Food is a fundamental human right, and global food security is threatened by crop production. Plant growth regulators (PGRs) play an essential role in improving crop yield and quality, and this study reports on a novel PGR, termed guvermectin (GV), isolated from plant growth-promoting rhizobacteria, which can promote root and coleoptile growth, tillering, and early maturing in rice. GV is a nucleoside analogue like cytokinin (CK), but it was found that GV significantly promoted root and hypocotyl growth, which is different from the function of CK in Arabidopsis. The Arabidopsis CK receptor triple mutant ahk2-2 ahk3-3 cre1-12 still showed a GV response. Moreover, GV led different growth-promoting traits from auxin, gibberellin (GA), and brassinosteroid (BR) in Arabidopsis and rice. The results from a four-year field trial involving 28 rice varieties showed that seed-soaking treatment with GV increased the yields by 6.2 to 19.6%, outperforming the 4.0 to 10.8% for CK, 1.6 to 16.9% for BR, and 2.2 to 7.1% for GA-auxin-BR mixture. Transcriptome analysis demonstrated that GV induced different transcriptome patterns from CK, auxin, BR, and GA, and SAUR genes may regulate GV-mediated plant growth and development. This study suggests that GV represents a novel PGR with a unique signal perception and transduction pathway in plants.

Phyllosphere microbiota play a crucial role in plant-environment interactions and are influenced by biotic and abiotic factors. However, there is little research on how pathogen s affect the microbial community. In this study, we collected 16 pumpkin (Cucurbita moschata) leaf samples showing symptoms of powdery mildew disease with different disease severity levels ranging from L1 (least severe) to L4 (most severe). We examined the fungal community structure and diversity by Illumina MiSeq sequencing of the internal transcribed spacer (ITS) region of ribosomal RNA genes. The fungal communities were dominated by members of the Basidiomycota and Ascomycota. The dominant genus was Podosphaera on the diseased leaves, which was the key pathogen responsible for the pumpkin powdery mildew. Ascomycota and Podosphaera increased in abundance as disease severity increased from L1 to L4, and were significantly more abundant than other microorganisms at disease severity L4 (P<0.05). The richness and diversity of the fungal community increased from L1 to L2, and then declined from L2 to L4, likely due to the biotic pressure at disease severity L4. Maintaining species richness in the phyllosphere will be an important part of managing disease control in this agroecological system and an essential step toward predictable biocontrol of powdery mildew in pumpkin. (Lebeda et al., 2010). 61The phyllosphere or leaf surface is an important microbial habitat for members of the major 62 bacterial and fungal groups, and Archaea (Lindow & Leveau, 2002; Lindow and Brandl, 2003).63 These microorganisms play a crucial role in helping their host against pathogens (Lacava et al., 64 2006; Mejía et al., 2008; Rajendran et al., 2008). In past years, most of the researchers focused 65 on screening plant growth-promoting microorganisms from plants which can help us manage 66 diseases (Compant et al., 2005;Everett et al., 2005;Hirano & Upper, 2000; Whipps et al., 67 2008). However, not all the microbes in the natural environment are considered culturable. In the 68 past few years, the development of next-generation rRNA sequencing techniques has enabled us 69 to obtain in-depth descriptions of the composition of the microbial communities associated with 70 leaves of Arabidopsis thaliana (Reisberg et al., 2013), potatoes (Becker et al., 2008), rice 71 (Mwajita et al., 2012), spinach (Lopez et al., 2011 Lopez et al., 2013), grape (Leveau et al., 72 2011, and various tree species including salt cedar (Redford et al., 2010;Finkel et al., 2011). 73Historically, scholars have begun to study the rhizosphere as a microbial habitat as early as 74 100 years ago (Hartmann et al., 2008) (Zhang et al., 2014). The phyllosphere microorganisms are influenced by 82 both biotic and abiotic factors, some of which are fairly stable and constant, such as habitat 83 conditions (Yang et al., 2016;Fonsecagarcía et al., 2016), the host genotype (Sapkota et al., 84 2015; Bodenhausen et al., 2014;Hunter et al., 2015), elevation gradient (Cordier et al., 2012; 85 Zh...

Pumpkin powdery mildew disease severity influences the fungal diversity of the phyllosphere. PeerJ 6:e4559 https://doi.org/10.7717/peerj.4559Pumpkin powdery mildew disease severity influences the fungal diversity of the phyllosphere Phyllosphere microbiota play a crucial role in plant-environment interactions and are influenced by biotic and abiotic factors. However, there is little research on how pathogen s affect the microbial community. In this study, we collected 16 pumpkin (Cucurbita moschata) leaf samples showing symptoms of powdery mildew disease with different disease severity levels ranging from L1 (least severe) to L4 (most severe). We examined the fungal community structure and diversity by Illumina MiSeq sequencing of the internal transcribed spacer (ITS) region of ribosomal RNA genes. The fungal communities were dominated by members of the Basidiomycota and Ascomycota. The dominant genus was Podosphaera on the diseased leaves, which was the key pathogen responsible for the pumpkin powdery mildew. Ascomycota and Podosphaera increased in abundance as disease severity increased from L1 to L4, and were significantly more abundant than other microorganisms at disease severity L4 (P<0.05). The richness and diversity of the fungal community increased from L1 to L2, and then declined from L2 to L4, likely due to the biotic pressure at disease severity L4. Maintaining species richness in the phyllosphere will be an important part of managing disease control in this agroecological system and an essential step toward predictable biocontrol of powdery mildew in pumpkin. (Lebeda et al., 2010). 61The phyllosphere or leaf surface is an important microbial habitat for members of the major 62 bacterial and fungal groups, and Archaea (Lindow & Leveau, 2002; Lindow and Brandl, 2003).63 These microorganisms play a crucial role in helping their host against pathogens (Lacava et al., 64 2006; Mejía et al., 2008; Rajendran et al., 2008). In past years, most of the researchers focused 65 on screening plant growth-promoting microorganisms from plants which can help us manage 66 diseases (Compant et al., 2005;Everett et al., 2005;Hirano & Upper, 2000; Whipps et al., 67 2008). However, not all the microbes in the natural environment are considered culturable. In the 68 past few years, the development of next-generation rRNA sequencing techniques has enabled us 69 to obtain in-depth descriptions of the composition of the microbial communities associated with 70 leaves of Arabidopsis thaliana (Reisberg et al., 2013), potatoes (Becker et al., 2008), rice 71 (Mwajita et al., 2012), spinach (Lopez et al., 2011 Lopez et al., 2013), grape (Leveau et al., 72 2011, and various tree species including salt cedar (Redford et al., 2010;Finkel et al., 2011). 73Historically, scholars have begun to study the rhizosphere as a microbial habitat as early as 74 100 years ago (Hartmann et al., 2008) (Zhang et al., 2014). The phyllosphere microorganisms are influenced by 82 both biotic and abiotic factors, some of which are fairly stable a...

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