Ecology and management of earthworm casting on sports turf

Earthworm activity is beneficial in most natural and agricultural systems, but excessive earthworm casting is a problem on sports fields worldwide. Expulsion of soil‐rich earthworm fecal matter, or casts, as mounds of soil on the turf canopy can muddy the surface, reduce photosynthesis, and lead to thinning, weed invasion and surface softening. Casts affect ball roll on sports fields, cause fouling of maintenance equipment, and dull mower blades. Build‐up of cast material on reel mower units can affect height and quality of cut. Casting activity is dependent on environmental conditions such as soil texture, temperature, moisture, pH, and organic matter. Response to environmental conditions varies by species. Management options are limited, because no pesticides are specifically labeled for earthworm control at this time, and cultural control methods such as soil modification, turfgrass clipping removal, and sand topdressing have limited and inconsistent efficacy. Products containing plant‐derived saponins and irritants show promise for earthworm management. Pest management practices to mitigate excessive earthworm casting will likely need to be species‐specific, but limited knowledge of earthworm identification by end‐users further inhibits the efficacy of control measures. © 2019 Society of Chemical Industry     

Enhanced muscle regeneration in freshwater prawn Macrobrachium rosenbergii achieved through in vivo silencing of the myostatin gene

Myostatin (MSTN) is an interesting negative growth‐regulating gene that has been well characterized in vertebrates but scantly described in invertebrates. The current study focuses on the downregulation of the MrMSTN gene and subsequently records any histological changes for giant freshwater prawn, Macrobrachium rosenbergii (Mr). In addition, the study also deals with the MrMSTN gene's influence on other growth‐related genes, which include myosin heavy chain, dystrophin‐dystroglycoprotein complex, tropomyosin, farnesoic acid o‐methyl transferase, arginine kinase, cyclophilin, and acyl CoA desaturase. The preliminary histological analysis following MrMSTN silencing favors muscle regeneration, which supports its functional role as a negative growth regulator and its significant effect on the expression of other growth‐related genes. Overall, our results show that the MrMSTN gene could therefore be a potential target for gene manipulation aimed at enhancing the growth and muscle development of M. rosenbergii, which could be beneficial in increasing the total mass production in the postlarva phase at the hatchery level.     

Molecular markers for improving control of soil-borne pathogen <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> in sugar beet

Fusarium spp. cause severe damage in many agricultural crops, including sugar beet, with Fusarium oxysporum historically being considered as the most damaging of all species. Sugar beet needs to be protected from this class of soil-borne pathogens in order to ensure an optimal sugar yield in the field. Genetic control of the disease is crucial in managing these pathogens. Identification of single nucleotide polymorphism (SNP) markers linked to resistance can be a powerful tool for the introgression of valuable genes needed to develop Fusarium-resistant varieties. A candidate gene approach was carried out to identify SNP markers linked to putative Fusarium resistance sources in sugar beet. Five resistant analogue genes (RGAs) were screened by means of high resolution melting (HRM) analysis in a set of sugar beet lines, considered as resistant and susceptible to Fusarium oxysporum. HRM polymorphisms were observed in 80% of amplicons. Two HRM polymorphisms were significantly associated with Fusarium resistance (P < 0.05). The amplicons that showed association were sequenced and two SNPs were identified. The association was further validated on 96 susceptible and 96 resistant plants using competitive allele-specific PCR (KASPar) technology. The selected SNPs could be used for marker-assisted breeding of Fusarium resistance in sugar beet.     

Crop rotation sequencing to minimize yield losses of summer-irrigated lowland rice in Myanmar caused by the rice root-knot nematode Meloidogyne graminicola

Abstract

The effect of different rice-based crop rotation sequences on the population densities of Meloidogyne graminicola and on the yield of rice was evaluated in a microplot experiment under lowland rice field conditions. Ten treatments of cropping sequences were grown in four successive growing seasons: continuous growing of the susceptible rice cultivar Thihtatyin (rice-rice-rice-rice), four treatments of 1- season crop rotation sequences (rice-rice-chickpea-rice, rice-rice-black gram-rice, rice-rice-soybean-rice, rice-rice-cowpea-rice), and five treatments of 2-season crop rotation sequences (groundnut-rice-chickpea-rice, green gram-rice-black gram-rice, cowpea-rice-soybean-rice, sesame-rice-cowpea-rice, sunflower-rice-sesame-rice). Population densities of M. graminicola recovered from the rice plants and the nematode multiplication factors (Mf) in the soil in the continuous rice cropping sequence (rice-rice-rice-rice) was the highest among the ten cropping sequences. Lowest nematode Mf in the soil was observed in the 2-season crop rotation sequence sunflower-rice-sesame-rice and the highest was observed in the 1-season crop rotation sequence rice-rice-cowpea-rice among the nine crop rotation sequences. Highest rice yield was obtained in the 2-season crop rotation sequences green gram-rice-black gram-rice, sesame-rice-cowpea-rice and sunflower-rice-sesame-rice, which were about 2 times higher compared with the 1-season crop rotation sequences and about 3 times higher compared with the continuous rice cropping sequence.     

基于随机森林算法和气象因子的砀山酥梨始花期预报

准确预报始花期是制定砀山酥梨花期管理措施和赏花活动方案的重要基础。该文利用1983-2018年砀山酥梨始花期的定位观测物候数据和平行观测的气象资料，采用线性趋势法，揭示始花期演变趋势；采用相关分析，筛选影响始花期的关键气象因子，依据不同预报日期构成特征变量集；采用随机森林算法（Random Forest, RF），自3月11日开始预报到3月25日终止预报，每日训练1个预报模型。结果表明，1）1983－2018年始花期呈极显著提早发生趋势，每10a约提前2.750 d（P＜0.001）。2）16个逐日气象预报模型中，共计有200个气象因子与始花期早迟密切相关，相关系数在0.469～0.789之间；各气象预报模型的训练集与测试集的平均正确率（Nd）分别为92.9%和75.5%、平均均方根误差（RMSE）分别为1.693～2.870和2.240～7.237、平均决定系数（R2）分别为0.891和0.701。3）2019年试验预报中，提前15日准确预报出当年始花期。该文研究表明RF在梨树始花期逐日气象预报中有一定业务应用潜力，预报准确率基本满足气象服务需求。     

Identification of resistant germplasm containing novel resistance genes at or tightly linked to the <Emphasis Type="Italic">Pi2/9</Emphasis> locus conferring broad-spectrum resistance against rice blast

Background

The rice Pi2/9 locus harbors multiple resistance (R) genes each controlling broad-spectrum resistance against diverse isolates of Magnaporthe oryzae, a fungal pathogen causing devastating blast disease to rice. Identification of more resistance germplasm containing novel R genes at or tightly linked to the Pi2/9 locus would promote breeding of resistance rice cultivars.

Results

In this study, we aim to identify resistant germplasm containing novel R genes at or tightly linked to the Pi2/9 locus using a molecular marker, designated as Pi2/9-RH (Pi2/9 resistant haplotype), developed from the 5′ portion of the Pi2 sequence which was conserved only in the rice lines containing functional Pi2/9 alleles. DNA analysis using Pi2/9-RH identified 24 positive lines in 55 shortlisted landraces which showed resistance to 4 rice blast isolates. Analysis of partial sequences of the full-length cDNAs of Pi2/9 homologues resulted in the clustering of these 24 lines into 5 haplotypes each containing different Pi2/9 homologues which were designated as Pi2/9-A5, ?A15, ?A42, ?A53, and -A54. Interestingly, Pi2/9-A5 and Pi2/9-A54 are identical to Piz-t and Pi2, respectively. To validate the association of other three novel Pi2/9 homologues with the blast resistance, monogenic lines at BC₃F₃ generation were generated by marker assisted backcrossing (MABC). Resistance assessment of the derived monogenic lines in both the greenhouse and the field hotspot indicated that they all controlled broad-spectrum resistance against rice blast. Moreover, genetic analysis revealed that the blast resistance of these three monogenic lines was co-segregated with Pi2/9-RH, suggesting that the Pi2/9 locus or tightly linked loci could be responsible for the resistance.

Conclusion

The newly developed marker Pi2/9-RH could be used as a potentially diagnostic marker for the quick identification of resistant donors containing functional Pi2/9 alleles or unknown linked R genes. The three new monogenic lines containing the Pi2/9 introgression segment could be used as valuable materials for disease assessment and resistance donors in breeding program.