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Control of fruit tree vigor induced by dwarfing rootstocks
No full textGrafting of fruit trees has been practiced for more than two millennia, and dwarfing rootstocks have been used to control scion vigor for several centuries. The fact that most commercial temperate fruit trees are compound plants composed of two separate genotypes (the scion selected for fruit and shoot characteristics, and the rootstock selected for root characteristics) makes them interesting objects for studying root–shoot interactions in plants. The size-controlling effect of certain rootstocks in various fruit tree species is perhaps the most intriguing and commercially important example of how genetics of one part (the root) of compound plants can influence the behavior of the other part (the shoot). While there is no debate about the potential of rootstocks to affect the growth and productivity of the scion in compound fruit trees, there is no consensus on the physiological and/or anatomical mechanisms involved in the dwarfing phenomenon. Indeed, different hypotheses focusing on various aspects of plant function have been proposed to explain the dwarfing mechanism. This review discusses the concepts and the experimental support for six of the primary theories proposed to explain the dwarfing mechanism induced by rootstocks in fruit trees. These theories are based on the idea that dwarfing is caused by semi-incompatibility between the rootstock and scion or anatomical, morphological, or physiological characteristics of the rootstock or graft union that affect tree water relations, tree nutrition, scion–rootstock hormonal and metabolic signaling, carbohydrate storage and mobilization, and/or the relative abilities of the scion and rootstock components of the tree to compete for resources. Each of the proposed theories has received some experimentally based support in selected crops. Scion–rootstock semi-incompatibility is a general mechanism that may be involved in many scion–rootstock combinations and could cause responses that appear to involve the factors common to the other theories. None of the theories have been documented to be involved in all rootstock–scion combinations or to be solely responsible for the dwarfing response of scions associated with specific rootstocks. However, there is good evidence that changes in water relations are related to the dwarfing response in several species. In retrospect, it is perhaps unrealistic to think that any single one of these or other mechanisms could be solely responsible for orchestrating all of the complex interactions involved in rootstock-induced vigor reduction of the scion
Yield in almond is related more to the abundance of flowers than the relative number of flowers that set fruit
Get PDFAlmond tree yield is a function of the number of flowers on a tree and the percentage of flowers that set fruit. Almonds are borne on spurs (short proleptic shoots that can have both leaves and flowers). Almond tree spur dynamics research has documented that previous year spur leaf area is a predictive parameter for year-to-year spur survival, spur flowering and to a lesser extent spur fruiting, while previous year fruit bearing has a negative impact on subsequent year flowering. However, a question remained about whether yields are more dependent on flower numbers or relative fruit set of the flowers that are present. The aim of the present work was to compare the importance of flower abundance with that of relative fruit set in determining the productivity of a population of tagged spurs in almond trees over a 6-year period. Overall tree yield among years was more sensitive to total number of flowers on a tree rather than relative fruit set. These results emphasize the importance of maintaining large populations of healthy flowering spurs for sustained high production in almond orchards
Late-season nitrogen applications in high-latitude strawberry nurseries improve transplant production pattern in warm regions
Get PDFThe influence of late-season nitrogen (N) applications on the fruiting pattern of strawberry runner plants of ‘Camarosa’ was determined over three growing seasons. Experiments were carried out in high-latitude nurseries in northern California and fruit production trials were established in southern California. A total of 80 kg/ha of foliar nitrogen was delivered in three applications to the nursery in late summer. Late-season foliar nitrogen applications: (1) increased early yields (+22% on average) as well as the number of early marketable fruit, (2) did not affect total season yields, fruit size, appearance and firmness and (3) resulted in greater N concentration in leaves, crowns and roots. Runner plants with leaf N concentration within the sufficiency range (1.9 - 2.8% of dry mass) produced the highest early yields. Total nonstructural carbohydrate concentrations decreased in most of the N-treated plants. Apparently, nursery late-season foliar nitrogen applications enhance N mobilization to crown and root, stimulate plant activity during the period of flower differentiation after planting, accelerating flower development and contributing to the advancement of fruit production.EEA FamailláFil: Kirschbaum, Daniel Santiago. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Famaillá; ArgentinaFil: Larson, Kirk D. University of California Davis. Department of Plant Sciences; Estados UnidosFil: Weinbaum, Steven A. University of California Davis. Department of Plant Sciences; Estados UnidosFil: DeJong, Theodore M. University of California Davis. Department of Plant Sciences; Estados Unido
Unlocking the black box of plant biostimulants
No full textOver the recent years, plant biostimulants have shifted from the margins of agricultural innovation to the forefront of global discussions towards sustainable crop production models. Despite their growing popularity and commercial relevance, key questions persist regarding their actual effects on plants, the validation of their claimed benefits, and the identification of reliable metrics to assess their impact. This editorial aspires to navigate through the definitions, scientific evidence, and regulatory frameworks shaping the current and future landscape of biostimulants. Building on this foundation, the present article reflects on the broader scientific discussion initiated during the ISHS HortForum on plant biostimulants, aiming to distil key conceptual and methodological challenges in the field. An integrated perspective on how biostimulants can be more effectively studied, functionally categorized, and applied in modern agriculture from a range of perspectives is discussed. This analysis provides a critical synthesis of current scientific thinking. It highlights key research priorities, particularly concerning mechanisms of action, quantifiable effects, and the role of biostimulants in promoting resilient, sustainable cropping systems
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A Smaller Tree Doesn’t Necessarily Mean Reduced Yields: Analysis of Pedestrian Peach Orchard Systems and the Relationships Between Fruit Size, Crop Load, and Light Interception.
Get PDFAnnual production costs for peaches (Prunus persica) grown in California are heavily dependent on the costs of labor for pruning, fruit thinning, and harvest, which is done from ladders because of large tree size (DeJong et al., 1999). To reduce production costs, dwarfing rootstocks have been developed which allow for the establishment of commercially viable orchards that eliminate need for ladders in orchard management. New dwarfing rootstocks for peach must reduce vigor, be graft compatible, and give good fruit production without reduction of fruit size and quality (Reighard, 2002). In April 2015, an orchard system trial was established at the University of California Kearney Agricultural Center, Parlier, CA. The research block consisted of two peach [Prunus persica (L.) Batsch] scion cultivars June Flame (early bearing cultivar) and August Flame (late bearing cultivar) grafted onto three different rootstock genotypes: HBOK 27(Controller 6, moderately dwarfing), P-30-135 (Controller 9, slightly dwarfing), and Nemaguard (CA commercial standard, vigorous). Controller 6 was used in two of four planting/pruning systems, each planting/pruning system had three replications per cultivar. Controller 6 systems were referred to as C-6 V and C-6 Quad. C-6 V was a high-density planting with an in-row spacing of 1.2m (1800 trees/hectare) and trained to the KAC-V perpendicular V system (DeJong et al., 1994). The C-6 Quad system was pruned to a Quad V with a larger in-row spacing of 2.4 m (895 trees/hectare). The Controller 9 Quad system (C-9 Quad) was identical to the C-6 Quad system with the only difference being their rootstock. Between-row spacing was 4.6m in all systems with size-controlling rootstocks. Nemaguard (Nema Quad) was used as the commercial standard rootstock with a planting density of 2.4m in-row spacing and 5.5m between-row spacing (750 trees/hectare). Systems with size-controlling rootstocks were topped to a height of 2.5m while the Nema Quad systems were topped at 3.5m. Harvest data were collected in the growing seasons 2017-2019. At harvest, fruit count per tree and total weight of fruit was recorded for each data tree. Results were analyzed to identify any significant differences in individual mean fruit weight, fruit produced per hectare, and the relationship between the two. Apart from the C-9 Quad system, yields per hectare and mean fruit size among systems were generally similar with both cultivars, during all three years. Since there were few performance differences among systems, and no consistent differences that occurred two or more years in a row, it appears that orchard systems with size-controlling rootstocks can produce yields on par with the current commercial standard systems. Further trials are necessary to determine long-term viability of these rootstocks and their production capabilities
Accumulation Pattern Of Total Nonstructural Carbohydrate In Strawberry Runner Plants And Its Influence On Plant Growth And Fruit Production
Get PDFThe pattern of total nonstructural carbohydrate (TNC) accumulation in strawberry (Fragaria ananassa Duch.) nursery runner plants, cv. ‘Camarosa’, was determined for three growing seasons. Plant growth and fruit production patterns were also evaluated. The experiments were carried out on plants propagated in high latitude (41°50' N) and high elevation (1292 m) nurseries in Siskiyou County, California. Plants were sampled beginning in late summer through early autumn and analyzed for dry mass (DM) and TNC. Plants from different digging dates were established in growth chambers (GC) at UC Davis or fruit evaluation plots in Irvine, California. In the nursery, TNC concentration in storage tissues increased steadily from the second week of September to the third week of October, and crown and root TNC concentration was positively correlated with the accumulation of chilling units (hours ≤7.2°C). The root TNC concentration consistently increased from 6 to 10% DM from mid-September to the first week of October. Transplant growth and fruiting pattern were affected by digging date. Overall, the roots were more sensitive to chilling in terms of TNC accumulation, than the crowns. Therefore, roots would be the appropriate organ for assessing TNC status and potential digging dates of strawberry nursery runner plants early in the fall.EEA FamailláFil: Kirschbaum, Daniel Santiago. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Famaillá; ArgentinaFil: Larson, Kirk D. University of California Davis. Department of Plant Sciences; Estados UnidosFil: Weinbaum, Steven A. University of California Davis. Department of Plant Sciences; Estados UnidosFil: DeJong, Theodore M. University of California Davis. Department of Plant Sciences; Estados Unido
Fruit tree crop models: an update
No full textFunctional structural plant models of tree crops are useful tools that were introduced more than two decades ago. They can represent the growth and development of a plant through the in silico simulation of the 3D architecture in connection with physiological processes. In tree crops, physiological processes such as photosynthesis, carbon allocation and growth are usually integrated into these models, although other functions such as water and nutrient uptake are often disregarded. The implementation of the 3D architecture involves different techniques such as L-system frameworks, pipe model concepts and Markovian models to simulate branching processes, bud fates and elongation of stems based on the production of metamers. The simulation of root architecture is still a challenge for researchers due to a limited amount of information and experimental issues in dealing with roots, because root development is not based on the production of metamers. This review aims to focus on functional–structural models of fruit tree crops, highlighting their physiological components. The potential and limits of these tools are reviewed to point out the topics that still need more attention
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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