Interspecific Grafting Research Articles

Progress in grafting watermelon to manage Verticillium wilt

AbstractVegetable grafting for disease management was first used successfully when watermelon grafted onto a Cucurbita moschata rootstock overcame Fusarium wilt. Interspecific grafting has since been used effectively to mitigate several soilborne pathogens in a variety of solanaceous and cucurbitaceous cropping systems. Verticillium wilt caused by Verticillium dahliae is a significant disease in watermelon crops and is difficult to manage. Current management practices, including crop rotation, soil fumigation, and host resistance, are insufficient due to the ability of microsclerotia to persist in absence of a host, lack of efficacy of soil fumigants, and limited availability of resistant cultivars. Watermelon grafted onto commercial cucurbit rootstocks have increased tolerance to Verticillium wilt, although no cucurbit rootstocks are known to be completely resistant. Verticillium wilt incidence decreased on grafted plants grown in artificially and naturally infested soils, while scion health and growth as well as rootstock root mass and vigour increased. Commonly used rootstocks are Lagenaria siceraria, C. moschata, and C. maxima × C. moschata; of these, only C. maxima × C. moschata ‘Tetsukabuto’ reduced severity of Verticillium wilt across several scion cultivars, locations, years, and soil densities of V. dahliae. Although studies on Verticillium wilt resistance of grafted watermelon are few, their combined results suggest the threshold of V. dahliae soil density for watermelon may be around 5–12 cfu/g. This review summarizes available information on Verticillium wilt of watermelon and effects of different rootstock × scion combinations, assisting growers and breeding programmes in decisions to adopt watermelon grafting for management of Verticillium wilt.

Interspecific grafting between Gossypium hirsutum, G. barbadense and G. herbaceum lines

Seedling grafting could provide additional crop improvement strategies for cotton. However, there existed limited studies on interspecific grafting and approaches. Four different grafting approaches were developed and compared between lines representing three of the four cultivated cotton species G. hirsutum, G. barbadense and G. herbaceum. Grafting approaches of this study focused on the cotyledon node and cotyledon leaves retained on scions, rootstocks, without cotyledon node and cotyledon leaves on scions and rootstocks or halved cotyledon node and single cotyledon leaf on scions and rootstocks. Evaluations of the grafting approaches were made by comparing survival and growth rate during the second and fifth weeks after transplantation, respectively. The formation of any lateral shoots at the grafted sites were studied in two of four grafting approaches in the first and the second year during flowering stage. DNA alterations due to grafting were investigated using microsatellite markers. There were no statistically significant differences between grafts and their control in survival rate and locus specific DNA alteration. Growth rate and lateral shoot formation, on the other hand, were different among grafting types and grafts. We concluded that grafting without cotyledon node and cotyledon leaves on rootstocks, and with cotyledon node but without cotyledon leaves on scions were easy to perform and suitable for interspecific cotton grafting. Results suggested that grafting seedlings and allowing time to heal graft wounds prior to spring transplanting or double cropping is suitable for wheat–cotton intercropping to prevent late or early chilling damage associated with seed sowing or conventional transplanting of susceptible seedlings. Furthermore, the rapid and consistent wound healing in seedling grafts along with lateral shoot formation occurring in two of four grafting approaches make them a suitable approach to investigate possible genetic and epigenetic movement between scions and rootstocks, especially across species.

AGROTEKNOLOGI KOPI GRAFTING UNTUK PENINGKATAN PRODUKSI

Lampung Province is the center of Robusta coffee production with an area of 2018 reaching 157.6 thousand hectares while Arabica coffee which has been programmed in 1998 by planting area reached 1.9 thousand hectares did not develop successfully even disappearing. Liberica coffee is commonly grown as a rootstock. This research aims to study the ethno-agronomy of various grafting coffees in Lampung, both Robusta- Liberica and Arabica-Robusta. This research was carried out using Focus Group Discussion (FGD) method with the farmer groups and the observation of coffee plantations in the field belonging to group members in each farmer group selected purposively in each district namely Sekincau Sub-district of West Lampung, Sumberejo Sub-district of Tanggamus, and Way Ratai Sub-district of Pesawaran, in May-October 2019. The results showed that farmers developed a various of intraspecific coffee grafting (Robusta/Robusta) using a variety of superior local clones and interspecific grafting (Robusta/Liberica and Arabica/Robusta) with specific agronomy practices such as cloning, planting, pruning, fertilizing, applying pesticide, soil conserving, and being non-resident farmers as creations, local wisdom and adaptation of farmers to site-specific conditions. Keywords : Clone, ethno-agronomy, fertilizing, interspesific grafting, local wisdom, rainfall

Expression of Gibberellin Metabolism Genes and Signalling Components in Dwarf Phenotype of Breadfruit (Artocarpus altilis) Plants Growing on Marang (Artocarpus odoratissimus) Rootstocks.

Breadfruit (Artocarpus altilis) is a traditional staple tree crop throughout the tropics. The species is an evergreen tree 15–20 m; there are currently no size-controlling rootstocks within the species. Through interspecific grafting, a dwarf phenotype was identified in breadfruit plants growing on Marang (Artocarpus odoratissimus) rootstocks, which displayed ~60% reduction in plant height with ~80% shorter internodes. To gain insight into the molecular mechanism underlying rootstock-induced dwarfing, we investigated the involvement of gibberellin (GA) in reduction of stem elongation. Expression of GA metabolism genes was analysed in the period from 18 to 24 months after grafting. In comparison to self-graft and non-graft, scion stems on marang rootstocks displayed decrease in expression of a GA biosynthetic gene, AaGA20ox3, and increase in expression of a GA catabolic genes, AaGA2ox1, in the tested 6-month period. Increased accumulation of DELLA proteins (GA-signalling repressors) was found in scion stems growing on marang rootstocks, together with an increased expression of a DELLA gene, AaDELLA1. Exogenous GA treatment was able to restore the stem elongation rate and the internode length of scions growing on marang rootstocks. The possibility that GA deficiency forms a component of the mechanism underlying rootstock-induced breadfruit dwarfing is discussed.

Injerto interespecífico como alternativa para la propagación asexual de Pinus rzedowskii Madrigal & Caball. Del. en riesgo de extinción

Introduction:Pinusrzedowskii Madrigal & Caball. Del. is endemic to Mexico, in danger of extinction and low natural reproduction. An alternative for propagation is interspecific grafting, under the assumption that the phylogenetically more related species positively influence survival. Objectives: To evaluate grafting survival of P. rzedowskii with rootstocks of five Pinus species. Materials and methods: Interspecific grafting of P. rzedowskii with P. pinceana Gordon & Glend, P. maximartinezii Rzed., P. ayacahuite var. veitchii (Roezl) Shaw, P. pseudostrobus Lindl. and P. rzedowskii (control treatment) was carried out. The grafting method was side-veneer graft; grafting was quantified for six months and survival was evaluated using the nonparametric Kaplan-Meier method. Results and discussion: The highest final grafting survival and expected survival function were obtained with rootstocks of P. rzedowskii (85.7 ± 0.21 %; m = 0.97), followed by P. pinceana (80 ± 0.31 %; m = 0.95); P. pseudostrobus had the lowest values (20 ± 0.89 %; m = 0.66).Significant differences (P < 0.0001) were observed between P. pseudostrobus and P. maximartinezii regarding P. rzedowskii a P. pinceana. Conclusion:P. pinceana, a species phylogenetically closer to P. rzedowskii and P. maximartinezii, was the one with the highest survival rate, which may be an alternative for the rescue and ex situ conservation of P. rzedowskii.

Rootstock determines the drought resistance of poplar grafting combinations.

To increase yield and/or enhance resistance to diseases, grafting is often applied in agriculture and horticulture. Interspecific grafting could possibly be used in forestry as well to improve drought resistance, but our understanding of how the rootstock of a more drought-resistant species can affect the grafted plant is very limited. Reciprocal grafts of two poplar species, Populus cathayana Rehder (less drought-resistant, C) and Populus deltoides Bart. ex Marsh (more drought-resistant, D) were generated. Four grafting combinations (scion/rootstock: C/C, C/D, D/D and D/C) were subjected to well-watered and drought stress treatments. C/D and D/C had a higher diameter growth rate, leaf biomass, intrinsic water-use efficiency (WUEi) and total non-structural carbohydrate (NSC) content than C/C and D/D in well-watered condition. However, drought caused greater differences between P. deltoides-rooted and P. cathayana-rooted grafting combinations, especially between C/D and D/C. The C/D grafting combination showed higher resistance to drought, as indicated by a higher stem growth rate, net photosynthetic rate, WUEi, leaf water potential, proline concentration and NSC concentration and maintenance of integrity of the leaf cellular ultrastructure under drought when compared with D/C. D/C exhibited severely damaged cell membranes, mitochondria and chloroplasts under drought. The scion genotype caused a strong effect on the root proline concentration: the P. cathayana scion increased the root proline concentration more than the P. deltoides scion (C/C vs D/C and C/D vs D/D) under water deficit. Our results demonstrated that mainly the rootstock was responsible for the drought resistance of grafting combinations. Grafting of the P. cathayana scion onto P. deltoides rootstock resulted in superior growth and biomass when compared with the other three combinations both in well-watered and drought stress conditions.

Interspecific grafting to solve the rootstock shortage in vegetative propagation of Lai-durian (Durio zibethinus x kutejensis) originated from East Kalimantan

Lai-durian (Durio zibethinus x kutejensis) is a durio species derived from a natural crossing between Durio zibethinus (Durian, local name) and Durio kutejensis (Lai, local name) showing high performance of fruit quality and economic value such as golden yellow aril color, sweet and odourless taste, soft and dry texture, long shelf life (7-10 days), high edible portion, and relatively high fruit weight and yield per plant per year. The vegetative propagation of Lai-durian especially using shoot or bud grafting is facing a problem due to the low rootstock availability since Lai-durian seeds show a high percentage of abnormal/undeveloped seeds. This research was performed to evaluate the compatibility and growth performance of the interspecific grafting of two different grafting types, chip budding and cleft grafting using three different rootstock sources, D. zibethinus, D. kutejensis, and D. zibethinus x kutejensis. Three superior national varieties of Lai-durian, i.e., Lai Kayan, Lai Mandong, and Holai Sentawar were used in this research as scion sources. The total number of 180 grafting occasions of chip budding and cleft grafting was conducted using 4–5 months-old seedling plants with 50-60 cm height as rootstocks. The survival rate of the successful grafting and several growth parameters, i.e., plant height, shoot and rootstock diameter, leaf number, and branch number increment were evaluated for two months. The interspecific grafting of Lai-durian on three different rootstock seedlings derived from D. zibethinus, D. kutejensis, and D..zibethinus x kutejensis was compatible and showed a successful graft union using chip budding (94%) or cleft grafting (60%). The use of D. zibethinus and D. kutejensis as rootstocks could replace those of D. zibethinus x kutejensis since there were no significant differences in the grafting compatibility and growth among the three varieties of rootstocks.

Peroxidase activity and initial growth of ‘Barbosa’ peach on clonal rootstocks

Abstract In the peach nursery trees production, the use of rootstocks with unknown genetic identity obtained from peach seeds in the canning industry is frequent. The hypothesis tested was that there are rootstocks that express greater graft compatibility, enabling greater survival and growth, and that peroxidase activity can be used as indication of graft incompatibility. The aim of this study was to evaluate the survival and the peroxidase activity efficiency in identifying graft incompatibility and the trunk diameter growth of ‘Barbosa’ peach grafted onto 18 Prunus clonal rootstocks, propagated by herbaceous cuttings, compared to own-rooted scion trees. The experimental design was three randomized blocks, with one tree per plot. The first three vegetative cycles of trees conducted in double Y (5.0m x 2.0m) without irrigation were evaluated. The highest trunk diameter growth was provided by ‘Okinawa’, ‘Tsukuba-1’, ‘Tsukuba-2’, Mexico F1 and ‘Flordaguard’ rootstocks, without differing from own-rooted ‘Barbosa’ peach. Peroxidase activity differs by rootstock effect at the beginning of the dormancy period, and is higher than in vegetative growth, especially in interspecific graft combinations. Peroxidase activity is a biochemical indicator of stress, but should not be used alone and generalized to characterize graft incompatibility.

Germination and interspecific grafting of passion fruit

The objective of this study is to evaluate the seed germination and efficiency of grafting yellow passion fruit on six Passifloraceae species. The species used as rootstocks were Passiflora foetida L., P. cincinnata Mast., P. ligularis Juss., P. caerulea L., P. gibertii N. E. Brown, and P. edulis Sims. The study involved six treatments with four replicates of eight plants per plot and was arranged in a completely randomized block design. The seedlings were produced on a non-sterile substrate composed of a mixture of soil and bovine manure at the ratio of 3:1. The percentage of germination was high for all studied species, and the rate of graft development and survival was higher than 70 and 85.71%, respectively, within 60 days after grafting.

Comparison of Root System Morphology of Cucurbit Rootstocks for Use in Watermelon Grafting

Grafting of watermelon (Citrullus lanatus) is an established production practice that provides resistance to soilborne diseases or tolerance to abiotic stresses. Watermelon may be grafted on several cucurbit species (interspecific grafting); however, little research exists to describe root systems of these diverse rootstocks. A greenhouse study was conducted to compare root system morphology of nine commercially available cucurbit rootstocks, representing four species: pumpkin (Cucurbita maxima), squash (Cucurbita pepo), bottle gourd (Lagenaria siceraria), and an interspecific hybrid squash (C. maxima × C. moschata). Rootstocks were grafted with a triploid watermelon scion (‘Exclamation’), and root systems were compared with nongrafted (NG) and self-grafted (SG) ‘Exclamation’. Plants were harvested destructively at 1, 2, and 3 weeks after transplant (WAT), and data were collected on scion dry weight, total root length (TRL), average root diameter, root surface area, root:shoot dry-weight ratio, root diameter class proportions, and specific root length. For all response variables, the main effect of rootstock and rootstock species was significant (P < 0.05). The main effect of harvest was significant (P < 0.05) for all response variables, with the exception of TRL proportion in diameter class 2. ‘Ferro’ rootstock produced the largest TRL and root surface area, with observed values 122% and 120% greater than the smallest root system (‘Exclamation’ SG), respectively. Among rootstock species, pumpkin produced the largest TRL and root surface area, with observed values 100% and 82% greater than those of watermelon, respectively. These results demonstrate that substantial differences exist during the initial 3 WAT in root system morphology of rootstocks and rootstock species available for watermelon grafting and that morphologic differences of root systems can be characterized using image analysis.

Growth Performance of Mature Trees Resulted from Intra and Inter-specific Grafting on Robusta Coffee

To improve yield and cup quality, mature coffee tree as rootstock could be grafted with scion of selected genotype. This research aimed to study growth performance of mature trees resulted from intra and inter-specific grafting on Robusta coffee. The research was arranged in Randomized Complete Block Design with 3 replications. There were 12 treatments of entrees/under-stump genotype for coffee grafting including 8 treatments of intraspecific local Robusta/Robusta grafting and 4 treatments of interspecific coffee grafting of Robusta/Liberica and Arabica/Robusta. The results showed that intraspecific grafting of Robusta/Robusta, Robusta/Liberica, and Arabica/Robusta resulted in grafting mortality of 9.8%, 10.9%, and 24.8%, respectively. Until 28 weeks after grafting, branch growth variables were significantly affected by scion/rootstock of Robusta/Robusta, Robusta/Liberica, and Arabica/Robusta grafting. Grafted Arabica/Robusta coffee showed the poor growth performance. In second year of Robusta/Robusta and Robusta/Liberica growth, generative growth of cherry inflorescence per branch and number of cherries per inflorescence were not affected by scion and rootstock genotypes. Leaf and branch growth were very important variables correlating with other variables.

Insight into the role of grafting and arbuscular mycorrhiza on cadmium stress tolerance in tomato.

Physiological, biochemical, metabolite changes, and gene expression analysis of greenhouse tomato (Solanum lycopersicum L.) were investigated in two grafting combinations (self-grafted ‘Ikram’ and ‘Ikram’ grafted onto interspecific hybrid rootstock `Maxifort'), with and without arbuscular mycorrhizal (AM), exposed to 0 and 25 μM Cd. Tomato plants responded to moderate Cadmium (Cd) concentration by decreasing yield and crop growth parameters due to the accumulation of Cd in leaf tissue, inhibition of the PS II activity, reduced nutrients translocation, and also to the oxidative stress as evidenced by enhanced hydrogen peroxide (H2O2) generation, ion leakage, and lipid peroxidation. AM inoculation significantly enhanced the metal concentration in shoots and reduced growth and yield. The Ikram/Maxifort combination induced higher antioxidant enzymes, higher accumulation of proline and reduction of lipid peroxidation products. This suggests that the use of Maxifort rootstock in tomato has a high reactive oxygen species scavenging activity since lower H2O2 concentrations were observed in the presence of Cd. The higher crop performance of Ikram/Maxifort in comparison to Ikram/Ikram combination was also due to the improved nutritional status (higher P, K, Ca, Fe, Mn, and Zn) and increased availability of metabolites involved in cadmium tolerance (phytochelatin PC2, fructans, and inulins). The up-regulation of LeNRAMP3 gene in leaf of Ikram/Maxifort could explain the better nutritional status of interspecific grafting combination (higher Fe, Mn, and Zn).

Ozark chinkapin demonstrates compatibility as a scion grafted to Chinese chestnut rootstocks: implications for ex situ conservation

The Ozark chinkapin ( Castanea ozarkensis Ashe [Fagaceae]) is a true chestnut that is native to the Ozark Highlands of Missouri, Arkansas, and Oklahoma and to the Ouachita Mountains of Arkansas. It has been decimated by chestnut blight, and the species’ long-term survival is precarious. Few seed-producing trees can now be found in the wild, and the species requires very specific soil and site conditions, making it difficult to cultivate. We studied grafting Ozark chinkapin scions to its readily grown congener, Chinese chestnut ( Castanea mollissima Blume) in controlled orchard settings at 2 Missouri sites, with orchard establishment in 2007 and grafting conducted in 2008. Our grafting success was 56% over all experimental parameters, but up to 83% with optimal combination of site, grafting technique, and scionwood type. Whip-and-tongue grafts were slightly (but not significantly) more successful than chip-bud grafts; however, a more vigorous scionwood type yielded significantly greater graft success (75%) compared with a second scionwood source (38%). By 2014, no indications of interspecific graft incompatibility were evident, and grafted trees were producing abundant nut yields. The successful demonstration that Chinese chestnut can be used as a rootstock for Ozark chinkapin has profound implications for the rapid propagation of Ozark chinkapin germplasm in ex situ orchards and as an important tool in a larger conservation context. In such settings, research, breeding, and mass propagation efforts with the threatened Ozark chinkapin can become much more simple, successful, and cost-efficient.

Plant grafting: new mechanisms, evolutionary implications.

Grafting, an old plant propagation practice, is still widely used with fruit trees and in recent decades also with vegetables. Taxonomic proximity is a general prerequisite for successful graft-take and long-term survival of the grafted, composite plant. However, the mechanisms underlying interspecific graft incompatibility are as yet insufficiently understood. Hormonal signals, auxin in particular, are believed to play an important role in the wound healing and vascular regeneration within the graft union zone. Incomplete and convoluted vascular connections impede the vital upward and downward whole plant transfer routes. Long-distance protein, mRNA and small RNA graft-transmissible signals currently emerge as novel mechanisms which regulate nutritional and developmental root/top relations and may play a pivotal role in grafting physiology. Grafting also has significant pathogenic projections. On one hand, stock to scion mechanical contact enables the spread of diseases, even without a complete graft union. But, on the other hand, grafting onto resistant rootstocks serves as a principal tool in the management of fruit tree plagues and vegetable soil-borne diseases. The ‘graft hybrid’ historic controversy has not yet been resolved. Recent evidence suggests that epigenetic modification of DNA-methylation patterns may account for certain graft-transformation phenomena. Root grafting is a wide spread natural phenomenon; both intraspecific and interspecific root grafts have been recorded. Root grafts have an evolutionary role in the survival of storm-hit forest stands as well as in the spread of devastating diseases. A more fundamental evolutionary role is hinted by recent findings that demonstrate plastid and nuclear genome transfer between distinct Nicotiana species in the graft union zone, within a tissue culture system. This has led to the formation of alloploid cells that, under laboratory conditions, gave rise to a novel, alloploid Nicotiana species, indicating that natural grafts may play a role in plant speciation, under certain circumstances.

Solanum torvum as a Compatible Rootstock in Interspecific Tomato Grafting

Two tomato scions (‘Celebrity’ and ‘CLN3212A’) were grafted onto Solanum torvum and tomato ‘Maxifort’ rootstock to determine compatibility. Experimental design included self-grafted and non-grafted control rootstocks. Seed vs. vegetative S. torvum rootstocks were also compared to further explore grafting options. Average number of days for graft fusion and survival rate was measured for each scion/rootstock combination. Vegetative S. torvum cuttings had the poorest grafting success rate as a rootstock (50% for both scions), while all other rootstock genotypes had statistically similar or higher success rates. There was no significant difference in time to graft fusion among any grafted genotypes. High compatibility of seed-derived S. torvum suggests its potential use as an interspecific grafting rootstock in areas where access to seed is readily available.

Propagation of Sophora toromiro through interspecific grafting to support species conservation. Cien Inv. Agr. 40(1):213-221.

This report provides information on applying the cleft grafting technique in the species Sophora toromiro (Phil.) Skottsb., focused on its propagation, and contributes to the conservation of the genetic base of this species in the medium and long term. A germplasm collection was obtained via interspecific grafting using Sophora cassioides (Phil.) Sparre as rootstock, employing two variations of cleft grafting sealing. The survival of 301 S. toromiro grafts of the Titze line at ten months was 64% or 95%, according to the type of sealing performed. A second experiment, comparing the origin of the material, indicated that the plants of Goteborg origin showed survival values close to 63%, versus 58% for those from the Jardin Botanico Nacional de Vina del Mar (Chile). This work presents a new approach for the recovery of S. toromiro and other woody species that are classified as endangered or highly threatened through the cleft grafting technique, in this case, onto S. cassioides.El presente documento entrega antecedentes de la tecnica de injerto por hendidura con la especie Sophora toromiro (Phil.) Skottsb., orientada a su propagacion y contribuir a la conservacion de su base genetica en el mediano y largo plazo. La captura de germoplasma se realizo por medio de injertos inter especificos, utilizando Sophora cassioides (Phil.) Sparre como porta injerto, con dos variantes de sellado de injerto de hendidura. La sobrevivencia de 301 injertos de S. toromiro de la linea Titze, a los diez meses, es de un 64 y 95%, segun el tipo de sellado utilizado. Un segundo experimento, para contrastar origen de material, entrega que la procedencia Goteborg alcanza valores cercanos al 63% de efectividad versus un 58% del Jardin Botanico Nacional de Vina del Mar (Chile). Este trabajo entrega un nuevo enfoque para la recuperacion de S. toromiro, y otras especies lenosas que estan catalogadas en peligro de extincion o bien amenazadas, mediante la tecnica de injerto de hendidura.

Root-to-shoot Translocation of Alkaloids is Dominantly Suppressed in Nicotiana alata

In tobacco (Nicotiana tabacum), nicotine and related pyridine alkaloids are produced in the root, and then transported to the aerial parts where these toxic chemicals function as part of chemical defense against insect herbivory. Although a few tobacco transporters have been recently reported to take up nicotine into the vacuole from the cytoplasm or into the cytoplasm from the apoplast, it is not known how the long-range translocation of tobacco alkaloids between organs is controlled. Nicotiana langsdorffii and N. alata are closely related species of diploid Nicotiana section Alatae, but the latter does not accumulate tobacco alkaloids in the leaf. We show here that N. alata does synthesize alkaloids in the root, but lacks the capacity to mobilize the root-borne alkaloids to the aerial parts. Interspecific grafting experiments between N. alata and N. langsdorffii indicate that roots of N. alata are unable to translocate alkaloids to their shoot system. Interestingly, genetic studies involving interspecific hybrids between N. alata and N. langsdorffii and their self-crossed or back-crossed progeny showed that the non-translocation phenotype is dominant over the translocation phenotype. These results indicate that a mechanism to retain tobacco alkaloids within the root organ has evolved in N. alata, which may represent an interesting strategy to control the distribution of secondary products within a whole plant.

Enxertia herbácea em Myrtaceae nativas do Rio Grande do Sul

O objetivo deste trabalho foi testar a viabilidade da técnica de enxertia herbácea em frutíferas nativas da família Myrtaceae. O experimento foi realizado em casa de vegetação do Departamento de Horticultura e Silvicultura/ UFRGS, em Porto Alegre. Duas espécies de Myrtaceae nativas foram usadas, tanto como porta-enxerto quanto como enxerto, Eugenia uniflora (Pitangueira) e E. involucrata (Cerejeira-do-rio-grande ou Cerejeira-do-mato), totalizando quatro combinações. O método de enxertia adotado foi por garfagem em fenda cheia, em ramos herbáceos, com diâmetro médio do porta-enxerto de 0,1cm, enquanto os ramos dos enxertos apresentavam diâmetro médio entre 0,08 a 0,1cm, para as duas espécies. As análises foram quinzenais e, após 70 dias, foram analisadas estatisticamente a pega e a altura média das brotações emitidas. O delineamento experimental foi o completamente casualizado, com quatro repetições, sendo cada unidade experimental composta de cinco enxertos. Os resultados indicaram pega de 60% na combinação Pitangueira-Pitangueira (porta enxerto - enxerto). As demais combinações mostraram-se ineficientes.

Characterization of 11 Juglandaceae Genotypes Based on Morphology, cpDNA, and RAPD

The interspecific and intergeneric relationships of eight species of Juglans (walnuts) and three other members of Juglandaceae were investigated. The following species were included: the American J. australis Griseb., J. neotropica Diels., J. olanchana Standl. et L.O. Williams, J. nigra L., and Carya illinoensis (Wang.) K. Koch.; two Juglans from South China, namely, J. sigillata Dode and an unidentified J. sp; an Engelhardia also from China and the Asian J. ailantifolia Carr., Pterocarya stenoptera var. tonkinensis Franchet and the Eurasian J. regia L. Cladistic analysis of 27 multistate morphological characters showed that the juvenile J. ailantifolia possessed similar physical traits to that of the juvenile American Juglans species. The chloroplast DNA in the trnL-trnF region indicated a close relationship between Juglans species. Pterocarya put the root of the cpDNA network among the American species. RAPD analysis was performed using eight primers. A total of 138 fragments were generated but only 78 clearly defined bands were used in the analysis. All the DNA data grouped the tropical/subtropical American Juglans with J. nigra, and the two new Asian species with J. ailantifolia and J. regia. The American species were closely related, more so than their Asian counter parts. The closeness of the investigated species predicts interspecific graft compatibility not only within the Asian and American groups, but also between them.

Control of photoperiod-regulated tuberization in potato by the Arabidopsis flowering-time gene CONSTANS.

Photoperiod controls several responses throughout the plant life cycle, like germination, flowering, tuber formation, onset of bud dormancy, leaf abscission, and cambium activity. From these processes, flowering has been most extensively studied, especially in Arabidopsis thaliana. Photoperiod sensing by the function of photoreceptors and the circadian clock appears to regulate flowering time via Arabidopsis CONSTANS (AtCO), a putative transcription factor that accelerates flowering in response to long days. The genetic factors controlling plant photoperiodic responses other than flowering are little known. However, interspecific grafting experiments demonstrated that the flower-inducing (florigen) and tuber- inducing (tuberigen) signals are functionally exchangeable. Here we show that constitutive overexpression in potato of the Arabidopsis flowering-time gene AtCO impairs tuberization under short-day inductive conditions; AtCO overexpressing lines require prolonged exposure to short days to form tubers. Grafting experiments using these lines indicated that AtCO exerts its inhibitory effect on tuber formation by acting in the leaves. We propose that a conserved photoperiodic functional module may be involved in controlling distinct photoperiod-regulated evocation responses in different species. This module would involve the action of CONSTANS in the production of the elusive and long-distance acting florigen-tuberigen signal(s) in the leaves.