Abstract
Understanding microbial interactions is a key cornerstone of our ability to protect our native flora and crops, but New Zealand native Apiaceae microbial interactions are poorly studied. Moreover, coastal species have exciting possibilities due to their ability to tolerate coastal conditions and saline substrates. Potyvirus Apium virus Y (ApVY) was initially identified in Australian native Apium prostratum but has recently been found in New Zealand endemic Scandia rosifolia. Susceptibility of native New Zealand A. prostratum to ApVY is unknown. Endophytes play a critical role in plant health and development, with recent research exploring community dynamics, ecological strategies, plant growth promoting properties, and the ability of coastal endophytes to confer salinity tolerance to novel plant hosts. This project explored viruses and endophyte interactions in A.prostratum across six coastal Otago sites: Tavora; Karitane; Warrington; Blackhead; Brighton; and Taieri beaches. Apium prostratum foliar samples and seeds were collected at each site (n=10). We tested field samples (n=60) for a range of viruses including ApVY and potyvirus, using a combination of ELISA and RT-PCR. Potyvirus was detected in 18 % (10/57) of A. prostratum at five out of six coastal Otago beaches (Karitane, Warrington, Blackhead, Brighton, and Taieri). Although potyvirus was not detected at Tavora, more extensive sampling is recommended to understand the presence of potyvirus in A. prostratum. Three-month-old glasshouse-raised A. prostratum seedlings were inoculated with several viruses including ApVY, then tested with ELISA to investigate susceptibility. The seedlings were susceptible to ApVY, cucumber mosaic virus, and tomato spotted wilt virus. Ongoing site monitoring is recommended to understand ApVY impacts on A. prostratum populations, understand disease triangle dynamics, continue surveillance for other potential threats, and gain meaningful data on virus incidence rates. To understand endophyte communities, foliar samples were used for isolations. Samples were collected from Karitane (n=10), Blackhead (n=10), Brighton (n=10), and Taieri (n=10) beaches in January and February 2025, and cultures from surface-sterilised leaf samples were grown on potato dextrose agar media (dark, 12 °C) for a minimum of twelve weeks before DNA extraction, PCR amplification, and sequencing. Colony and microscopic morphology alongside DNA sequences, were used to identify endophytes, via GenBank and UNITE databases. Fungal, bacterial, and yeast endophytes were isolated from foliar sections. Taieri had the richest endophyte diversity, with nineteen different endophytes from eight samples, while Karitane only produced four different endophytes from four samples. Stemphylium sp. was the most commonly isolated endophyte and was present at all sites. Stemphylium species are often associated with diseases, particularly Stemphylium blight. Ecological strategies of four endophyte isolates including Stemphylium sp. were explored using pathogenicity testing methods, but strategies were unable to be determined. Ecological strategies are often dynamic and can therefore be difficult to ascertain. Salinity stress amelioration in Phaseolus vulgaris was explored using three bacterial endophyte isolates from A. prostratum. Unfortunately, the results from this experiment were not valid. However, A. prostratum remains a potential source of saline tolerant endophytes with interesting plant growth promotional possibilities and should be further investigated.