Manipulation of canopy architecture and possible vigour control mechanisms in kiwifruit : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Physiology at Massey University, Manawatū, New Zealand

Full publications removed from thesis for copyright reasons: Abdullah, F., & Woolley, D.J. (2013). Effects of bark inversion on fruit weight, size and dry matter concentration of green kiwifruit (Actinidia deliciosa cv. 'Hayward'). Acta Horticulturae, 1012, 213-218. The original publication is available at https://doi-org/10.17660/ActaHortic.2013.1012.23 Abdullah, F., Woolley, D.J., van Hooijdonk, B.M., & Friend, A.P. (2015). Interspecific hybrid kiwifruit rootstocks have potential to modify scion architecture and vigour of young ‘Hayward‘ vines. Acta Horticulturae, 1096, 241-246. The original publication is available at https://doi-org/10.17660/ActaHortic.2015.1096.26Dwarfing or vigour-controlling rootstocks have been used in many fruit trees to reduce scions growth, improve precocity and yield efficiency, but they are not currently available for kiwifruit. Therefore, there is a strong need to evaluate the vigour-controlling rootstocks and/or other growth manipulation techniques for controlling excessive growth of kiwifruit. In this study, the initial growth and architecture of ‘Hayward‘ scions may have been modified by the inter-specific hybrid kiwifruit rootstocks, during the first- and second- year of growth following grafting. Rootstocks modified the trunk cross-sectional area and proleptic bud break of the ‘Hayward‘ primary shoots. The lengths of long and short proleptic shoots of the scions from particular rootstocks were also slightly reduced, thus reducing the total length of proleptic shoots on grafted scions. In the field, inter-specific hybrid kiwifruit rootstocks affected the duration and compactness of scions bud break. The most notable effect of hybrid rootstocks was on the growth rate of long proleptic axillary shoots of scions during early spring growth with ‘Hayward‘ scions on particular rootstocks had the slowest growth rate compared to other rootstocks. Rootstocks may affect scions floral precocity, with ‘Hayward‘ scions on particular kiwifruit rootstocks tended to produce higher flower numbers when they were first planted on the field. There was a strong trend that rootstocks affected the proportion of long shoots and this effect had contributed to the differences in the proportion of non-terminated and terminated shoots of the scions. Auxin transport inhibitor, 1-N-naphthylphthalamic acid (NPA) applied to the stem junction at graft-union on some rootstocks had decreased the length, node number and cross-sectional area of scion primary shoots. However, NPA treatment on particular rootstocks did not affect the growth of scion primary shoots on some of the rootstocks, suggesting that restriction of IAA did not influence the level of IAA transported from shoot to root system of those kiwifruit rootstocks. NPA reduced the leaf size of scions, indicating that sufficient IAA is needed for the leaf growth of kiwifruit, but it may be regulated by the rootstocks. The transport and uptake of radioactivity of IAA in the stem segment varied between the rootstocks, suggesting that the level of IAA in the stem tissues of inter-specific hybrid kiwifruit rootstocks may vary depending on the vigour and genetics of the kiwifruit rootstocks. Restriction of IAA by inverting a single piece of bark (180-degree orientation) and grafted back to the main stem did not completely reduce the vigour of young ‘Hort16A‘ vines. However, the growth and vigour of young ‘Hort16A‘ vines in terms of total length, total node number and total leaf area were greatly reduced when grafted three rings of bark from other cultivars in an inverted orientation. In the field, the bark grafting treatments along with girdling were evaluated to regulate the characteristics of ‘Hayward‘ fruits. All treatments did not consistently produce similar effects in each season and year. Comparison between treatment, season (i.e. early and late summer) and year indicated that the treatment effects on fruit fresh weight, dry weight and dry matter concentration were only evident in the first harvesting year, and the effects were lessened in the following year. In this study, four distinct phenotypes were found from the kiwifruit seedlings population based on their main primary shoots; i) Long Multiple Stems (LMS), ii) Short Multiple Stems (SMS), iii) Long Single Stem (LS), and iv) Short Single Stem (SS). Gibberellins (GA3+GA4+7) treatment on these phenotypes at an early stage of bud break has transformed the morphology and characteristics of proleptic axillary shoots. The mean total number of proleptic and sylleptic axillary shoots (i.e. branching) was increased with gibberellins treatment, suggesting that gibberellins can promote meristematic activity by regulating both apical and sub-apical meristem of kiwifruit shoots

Evaluation of the resistance of few citrus rootstocks to alkalinity by applying a faste test of secreening

Alkalinity of Moroccan soils is the major abiotic constraint on citrus production area. The best choice of citrus rootstocks adequate and resistant is a better solution to avoid this problem. The aim of this study is to develop a fast test of citrus rootstocks screening towards alkalinity. The alkaline stress was applied on ten citrus rootstocks two month old, using irrigation with a Hoagland and Arnon solution added with 1 g CaCO(3)/L and adjusted at various pH levels 6, 7 and 9. Observations concerned symptoms incidence and severity of iron chlorosis after two months of rearing. Results permitted to classify Poncirus trifoliata and Flying dragon as the most sensitive to alkalinity stresses, whereas, Citrus volkameriana and Citrus macrophylla were resistant. These conclusions are equivalent with those obtained with old citrus rootstocks in field trials

Suitable rootstocks for organically grown tomato and cucumber in relation to Meloidogyne SPP.

In organic greenhouse vegetable production, significant yield loss occurs due to root-knot nematodes (Meloidogyne spp.). Soil steaming is effective; however, it is not preferred, since beneficial soil micro organisms are eliminated. An inclusion of resistant hosts within the crop rotation is complicated by the broad host range of the nematode and the high level of specialization of companies towards production of fruit vegetables. Nearly all species of fruit vegetables are susceptible to a varying degree and complete resistance is absent. Even when rootstocks show partial resistance, this is broken down at high temperatures and with an increase in nematode densities. In addition, a lack of compatibility between the rootstock and graft is reported. The objective of the research was to find a rootstock with a high resistance against the most important Meloidogyne species in greenhouses in the Netherlands, M. incognita and M. hapla. Secondly, rootstocks should combine resistance with high yield and quality. In five experiments, 16 to 28 rootstocks per vegetable crop were tested for susceptibility, based on the number and size of root-knots and degree of nematode reproduction. In tomato (Solanum lycopersicum L.), one of the best performing rootstocks was ‘PG76’; in cucumber (Cucumis sativus L.) ‘RZ64-10’ and ‘Harry’ performed well. In general, tomato rootstocks have a higher level of resistance against M. incognita compared with M. hapla. However, cucumber rootstocks seem to be more susceptible to M. incognita than to M. hapla

RNA-Mediated Gene Silencing Signals Are Not Graft Transmissible from the Rootstock to the Scion in Greenhouse-Grown Apple Plants Malus sp.

RNA silencing describes the sequence specific degradation of RNA targets. Silencing is a non-cell autonomous event that is graft transmissible in different plant species. The present study is the first report on systemic acquired dsRNA-mediated gene silencing of transgenic and endogenous gene sequences in a woody plant like apple. Transgenic apple plants overexpressing a hairpin gene construct of the gusA reporter gene were produced. These plants were used as rootstocks and grafted with scions of the gusA overexpressing transgenic apple clone T355. After grafting, we observed a reduction of the gusA gene expression in T355 scions in vitro, but not in T355 scions grown in the greenhouse. Similar results were obtained after silencing of the endogenous Mdans gene in apple that is responsible for anthocyanin biosynthesis. Subsequently, we performed grafting experiments with Mdans silenced rootstocks and red leaf scions of TNR31-35 in order to evaluate graft transmitted silencing of the endogenous Mdans. The results obtained suggested a graft transmission of silencing signals in in vitro shoots. In contrast, no graft transmission of dsRNA-mediated gene silencing signals was detectable in greenhouse-grown plants and in plants grown in an insect protection tent

Krymsk®1 (VVA-1), A dwarfing rootstock suitable for high density plum orchards in the Netherlands

Krymsk®:1 (Prunus tomentosa × Prunus cerasifera) was selected by Gennady Eremin at the Krymsk Breeding Station in Russia in 1966. Since 1994, it has been tested as a rootstock for several plum cultivars in The Netherlands. Graft compatibility was good for scion cultivars ‘Avalon’, ‘Excalibur’, ‘Jubileum’, ‘Opal’, and ‘Victoria’. Growth and production efficiency of plum on Krymsk®:1 was compared with that of plum on St. Julien A and, depending on the cultivar, also with Ferlenain, Otesani 8 and Pixy. With all cultivars, trees on rootstock Krymsk®:1 were by far the least vigorous, most precocious, and most production efficient. The production efficiency of ‘Avalon’ and ‘Excalibur’ on Krymsk®:1 grown for 10 years was 0.41 and 0.26 kg/cm² trunk cross sectional area, respectively, 3.4 and 4.3 times higher on Krymsk®:1 than on St. Julien A. With ‘Opal’ the production efficiency calculated over the first 5 years after planting was 2 to 3 times higher than on St. Julien A, but this difference became non significant after 7 years of cultivation. This was due to the much higher increase in production per tree during the 5th and 6th leaf of the trees on St. Julien A than on Krymsk®:1. Fruit size of ‘Opal’, ‘Avalon’ and ‘Excalibur’ was similar for trees grown on Krymsk®:1 and St. Julien A. With ‘Victoria’ fruit size was significantly larger (5 g) with Krymsk®:1 than with St. Julien A. Krymsk®:1 also increased the percentage of first pick by 15%, the sugar content by 9%, enhanced the development of fruit overcolour and reduced the percentage of fruits with gummosis in ‘Victoria’ plums. Dutch fruit growers show great interest in Krymsk®:1 as a rootstock for plum, as this rootstock makes high density plum orchards feasible. Growers switching to trees on Krymsk®1 have to take more care of their trees, especially in the first years after planting. Pruning, irrigation, and fertilization of the trees need much more attention in order to keep the trees vigorous and ensure good production levels. From 2002 to spring 2008, 120,000 plum trees on Krymsk®1 have been planted in The Netherlands and planting densities have increased from 830 up to 2,285 trees/ha. The main cultivar planted is ‘Victoria’

Decomposition tables for experiments. II. Two--one randomizations

We investigate structure for pairs of randomizations that do not follow each other in a chain. These are unrandomized-inclusive, independent, coincident or double randomizations. This involves taking several structures that satisfy particular relations and combining them to form the appropriate orthogonal decomposition of the data space for the experiment. We show how to establish the decomposition table giving the sources of variation, their relationships and their degrees of freedom, so that competing designs can be evaluated. This leads to recommendations for when the different types of multiple randomization should be used.Comment: Published in at http://dx.doi.org/10.1214/09-AOS785 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org