Gall disease in the alginophyte Lessonia berteroana: A pathogenic interaction linked with host adulthood in a seasonal-dependant manner

The Reemergence of Phycopathology: When Algal Biology Meets Ecology and Biosecurity

Viruses, bacteria, and eukaryotic symbionts interact with algae in a variety of ways to cause disease complexes, often shaping marine and freshwater ecosystems. The advent of phyconomy (a.k.a. seaweed agronomy) represents a need for a greater understanding of algal disease interactions, where underestimated cryptic diversity and lack of phycopathological basis are prospective constraints for algal domestication. Here, we highlight the limited yet increasing knowledge of algal pathogen biodiversity and the ecological interaction with their algal hosts. Finally, we discuss how ecology and cultivation experience contribute to and reinforce aquaculture practice, with the potential to reshape biosecurity policies of seaweed cultivation worldwide.

Morphological, genotypic and metabolomic signatures confirm interfamilial hybridization between the ubiquitous kelps Macrocystis (Arthrothamnaceae) and Lessonia (Lessoniaceae)

Macrocystis pyrifera and Lessonia spicata are economically and ecologically relevant brown seaweeds that recently have been classified as members of two separated families within Laminariales (kelps). Here we describe for the first time the Macrocystis pyrifera x Lessonia spicata hybridization in the wild (Chiloe Island, Southeastern Pacific), where populations of the two parents exist sympatrically. Externally, this hybrid exhibited typical features of its parents M. pyrifera (cylindrical and flexible distal stipes, serrate frond margins and presence of sporophylls) and L. spicata (rigid and flat main stipe and first bifurcation), as well as intermediate features between them (thick unfused haptera in the holdfast). Histological sections revealed the prevalence of mucilage ducts within stipes and fronds (absent in Lessonia) and fully developed unilocular sporangia in the sporophylls. Molecular analyses confirmed the presence of the two parental genotypes for ITS1 nrDNA and the M. pyrifera genotype for two predominantly maternally inherited cytoplasmic markers (COI and rbcLS spacer) in the tissue of the hybrid. A metabolome-wide approach revealed that this hybrid is more chemically reminiscent to M. pyrifera. Nevertheless, several hits were identified as Lessonia exclusive or more remarkably, not present in any of the parent. Meiospores developed into apparently fertile gametophytes, which gave rise to F1 sporophytes that reached several millimeters before suddenly dying. In-vitro reciprocal crossing of Mar Brava gametophytes from both species revealed that although it is rare, interfamilial hybridization between the two species is possible but mostly overcome by pseudogamy of female gametophytes.