LI Jianhao

2020, 32(11): 1963-1969. DOI: 10.3969/j.issn.1004-1524.2020.11.05

Abstract ( 788 )

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To explore the growth characteristics and cross utilization of Tibetan pig in subtropical area, Tibetan pig, Duroc pig and Guangdong small-ear spotted pig were used to carry out various cross experiments in subtropical area Guangzhou. In addition, the reproductive performance, growth performance, carcass traits and meat quality of Tibetan and hybrid pigs were analysed and compared. Our results showed that, in the subtropical environment, the number of live births of Tibetan pig, Duzang pig and Zangduhua pig had no significant difference between the different experimental groups, but the 35-days-old weaning weight of Duzang pig was higher than that of Tibetan pig. Growth test indicated that average weaning weights of Tibetan pig, Duzang pig and Zangduhua pig were respectively (201.43±25.41), (469.67±41.13) and (425.54±58.37) g. These data suggested the growth rates of Duzang pig and Zangduhua pig were significant higher than purebred Tibetan pig, the hybrid vigour of growth rate was obvious. The carcass weight of Duzang and Zangduhua pig was significantly higher than that of Tibetan pig, and skin percentage of Duzang pig was significantly lower than that of Tibetan pig. The results of meat quality analysis showed that the marbling score and intramuscular fat content were highest in Duzang pig,while the tenderness of meat was best. In conclusion, in the subtropical area, crossing Tibetan pig with Duroc pig and Guangdong small-ear spotted pig can significantly improve the growth rate and meat quality that can help to improve the breeding efficiency and shorten the raising period. Meanwhile, this study also provided basic data support for the cross utilization of Tibetan pigs.

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Detection and genetic variation analysis of prevalent porcine circovirus type 2 strains in Zhejiang Province

XU Lihua, LAN Shengzhi, YU Bin, LI Junxing, ZHANG Pengchao, LI Baochen, SU Fei, YUAN Xiufang

2020, 32(11): 1970-1977. DOI: 10.3969/j.issn.1004-1524.2020.11.06

Abstract ( 1057 )

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To investigate molecular epidemiology and genetic variation of porcine circovirus type 2 (PCV2) in Zhejiang province,a total of 329 clinical samples collected in 2018 were subjected to PCR, and the whole genome of PCV2 from 7 positive samples were sequenced. The results demonstrated that the total positive rate of PCV2 was 27.4% (90/329), and the highest positive rate (52%) was in Ningbo district. By age, the highest positive rates were from fattening pigs and growing pigs (38.8% and 68.8%). Three or four clones of each of the seven randomly selected positive samples were sequenced, and genetic variation were analyzed with MEGA 6.0. Sequence comparison showed that the nucleotide sequence homologies among the 22 PCV2 strains were up to 93.3%~99.8%; and were up to 93.5%~99.8% compared with the 16 reference strains. The phylogenetic analysis revealed that these 22 strains belonged to 3 subtypes: PCV2a(6/22)、PCV2b(6/22) and PCV2d(10/22). It was indicated that PCV2d was the dominant subtype in Zhejiang province. The genetic variation analysis of ORF2 gene showed lower homology than the whole genome. The phylogenetic tree analysis of ORF2 showed that the strains were located in subtype of PCV2b, PCV2d and PCV2e respectively, indicating that the prevalent strains in Zhejiang may be shifting to PCV2e. This study explored the molecular epidemiology of PCV2 in Zhejiang province, and provided the basis for screening the candidate strain for the development of PCV2 vaccine.

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Hyperspectral characteristics of typical tree vegetation in central Yunnan

SONG Chunyu, GAN Shu, YUAN Xiping, HU Lin, LI Yan, YAN Xinfang

2020, 32(11): 1978-1986. DOI: 10.3969/j.issn.1004-1524.2020.11.07

Abstract ( 787 )

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Using the hyperspectral remote sensing technology to extract and analyze the characteristic bands of vegetation to solve the problem of less research on tree vegetation spectrum in central Yunnan, which could be used to supplement the spectrum of tree in central Yunnan Province and provide scientific basis in identifying vegetation classification, monitoring tree growth and vegetation inversion for remote sensing. Three vegetation of Platycladus orientalis, Cinnamomum longepaniculatum and Cryptomeria fortunei in central Yunnan Province were measured in reflective spectrum by using SOV710VP surface spectrometer to analyze the difference of leaf spectral characteristics of the three vegetation, and then the original spectrum of three vegetation were processed and analyzed by using the first derivative of spectrum and continuum removal method. The original reflectance curve showed that the curve of Cryptomeria fortunei showed a downward trend in the range of 400 nm to 420 nm, which was different from Cinnamomum longepaniculatum and Platycladus orientalis. There were significant differences in reflectance values of the three vegetation between 700 nm to 760 nm. The first-order derivative of the red band spectrum highlighted unique characteristics of the peaks and valleys of three tree vegetation. The peak-valley characteristic of Platycladus orientalis was particularly prominent and the recognition was more obvious. The continuum removal transformation could highlight the differences in absorption and reflection characteristics of the three tree vegetation in the visible light band. The continuum removal values of Cinnamomum longepaniculatum and Cryptomeria fortunei varied greatly in the range of 440-760 nm and 950-1 000 nm. To a certain extent, the three vegetation could be distinguished by analyzing and comparing the original spectral characteristics and reflectivity values of the three vegetation. Through the first derivative and continuum removal transformation of spectrum, other features besides the original spectral features could be highlighted, and the characteristic band for distinguishing the three vegetation was added, which had a more remarkable effect for distinguishing and identifying the three vegetation.

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Introduction experiment and phenotype cluster analysis of Chinese bayberry in Jingzhou

MA Xiaohua, YU Zheping, ZHENG Xiliang, HU Xiaojin, ZHANG Shuwen, QI Xingjiang, MA Jingyan

2020, 32(11): 1987-1993. DOI: 10.3969/j.issn.1004-1524.2020.11.08

Abstract ( 1263 )

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In this study, with two local varieties Mudongguangye (MDGY) and Mudongdaye (MDDY) as controls, the leaf morphology, fruit quality, mature period of six introduced varieties of Chinese bayberry Zaojia (ZJ), Zaoqimimei (ZQMM), Wanqimimei (WQMM), Heijing (HJ), Biqizhong (BQ) and Dongkui (DK) were observed and compared, and further the cluster analysis of fruit and leaf phenotypes among those varieties was performed. The results showed that ZJ and MDGY were clustered into the same group. In addition, the mature period of ZJ was 7 days earlier than that of MDGY, indicating its excellent application prospects with early fruiting and maturing characteristics. BQ had the characteristics of small nucleus and high edible rate, which highlighted its good adaptability in Jingzhou.The average plant yield and price of DK were 1.96-1.98 times and 2.67-3.48 times of the local varieties, and the economic benefit of its cultivation was remarkable.

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Effects of three endophytic bacteria with the characteristic of controlling citrus canker on the activity of several defensive enzymes in navel orange

LAI Jiahao, SONG Shuilin, LIU Bing

2020, 32(11): 1994-2000. DOI: 10.3969/j.issn.1004-1524.2020.11.09

Abstract ( 996 )

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The activity of the defense enzyme is an important index of the host defense response ability, and many biocontrol factors can cause the activity of the defense enzyme of the plant to be enhanced. In the previous work, three endophytic bacteria Bacillus sp. GN222, Kosakonia cowanii GN223 and Bacillus subtilis GN232 with control effect on citrus canker were selected. To clarify the control mechanism, the effects of three bacterial strains on the activities of several defensive enzymes in Newhall navel orange infected by Xanthomonas citri pv. citri were determined in this experiment. The results showed that three endophytic bacteria could induce and enhance the activity of defensive enzyme in navel orange trees which were infected by Xanthomonas citri pv. citri. The induction intensity of endophytic bacteria to polyphenol oxidase (PPO) and superoxide dismutase (SOD) was lower than that induced by Xanthomonas citri pv. citri, the enhancement effect of strain GN222 on catalase (CAT) was significantly stronger than that of other strains, the induction effect of strain GN223 on peroxidase (POD) was stronger than that of other strains, and the activity of SOD was weaker in all treatments. In a word, endophytic bacteria to be tested have a certain inducing effect on defensive enzymes in the process of navel orange infected by Xanthomonas citri pv. citri, but the time and range of enzyme activity increased variously with different bacterial strains. The results could provide a theoretical basis for the application of three endophytic bacteria in the biological control of citrus canker.

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Resistance mechanism of biocontrol strain DZSG23 against wheat scab

XU Li, CHEN Xiaojie, CAO Jingting, LIU Chuchu, DING Ting, JIANG Teng

2020, 32(11): 2001-2008. DOI: 10.3969/j.issn.1004-1524.2020.11.10

Abstract ( 1158 )

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In our previous work, a strain of endophytic bacteria Bacillus subtilis DZSG23 was isolated from the leaves of Eucommia ulmoides Oliv, which could effectively control the wheat scab. This study was carried out to explicit the resistance mechanism of endophytic bacteria DZSG23 against wheat scab.The colonization property of DZSG23 in wheat was analysed by antibiotic label method, then the expression of PR-1, AOS, ACOI, ERF and SAM genes in wheat treated with DZSG23 at different growth stages were detected by quantitative realtime PCR. The results indicated that DZSG23 could successfully colonize wheat plant at seedling stage and surface of the spike. At the 34 d after inoculation with DZSG23 by pouring, the colonization of DZSG23 in roots, stems and leaves of wheat plants at seedling stage reached 1.437×10⁶ CFU·g^-1, 3.285×10³ CFU·g^-1 and 2.377×10³ CFU·g^-1, respectively. After 15 days of inoculation with DZSG23 strain by spraying on the surface of spikes, the surface microbial density of spike tissue still reached 7.146×10³ CFU·g^-1. Expression of defense response genes PR-1 and AOS in wheat spike treated with DZSG23 were significantly higher than those of normal control groups at different growth stages, showing DZSG23 could induce systemic response through SA-and JA-dependent signaling pathways and enhance its disease resistance.

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Identification and biological characteristics of anthracnose pathogen on Tetrastigma hemsleyanum

LI Xuqing, YAN Jianli, RUAN Songlin

2020, 32(11): 2009-2019. DOI: 10.3969/j.issn.1004-1524.2020.11.11

Abstract ( 1511 )

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Leaf spot occurred severely in Chun'an city, Zhejiang Province, and caused serious economic losses in local Tetrastigma hemsleyanum production. To clarify the species and biological characteristics of the pathogen caused leaf spot could provide scientific data for the disease effective control. The pathogen was isolated by plate confrontation assay and identified as Colletotrichum gloeosporioides based on combination of morphological characters, molecular data (rDNA-ITS, β-tubulin, ACT, gpd, CaM)and pathogenicity tests. And the biological characteristics determined by crossing and haemocytometer methods showed that the fungus was able to grow at temperature between 20-35 ℃ with an optimum of 25 ℃ for both mycelia growth and sporulation; the continuous darkness was good for both mycelia growth and sporulation; In addition, the optimal pH for mycelia growth and sporulation was 5.0 and 8.0, respectively.There were various kinds of carbohydrates and nitrogen known to provide growth of the fungus. Maltose,sorbitol and yeast were the best carbon and nitrogen source for mycelia growth, respectively, while ethanol and glutamine were the worst, respectively. Sorbitol and yeast were the best carbon and nitrogen source for sporulation, respectively, while mannitol and casein tryptone were the worst, respectively.

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Effects of anthracnose disease on photosynthetic characteristics in tea leaves (Camellia sinensis L.)

ZHANG Zheng, WANG Xiaorong, QIAN Hong, ZHANG Lan, YAN Peng, ZHANG Liping, ZHANG Xinfu, LI Xin, HAN Wenyan

2020, 32(11): 2020-2026. DOI: 10.3969/j.issn.1004-1524.2020.11.12

Abstract ( 1376 )

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Anthracnose caused by Colletotrichum camelliae is an important foliar disease that severely damages the yield and quality of tea. It occurs widely in most of the tea production areas in China. In this study, Longjing 43 and Zhongcha 108 were used as experimental materials to explore the effects of anthracnose on photosynthetic rate, Rubisco activity, photosynthetic genes expression and H₂O₂ content in tea leaves. It was revealed that there was no significant difference in photosynthetic rate between Longjing 43 and Zhongcha 108 under mock treatment. However, after inoculation with the pathogen, the photosynthetic rate decreased significantly along with the post-inoculation time. At 6 days post-inoculation, the photosynthetic rate of Longjing 43 and Zhongcha 108 decreased by 61.76% and 42.04%, maximum carboxylation rate of Rubisco (V_cmax) decreased by 33.78% and 20.22%, and maximum rates of RuBP regeneration (J_max) decreased by 37.67% and 20.83%, respectively. The expression of photosynthetic genes decreased significantly after inoculation. Notably, the expression of CsRbcL in the leaves of Longjing 43 and Zhongcha 108 decreased by 47.08% and 36.36%, and CsRbcS decreased by 34.99% and 23.90%, respectively. In addition, the content of H₂O₂ in the leaves of Longjing 43 and Zhongcha 108 increased by 174.91% and 96.69%, respectively. The study further confirmed that Longjing 43 was more susceptible to anthracnose than Zhongcha 108. It was also suggested that the decrease of leaf photosynthetic rate and Rubisco activity after pathogen inoculation was mainly attributed to the excessive accumulation of H₂O₂ in tea leaves.

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Effects of applying green waste compost on physiological characteristics of pakchoi in Pb, Zn contaminated soil

MA Qixue, SUN Xiangyang, LI Suyan, LI Song, LIU Yuanxin, ZHOU Wenjie

2020, 32(11): 2027-2034. DOI: 10.3969/j.issn.1004-1524.2020.11.13

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To investigate the effects of green waste compost (GWC) on the physiological characteristics of pakchoi (Brassica chinensis L.) under heavy metal pollution, a greenhouse pot experiment was carried out. Soils of lead (Pb) contamination (500 mg·kg^-1), zinc (Zn) contamination (1 000 mg·kg^-1) and Pb-Zn combined contamination were amended with three levels of GWC (1%, 2%, 5%) to study the effects on the biomass, chlorophyll content, malondialdehyde (MDA) content, superoxide dismutase (SOD) and catalase (CAT) activity, and free proline content in pakchoi. The results showed that the biomass, chlorophyll content and free proline content of pakchoi increased with the increasing application rate of GWC, but MDA content decreased. The GWC application increased the CAT activity of pakchoi under Pb, Zn and Pb-Zn combined contamination. In conclusion, GWC could promote the growth of pakchoi, improve the physiological characteristics of pakchoi and enhance the resistance to the stress of Pb and Zn with appropriate application level.

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Preparation of coal gangue fertilizer based on high-efficiency phosphate solubilizing bacteria and its application potential

WANG Yinglan, JIANG Xiong, JI Li, ZHANG Jingning, XIE Chengwei

2020, 32(11): 2035-2041. DOI: 10.3969/j.issn.1004-1524.2020.11.14

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In this study, coal gangue was treated with high-efficiency phosphate solubilizing bacteria to prepare fertilizer. A strain named GZU-Mic02 with phosphate solubilizing ability was isolated from the weathered coal gangue, which was identifiied as Micrococcus luteus. Compared with the untreated coal gangue samples, the contents of available nitrogen, available phosphorus and available potassium of the prepared coal gangue fertilizers treated with GZU-Mic02 and Bacillus megaterium strain ACCC1011 were increased. The prepared coal gangue fertilizer treated with GZU-Mic02 had higher contents of available phosphorus and available nitrogen than the prepared coal gangue fertilizer treated with Bacillus megaterium, yet the content of available potassium was higher in the prepared coal gangue fertilizer treated with Bacillus megaterium. The pot experiment was conducted with tobacco to verify the effect of the prepared coal gangue fertilizer. It was shown that the plant height, stem circumference and leaf size of tobacco grown after 25 d with the two kinds of prepared coal gangue fertilizer were higher than those in the control without fertilizer, and the effect of prepared coal gangue fertilizer treated with GZU-Mic02 strain was better.

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Safety evaluation of Cry-transgenic insect-resistant maize on silkworm, Bombyx mori

JIANG Yuanyuan, JI Yi, LAI Yongmin, CHEN Xiaoyun, XU Junfeng, XU Xiaoli, MA Lianju

2020, 32(11): 2042-2049. DOI: 10.3969/j.issn.1004-1524.2020.11.15

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Larvae of the domestic silkworm, Bombyx mori(Linnaeus) could be influenced by Cry protein expressed in genetically engineered maize by consuming maize pollen. Laboratory experiments were conducted to evaluate the potential effects of transgenic maize GAB-3 expressing Cry1Ab and Cry2Ab. The toxicity of six purified Cry proteins that have been used in transgenic maize to silkworm were tested using dietary exposure assays. When the concentration of GAB-3 pollen on the leaves of mulberry was about 50 grains·cm^-2, no significant effect was detected on the survival rate of the neonate larvae of silkworm. The neonate larvae of silkworm could not survive beyond 14 d when the GAB-3 pollen concentration was about 500 grains·cm^-2. No adverse effect on the larvae weight was detected when they were fed with 10 grains·cm^-2 GAB-3 pollen for 7 days. But when the feeding time was prolonged or the density of GAB-3 pollen was more than 50 grains·cm^-2, the larvae weight was significantly decreased compared with the control larvae. The weight of the larvae decreased when they were fed with GAB-3 pollen or the non-transgenic maize pollen for 14 days or more. There was no significant difference in pupation rate, cocoon weight, pupa weight, cocoon shell weight between larvae fed with GM corn pollen or the non-transgenic corn pollen. Both of transgenic and non-transgenic maize pollen prolonged the development time of the larvae. The LC₅₀ of GAB-3 pollen to the neonate larvae of silkworm was 261.18 grains·cm^-2. While the treating time was prolonged, the LC₅₀ value decreased. Six purified Cry proteins that have been used for plant transformation were tested using dietary exposure assays. The toxicities of the tested six Cry proteins to B. mori were in the order: Cry1C>Cry1Fa>Cry1B>Cry2A>Cry1Ab>Cry1Ac. Cry1Ab and Cry2A were low toxicity to B. mori and they were commonly used in transgenic maize which was approaching commercialization in China. As in actual conditions, maize pollen density consumed by B. mori was lower than in lab, suggesting that the risk of Bt maize pollen on silkworm was negligible.

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Degradation of carbosulfan after its application in different growth stage of cowpea

WANG Di, DI Shanshan, WANG Xinquan, ZHANG Changpeng, WANG Xiangyun, WANG Meng

2020, 32(11): 2050-2058. DOI: 10.3969/j.issn.1004-1524.2020.11.16

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The degradation and risk assessment of carbosulfan application in different growth stages of cowpea (sowing, seedling and podding) were investigated. In field experiments, carbosulfan EC (emulsifiable concentrate) was applied in the different growth stages of cowpea with different doses (low dose, high dose and 1.5-fold high dose according to the registration). Cowpea samples were collected at mature stage, which were extracted with acetonitrile and purified by C18. The residue levels of carbosulfan and its metabolites (carbofuran and 3-hydroxycarbofuran) were determined by LC-MS/MS (liquid chromatography-tandem mass spectrometry). The limit of quantification (LOQ) values of carbosulfan, carbofuran and 3-hydroxycarbofuran were all 0.01 mg·kg^-1. The average recoveries of carbosulfan and its metabolites in cowpea at 4 spiked levels (0.01, 0.05, 0.2, 1 mg·kg^-1) ranged from 72% to 105% with relative standard deviation (RSD) in the range of 1.4%-20.1%. The residue risk of carbosulfan was mainly due to its metabolites (carbofuran and 3-hydroxycarbofuran). When carbosulfan was applied at sowing stage of cowpea, the residue levels of carbosulfan and its metabolites were below LOQ. After application at 1.5-fold high dose in the seedling stage, the residue level of carbofuran (including 3-hydroxycarbofuran) in cowpea on the 10th day exceeded the maximum residue limit (MRL) in China. When carbosulfan was applied in the podding stage two or three times, the residue level of carbofuran (including 3-hydroxycarbofuran) in cowpea within 7 d exceeded the MRL. When carbosulfan was applied in the podding stage of cowpea, the risk of chronic dietary intake and acute dietary intake of carbosulfan was lower than 100%, but the risk of acute dietary intake of carbofuran (including 3-hydroxycarbofuran) was higher than 100% within 7 d. Therefore, the application of carbosulfan in the sowing stage of cowpea was recommended, while application in the seedling and podding stage existed high risk, which should be forbiden.

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Research on multi-target leaf segmentation and recognition algorithm under complex background based on Mask-RCNN

ZHONG Weizhen, LIU Xinlei, YANG Kunlong, LI Fengguo

2020, 32(11): 2059-2066. DOI: 10.3969/j.issn.1004-1524.2020.11.17

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The accurate segmentation and recognition of plant target leaves is the premise and foundation for the plant recognition and growth state monitoring based on leaf images, but the complex background brings great challenges to the segmentation and recognition of leaves. In this study, an algorithm based on the Mask-RCNN deep learning network to segment and identify multi-target leaves in the complex background was proposed. A total of 7 357 images of common plant leaves in the nature were taken, and 3 000 images of four plant leaves were labeled as training databases. The 3 000 images contained four species of plants: Calathea makoyana, Viburnum odoratissinum, Hedera helix L. and Bauhinia tomentosa. 80 sample images of the four plant species were selected for the segmentation, identification and misclassification rate analysis. The results showed that the Mask-RCNN deep learning network had a good recognition effect for the four plants and there was no false recognition. The average segmentation error rate was 0.93%, with the maximum value not exceeding 2.49%, which meant the segmentation accuracy was 97.51%. At the same time, the algorithm had strong migration ability.

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Origin, implementation difficulties and countermeasures of essential derived variety system

WAN Zhiqian, ZHANG Yuan

2020, 32(11): 2067-2076. DOI: 10.3969/j.issn.1004-1524.2020.11.18

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The essential derived variety (EDV) system is helpful to prevent modified breeding and encourage original innovation. However, this system has not been introduced into the legal protection system of variety rights in China. Therefore, the present assay systematically analyzed the origin, implementation difficulties and countermeasures of EDV system. The EDV system stems from the restriction of breeding exemption. As far as factual effects are concerned, the EDV system does not affect others to use original varieties for breeding. In terms of legal effects, the EDV system has certain restriction on breeding exemption, so the commercial use must be authorized by the original variety owner. The implementation of the EDV system may face difficulties in judging essential, obstacles to the commercialization of derived varieties and increasing the burden on farmers. Based on the consideration of professional technology, the judgment standard of threshold should be determined by the department of variety authorization. The court should apply the judgment standard in the dispute of variety infringement, to appropriately judge “essential” by means of the technical investigation officer system. Liability rules should be introduced to remove the obstacles in commercialization of derived varieties. And state subsidies should be adopted to alleviate the cost burden that the EDV system may impose on farmers. If the EDV system were introduced into China, the relevant supporting systems should be well designed.

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Evolution of grain supply and demand pattern in major grain-producing areas in China based on contribution rate to food security

LUO Haiping, PAN Liuxin, YU Zhaopeng

2020, 32(11): 2077-2087. DOI: 10.3969/j.issn.1004-1524.2020.11.19

Abstract ( 583 )

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Based on the FSP model analysis framework of contribution rate to food security, the contribution rate of 13 main grain-producing provinces (autonomous region) to national food security in China was calculated and analyzed from the perspective of inter-provincial grain supply and demand balance, and the evolution characteristics of grain supply and demand pattern were explored in major grain-producing areas. It was shown that except for the grain supply gap caused by the sharp drop in grain output from 2000 to 2003, the grain surplus (export volume) in major grain-producing areas showed a “U”-shaped trend of “steady decline-absolute growth” from 1991 to 1999 and from 2004 to 2018. Over the years, the contribution rate to food security of the major grain-producing areas was higher than 85%, and the status was relatively stable. The main function of major grain-producing areas in China has undergone inter-provincial differentiation and reorganization. On one hand, grain supply was concentrated in central and northern regions, while the grain production and demand in the southern regions was tightly balanced, which resulted in a serious mismatch between food supply and demand. On the other hand, the spatial difference of grain supply and demand was obvious. Since 2000, the total contribution rate to food security of Heilongjiang, Henan and Jilin has reached about 50%. The contribution of Hunan, Jiangxi, Jiangsu, Hebei, Hubei, Sichuan and Liaoning to grain security over the years was less than 5%, respectively, and the total amount of grain transferred from the later seven provinces only accounted for 10%-20% of the total amount of grain-transferred from the major grain producing-areas.

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Influence of imported honey on market of bee products of China

GAO Yun, ZHAO Zhijun

2020, 32(11): 2088-2093. DOI: 10.3969/j.issn.1004-1524.2020.11.20

Abstract ( 614 )

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Honey import of China experienced soaring in terms of scales and value in recent years and trade price is 6 times of that of global average at the same time. The imports characteristics were analyzed by using data of UNcomtrade and China Customs. Based on market survey data of National Bee Industry Economic Research, the price characteristics were summarized, the honeys produced in different countries were compared, and the causes and effects were discussed. The results showed that imported honey accounted for 0.85% of China's honey consumption, which would not hurt domestic bee industry, while the price gap between imported and domestic was widened from 204 Yuan to 1 053.4 Yuan per kg. And it probably created psychological presupposition for consumers and influence on consumer choice and preference as consequence. The paper recommened China should learn marketing experience from New Zealand and other countries. The measurements would be taken to select honey products with significant competitive advantage and quality characteristics, and build quality evaluation index system for single nectar honey based on stable physical and chemical indexes, with the aim to avoid “the market for lemons” and achieve high quality and good price.

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Empirical study on relationship between agricultural manager pressure and cooperative performance

CHENG Ya, LI Xinyue, ZHANG Chun, ZHANG Shemei

2020, 32(11): 2094-2102. DOI: 10.3969/j.issn.1004-1524.2020.11.21

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The introduction of agricultural managers played an important role in improving the governance structure of farmer cooperatives, enhancing the organization's human capital stock and the cooperation performance. However, complex decision-making processes, fragmented membership and an increasingly competitive environment can also put managers under pressure. Based on the field survey data of 207 cooperative agricultural managers in Sichuan province, the relationship between the pressure of agricultural managers and the performance of farmer cooperatives was studied from the two dimensions of challenge and obstacle by using the structural equation model. The results showed that the standardized path coefficient values of challenging pressure represented by workload and career development were 0.204 and 0.259, respectively, which had a significant positive impact on cooperative performance. The standardized path coefficient value of obstructive pressure represented by role conflict was -0.276, which had a significant negative impact on cooperative performance. Different dimensions of stress present different performance attributes. Challenging pressures such as workload and career development contribute to the improvement of cooperative performance, while hindering pressures such as role conflict reduce the performance of cooperative. Therefore, suggestions were put forward to alleviate the pressure of agricultural managers and improve the performance of cooperatives from three aspects internal system, external environment and managers themselves.

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Advances in ROS promoting fruit development and ripening

WANG Zhenguang, YU Yihe, GUO Dalong

2020, 32(11): 2103-2110. DOI: 10.3969/j.issn.1004-1524.2020.11.22

Abstract ( 837 )

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ROS is produced along the fruit development, which often damages proteins, lipids, carbohydrates, and DNA, causing severe cell membrane damage and inducing programmed cell death. But moderate oxidative stress is conducive to fruit ripening. The physiological mechanism of ROS affecting the fruit ripening, the interaction mechanism of ROS and hormones regulating fruit ripening, the molecular mechanism of ROS directly regulating the fruit ripening, the cooperative interaction of ROS and calcium ions regulating postharvest fruit ripening were summarized, to provide a theoretical basis and reference for employing ROS to regulate fruit ripening directly or indirectly.

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