Shenghao Ye

Small Tail Han sheep that has significant characteristics of high prolificacy and nonseasonal ovulatory activity is an excellent local sheep breed in P.R. China. The lambing percentage averaged 260% in Small Tail Han sheep. Growth differentiation factor 9 (GDF9) gene, which was essential for growth and differentiation of early ovarian follicles, was considered as a possible candidate gene for litter size in Small Tail Han sheep. The genetic polymorphism of a part of the GDF9 gene was detected in 130 ewes of Small Tail Han sheep by PCR-SSCP. The results indicated that there were two genotypes (AA and AB) detected by two primer pairs. In both exon 1 and exon 2 of the GDF9 gene in Small Tail Han sheep, frequencies of AA genotype were 0.846 and 0.908, frequencies of AB genotype were 0.154 and 0.092, frequencies of A allele were 0.923 and 0.954, and frequencies of B allele were 0.077 and 0.046, respectively. The results of chi2 fitness test indicated that both exon 1 and exon 2 of the GDF9 gene were in Hardy-Weinberg equilibrium (p > 0.05) in Small Tail Han sheep. Least squares means of litter size in the first and the second parity for genotype AA were 0.30 (p <0.05) and 0.77 (p <0.0001) more than those for genotype AB detected in exon 1 of the GDF9 gene in Small Tail Han sheep, respectively. Fragments detected in exon 2 of the GDF9 gene had no significant effect (p > 0.05) on litter size in both the first and the second parity in Small Tail Han sheep. Litter size in sheep is lowly heritable, expressed only in females, and manifested relatively late in life. Access to genetic markers would thus be advantageous in selection programs.

Although there are existing interplant weed control devices for soybeans, they mostly rely on image recognition and intelligent navigation platforms. Simultaneously, automated weed control devices are not yet fully mature, resulting in issues such as high seedling injury rates and low weeding rates. This paper proposed a reciprocating interplant weed control device for soybeans based on the idea of intermittent reciprocating opening and closing of weeding execution components. The device consists of a laser ranging sensor, servo motor, Programmable Logic Controller (PLC), and weeding mechanism. Firstly, this paper explained the overall structure and working principle of the weed control device, and discussed the theoretical analysis and structural design of the critical component, elastic comb teeth. This paper also analyzed the working principle of the elastic comb teeth movement trajectory and seedling avoidance action according to soybean agronomic planting requirements. Then, field experiments were conducted, and the experiment was designed by the quadratic regression general rotation combination experimental method. The number of combs, the speed of the field management robot, and the stabbing depth were taken as the test factors to investigate their effects on the test indexes of weeding rate and seedling injury rate. The experiment utilized a response surface analysis method and designed a three-factor, three-level quadratic regression general rotation combination experimental method. The results demonstrate that the number of comb teeth has the most significant impact on the weeding rate, while the forward speed has the most significant impact on the seedling injury rate. The optimal combination of 29.06 mm stabbing depth, five comb teeth, and a forward speed of 0.31 m/s achieves an optimal operational weeding rate of 98.2% and a seedling injury rate of 1.69%. Under the optimal parameter combination conditions, the machine’s performance can meet the requirements of intra-row weeding operations in soybean fields, and the research results can provide a reference for the design and optimization of mechanical weed control devices for soybean fields.

Under soybean–corn intercropping in China, quizalofop-p-ethyl is recommended as a herbicide for stem and leaf treatment after soybean seedling. Nonetheless, herbicide drift during spraying may lead to environmental contamination and damage to the corn plants. In order to clearly show the threshold of the drift deposition amount of quizalofop-p-ethyl that causes herbicide damage to corn, we used a bioassay spray tower to spray quizalofop-p-ethyl herbicide on corn in the laboratory and a boom sprayer to spray quizalofop-p-ethyl herbicide, which drifts to corn in the field, to study and evaluate the damage quizalofop-p-ethyl herbicide causes to corn under different spray volumes and drift deposition rates. The results showed that under a drift deposition rate of 1% of three spray volumes, the corn showed no symptoms of herbicide damage and their plant height was not inhibited 14 days after spray; under a spray volume of 150 L/ha and a drift deposition rate of 5%, the corn showed symptoms of mild herbicide damage but their plant height was not inhibited 14 days after spray, while the corn showed symptoms of moderate herbicide damage and their plant height was slightly and moderately inhibited, respectively, under the spray volumes of 300 L/ha and 450 L/ha; under drift deposition rates of 10% and 30% of three spray volumes, half or more of the corn in each treatment withered and their plant height was severely inhibited or completely inhibited. Under the same spray volume, the symptoms of herbicide damage and the inhibition rate of plant height increased with the increase in the drift deposition rate; under the same drift deposition amount, the symptoms of herbicide damage and the inhibition rate of plant height increased with a decrease in the spray volume. The effect of the drift deposition rate on the symptoms of herbicide damage and plant height was extremely significant, but the spray volume was not significant. The drift deposition rates for 10% inhibition and no inhibition of corn plant height were 5.70% (R10) and 5.05% (R0) under spray volume of 150 L/ha, 4.56% (R10) and 1.23% (R0) under 300 L/ha, and 3.31% (R10) and 1.86% (R0) under 450 L/ha, respectively. When the herbicide was sprayed in the field using a soybean–corn-dedicated plant protection machine under the spray volume of 450 L/ha, the drift deposition rate ranged from 1.22% to 1.69%, and the corn did not produce symptoms of herbicide damage and plant height was not inhibited 14 days after the spray. In actual weeding operations, it is better to ensure that the drift deposition rate of quizalofop-p-ethyl is below R0 by setting reasonable operational parameters, using anti-drift nozzles or additives, and so on, and, at most, not more than R10. This study clarified the drift hazard of quizalofop-p-ethyl herbicide on corn and the safety value of the herbicide drift deposition amount, which provided data support for the standardized use of quizalofop-p-ethyl herbicide under soybean–corn intercropping and guidance for the safe production of field corn.

Abstract Small Tail Han sheep that has significant characteristics of high prolificacy and nonseasonal ovulatory activity is an excellent local sheep breed in P.R. China. The lambing percentage averaged 260% in Small Tail Han sheep. Growth differentiation factor 9 (GDF9) gene, which was essential for growth and differentiation of early ovarian follicles, was considered as a possible candidate gene for litter size in Small Tail Han sheep. The genetic polymorphism of a part of the GDF9 gene was detected in 130 ewes of Small Tail Han sheep by PCR-SSCP. The results indicated that there were two genotypes (AA and AB) detected by two primer pairs. In both exon 1 and exon 2 of the GDF9 gene in Small Tail Han sheep, frequencies of AA genotype were 0.846 and 0.908, frequencies of AB genotype were 0.154 and 0.092, frequencies of A allele were 0.923 and 0.954, and frequencies of B allele were 0.077 and 0.046, respectively. The results of χ 2 fitness test indicated that both exon 1 and exon 2 of the GDF9 gene were in Hardy-Weinberg equilibrium (p > 0.05) in Small Tail Han sheep. Least squares means of litter size in the first and the second parity for genotype AA were 0.30 (p < 0.05) and 0.77 (p < 0.0001) more than those for genotype AB detected in exon 1 of the GDF9 gene in Small Tail Han sheep, respectively. Fragments detected in exon 2 of the GDF9 gene had no significant effect (p > 0.05) on litter size in both the first and the second parity in Small Tail Han sheep. Litter size in sheep is lowly heritable, expressed only in females, and manifested relatively late in life. Access to genetic markers would thus be advantageous in selection programs.