Identification of SSR markers linked to the abscission of cotton boll traits and mining germplasm in Cotton

Background Cotton is an economically important crop.It is crucial to find an effective method to improve cotton yield,and one approach is to decrease the abscission of cotton bolls and buds.However,the lack of knowledge of the genetic and molecular mechanisms underlying cotton boll abscission traits has hindered genetic improvements.Results Pearson’s correlation analysis revealed a significant positive correlation between boll abscission rates 1(AR1)and boll abscission rates 2(AR2).A genome-wide association study was conducted on 145 loci that exhibited high polymorphism and were uniformly distributed across 26 chromosomes(pair).The study revealed 18,46,and 62 markers that were significantly associated with boll abscission,fiber quality,and yield traits(P<0.05),explaining 1.75%–7.13%,1.16%–9.58%,and 1.40%–5.44%of the phenotypic variation,respectively.Notably,the marker MON_SHIN-1584b was associated with the cotton boll abscission trait,whereas MON_CGR5732a was associated with cotton boll abscission and fiber quality traits.Thirteen of the marker loci identified in this study had been previously reported.Based on phenotypic effects,six typical cultivars with elite alleles related to cotton boll abscission,fiber quality,and yield traits were identified.These cultivars hold great promise for widespread utilization in breeding programs.Conclusions These results lay the foundation for understanding the molecular regulatory mechanism of cotton boll abscission and provide data for the future improvement of cotton breeding.

PbrARF4 contributes to calyx shedding of fruitlets in ‘Dangshan Suli’ pear by partly regulating the expression of abscission genes

Fruitlet calyx shedding in pear plants is apparently regulated via numerous pathways that involve both environmental triggers and phytohormones cues such as auxin. In this study, we found at 10 days after full bloom (DAFB) higher levels of indoleacetic acid (IAA) and tryptophan (Trp) in calyx persistence fruitlet (CPF) than calyx shedding fruitlet (CSF) ofDanshan Suli’ pear (Pyrus bretschneideri Rhed.). Consisting with this, the activity of indolealdehyde oxidase (IAAIdO), which promotes IAA synthesis, was remarkably increased, and that of peroxidase(POD), which degrades IAA, dropped markedly in CPF but not in CSF. Further, qRT-PCR results revealed that most of 31 PbrARFs (encoding auxin response factors) in Pyrus bretschneideri were highly expressed in CPF, whereas PbrARF4, PbrARF24 and PbrARF26 were significantly downregulated in CPF vis-a-vis CSF. Phylogenetic analysis revealed that 6 PbrARFs clustered in the group III, where PbrARF4 showed the closest affinity with AtARF1 that promotes organ abscission, indicating a putative role of PbrARF4 in mediating the process of calyx shedding in pear. In fact, the ectopic overexpression of PbrARF4 in Solanum lycopersicum resulted in an earlier-formed and deeper abscission layer (AL) in the transgenic plants, whose calyxes were more prone to wilt at the mature red stage (MR) compared with the control plants (wild-type). More importantly, expression levels of the abscission genes SILS and Sl Cel2 in transgenic plants overexpressing PbrARF4 were significantly upregulated in comparation with the WT, whereas those of Sl BI and Sl TAPG2 were considerably inhibited. Further, PbrJOINTLESS and PbrIDA,the two genes related to calyx shedding in pear, were up-regulated more in CSF than CPF. The findings contribute to a better understanding of PbrARFs involved in fruitlet calyx shedding of pear, which could prove beneficial to improving the quality of pear fruit.

Organ Abscission in Plants: With Special Emphasis on Bell Pepper

Bell pepper(Capsicum annuum L.),along with potato and tomato,is one of the three most cultivated vegetables in the world.Bell pepper is worldwide accepted due to its characteristics of color,smell,flavor,and texture.Bell pepper is also considered a nutritious food due to its vitamin and antioxidant contents.In Mexico,bell pepper production has a high value because it is grown for the international markets,particularly the United States of America.Nevertheless,the abscission offlowers and fruits is a factor that limits the yield,hinders the planning of activities,and causes a variation in the prices of peppers.Due to the importance of this process,in this work we did a bibliometric analysis and literature review of scientific advances for the understanding of the abscission pro-cess in plants,and in particular for the bell pepper.Finally,we introduce new perspectives that would help direct future research about organ abscission in plants.Likewise,the lack of research that would further clarify abscis-sion process in the bell pepper plant is discussed.

Molecular regulatory events of flower and fruit abscission in horticultural plants

Flower and fruit abscission is a highly programmed physiological process,which is closely related to the yield of horticultural plants.The coordination of many regulatory factors associated with metabolic and signaling pathways plays a key role in the flower and fruit shedding.Hormones,peptides,carbohydrates,polyamines or cell wall modifying proteins regulate flower and fruit shedding.This article reviewed the recent studies of flower and fruit abscission,including the molecular regulation mechanism of abscission zone formation,typical structure and location of abscission zones,and other factors affecting flower and fruit abscission,such as stresses,hormones,peptides,carbohydrates,polyamines and cell wall modifying proteins.Overall,the review summarizes the developmental mechanism and the diversity of abscission zones,and the key factors affecting flower and fruit abscission of horticultural plants,aiming to provide guidance for studying the molecular regulatory mechanism of flower and fruit abscission.

Molecular characterization of the SAUR gene family in sweet cherry and functional analysis of PavSAUR55 in the process of abscission

Small auxin up RNA(SAUR) is a large gene family that is widely distributed among land plants. In this study, a comprehensive analysis of the SAUR family was performed in sweet cherry, and the potential biological functions of PavSAUR55 were identified using the method of genetic transformation. The sweet cherry genome encodes 86 SAUR members, the majority of which are intron-less. These genes appear to be divided into seven subfamilies through evolution. Gene duplication events indicate that fragment duplication and tandem duplication events occurred in the sweet cherry. Most of the members mainly underwent purification selection pressure during evolution. During fruit development, the expression levels of Pav SAUR16/45/56/63 were up-regulated, and conversely, those of Pav SAUR12/61were down-regulated. Due to the significantly differential expressions of PavSAUR13/16/55/61 during the fruitlet abscission process, they might be the candidate genes involved in the regulation of physiological fruit abscission in sweet cherry. Overexpression of PavSAUR55 in Arabidopsis produced earlier reproductive growth, root elongation, and delayed petal abscission. In addition, this gene did not cause any change in the germination time of seeds and was able to increase the number of lateral roots under abscisic acid(ABA) treatment. The identified SAURs of sweet cherry play a crucial role in fruitlet abscission and will facilitate future insights into the mechanism underlying the heavy fruitlet abscission that can occur in this fruit crop.

Qualitative Assessment of Postharvest Stomata and Chloroplast Degradation in Contrasting Abscission Resistant Balsam Fir (Abies balsamea (L.) Mill.)

Balsam fir is an important Christmas tree species, especially in eastern Canada. The natural Christmas tree industry faces a challenge in postharvest needle abscission. Though there have been many studies describing the physiological triggers and consequences in postharvest balsam fir, there have been no studies describing morphological or ultrastructural changes. Therefore, the objective of this study was to examine changes in stomata and chloroplast of postharvest needles. Branches were collected from low and high needle abscission resistance balsam fir genotypes, placed in water, and displayed in typical household conditions for 11 weeks. Needle abscission, chlorophyll fluorescence, and water uptake were monitored throughout. Needles stomata and chloroplasts were examined under a scanning and transmission electron microscope, respectively, each week. All branches had increased abscission, decreased chlorophyll fluorescence, and decreased water uptake over time. Needle surfaces accumulated fungal hyphae, especially in stomata. Chloroplasts demonstrated some dysfunction within two weeks, with notable decreases in chloroplast starch and increases in plastoglobulins. Within several weeks thylakoid membranes had been dismantled as chloroplasts transformed into gerontoplasts. All biophysical and structural changes were more pronounced in low needle abscission resistant genotypes. This research identifies a potential role for needle fungi in postharvest needle abscission and confirms the postharvest senescence of chloroplasts. Though it was previously speculated that chloroplasts must senesce postharvest, this study identifies how quickly this process occurs and that it occurs at different rates in contrasting genotypes.

Analysis of Calcium Content, Hormones, and Degrading Enzymes in Tomato Pedicel Explants During Calcium-Inhibited Abscission

This study was designed to analyze the changes of phytohormone concentrations, calcium fraction, and the activities of degrading enzymes during calcium-inhibited and ethyleneglycol-bis-（β-aminoethyl ether）N, N＇-tetraacetic acid （EGTA）-induced abscission of tomato pedicel explants. Added calcium caused an increase in the total calcium content within the abscission zone and produced a corresponding reduction （20%） in pedicel explant abscission. As expected, EGTA treatment produced the opposite effect and resulted in a decrease in the total calcium content, while accelerating abscission of pedicel explants. Hormone analysis revealed that indole-3-acetic acid （IAA） concentrations in the abscission zone first decreased and then increased before the occurrence of abscission in all treatments, with the greatest effect produced by addition of EGTA. Similarly, abscisic acid （ABA）, and gibberellin （GA1＋3） concentrations, and ethylene production were elevated in the abscission zone during the first 16 h before abscission when explants imbibed EGTA. With calcium treatment, the concentrations of ABA, ethylene, and GA1＋3 also increased in pedicels throughout the first 16 h following exposure, but the increase was slower and less dramatic than with EGTA. Both cellulase and polygalacturonase were induced in the explants during abscission and the activities were also strengthened by treatment with EGTA. Calciumtreated explants produced lower hydrolysing enzyme activities than controls throughout abscission. Calcium played a role of mediating hormone balance and degrading enzymes activities and affected on abscission.

Potential Roles of Fatty Acids and Lipids in Postharvest Needle Abscission Physiology

Our understanding of postharvest needle abscission physiology in conifers has greatly improved in the last decade. Abscission is initially triggered by root detachment, which begins a cascade of changes such as decreased water uptake, water potential, and auxins and increased membrane injury, ethylene, abscisic acid, volatile terpenes, and catalytic enzymes. Needle abscission is also affected by environmental factors. For example, a period of cold acclimation generally delays postharvest abscission. The aforementioned pieces of evidence, along with previous studies, strongly points to a role for plant lipids and fatty acids. Studies from other species have pointed out key roles in abscission and stress responses for a variety of phospholipids and galactolipids, which has not been studied in balsam fir. It is imperative to have an understanding of the role of plant lipids and fatty acids to further our overall understanding of the physiological mechanisms of postharvest abscission and needle abscission resistance. This review is an overview of membrane lipids and fatty acids, changes that occur postharvest and the interaction that lipids may have in the phenomenon of postharvest abscission.

Eco-physiological mechanisms of Caragana korshinskii Kom. adaptation to extreme drought stress: Leaf abscission and maintaining stem chloroplast integrity

In order to study the eco-physiological mechanisms of C. korshinskii adaptation to extreme drought stress, we investigated the variations of water content in soil, leaves, and stems, the chlorophyll a and b and the carotenoid content in leaves and stems, as well as changes of chloroplast ultrastructure in 2-year-old C. korshinskii specimens during a progressive soil drought process （by ceasing watering until all leaves were shed） and a subsequent rehydmtion process. During the dehydration process, the chlorophyll a and b and carotenoid contents in the leaves decreased, as did the carotenoid content in the stems. During the 4-day rehydration process, the chlorophyll a and b and carotenoid contents in the leaves and stems increased and gradually returned to normal levels. During ongoing drought stress, chloroplasts in the leaves broke away from cell walls and appeared in the center of cells. Under severe drought stress, the mesophyll ultrastmcture and chloroplast configuration in leaves were irreversibly disturbed, as mani- fested by the inner and outer membranes being destroyed; the thylakoid system disintegrated, the starch grain disappeared, and parts of cell tissue were dismantled into debris. However, the mesophyll ultrasWacture and chloroplast configuration in the stems remained complete. This indicates that C. korshinskii utilizes leaf abscission to reduce the surface area to avoid damage from ex- treme drought stress, and maintains chloroplast integrity and a considerable amount of chlorophyll to enable a rapid recovery of photosynthesis under the rehydration process.

The transcriptional control of LcIDL1–LcHSL2 complex by LcARF5 integrates auxin and ethylene signaling for litchi fruitlet abscission

At the physiological level,the interplay between auxin and ethylene has long been recognized as crucial for the regulation of organ abscission in plants.However,the underlying molecular mechanisms remain unknown.Here,we identified transcription factors involved in indoleacetic acid(IAA)and ethylene(ET)signaling that directly regulate the expression of INFLORESCENCE DEFICIENT IN ABSCISSION(IDA)and its receptor HAESA(HAE),which are key components initiating abscission.Specifically,litchi IDAlike 1(LcIDL1)interacts with the receptor HAESA-like2(LcHSL2).Through in vitro and in vivo experiments,we determined that the auxin response factor LcARF5 directly binds and activates both LcIDL1 and LcHSL2.Furthermore,we found that the ETHYLENE INSENSITIVE 3-like transcription factor LcEIL3 directly binds and activates LcIDL1.The expression of IDA and HSL2 homologs was enhanced in Lc ARF5and Lc EIL3 transgenic Arabidopsis plants,but reduced in ein3 eil1 mutants.Consistently,the expressions of LcIDL1 and LcHSL2 were significantly decreased in Lc ARF5-and LcEIL3-silenced fruitlet abscission zones(FAZ),which correlated with a lower rate of fruitlet abscission.Depletion of auxin led to an increase in 1-aminocyclopropane-1-carboxylic acid(the precursor of ethylene)levels in the litchi FAZ,followed by abscission activation.Throughout this process,LcRF5 and LcEIL3 were induced in the FAZ.Collectively,our findings suggest that the molecular interactions between litchi AUXIN RESPONSE FACTOR 5(LcARF5)-LcIDL1/LcHSL2 and LcEIL3–LcIDL1 signaling modules play a role in regulating fruitlet abscission in litchi and provide a long-sought mechanistic explanation for how the interplay between auxin and ethylene is translated into the molecular events that initiate abscission.

Letting Go is Never Easy:Abscission and Receptor- Like Protein Kinases

Abscission is the process by which plants discard organs in response to environmental cues/stressors, or as part of their normal development. Abscission has been studied throughout the history of the plant sciences and in numerous species. Although long studied at the anatomical and physiological levels, abscission has only been elucidated at the molecular and genetic levels within the last two decades, primarily with the use of the model plant Arabidopsis thaliana. This has led to the discovery of numerous genes involved at all steps of abscission, including key pathways involving receptor-like protein kinases （RLKs）. This review covers the current knowledge of abscission research, highlighting the role of RLKs.

Protective mechanism of desiccation tolerance in Reaumuria soongorica: Leaf abscission and sucrose accumulation in the stem

Reaumuria soongorica (Pall.) Maxim., a perennial semi-shrub, is widely found in semi-arid areas in northwestern China and can survive severe desiccation of its vegetative organs. In order to study the protective mechanism of desiccation tolerance in R. soongorica, diurnal patterns of net photosynthetic rate (Pn), water use efficiency (WUE) and chlorophyll fluorescence parameters of Photosystem II (PSII), and sugar content in the source leaf and stem were investigated in 6-year-old plants during progressive soil drought imposed by the cessation of watering. The results showed that R. soongorica was char-acterized by very low leaf water potential, high WUE, photosynthesis and high accumulation of sucrose in the stem and leaf abscission under desiccation. The maximum Pn increased at first and then de-clined during drought, but intrinsic WUE increased remarkably in the morning with increasing drought stress. The maximal photochemical efficiency of PSII (Fv/Fm) and the quantum efficiency of noncyclic electric transport of PSII(ΦPSII) decreased significantly under water stress and exhibited an obvious phenomenon of photoinhibition at noon. Drought stressed plants maintained a higher capacity of dis-sipation of the excitation energy (measured as NPQ) with the increasing intensity of stress. Conditions of progressive drought promoted sucrose and starch accumulation in the stems but not in the leaves. However, when leaf water potential was less than –21.3 MPa, the plant leaves died and then abscised. But the stem photosynthesis remained and, afterward the plants entered the dormant state. Upon re-watering, the shoots reactivated and the plants developed new leaves. Therefore, R. soongorica has the ability to reduce water loss through leaf abscission and maintain the vigor of the stem cells to survive desiccation.

Requirement of KNAT1/BP for the Development of Abscission Zones in Arabidopsis thaliana

The KNAT1 gene is a member of the Class I KNOXhomeobox gene family and is thought to play an important role in meristem development and leaf morphogenesis. Recent studies have demonstrated that KNAT1/BP regulates the architecture of the inflorescence by affecting pedicle development in Arabidopsis thaliana. Herein, we report the characterization of an Arabidopsis T-DNA insertion mutant that shares considerable phenotypic similarity to the previously identified mutant brevipedicle （bp）. Molecular and genetic analyses showed that the mutant is allelic to bp and that the T-DNA is located within the first helix of the KNAT1 homeodomain （HD）. Although the mutation causes a typical abnormality of short pedicles, propendent siliques, and semidwarfism, no obvious defects are observed in the vegetative stage. A study on cell morphology showed that asymmetrical division and inhibition of cell elongation contribute to the downward-pointing and shorter pedicle phenotype. Loss of KNAT/BPfunction results in the abnormal development of abscission zones. Mlcroarray analysis of gene expression profiling suggests that KNAT1/BP may regulate abscission zone development through hormone signaling and hormone metabolism in Arabidopsis.

A comprehensive framework for seasonal controls of leaf abscission and productivity in evergreen broadleaved tropical and subtropical forests

Relationships among productivity,leaf phenology,and seasonal variation in moisture and light availability are poorly understood for evergreen broadleaved tropical/subtropical forests,which contribute 25% of terrestrial productivity.On the one hand,as moisture availability declines,trees shed leaves to reduce transpiration and the risk of hydraulic failure.On the other hand,increases in light availability promote the replacement of senescent leaves to increase productivity.Here,we provide a comprehensive framework that relates the seasonality of climate,leaf abscission,and leaf productivity across the evergreen broadleaved tropical/subtropical forest biome.The seasonal correlation between rainfall and light availability varies from strongly negative to strongly positive across the tropics and maps onto the seasonal correlation between litterfall mass and productivity for 68 forests.Where rainfall and light covary positively,litterfall and productivity also covary positively and are always greater in the wetter sunnier season.Where rainfall and light covary negatively,litterfall and productivity are always greater in the drier and sunnier season if moisture supplies remain adequate;otherwise productivity is smaller in the drier sunnier season.This framework will improve the representation of tropical/subtropical forests in Earth system models and suggests how phenology and productivity will change as climate change alters the seasonality of cloud cover and rainfall across tropical/subtropical forests.

Phenotypical and gene co-expression network analyses of seed shattering in divergent sorghum(Sorghum spp.)

Sorghum[Sorghum bicolor(L.)Moench],a multipurpose C4 crop,is also a model species of the Poaceae family for plant research.During the process of domestication,the modification of seed dispersal mode is considered a key event,as the loss of seed shattering caused a significant increase in yield.In order to understand the seed shattering process in sorghum,we further studied eight previously identified divergent sorghum germplasm with different shattering degrees.We described their phenotypes in great detail,analyzed the histology of abscission zone,and conducted a gene co-expression analysis.We observed that the abscission layer of the most strong-shattering varieties began to differentiate before the 5-10 cm panicles development stage and was completely formed at flag leaf unfolding.The protective cells on the pedicels were also fully lignified by flowering.Through the weighted gene correlation network analysis(WGCNA),we mined for candidate genes involved in the abscission process at the heading stage.We found that these genes were mainly associated with such biological processes as hormone signal transmission(SORBI_3003G361300,SORBI_3006G216500,SORBI_3009G027800,SORBI_3007G077200),cell wall modification and degradation(SORBI_3002G205500,SORBI_3004G013800,SORBI_3010G022400,SORBI_3003G251800,SORBI_3003G254700,SORBI_3003G410800,SORBI_3009G162700,SORBI_3001G406700,SORBI_3004G042700,SORBI_3004G244600,SORBI_3001G099100),and lignin synthesis(SORBI_3004G220700,SORBI_3004G062500,SORBI_3010G214900,SORBI_3009G181800).Our study has provided candidate genes required for shedding for further study.We believe that function characterization of these genes may provide insight into our understanding of seed shattering process.

Plant Senescence: The Role of Volatile Terpene Compounds (VTCs)

Senescence is a natural, energy-dependent, physiological, developmental and an ecological process that is controlled by the plant’s own genetic program, allowing maximum recovery of nutrients from older organs for the survival of the plant, as such;it is classified as essential component of the growth and development of plants. In some cases, under one or many environmental stresses, senescence is triggered in plants. Despite many studies in the area, less consideration has been given to plant secondary metabolites, especially the role of VTCs on plant senescence. This review seeks to capture the biosynthesis and signal transduction of VTCs, the physiology of VTCs in plant development and how that is linked to some phytohormones to induce senescence. Much progress has been made in the elucidation of metabolic pathways leading to the biosynthesis of VTCs. In addition to the classical cytosolic mevalonic acid (MVA) pathway from acetyl-CoA, the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway, originating from glyceraldehyde-3-phosphate (GAP) and pyruvate, leads to the biosynthesis of isoprenoid precursors, isopentenyl diphosphate and dimethyl allyl diphosphate. VTCs synthesis and emission are believed to be tightly regulated by photosynthetic carbon supply into MEP pathway. Thus, under abiotic stresses such as drought, high salinity, high and low temperature, and low CO2 that directly affect stomatal conductance and ultimately biochemical limitation to photosynthesis, there has been observed induction of VTC synthesis and emissions, reflecting the elicitation of MEP pathway. This reveals the possibility of important function(s) of VTCs in plant defense against stress by mobilizing resources from components of plants and therefore, senescence. Our current understanding of the relationship between environmental responses and senescence mostly comes from the study of senescence response to phytohormones such as abscisic acid, jasmonic acid, ethylene and salicylic acid, which are extensively involved in response to various abiotic and biotic stresses. These stresses affect synthesis and/or signaling pathways of phytohormones to eventually trigger expression of stress-responsive genes, which in turn appears to affect leaf senescence. Comparison of plant response to stresses in relation to patterns of VTCs and phytohormones biosynthesis indicates a considerable crosstalk between these metabolic processes and their signal to plant senescence.

Effect of 1-MCP on Boll Development and Subtending Leaves of Cotton (<i>Gossypium hirsutum</i>L.) Plants

Ethylene regulates multiple physiological processes in cotton (Gossypium hirsutum L.) ranging from square and boll abscission to senescence. This field study investigated the effect of an ethylene inhibiting compound 1-methylcyclopropene (1-MCP) on boll development and the corresponding subtending leaves. The study was conducted in 2011 and 2012 at the Texas A & M Agri-LIFE Research Farm in Burleson County, TX. The study consisted of two rates of 1-MCP (0 and 10 g a.i. ha-1) applied at one and two weeks after first flower. Boll development and subtending leaves were studied on the tagged flowers during the growing season. 1-MCP treatment increased cotton boll weight at 20 days after flowering. This study showed that 1-MCP-treated subtending leaves exhibited decreased membrane damage and lipid peroxidation, and higher chlorophyll content and photosynthetic efficiency at 20 to 30 days after flowering. The healthier state of subtending leaves should have provided more carbohydrates for the fruits which could partially explain the reason for the increased boll weight. However, this beneficial effect of 1-MCP did not last to the end of the growing season and failed to result in a yield increase ultimately. Multiple applications or extending effective duration of 1-MCP is desirable to enhance the activity of 1-MCP to make a significant difference in cotton yield.

Expression and Interaction Analysis of FAZ1 Protein in Brassica oleracea

To identify and characterize genes involved in reproductive tissue abscission in Brassica oleracea,the transcript data of pollinated pistil was analyzed.A differentially expressed gene,named BoFAZ1(FLOWER ABSCISSION ZONE1)was identified,which contains one exon and encompass a 139aa.Furthermore,a T-DNA insertion mutant(SALK_302_G01)(faz1 mutant)was obtained from Arabidopsis thaliana mutant library.Floral organ shedding from mutants was delayed and a V-shaped structure in the boundary region between the stalk and torus of the sepal abscission zone was obtained in faz1 mutant.The cell density of this structure was lower than that of the corresponding region in the wild-type control.In the transgenic plants,the normal development of the stalk zone of faz1 was recovered completely by transforming a 1919-bp DNA fragment of BoFAZ1 into the faz1 mutant.In Addition,our data showed that BoFAZ1 was expressed in mature pollen grains,but not in the bracts,roots,stems,leaves,and sepals.Its expression in the filaments,stigma,and pistil exfoliation layer gradually increased after pollination.Subcellular localization experiments showed that BoFAZ1 was located in the cell membrane.A myristoylation site was found at the N-terminus of BoFAZ1.Removal of this site resulted in protein dislocation in the cytoplasm,cell membrane and nucleus.Finally,a yeast two-hybrid test indicated that BoH3.2(histone H3.2),a protein involved in abscission zone development,interacted with BoFAZ1.This interaction was verified by a GST pull-down assay.In summary,our data indicated that BoFAZ1 was involved in the formation of the pistil abscission zone in B.oleracea.

An Opportunistic Pantoea sp. Isolated from a Cotton Fleahopper That Is Capable of Causing Cotton (<i>Gossypium hirsutum</i>L.) Bud Rot

Pantoea ananatis (Serrano) representatives are known to have a broad host range including both humans and plants. The cotton fleahopper (Pseudatomoscelis seriatus, Reuter) is a significant pest that causes cotton bud damage that may result in significant yield losses. In this study, a bacterial strain previously isolated from a fleahopper was tested for cotton infectivity using simulated insect feeding. In addition, cotton fleahoppers collected from the field were raised on green beans in the laboratory to test the insects’ capacity to vector cotton pathogens. Adult insects were then caged with greenhouse grown cotton buds. Buds that remained or abscised from the plants following feeding by the insect consistently showed necrosis of the ovary including the wall. A collection of bacterial isolates from both caged insects and diseased buds was analyzed using carbon utilization and enzyme production tests, fatty acid methyl ester profile analysis, and by cloning and sequencing 16S RNA genes. Results showed that the majority of the isolates were best classified as P. ananatis. Upon simulated fleahopper feeding (i.e., penetrative inoculation), the fleahopper isolate rotted cotton buds. These results indicated the fleahoppers are vectors of opportunistic P. ananatis strains causing loss of the cotton fruiting structures.

Assessing Influence of Ozone in Tomato Seed Dormancy Alleviation

The study was made on the role of ozone (O3) gas treatment on seeds of Lycopersicon esculentum cv. PKM1 (tomato) to release dormancy in advance. The experimental conditions followed a complete factorial design with 3 independent factors, i.e. A faster start of germination in T2 treatment (98% - 99%) was observed than in other treatments (T1, T3 and T4) compared to control seeds by measuring seedling growth rate on 5th day after treatment. Never the less a too long and high concentration of O3 treatment seemed to be penalizing on germination rate whereas low O3 concentration (T2) for a moderate time interval (20 min) seemed to be most beneficial. The treated seeds were stored, checked 1, 3, 6 months later and found that, the seeds have retained their accelerated germination efficiency. In particular 1T2 (1 month storage), 3T2 (3 month storage) had maximum germination rate among all the stored treated seeds, but 6T2 (6 month storage) didn’t show sustained germination acceleration efficiency. Therefore it was found that when time prolongs, O3 treatment loss its effect steadily and the germination efficiency of all the treatments are more or less same at six months after treatment. It is hypothesized that the application of O3 acts as an important phenomenon in accelerating seed germination by breaking the dormancy in advance which is associated with reduced level of ABA in O3 treated seeds.