Symptomatic sweet potato cv Arapey INIA samples were collected from a commercial production field in Colonia Molina, Guaymallén department, Mendoza province, Argentina. They showed dark rounded lesions, sometimes coalescing with white granular mycelium. Fungus was obtained from symptomatic sweet potatoes, which represented the generalized infection that affected the crop. They were seeded in PDA with streptomycin sulfate and incubated for seven days at 21°C, alternating white/black (UV400nm) light. Observations with an optical microscope revealed the presence of hyaline, not septated, cylindrical endoconidia with rounded ends. They were 8-16 μm length and 4–6 μm width. Phialides were 43-46 μm length, rounded bases (7-9 μm width) and tapering to the neck´s tip (4-6 μm width). Brown chlamydospores (aleuriospores), 9-13 μm length and 8-12 μm width, in chains of 2-8 spores were observed. For molecular identification, total genomic DNA was extracted. ITS fragment of 565 pb was amplified using ITS5/ITS4 primers and sequenced. The sequence indicated 99% identity with Berkeleyomyces basicola (synonymous: Thielaviopsis basicola). This was deposited in GenBank as (KX580957) (CBS: C430.74, Gen Bank accession number AF275482.1). This is the first report of B. basicola in sweet potato in Argentina, a potential threat to storage root yields.
Highlights:
Sweet potato black root rot, new disease in Argentina.
First report of Berkeleyomyces basicola causing black root rot on sweet potato in Mendoza, Argentina.
Panicum coloratum var. coloratum is a subtropical grass for potentially increasing forage production in lowly productive environments where cattle-raising activities have been relocated. Heritability was estimated for characters related to salinity tolerance under saline and non-saline conditions to explore the possibility of improving tolerance by selection. From a base germplasm collected in a very harsh environment, heritability and gain after selection were calculated using 2 recombination units: individual and phenotypic family mean (PFM). Heritability estimates were very low for all characters both in saline and non-saline conditions, suggesting a complex genetic control of salinity tolerance, with a high proportion of non-additive genetic effects. Estimates were higher using individual selection than with PFM and expected genetic gains were higher for individual selection. When compared in both saline and non-saline conditions, predicted means were greater than for plants of cv. Klein, the most common cultivar in use. It appears that the analyzed germplasm would be a valuable source of genes to be included in breeding programs to increase salinity tolerance in Panicum coloratum.
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