Rubber particles are important components in latex, and have important effects on latex stability, rubber biosynthesis and processing properties. However, the difference of rubber particle size and distribution among different germplasms and the annual changes have not been systematically studied. In this study, 486 wild and cultivated Hevea germplasm planted in National Rubber Germplasm Respository were selected, and the latex were collected monthly during the tapping period from 2020 to 2021. The average diameter (Da), intermediate diameter (Di), intermediate diameter/average diameter (Di/Da), particle size≤0.259 μm frequency and particle size≤0.197 μm frequency of rubber particles were analyzed and studied. Da varied from 0.313 μm to 0.439 μm, and the coefficient of variation (CV) was 0.008-0.206. Di varied 0.209-0.366 μm, and the CV was 0.009-0.235. Di/Da varied 58.3%-84.9%, and the CV was 0.015-0.123. particle size≤0.259 μm frequency varied 31.1%-61.8%, and the CV was 0.013-0.322; particle size≤0.197 μm frequency varied 17.6%-46.4%, and the CV was 0.018-0.588. The five indexes showed significant differences among germplasm, which were suitable to be latex characteristic index. The correlation analysis of the five indexes showed that the correlation coefficient of Di and Da was 0.781; The correlation coefficient of particle size≤0.259 μm frequency and particle size≤0.197 μm frequency was 0.976; The correlation between Di and Di/Da was higher than that of Da, and the correlation coefficient reached 0.814. Di was also more correlated with particle size≤0.259 μm frequency and particle size≤0.197 μm frequency than Da, and the correlation coefficient reached 0.520 and 0.632, indicating that Di had a stronger statistical significance. Annual changes of Da, Di and Di/Da showed some difference. Da in June, July, August, October and December was not significant, and September and November were lower than other months. Di was not significantly different in June, July, August, September, November and December, and just a little lower in October. Di/Da had no significant difference in June, August and September, increased in November and December, but declined obviously in July and October. Da, Di, Di/Da, ≤0.259 μm frequency, ≤0.197 μm frequency in each month were all significantly correlated with the annual average. However, correlation coefficient were higher between alternate monthly measurements (June, August, October; July, September, November; August, October, December) and the annual average, reaching more than 0.850. That can be used for future rubber particle size testing.

The study of crop spatial pattern has important theoretical and practical significance, and has become the frontier and hotspot of geography and ecology. This paper systematically summarized the current progress of allocation method, driving force analysis and simulation of crop spatial pattern. And in this paper, a mind map of research work is presented based on the discussion of the deficiencies and the trends in the study of crop spatial pattern. It is showed that the methods of statistical investigation, remote sensing and spatial model have their advantages and disadvantages in the work of crop spatial information allocation. And it is difficult to fully understand the process of crop spatial pattern change only from the perspective of natural driving force or socio-economic driving force in the work of driving force analysis and simulation of crop spatial pattern. It is suggested that the spatial information comprehensive allocation technology based on spatial model, the multi-factor and multi-scale driving force analysis method combining natural and socio-economic factors, and the simulation model coupling geographical model and socio-economic model will be the important development directions in the field of crop spatial pattern research.

MNP (multiple nucleotide polymorphism, MNP) is a new molecular marker technology emerged with the development of molecular marker technology. While genotyping by target sequencing (GBTS) amplifies only one SNP site in one amplicon, MNP can amplify multiple SNP sites simultaneously in one amplicon based on GBTS. This technology has the features of low cost, high detection efficiency, flexible application and wide adaptability, Compared with SNP, MNP has better ability to differentiate varieties. In order to establish a rapid, accurate and efficient method for cassava variety identification and to screen MNP molecular markers suitable for cassava variety identification, this study screened highly polymorphic regions and designed primers in the whole genome range, and finally obtained 623 cassava MNP marker loci in the whole genome range, the cassava MNP markers were evaluated using 28 cassava varieties. The results showed that the MNP marker typing reproducibility was up to 100%. 4.07±1.68 alleles were detected in 28 cassava varieties, with a maximum of 12 alleles. When all cassava varieties were compared one by a one, 99.47%(376/378) of the differences between pairs were greater than 46%, with the proportion ranging from 0.3% to 81.0%, with a mean value of 71.78%. Meanwhile, MNP markers can be used for identification in the breeding process. In conclusion, the cassava MNP molecular markers developed in this study have high reproducibility, polymorphism and variety differentiation ability, and could be widely used for research on germplasm diversity, new variety breeding and variety identification of cassava.

Cassava is an important food crop in tropical regions, and one of the main breeding goals is to cultivate new lines with high β-carotene, low cyanogenic glucoside and waxy taste. In order to screen promising edible lines from breeding materials, the study developed a MATE-SNAP marker based on a mutation of G→A in the coding region of cyanogenic glucoside transporter gene MATE which resulted to amino acid change and affected its transmembrane structure stability. Combining with the β-carotene PSY2-SNAP and waxy quality GBSSⅠ-SNAP markers, 12 parent lines, carrying 1-2 target alleles, were selected from 50 cassava germplasms, and totally hybridized 10 cross-combinations according to flowering period among different years. Firstly, 134 erect or middle branched candidate lines were screen out through seedling, transplanting and preliminary field trial. Secondly, 13 edible promising lines which aggregated 2-3 target alleles, were chosen by using MATE/PSY2/GBSSⅠ-SNAP markers together. The content of of cyanogenic glucoside in root flesh was determined by spectrophotometry, the value of SC9 was 49.24 μg/g, and those of 13 promising lines were in the range of 38.82-76.51 μg/g; the content of β-carotene in root flesh was determined by acetone colorimetry, the value of SC9 was 184.75 μg/hg, and those of the six yellow-root lines were within the limits of 101.58-154.10 μg/hg; the content of amylopectin in root flesh was determined by dual wavelength spectrophotometry, the values of P13-1 and V7-14, whose alleles were GG that genotyped by GBSSⅠ-SNAP marker, was 82.46% and 83.79%, respectively. Based on this, 5 lines, A5-138, A2-213, P7-6, V4-8 and V4-19, were found to be the potential new edible cassava varieties by taste grading. In conclusion, marker-assisted selection can quickly and accurately screen out the target lines from breeding materials and improve the efficiency of cassava genetic improvement.

In order to understand the diversity of phenotypic traits in F₁ segregation populations of date palm, this study used 143 F₁ segregation populations of date palms as test materials to analyze the diversity, correlation, principal component and cluster analysis of 17 phenotypic traits, including plant height, crown breadth, stem girth, number of branches and leaf spot incidence. The results showed that there was a high degree of phenotypic variation and rich diversity in F₁ segregation population of date palms. The variation degree of quantitative characters was high, the coefficient of variation ranged from 10.927% to 43.350%, and the coefficient of variation of stem girth was the largest. The coefficients of variation of quality traits ranged from 31.447% to 44.619%, among which the coefficients of variation of tiller leaf color and leaf hardness were 44.619% and 42.571%, respectively. The correlation analysis showed that plant height, crown breadth, stem girth, number of branches, the third branch of long, the thorn area length, the total number of tiller leaves, tiller leaves length, tiller leaves width, tiller leaf thickness and leaf color were positively correlated with each other. The incidence of leaf spot was negatively correlated with the other 16 traits. The principal component analysis showed that the cumulative contribution rate of the six principal components reached 87.51%, of which the characteristic value of the first principal component was 10.0836, and the contribution rate was 59.32%. It is mainly affected by the five indicators of plant height, third branch length, crown breadth, stem girth and branch number. The characteristic value of plant height is the largest, which is 0.2948, which mainly reflects the height and growth trend of date palm. The cluster analysis showed that the 143 F₁ generation dates could be divided into five groups: Group Ⅰ included 33 dates with the smallest crown, the least number of branches, the shortest tiller leaves length, and the highest incidence of leaf spot disease. Group Ⅱ included 39 dates resources with the shortest plant height, the smallest stem girth, the shortest third branch length, and the heaviest incidence of leaf spot disease. Group Ⅲ included 23 dates resources with longer tiller leaves, darker tiller leaves, erect plant type and mild incidence of leaf spot disease. Group Ⅳ included 33 dates resources with excellent phenotypic traits such as large ratio of leaf length to width of tiller leaves, stiffer tiller leaves and the least incidence of leaf spot disease. Group Ⅴ included 14 dates resources with small ratio of tiller leaves length to width ratio and open plant type. The results of this study can provide a theoretical basis for the breeding of superior parental traits in later stage of date palm.

Chalcone synthase (CHS) is the first limiting enzyme in flavonoid synthesis pathway and plays an important role in flower color formation, growth and development, and abiotic stress. In order to clarify the characteristics of cassava MeCHS gene family and its expression in cassava postharvest physiological deterioration (PPD), the MeCHS gene family was analyzed using bioinformatics, including physicochemical property and subcellular location. qRT-PCR was carried out to detect the expression levels of MeCHS genes in different varieties, different tissues and PPD process. The genes with significant relative expression were selected for cloning and subcellular localization verification. A total of 5 MeCHS gene members were identified in the cassava genome. The secondary structure analysis showed that the MeCHS gene family was mainly composed of α-helices and random coils. Tissue specific expression indicated that the expression levels of MeCHS genes were higher in stems. The major expressed MeCHS genes in cassava were MeCHS1, MeCHS2 and MeCHS3; and the expression levels of these three genes were gradually increase with PPD. MeCHS1, MeCHS2 and MeCHS3 were successfully cloned; and fluorescence transient expression showed that MeCHS1, MeCHS2 and MeCHS3 were localized in the cytoplasm, which was consistent with the predicted results. This study will provide a theoretical basis for further revealing the function of MeCHS gene family and improving the PPD tolerance of cassava.

To study the differences in the physical and chemical properties of biochar obtained from three legumes at different temperatures, and to determine the appropriate temperature range for legume biochar. Using leguminous plant peanut straw, soybean straw and stylofoam as raw materials, peanut straw biochar (Pe), soybean straw biochar (Be) and stylofoam biochar (St) were prepared at 300 ℃, 500 ℃ and 700 ℃. A Fourier infrared spectrometer was used to qualitatively analyze the functional groups on the surface of the biochar, and the surface morphology of the biochar was observed with a scanning electron microscope, and the physical and chemical properties, such as pH, C and N content, were measured. The results showed that the carbon content of biochar prepared from three kinds of raw materials increased with the increase of pyrolysis temperature at 300 ℃ to 500 ℃, and was basically stable after 500 ℃; the nitrogen content and yield of biochar decreased with the increase of temperature. Among the biomass charcoal prepared from the three materials, Be has the highest carbon content and C/N, and N content and yield are the lowest. The ash content, ash alkalinity and pH of biochar all increase with the increase of pyrolysis temperature. The same pyrolysis ash alkalinity and pH of biochar all increase with the increase of pyrolysis temperature. The same pyrolysis temperature and different materials are all expressed as Be>St>Pe. Both the pore size and specific surface area of biochar increase with increasing temperature. The three raw materials of biochar form more stable aromatic compounds with increasing temperature, and the structure is mainly C=O and C=C. In this study, the suitable pyrolysis temperature of legume biochar is 500 ℃, and the temperature rises again, which has little effect on the physical and chemical properties of biochar. In summary, the soybean biochar produced by cracking at 500 ℃ is more used in farmland soil improvement, and can also try soil remediation, carbon sequestration and emission reduction applications.

This article is the first to conduct prevention and control experiments on rubber tree powdery mildew and anthracnose using a heavy-load plant protection UAV (FBH300T), analyzing the effects of flight heights of 3 m, 5 m, 7 m, and application amount of 60 L/hm², 90 L/hm², 105 L/hm² on the distribution of droplet deposition on the upper and lower leaves of rubber trees. This study found that flight altitude and application amount has a very significant impact on droplet density and droplet coverage. It has been selected that the optimal application parameters for this aircraft model are a flight height of 5 m above the canopy, an application amount of 90 L/hm², and a flight speed of 5 m, this study utilized a new specialized agent 19% Baoyeqing ME, which can simultaneously treat various leaf diseases of rubber trees, as well as efficient agents such as 60% sulfur powder SC, 45% pentazolamide EW, and 50% sulfur triadimefon SC, which were used in conjunction with heavy-load plant protection UAV (FBH300T) to analyze the control effects of each agent on the powdery mildew and anthracnose of rubber trees. The results showed that among the four single agents, the 50% sulfur triadimefon SC had the best control effect on powdery mildew, followed by the 19%Baoyeqing ME; The best control effect on Anthracnose is 19% Baoyeqing ME, followed by 45% pentazole imidamide EW. Under the mixed application of chemical agents, the best control effect against powdery mildew and anthracnose was achieved by mixing 19% Baoyeqing ME and 60% sulfur powder SC at a ratio of 1∶1, followed by mixture of 19% Baoyeqing ME and 50% sulfur triadimefon SC at a ratio of 1∶1. The experimental results can provide a good reference basis for the maturation of UAV flight defense technology and the selection of special flight prevention agents for rubber tree leaf disease.

The problem of soil salinization in my country is becoming more and more serious. Rice is the preferred food crop for the improvement of salinized land, but salt stress is one of the main abiotic stresses that influence the growth and yield of rice. In order to fully understand the effect of salt stress on the rice, 31 varieties (lines) of tropical rice with different salt tolerance were used as experimental materials, and experiments were carried out by hydroponics in seedling stage incubator and potted soil cultivation method in the whole growth period, to study the effects of 0 NaCl (CK), 0.3% NaCl and 0.6% NaCl on the growth, physiological and biochemical characteristics, and yield composition of tropical rice. The result showed that: (1) The seedlings and roots growth of tropical rice were inhibited under salt stress. The seedling height and root number were significantly decreased with the increase of NaCl concentration, the root length in 0.3% NaCl and 0.6% NaCl treatments was significantly lower than CK treatments; and the fresh weight of seedling in 0.6% NaCl treatments was significantly lower than CK and 0.3% NaCl treatments. (2) Chlorophyll accumulation of tropical rice leaves were decreased under salt stress. The contents of chlorophyll a, chlorophyll b and Car in the treatments with 0.3% NaCl and 0.6% NaCl concentrations were significantly lower than CK treatments. The accumulation of proline (Pro), malondialdehyde (MDA) and Na⁺ were increased. The content of Pro and MDA and Na⁺ in the treatments with 0.6% NaCl concentration were significantly higher than treatments with CK and 0.3% NaCl concentration. The accumulation of K⁺were decreased. The K⁺ content in the 0.3% NaCl and 0.6% NaCl concentration treatments was significantly lower than the CK concentration treatments. (3) Under salt stress, the tiller number, panicle number, panicle length, panicle grain number, thousand-kernel weight and yield of per plant were significantly decreased with the increase of NaCl concentration.

Anoectochilus roburghii is a rare and endangered medicinal orchid with high economic value. High temperature is the primary limiting factor for its extensive production and cultivation. Breeding heat-resistant varieties is one of the most economical and effective measures to resist heat damage caused by high temperature. In this study, we analyzed the genetic diversity of 24 A. roburghii germplasm resources by Start codon targeted polymorphism (SCoT) molecular markers, and evaluated the heat tolerance of 20 samples by multivariate statistical analysis. The results of genetic diversity analysis showed that at the genetic coefficient was 0.602, A. roburghii germplasm could be divided into two groups: I and II, Group I was divided into two subgroups A and B, Anoectochilus formosanus was classifiedd into Group II alone. In subgroup A, except W from Yunnan, all the other resources were collected in the north and west of Fujian. Subgroup B mainly came from Southern Fujian and Guangxi. The cluster diagram showed that the relatives of A. roburghii from the same origin was close, and the presence or absence of reticulated veins was not the basis for the classification. Five physiological parameters were measured in the 20 samples. It was found that the chlorophyll content and SOD activity decreased obviously after heat treatment, and the relative conductance increased obviously, while the malondialdehyde and soluble protein contents of each resource were different after heat treatment. The preliminary evaluation of heat resistance was conducted by the multivariate statistical analysis method, and the results showed that four resources (TL, L1, A20, GZ1) were heat resistant, while five resources (TJ, HX, L, M, A21) were not.