Effects of Different Planting Years on Physicochemical Properties and Enzyme Activities in Soil of Rice-Cherry Tomato Rotation

Crop rotation periodicity has always been one of the research focuses currently. In this study, the physicochemical properties, nutrient contents and enzyme activities were investigated in soils from rice-cherry tomato rotation for one year (1a), three years (3a), five years (5a), seven years (7a) and ten years (10a), respectively. The major objective was to analyze the optimal rotation years of rice-cherry tomato from soil perspective, so as to provide theoretical basis for effectively avoiding continuous cropping obstacles of cherry tomato via studying the response characteristics of soil physicochemical properties, nutrient contents and enzyme activities to planting years of rice-cherry tomato rotation system. The results were as follows: 1) Soil pH value was increased year by year during 1a to 5a, reached the highest value 5.32 at 5a. However, soil acidity was sharply enhanced during 7a to 10a (P P •kg-1 at 5a. 3) The content of soil available phosphorus was increased year by year with increasing of crop rotation years, and increased by 110% to 173% during 3a to 10a (P P P < 0.05). In conclusion, long-term single rotation pattern of rice-cherry tomato would aggravate soil acidification, prompt soil nutrient imbalance and reduce soil enzyme activity. 5a to 7a would be the appropriate rotation period for rice-cherry tomato, or else it would reduce soil quality, resulting in a new continuous cropping obstacle of cherry tomato.

Unraveling the skatole biodegradation process in an enrichment consortium using integrated omics and culture-dependent strategies

3-Methylindole(skatole)is regarded as one of the most offensive compounds in odor emission.Biodegradation is feasible for skatole removal but the functional species and genes responsible for skatole degradation remain enigmatic.In this study,an efficient aerobic skatole-degrading consortium was obtained.Rhodococcus and Pseudomonas were identified as the two major and active populations by integrated metagenomic and metatranscriptomic analyses.Bioinformatic analyses indicated that the skatole downstream degradation wasmainly via the catechol pathway,and upstream degradation was likely catalyzed by the aromatic ring-hydroxylating oxygenase and flavin monooxygenase.Genome binning and gene analyses indicated that Pseudomonas,Pseudoclavibacter,and Raineyella should cooperate with Rhodococcus for the skatole degradation process.Moreover,a pure strain Rhodococcus sp.DMU1 was successfully obtained which could utilize skatole as the sole carbon source.Complete genome sequencing showed that strain DMU1 was the predominant population in the consortium.Further crude enzyme and RT-qPCR assays indicated that strain DMU1 degraded skatole through the catechol ortho-cleavage pathway.Collectively,our results suggested that synergistic degradation of skatole in the consortium should be performed by diverse bacteria with Rhodococcus as the primary degrader,and the degradation mainly proceeded via the catechol pathway.