Massey Research Online - Browsing by Author "McGill C"

Browsing by Author "McGill C"

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Comparing vegetative growth patterns of cultivated (Daucus carota L. subsp. sativus) and wild carrots (Daucus carota L. subsp. carota) to eliminate genetic contamination from weed to crop
(Elsevier B.V., 2024-05-20) Godwin A; Pieralli S; Sofkova-Bobcheva S; Ward A; McGill C
Wild carrot is a problematic weed that can threaten the genetic purity of cultivated carrots by hybridization. Wild carrots must be controlled before flowering to avoid the undesirable crossing with cultivated carrots. Understanding wild carrot's vegetative growth pattern helps formulate sustainable weed management practices. However, little is known about the vegetative growth patterns of wild and cultivated carrots. A pot experiment was carried out to compare and model the vegetative growth pattern of different morphological traits in both wild and cultivated carrots. This study was executed in a glasshouse located in Palmerston North, New Zealand. A factorial randomized complete block design (RCBD) with two factors and four replications was used. The first factor was assigned to the carrot genotype (cultivated and wild) and the second factor to length of juvenile stages (12-weeks, 8-weeks, and 4-weeks). Plant height, leaf number, shoot fresh and dry weight, root fresh and dry weight, root diameter and root length were measured. Data were analyzed using analysis of variance (ANOVA), principal component analysis (PCA), correlation, and regression analysis. At the 8-week juvenile stage (9–11 leaves stage), wild carrot's shoot and root characteristics exhibited rapid growth. Correlation analysis indicated positive and significant (p < 0.05) correlations between above and below-ground morphological traits. PCA showed that morphological characteristics, except plant height, can be used to distinguish wild and cultivated carrots. To predict the vegetative growth pattern of most of the morphological traits of wild and cultivated carrots, power regression models were selected based on higher R2 and adj-R2 values and lower values of RMSE, AIC and BIC. The study showed wild carrots grew more quickly than cultivated carrots during the vegetative phase. It is recommended that appropriate weed management practices, such as hoeing, tilling, hand pulling, or herbicide spraying, be implemented before wild carrot leaf stages 9–11.
Methylobacterium, a major component of the culturable bacterial endophyte community of wild Brassica seed
(PeerJ, Inc, 2020-07-10) Roodi D; Millner JP; McGill C; Johnson RD; Jauregui R; Card SD; Souza V
BACKGROUND: Plants are commonly colonized by a wide diversity of microbial species and the relationships created can range from mutualistic through to parasitic. Microorganisms that typically form symptomless associations with internal plant tissues are termed endophytes. Endophytes associate with most plant species found in natural and managed ecosystems. They are extremely important plant partners that provide improved stress tolerance to the host compared with plants that lack this symbiosis. Plant domestication has reduced endophyte diversity and therefore the wild relatives of many crop species remain untapped reservoirs of beneficial microbes. Brassica species display immense diversity and consequently provide the greatest assortment of products used by humans from a single plant genus important for agriculture, horticulture, bioremediation, medicine, soil conditioners, composting crops, and in the production of edible and industrial oils. Many endophytes are horizontally transmitted, but some can colonize the plant's reproductive tissues, and this gives these symbionts an efficient mechanism of propagation via plant seed (termed vertical transmission). METHODS: This study surveyed 83 wild and landrace Brassica accessions composed of 14 different species with a worldwide distribution for seed-originating bacterial endophytes. Seed was stringently disinfected, sown within sterile tissue culture pots within a sterile environment and incubated. After approximately 1-month, direct isolation techniques were used to recover bacterial endophytes from roots and shoots of symptomless plants. Bacteria were identified based on the PCR amplification of partial 16S rDNA gene sequences and annotated using the BLASTn program against the NCBI rRNA database. A diversity index was used as a quantitative measure to reflect how many different bacterial species there were in the seed-originating microbial community of the Brassica accessions sampled. RESULTS: Bacterial endophytes were recovered from the majority of the Brassica accessions screened. 16S rDNA gene sequencing identified 19 different bacterial species belonging to three phyla, namely Actinobacteria, Firmicutes and Proteobacteria with the most frequently isolated species being Methylobacterium fujisawaense, Stenotrophomonas rhizophila and Pseudomonas lactis. Methylobacterium was the dominant genus composing 56% of the culturable isolated bacterial community and was common in 77% of accessions possessing culturable bacterial endophytes. Two selected isolates of Methylobacterium significantly promoted plant growth when inoculated into a cultivar of oilseed rape and inhibited the growth of the pathogen Leptosphaeria maculans in dual culture. This is the first report that investigates the seed-originating endophytic microorganisms of wild Brassica species and highlights the Brassica microbiome as a resource for plant growth promoting bacteria and biological control agents.
Phenological phase affects carrot seed production sensitivity to climate change - A panel data analysis
(Elsevier BV, 2023-09-20) Godwin A; McGill C; Ward A; Sofkova-Bobcheva S; Pieralli S; Paoletti E
New Zealand is a major producer of carrot seeds globally. Carrots are an important nutritional crop for human consumption. Since the growth and development of carrot seed crops mainly depend on climatic factors, seed yield is extremely susceptible to climate change. This modeling study was undertaken using a panel data approach to determine the impact of the atmospheric conditions (proxied by maximum and minimum temperature) and precipitation during the critical growth stages for seed production in carrot, viz., juvenile phase, vernalization phase, floral development phase, and flowering and seed development phase on carrot seed yield. The panel dataset was created using cross-sections from 28 locations within the Canterbury and Hawke's Bay regions of New Zealand that cultivate carrot seed crops and time series from 2005 to 2022. Pre-diagnostic tests were performed to test the model assumptions, and a fixed effect model was selected subsequently. There was significant (p < 0.01) variability in temperature and rainfall throughout different growing phases, except for precipitation at the vernalization phase. The highest rate of changes in maximum temperature, minimum temperature, and precipitation were recorded during the vernalization phase (+0.254 °C per year), floral development phase (+0.18 °C per year), and juvenile phase (-6.508 mm per year), respectively. Based on marginal effect analysis, the highest significant influence of minimum (187.724 kg/ha of seed yield decrease for each 1 °C increment) and maximum temperature (1 °C rise increases seed yield by 132.728 kg/ha), and precipitation (1 mm increment of rainfall decreases the seed yield by 1.745 kg/ha) on carrot seed yield were reported at vernalization, and flowering and seed development, respectively. The minimum and maximum temperatures have a higher marginal effect on carrot seed production. Analysis of the panel data demonstrates that the production of carrot seeds will be vulnerable to climatic change.
Seed desiccation sensitivity varies with geographic distribution in two New Zealand native Pittosporum species
(2023-09-05) Kai Y; Pinto AA; McCormick AC; Nadarajan J; He XZ; MacKay M; McGill C
Seed Morphology of Three Neotropical Orchid Species of the Lycaste Genus
(MDPI (Basel, Switzerland), 2023-09) Alfaro Pinto A; McGill C; Nadarajan J; Archila Morales F; Clavijo McCormick AC; Cortés JAH; Lombraña AC
Neotropical orchids are vulnerable to extinction due to overharvesting, habitat destruction and climate change. However, a basic understanding of orchid seed biology to support conservation efforts is still lacking for most species. Seed morphology is linked to plant adaptation and evolution, influencing seed dispersal, dormancy, longevity, and germination, which are valuable traits for conservation. In this study, we characterized and compared the morphological traits of seed capsules (size, shape, and colour) and seeds (seed and embryo shape and size and internal airspace volume) for three epiphytic Neotropical orchid species of the genus Lycaste native to Guatemala: L. cochleata, L. lasioglossa, and L. virginalis. The three species show qualitative similarities in seed capsule colour and appearance and in seed morphology (i.e., scobiform oval-shaped seeds and prolate-spheroid embryos). All species have small-sized seeds (length of L. cochleata: 210 µm, L. lasioglossa: 230 µm, and L. virginalis: 260 µm), with proportionally large embryos (length of L. cochleata: 140 µm, L. lasioglossa: 120 µm, and L. virginalis: 150 µm) and an internal air-space volume that occupies less than half of the seed (L. cochleata: 17%, L. lasioglossa: 42%, and L. virginalis: 30%). This finding is consistent with previous reports for other epiphytic orchid species, which typically have lower air volumes than terrestrial orchids. These differences are likely a result of evolutionary changes associated with different habits and may influence seed dispersal. We also found some significant differences in seed morphology between the studied species, but their taxonomic, biological, and ecological relevance remain to be elucidated. More comparative studies, including on other Lycaste species with different habits, are needed to explore relationships between seed morphology, taxonomy, biology, and ecology in this genus to support its conservation.

Browsing by Author "McGill C"

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