Analytical purity of old New Zealand forage seed samples and detection of fungal and insect contaminants including ryegrass endophyte and Argentine stem weevil

Stewart, Alan V.; Goldson, S. L.; Marris, John W. M.; Rubenstein, Jesse M.; Rolston, M. P.

doi:10.1080/00288233.2022.2066140

Cited by 8 publications

(4 citation statements)

References 23 publications

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“…Unbeknown at the time, a key part of the success of locally adapted cultivars was most likely due to the insect‐protective properties of high levels of the asexual, obligate, mutualistic, seed‐transmitted Epichloë fungal endophyte infecting the perennial ryegrass ( L. perenne ) ecotypes (Caradus et al, 2023; Stewart, 2006; Stewart, Goldson, et al, 2022). A similar paradigm is likely with regard to the development of superior locally adapted endophyte‐infected perennial ryegrasses in Australia and tall fescues ( Festuca arundinacea Schreb.…”

Section: Introductionmentioning

confidence: 99%

Stability and purity of selected ryegrass Epichloë endophytes in New Zealand dairy pastures

Hume,

Luo,

Rennie

et al. 2024

Grassland Research

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BackgroundPerennial ryegrass (Lolium perenne) in New Zealand pastures is typically infected with the mutualist Epichloë fungal endophyte. This endophyte assists the plant in resisting biotic and abiotic stresses, but the standard strain of endophyte is toxic to livestock. Elite ryegrasses with selected endophytes have been developed to provide protective properties to the grass plant and lessen or eliminate the negative impacts on livestock.MethodsUsing immunology and molecular techniques, the presence of endophyte infection and endophyte strain in ryegrass tillers was determined for 24 dairy pastures sampled for up to 7 years in regions of the North and South Islands.ResultsIn general, infection levels were high and showed small increases over time. Some pastures failed to reach 70% infection. The sown, selected endophytes were the dominant endophyte strains present and these were stable over time. Standard endophyte was the primary nonsown endophyte, and while generally low and so of little importance, it increased over time and for some pastures, this would have been detrimental to livestock. Pasture establishment technique influenced the level of contamination.ConclusionsResults reinforce the importance of following best practice procedures in the seed industry and on‐farm. Researchers should monitor trials for contaminating nonsown standard endophyte.

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Section: Introductionmentioning

confidence: 99%

Stability and purity of selected ryegrass Epichloë endophytes in New Zealand dairy pastures

Hume,

Luo,

Rennie

et al. 2024

Grassland Research

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“…Mitigating the impacts of weeds, pests, diseases or other invasive species in seed‐for‐sowing systems is a shared goal of farmers, seed producers and national/international plant protection organizations. Phytosanitary, quality and seed purity standards are used to mitigate these impacts and have a long history in the agricultural sector 4–6 . Farmers want to avoid any crop‐weed competition and seed contamination such that the impacts are negligible, while government regulators want to avoid the introduction of biosecurity risk organisms while supporting free and fair enterprise 7–9 .…”

Section: Introductionmentioning

confidence: 99%

“…Phytosanitary, quality and seed purity standards are used to mitigate these impacts and have a long history in the agricultural sector. 4 , 5 , 6 Farmers want to avoid any crop‐weed competition and seed contamination such that the impacts are negligible, while government regulators want to avoid the introduction of biosecurity risk organisms while supporting free and fair enterprise. 7 , 8 , 9 At the field‐level, management of pests, weeds and diseases can be mitigated by seed treatments or seed cleaning.…”

Section: Introductionmentioning

confidence: 99%

Factors impacting the detection of weed seed contaminants in seed lots

Buddenhagen

Hackell

Henderson

et al. 2022

Pest Management Science

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BACKGROUND The setting and following of phytosanitary standards for weed seeds can lessen the impacts of weeds on agriculture. Standards adopted by seed companies, laboratories and regulators ensure the contamination rates do not exceed some thresholds. Globally sample size standards are set based on the amount needed to obtain a contaminant in a random sample of the seed lot, not detectability. New Zealand requires a 95% confidence that the maximum pest limit of 0.01% of quarantine weed seed contamination is not exceeded in an imported seed lot. We examined 24 samples each containing approximately 150 000 seeds of either perennial ryegrass (12 samples) or white clover seeds (12 samples) that were then spiked with seeds (contaminants) from 12 non‐crop species (3–8 seeds of each). We considered factors that may impact detection rates: shape, color, size, and texture relative to the crop, and technician (including a commercial seed laboratory). RESULTS A linear mixed model fitted to the data indicated significant observer, crop, and seed color, shape, and size effects on detection. Detectability increased by 20% ± 7.7 (± standard error) when seeds had a distinct shape or color (28% ± 8.1), or were larger (23% ± 8.7) rather than smaller, relative to the crop. Commercial laboratory identifications were usually correct at the level of genus, and species for common weeds, but some misidentifications occurred. CONCLUSION Sample sizes for border inspections should be based on detectability of regulated weed seeds in the crop in combination with weed risk for the crop and location. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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“…Listronotus bonariensis is the most serious pest of Gramineae in New Zealand’s improved pastures, causing NZD $200 million worth of damage per annum ( Ferguson et al, 2019 ). The species was first described in New Zealand in 1927 ( Marshall, 1937 ) but it probably arrived far earlier ( Stewart et al, 2022 ). Its biology has been extensively described (e.g., Barker et al, 1989 ; Goldson et al, 2011 ).…”

Section: Introductionmentioning

confidence: 99%

Plant-Mediated Behavioural Avoidance of a Weevil Towards Its Biological Control Agent

et al. 2022

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New Zealand pastures largely comprising Lolium ryegrass species (Poales: Poaceae) are worth $19.6B and are subject to major pest impacts. A very severe pest is the Argentine stem weevil Listronotus bonariensis (Kuschel) (Coleoptera: Curculionidae). This has been previously suppressed by the importation biological control agent, Microctonus hyperodae Loan (Hymenoptera: Braconidae). However, this suppression has recently declined and is subject to investigation. It has been hypothesised that grass type influences the parasitism avoidance behaviour by the weevil and thus parasitism rates. This study explored the hypothesis using three common pasture grasses: a diploid Lolium perenne x Lolium multiflorum hybrid ryegrass (cv. Manawa), a tetraploid Italian ryegrass L. multiflorum Lam. (cv. Tama), and a diploid perennial ryegrass L. perenne L. (cv. Samson). The described laboratory-based microcosm methodology determined the extent of weevil avoidance behaviour on each of these three grasses when subjected to the parasitoid. Such reaction was gauged by the extent of reduced weevil on-plant presence and feeding compared to the control populations. In the absence of the parasitoid, the hybrid cv. Manawa ryegrass is as highly favoured by the weevil as the tetraploid cv. Tama. On diploid cv. Samson, feeding is considerably less. In the presence of the parasitoid, weevils on the tetraploid cv. Tama plants showed little avoidance activity in response to the parasitoid and it can be argued that the benefits of staying on this plant outweighed the possibility of parasitism. Conversely and surprisingly, in the parasitoid’s presence, weevils on diploid cv. Manawa showed very strong avoidance behaviour leading to levels of exposure similar to those found on the less-preferred diploid cv. Samson. These findings reflect how weevil parasitism rates have declined in most Lolium grasses, particularly diploids, since the 1990s, but not in the tetraploid L. multiflorum. This contribution supports the hypothesis that the decline in weevil parasitism rates has been the result of rapid evolution arising from parasitoid-induced selection pressure and the countervailing effect of the nutritional quality of the host plants.

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Analytical purity of old New Zealand forage seed samples and detection of fungal and insect contaminants including ryegrass endophyte and Argentine stem weevil

Cited by 8 publications

References 23 publications

Stability and purity of selected ryegrass Epichloë endophytes in New Zealand dairy pastures

Stability and purity of selected ryegrass Epichloë endophytes in New Zealand dairy pastures

Factors impacting the detection of weed seed contaminants in seed lots

Plant-Mediated Behavioural Avoidance of a Weevil Towards Its Biological Control Agent

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