Hopp til hovedinnholdet

Publications

NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.

2020

To document

Abstract

The aim of this study was to evaluate the thinning efficacy of metamitron (Brevis®) as fruitlet thinner compared to ammonium thiosulphate (ATS) and ethephon (Cerone) as flower thinning agents to ‘Rubinstep’ apple. The thinning efficacy of the flower thinning agents was compared to different timings (8-10 and 12-14 mm fruitlet diameters) and dosages (165 and 330 ppm) of the fruitlet thinner metamitron at the experimental farm at Nibio Ullensvang, western Norway (60°19’8.03”N; 6°39’14.31”E) in 2018. Untreated trees and trees manually thinned after June drop were used as reference treatments. Fruit set, yield data and fruit quality parameters for each treatment were recorded. None of the chemical thinning treatments resulted in a significant reduction in the final number of fruits and yield tree-1. Crop load of the untreated trees was almost twice the target crop load of the hand-thinned trees. Ammonium thiosulphate (ATS) was the only chemical thinning treatment that significantly increased fruit weight above the untreated trees, but to a lesser extent than achieved by hand thinning. Qualitative traits of ‘Rubinstep’ apples (ground and over colour, firmness, starch index and soluble solid contents were not correlated with the fruit set. Return bloom of the untreated trees was 50% of the bloom of the previous year. The ammonium thiosulphate-treated trees showed a significant higher percentage return bloom of 122%. Return bloom in all other treatments did not differ significantly from the untreated controls. However, the average values showed a clear trend of a decrease in return bloom in metamitron-treated trees in comparison with the untreated and hand-thinned trees. The exceptionally high levels of solar radiation in May 2018 and the excellent pollination conditions resulting in very high seed numbers fruit-1 are likely the reasons for the lack of thinning efficacy of Brevis®.

To document

Abstract

Plants evolved in close contact with a myriad of microorganisms, some of which formed associations with their roots, benefitting from carbohydrates and other plant resources. In exchange, they evolved to influence important plant functions, e.g. defense against insect herbivores and other antagonists. Here, we test whether a fungus, Metarhizium brunneum, which is mostly known as an insect pathogen, can also associate with plant roots and contribute to above-ground plant defense. Cauliflower (Brassica oleracea var. botrytis) seeds were sown together with M. brunneum-inoculated rice grains, and the resulting plants subjected to leaf herbivory by the specialist Plutella xylostella. Activity of myrosinases, the enzymes activating glucosinolates, was measured before and after herbivory; larval consumption and plant weight at the end of experiments. Metarhizium brunneum clearly established in the plant roots, and after herbivory myrosinase activity was substantially higher in M. brunneum-treated plants than in controls; before herbivory, M. brunneum-treated and control plants did not differ. Leaf consumption was slightly lower in the M. brunneum-treated plants whereas total biomass and allocation to above- or below-ground parts was not affected by the Metarhizium treatment. Thus, M. brunneum associates with roots and primes the plant for a stronger or faster increase in myrosinase activity upon herbivory. Consistent with this, myrosinase function has been suggested to be rate-limiting for induction of the glucosinolate-myrosinase defense system. Our results show that M. brunneum, in addition to being an insect pathogen, can associate with plant roots and prime plant defense.