Mechanisms controlling phosphorus (P) availability and the roles of microorganisms in the efficient utilization of soil P in the wheat–maize double cropping system are poorly understood.  In the present study, we conducted a pot experiment for four consecutive wheat–maize seasons (2016–2018) using calcareous soils with high (30.36 mg kg^–1) and low (9.78 mg kg^–1) initial Olsen-P content to evaluate the effects of conventional P fertilizer application to both wheat and maize (Pwm) along with a reduced P fertilizer application only to wheat (Pw).  The microbial community structure along with soil P availability parameters and crop yield were determined.  The results showed that the Pw treatment reduces the annual P input by 33.3% without affecting the total yield for at least two consecutive years as compared with the Pwm treatment in the high Olsen-P soil.  Soil water-soluble P concentrations in the Pw treatment were similar to those in the Pwm treatment at the 12-leaf collar stage when maize requires the most P.  Furthermore, the soil P content significantly affected soil microbial communities, especially fungal communities.  Meanwhile, the relative abundances of Proteobacteria and alkaline phosphatase (ALP) activity of Pw were significantly higher (by 11.4 and 13.3%) than those of Pwm in soil with high Olsen-P.  The microfloral contribution to yield was greater than that of soil P content in soil with high Olsen-P.  Relative abundances of Bacillus and Rhizobium were enriched in the Pw treatment compared with the Pwm treatment.  Bacillus showed a significant positive correlation with acid phosphatase (ACP) activity, and Rhizobium displayed significant positive correlations with ACP and ALP in soil with high Olsen-P, which may enhance P availability.  Our findings suggested that the application of P fertilization only to wheat is practical in high P soils to ensure optimal production in the wheat and maize double cropping system and that the soil P availability and microbial community may collaborate to maintain optimal yield in a wheat–maize double cropping system.

    Alcohol dehydrogenase (ADH) catalyzes the interconversion of aldehydes and their corresponding alcohols, and is a key enzyme in volatile ester biosynthesis. However, little is known regarding ADH and ADH encoding genes (ADHs) in pear. We identified 8 ADHs in the pear’s genome (PbrADHs) by multiple sequences alignment. The PbrADHs were highly homologous in their coding regions, while were diversiform in structure. 9 introns were predicted in PbrADH₃–PbrADH₈, while 8 introns, generated through exon fusion and intron loss, were predicted in PbrADH₁ and PbrADH₂. To study the genetic regulation underlying aroma biogenesis in pear fruit, we determined the PbrADH transcripts, ADH activities and volatile contents of fruits during ripening stage for Nanguoli and Dangshansuli, two cultivars having different aroma characteristics. ADH activity was strongly associated with the transcription of ADH6 in the two cultivars during fruit ripening stage. The higher ester content paralleling to a higher ADH activity was detected in Nanguoli than in Dangshansuli, so it is induced that the lower ester content in Dangshansuli fruit may be the result of weak ADH activity. The present study revealed that total ADH activity and volatile ester production correlated with increased PbrADH₆ transcript levels. PbrADH6 may contribute to ADH activity catalyzing aldehyde reduction and ester formation in pear fruit.

Complete genome sequence of Potato virus Y Liaoning isolate (PVY-LN) causing tobacco vein necrosis symptoms were isolated from Liaoning Province in China. Genome sequences of PVY-LN was 9 714 nucleotides in length, excluding the 3´- terminal poly (A) tail. PVY-LN encodes a single long open reading frame (ORF) of polyprotein that is predicted to be cleaved into ten mature proteins by three viral proteases. No recombination can be predicted in PVY-LN sequences compared with that of the other PVY strains using Recombination Detection Programe v. 4.16 (RDP4). Complete genome sequence comparison and phylogenetic analysis indicated that PVY-LN is closely related to PVY necrosis strain (PVYN).