Reciprocal Effect of Parental Lines on the Physiological Potential and Seed Composition of Corn Hybrid Seeds

Obtaining corn hybrid seeds (Zea mays L.) with high vigour depends on the parental lines and the direction of the cross, and this relates to seed desiccation tolerance and composition. This research studied reciprocal crosses between pairs of proprietary, elite parent lines (L1 and L5; L2 and L4) producing hybrid seeds with different qualities attempting to correlate vigour with seed composition, focusing on storage proteins, starch and soluble sugar amounts. Four corn hybrid seed lots produced from reciprocal crosses were compared (HS 15 with HS 51, and HS 24 with HS 42) by assessing germination, vigour, and seedling emergence in the field. Seed composition was assessed in mature, dehydrated seeds. Proteins were extracted, quantified, and analysed by electrophoresis and densitometry. Starch amounts were assessed using a kit and soluble sugars were determined using high performance liquid chromatography with pulsed electrochemical detection. The L1 and L2 lineages, used as female parents, provided seeds with lower vigour; however, the quantification of major protein bands, and sucrose, raffinose and stachyose were similar between seed lot pairs. While both total seed protein and starch varied between reciprocal hybrids for one of the two sets of crosses, the amounts of neither correlated with seed vigour. Interestingly, hybrids with low seed vigour (HS 15, HS 24) accumulated greater amounts of fructose relative to their reciprocal; correlation analysis confirmed these results. We demonstrate different effects on seed vigour dependent on the maternal parent in reciprocal crosses producing hybrid corn seeds. We also show that vigour is negatively correlated with seed reducing sugar contents

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

Economic and agronomic feasibility of organic vegetable seed production in the UK, and subsequent seed quality (OF0166)

This is the final report of Defra project OF0166. There is a longer summary at the start of the attached main report. For many farmers and growers, a move to organic production presents major challenges. Among these, the issues regarding the use of organic seeds could yet be a stumbling block, as growers and the seed trade have reservations about using and producing them for four major reasons: 1) The availability of a wide range of organic varieties appropriate to all year round crop scheduling, and differing production techniques and markets 2) The impact of derogation on managing the supply and demand for organic seed 3) The technical issues of organic seed production 4) Maintaining high standards of seed quality, hygiene and vigour. Three biennial vegetable crops: parsnips, winter cauliflower, and bulb onions and a small range of annual crops including lettuces, runner beans, spinach, broccoli were grown for seed production. All the crops were grown under a Spanish “Haygrove” tunnel. These relatively cheap structures allow good ventilation whilst offering protection against wet weather. All the crops were grown following organic protocols. Seed yields were recorded, and comparisons with disease contamination, germination and vigour were made against seed of the same variety produced conventionally by the collaborating seed company. Yields were unpredictable for some crops in the early stages of the project, but this problem was overcome as techniques were better understood and more experience gained. Seed quality was generally very good for most crops, and few problems were encountered with seed borne diseases for most crops. High levels of seed surface contamination with saprophytic fungi (Penicillium and Cladosporium) may have masked the presence of other fungi. Where equivalent comparisons with conventional seedlots could be tested for disease and vigour differences were small. However, major problems were encountered with bulb onion seed production as neck rot resulted in loss of stock material (around 50% of bulbs were lost). Hot water treatments were used in this project and were found to be successful against a range of pathogens on infected onion seed. More research into organic seed treating is advocated. The project has shown that on a small scale at least, good quality organic seed can be produced under relatively inexpensive polythene tunnels. The yields attained can be as good as those from conventional production, but there are without doubt greater risks involved. It is suggested that should diseases or pests become rampant then their control will be difficult. This project has shown that crops like onions are extremely difficult to produce, and that neck rot in particular will be a problem for the seed producer and grower. The use of tunnels is strongly supported; they can keep crops dry at harvest, they do not necessarily encourage disease build up and natural predator populations can be built up in and around them. It can be summed up that 1) Organic seed production was found to feasible, but higher risk than conventional production 2) Seed quality differences were small 3) Costs in terms of management input were high 4) Neck rot ( Botrytis allii) on bulb onions was, and is likely to remain, a persistent problem 5) Hot water treatment was found to be satisfactory for the small volumes of seed treated. Urgent attention is needed to identify other more consistent methods than this which will satisfy Organic protocols

Longevity and mortality of owned dogs in England

Improved understanding of longevity represents a significant welfare opportunity for the domestic dog, given its unparalleled morphological diversity. Epidemiological research using electronic patient records (EPRs) collected from primary veterinary practices overcomes many inherent limitations of referral clinic, owner questionnaire and pet insurance data. Clinical health data from 102,609 owned dogs attending first opinion veterinary practices (n = 86) in central and southeast England were analysed, focusing on 5095 confirmed deaths. Of deceased dogs with information available, 3961 (77.9%) were purebred, 2386 (47.0%) were female, 2528 (49.8%) were neutered and 1105 (21.7%) were insured. The overall median longevity was 12.0 years (IQR 8.9–14.2). The longest-lived breeds were the Miniature poodle, Bearded collie, Border collie and Miniature dachshund, while the shortest-lived were the Dogue de Bordeaux and Great Dane. The most frequently attributed causes of death were neoplastic, musculoskeletal and neurological disorders. The results of multivariable modelling indicated that longevity in crossbred dogs exceeded purebred dogs by 1.2 years (95% confidence interval 0.9–1.4; P < 0.001) and that increasing bodyweight was negatively correlated with longevity. The current findings highlight major breed differences for longevity and support the concept of hybrid vigour in dogs

Molecular and cellular characteristics of hybrid vigour in a commercial hybrid of Chinese cabbage

Abstract Background Heterosis or hybrid vigour is a phenomenon in which hybrid progeny exhibit superior performance compared to their parental inbred lines. Most commercial Chinese cabbage cultivars are F1 hybrids and their level of hybrid vigour is of critical importance and is a key selection criterion in the breeding system. Results We have characterized the heterotic phenotype of one F1 hybrid cultivar of Chinese cabbage and its parental lines from early- to late-developmental stages of the plants. Hybrid cotyledons are larger than those of the parents at 4 days after sowing and biomass in the hybrid, determined by the fresh weight of leaves, is greater than that of the larger parent line by approximately 20 % at 14 days after sowing. The final yield of the hybrid harvested at 63 days after sowing is 25 % greater than the yield of the better parent. The larger leaves of the hybrid are a consequence of increased cell size and number of the photosynthetic palisade mesophyll cells and other leaf cells. The accumulation of plant hormones in the F1 was within the range of the parental levels at both 2 and 10 days after sowing. Two days after sowing, the expression levels of chloroplast-targeted genes in the cotyledon cells were upregulated in the F1 hybrid relative to their mid parent values. Shutdown of chlorophyll biosynthesis in the cotyledon by norflurazon prevented the increased leaf area in the F1 hybrid. Conclusions In the cotyledons of F1 hybrids, chloroplast-targeted genes were upregulated at 2 days after sowing. The increased activity levels of this group of genes suggested that their differential transcription levels could be important for establishing early heterosis but the increased transcription levels were transient. Inhibition of the photosynthetic process in the cotyledon reduced heterosis in later seedling stages. These observations suggest early developmental events in the germinating seedling of the hybrid may be important for later developmental vigour and yield advantage.This work was supported in part by a grant-in-aid for Scientific Research on Innovative Areas (24113509) (JSPS), by the Sasakawa Scientific Research Grant (24–517) from The Japan Science Society, by Grant for Promotion of Niigata University Research Projects (23C024) and by PREST (12101066) (JST) to R. Fujimoto

A study of some aspects of growth and reproduction in two inbred lines of mice and their crosses : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Massey University of Manawatu

The mating of closely related individuals is generally believed to result in inferior offspring. Recognition of this danger has been suggested as the reason for evolution of human social customs. However, historical researches suggest that inbreeding unavoidably occurred in small, isolated, ancient communities, and marriage of close relatives was encouraged in the Egyptian, Greek and Hebrew civilisations (Zirkle, 1952). Inbreeding is likely to have occurred in the isolated flocks of nomads, but it is probable that inbreeding depression, as such, was not recognised until the eighteenth century when the early livestock improvers are reputed to have found that the fertility of their animals deteriorated with continued inbreeding. Hybrid vigour from cross breeding plants was described by Koelreuter (1766) and confirmed by later botanists., .After much detailed work, Darwin (1876) concluded: " •••cross fertilisation is generally beneficial and self fertilisation injurious." and that (a) Mechanisms exist widely for the avoidance of inbreeding. (b) Inbreeding has effects likely to incur selective disadvantages. No suitable hypothesis could account for the usually deleterious effects of inbreeding, or the reverse phenomenon of hybrid vigour until the rediscovery of Mendel's work in 1900. The effects of inbreeding can now be explained in terms of the dominance and recessiveness of genes. (Falconer, 1960). The aim of experiments reported in this thesis was to study growth, reproduction and mortality in two inbred lines of mice, derived from common ancestors, to find if differences between them had arisen during inbreeding. Reciprocal crosses and matings of the F1 progeny of these crosses were made to find if hybridisation of the parent lines led to improvements of these charact­eristics. This study was suggested by Drs. D.S.. Flux, M.F. McDonald and R.E. Munford to whom the author is indebted for advice and guidance. The author also wishes to acknowledge the assistance of Mr. E. Ormsby in histological preparations, of Mr. P .S. Dale in photomicrography, and of Mr. C. Muir who drew some of the figures reproduced in this thesis. Thanks are also due to the staff of the University Library for their efforts in obtaining literature. [From Preface

Evaluation of the risks of contaminating low erucic acid rapeseed with high erucic rapeseed and identification of mitigation strategies

High erucic acid rapeseed (HEAR) oil is under increasing demand for various industrial applications. However, many growers are concerned that if they grow the crop, they will not be able to revert to other rapeseed varieties in the future due to the risk of erucic acid (EA) contamination of the harvested seed and inability to maintain acceptable erucic acid thresholds. This review considered published literature and, using the same criteria as that used to contain transgenic crops, aimed to identify the key risks of erucic acid contamination, broadly prioritise them and identify pragmatic mitigation options. Oilseed rape has a number of traits that increase the risk of low erucic acid rapeseed (LEAR) crops being contaminated with EA from HEAR varieties. The quantity of seed produced and the potential for seed dormancy coupled with partial autogamy (self-fertilisation) facilitate the establishment and persistence of volunteer and feral populations. The large quantities of pollen produced when the crop is in flower mean there is also a high potential for cross-pollination. Self-sown volunteer plants represent the highest potential contamination risk, followed by the presence of arable weeds (e.g., wild mustard) whose seeds are also high in EA. Other risks arise from the cross-pollination of compatible wild relatives and the mixing of seed prior to sowing. It is important that both HEAR and LEAR varieties are appropriately managed since risks and their potential for mitigation arise throughout the entire LEAR crop production process. The length of rotation, type of tillage, cultivar choice, buffer zones, effective weed management and basic machinery hygiene are all factors that can reduce the risk of erucic acid contamination of LEAR crops and maintain the required thresholds.Peer reviewedFinal Published versio

Effect of elevated CO2 and high temperature on seed-set and grain quality of rice

Hybrid vigour may help overcome the negative effects of climate change in rice. A popular rice hybrid (IR75217H), a heat-tolerant check (N22), and a mega-variety (IR64) were tested for tolerance of seed-set and grain quality to high-temperature stress at anthesis at ambient and elevated [CO2]. Under an ambient air temperature of 29 °C (tissue temperature 28.3 °C), elevated [CO2] increased vegetative and reproductive growth, including seed yield in all three genotypes. Seed-set was reduced by high temperature in all three genotypes, with the hybrid and IR64 equally affected and twice as sensitive as the tolerant cultivar N22. No interaction occurred between temperature and [CO2] for seed-set. The hybrid had significantly more anthesed spikelets at all temperatures than IR64 and at 29 °C this resulted in a large yield advantage. At 35 °C (tissue temperature 32.9 °C) the hybrid had a higher seed yield than IR64 due to the higher spikelet number, but at 38 °C (tissue temperature 34–35 °C) there was no yield advantage. Grain gel consistency in the hybrid and IR64 was reduced by high temperatures only at elevated [CO2], while the percentage of broken grains increased from 10% at 29 °C to 35% at 38 °C in the hybrid. It is concluded that seed-set of hybrids is susceptible to short episodes of high temperature during anthesis, but that at intermediate tissue temperatures of 32.9 °C higher spikelet number (yield potential) of the hybrid can compensate to some extent. If the heat tolerance from N22 or other tolerant donors could be transferred into hybrids, yield could be maintained under the higher temperatures predicted with climate change