Cotton leafroll dwarf virus (CLRDV) was first reported in the United States (US) in 2017 from cotton plants in Alabama (AL) and has become widespread in cotton-growing states of the southern US. To investigate the genomic variability among CLRDV isolates in the US, complete genomes of the virus were obtained from infected cotton plants displaying mild to severe symptoms from AL, Florida, and Texas. Eight CLRDV genomes were determined, ranging in size from 5865 to 5867 bp, and shared highest nucleotide identity with other CLRDV isolates in the US, at 95.9–98.7%. Open reading frame (ORF) 0, encoding the P0 silencing suppressor, was the most variable gene, sharing 88.5–99.6% and 81.2–89.3% amino acid similarity with CLRDV isolates reported in cotton growing states in the US and in Argentina and Brazil in South America, respectively. Based on Bayesian analysis, the complete CLRDV genomes from cotton in the US formed a monophyletic group comprising three relatively divergent sister clades, whereas CLRDV genotypes from South America clustered as closely related sister-groups, separate from US isolates, patterns reminiscent of phylogeographical structuring. The CLRDV isolates exhibited a complex pattern of recombination, with most breakpoints evident in ORFs 2 and 3, and ORF5. Despite extensive nucleotide diversity among all available CLRDV genomes, purifying selection (dN/dS < 1) was implicated as the primary selective force acting on viral protein evolution.
The southern root-knot nematode, Meloidogyne incognita, is one of the most important nematode pathogens in Alabama owing to its wide host range and yield loss on major agronomic crops. Management of root-knot nematode is undervalued in corn production owing to relatively low prices for corn at the market, less obvious symptoms, and smaller yield losses compared with cotton and soybeans, plus an overall lack of management options. However, growing successive susceptible crops in root-knot nematode-infested fields only heightens the risk of future yield loss. We evaluated use of starter fertilizers and plant growth regulators with nematicides as an economically viable option to reduce the impact of M. incognita on corn. In 2 years of research, we concluded that the combination of all three inputs provided positive economic returns in only one out of four trials. In 2016, the location with the lower root-knot nematode population density saw significant advantages with these input combinations. In 2017, dramatic advantages in early plant growth were observed with a variety of combinations, but owing to unfavorable growing conditions, yield increases were not observed. We concluded that an early plant growth increase due to applications of starter fertilizers, plant growth regulators, and nematicides often did not correlate to increased yield, although the potential exists.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.