Acala SJ-2 Research Articles

Investigation of the Effects of Some Plant Activators Against Verticillium Wilt (Verticillium dahliae Kleb.) on Cotton

Wilt disease caused by Verticillium dahliae Kleb. is one of the stress factors affecting yield and fiber quality traits in cotton cultivation. Plant activators provide resistance by stimulating genes that activate the resistance mechanism in the plant. The aim of this study is to determine the effect of plant activators such as auxiGRO, Green Miracle, Maxicrop, ProAct Plus, and Sojall Vitanal against Verticillium wilt under both in vitro and in vivo conditions. Firstly, the effect of various concentrations of plant activators (0, 1, 5, 25, 100, 250, and 500 ppm) on mycelial growth of two fungal isolates of V. dahliae (PHCVd3-non-defoliating pathotype and PHCVd47-defoliating pathotype) in potato dextrose agar (PDA) media was investigated in vitro. The effect of plant activators on V. dahliae was determined in tolerant cotton plants (cv Carmen) and susceptible cotton plants (cv Acala SJ2) in two different ways seed coating and foliar application in vivo. In vitro experiments were carried out with three replicates, and in vivo experiments were with five replicates depending on a completely randomized plot design. 500 ppm dose of all plant activators inhibited the mycelial growth of both isolates by approximately 90%. The lowest disease index (DI) against PHCVd3 was determined as 1.43 in the tolerant cv Carmen with seed coating of auxiGRO. The lowest DI against PHCVd47 was found in Sojall Vitanal and ProAct Plus at 2.09 and 2.12, respectively. The lowest DI against both isolates was found as 1.42 and 2.18 in cv Carmen by foliar application of ProAct Plus, respectively. Plant activators did not show any inhibitory effect on disease severity against both isolates in cv Acala SJ2. The combination of tolerant cultivar + plant activators can be suggested against Verticillium wilt disease as an alternative control.

The antifungal effect of propolis extract against cotton wild disease (Verticillium dahliae Kleb.)

The aim of this study is to investigate the antifungal activity of propolis against V. dahliae Kleb. under both in vitro and in vivo conditions. Firstly, the inhibitory effect of the propolis on mycelial growth in Potato Dextrose Agar (PDA) media containing its ethanol extract (PE) at various concentrations (0.003, 0.06, 0.125, 0.25, 0.5, and 1 ppm/mL) was investigated under in vitro conditions. Then to assess the effect of PE on non-defoliating (PHCVd3 isolate) and defoliating (PHCVd47 isolate) pathotypes of V. dahliae, the varieties Giza 45 (resistant), Carmen (tolerant), and Acala SJ2 (susceptible) treated with PEE (1 ppm/mL) were observed in the plant growth chamber up to the 4-6 leaf stage. The whole in vitro experiments were carried out with three replicates, and the studies in vivo experiment were with five replicates depending on a completely randomized parcels design. The most effective dose of PEE with1 ppm/mL dose resulted in 75.2% suppression against the PHCVd3 isolate, while the effect of the same dose against the PHCVd47 isolate was 74.4%. The lowest disease severity index (DSI) values against PHCVd3 and PHCVd47 isolates in cotton cultivars treated with PE were 1.34 and 1.64 in the Giza 45, respectively, and the highest DSI values were 3.80 and 3.90 in the Acala SJ2 cultivar in vivo experiment, respectively. The findings indicate that PE treatment has a promising effect against cotton wilt disease that could be combined with known plant protection strategies.

Root-Knot Nematode Resistance in Gossypium hirsutum Determined by a Constitutive Defense-Response Transcriptional Program Avoiding a Fitness Penalty.

Cotton (Gossypium spp.) is the most important renewable source of natural textile fiber and one of the most cultivated crops around the world. Plant-parasitic nematode infestations, such as the southern Root-Knot Nematode (RKN) Meloidogyne incognita, represent a threat to cotton production worldwide. Host-plant resistance is a highly effective strategy to manage RKN; however, the underlying molecular mechanisms of RKN-resistance remain largely unknown. In this study, we harness the differences in RKN-resistance between a susceptible (Acala SJ-2, SJ2), a moderately resistant (Upland Wild Mexico Jack Jones, WMJJ), and a resistant (Acala NemX) cotton entries, to perform genome-wide comparative analysis of the root transcriptional response to M. incognita infection. RNA-seq data suggest that RKN-resistance is determined by a constitutive state of defense transcriptional behavior that prevails in the roots of the NemX cultivar. Gene ontology and protein homology analyses indicate that the root transcriptional landscape in response to RKN-infection is enriched for responses related to jasmonic and salicylic acid, two key phytohormones in plant defense responses. These responses are constitutively activated in NemX and correlate with elevated levels of these two hormones while avoiding a fitness penalty. We show that the expression of cotton genes coding for disease resistance and receptor proteins linked to RKN-resistance and perception in plants, is enhanced in the roots of RKN-resistant NemX. Members of the later gene families, located in the confidence interval of a previously identified QTL associated with RKN resistance, represent promising candidates that might facilitate introduction of RKN-resistance into valuable commercial varieties of cotton. Our study provides novel insights into the molecular mechanisms that underlie RKN resistance in cotton.

Susceptibility of several cotton varieties to the cotton flea beetle, Podagrica puncticollis Weise (Coleoptera: Chrysomelidae), in a hot dry tropical environment of Ethiopia

Field trials were conducted to determine the reaction of cotton varieties to cotton flea beetle infestation. The experiment was laid out in a Randomized Complete Block Design with three replications comprising twelve cotton varieties. The results showed significant (P < 0.01) differences among varieties in the populations of adult beetle they hosted and the injury they sustained at 15, 22, 29, 36 and 43 days after sowing (DAS). At 15 DAS, the highest numbers of adult beetle per plant (6.3), percent leaf area damaged (60.32 %) and number of shot-holes per attacked leaf (53.4) was recorded in Cucurova variety, whereas the lowest in Bulk-202 (2.05 beetles, 26.15% leaf area damaged and 23.16 shot-holes). The rate of incidence and damages decreased with the increase of the age of the cotton plants. Significant differences were also observed among cotton varieties in some agronomic characteristics i.e. in number of plants counted per plot at harvest and seed cotton yield in terms of kilogram per hectare. Seed cotton yield obtained from all cotton varieties varied from 602.36 to 1644.71 kilogram per hectare and the highest was obtained from Bulk-202, while the lowest from Local variety. Based on these findings, Cucurova, Local, Ionia and Acala SJ-2 varieties showed highly susceptible response, while Candia, Sille-91 and Deltapine-90 were moderately susceptible to cotton flea beetle. However, Bulk-202, Delcero and Claudia were relatively more tolerant varieties followed by CCRI-12 and Cuokra. These results will be important for the most proper management of cotton flea beetle.

Screening of upland cotton genotypes (Gossypium hirsutum L.) against cotton verticillium (Verticillium dahliae Kleb.) Wilt

Screening of upland cotton genotypes against Verticillium wilt disease was conducted. The 268 upland cotton genotypes (Carmen and Acala Maxxa cultivar were tolerant- control while cvs. Cukurova 1518 and Acala SJ2 were susceptible-control) were screened against defoliating (PYDV6) and non-defoliating (Vd11) pathotypes of the fungus in a randomized plot design with four replications in growth chamber. Field experiment was established according to the augmented experimental design. Variance analysis was significant (p ≤ 0.05) for all traits against Verticillium wilt. Cvs. Semerkant Uzbek and Taskent 6 were more tolerant than the tolerant-control cultivars against both pathotypes. Most of the genotypes were tolerant in field trial in terms of disease severity that was the lowest for STN K311 genotype in both periods. The highest seed cotton yield was obtained in genotypes as BA119, Okra 204, H-23, Gedera-5, PI 528420 and Acala Royale, which were moderately tolerant to the wilt disease.

Effect of ginning on tenacity, elongation and other fibre quality properties

Based on single and bundle fibre properties measurements before and after ginning treatment of three commercial varieties, statistical parameters with ANOVA showed that, Acala SJ-2 genotype with greater mean fibre tenacity and elongation as well as less coefficient of variation of tenacity and elongation values before ginning treatment, maintains its higher rank position after the ginning treatment against its competitors Arba and DP-90. In this study, the variety Acala SJ-2 with greater single and bundle tenacity and elongation properties before ginning treatment was also favoured by having less amount of fibre breakage as well as relatively fewer levels of neps when compared against its competitor commercial varieties Arba and DP-90. This study shows that fibre data from single and bundle testing, before and after the application of ginning treatment, could be invaluable for the cotton breeders for cultivar selection and for the spinners to control cotton processability and improve quality of products.

Determination of the Response of Some Cotton Varieties to Cotton Wilt Disease Caused by Verticillium dahliae Kleb

Verticillium Wilt Disease is one of the most important diseases affecting the rate of cotton yield. There is no economic chemical control for Verticillium wilt, but it is recommended to use resistant varieties to control this disease. This experiment was carried out in a randomized plot design with four replications in the growth chamber to determine the response of some cotton cultivars against a defoliating and non-defoliating pathotypes of Verticilllium dahliae Kleb. In the study, a total of twenty cotton cultivars i.e. the resistant control GIZA 75, the tolerant control CARMEN and the susceptible control ACALA SJ2, defoliating (PYDV6 isolate) and non-defoliating (Vd 11 isolate) pathotypes were used, and cotton varieties were tested using conidial suspension technique. Analysis of variance showed significantly (P

Vegetative compatibility of cotton-defoliating Verticillium dahliae in Israel and its pathogenicity to various crop plants

Verticillium dahliae isolates recovered from a new focus of severe Verticillium wilt of cotton in the northeast of Israel were tested for vegetative compatibility using nitrate non-utilizing (nit) mutants and identified as VCG1, which is a new record in Israel. Other cotton isolates of V. dahliae from the northern and southern parts of the country were assigned to VCG2B and VCG4B, respectively. VCG1 isolates induced severe leaf symptoms, stunting and defoliation of cotton cv. Acala SJ-2, and thus were characterized as the cotton-defoliating (D) pathotype, whereas isolates of VCG2B and VCG4B were confirmed as the earlier described defoliating-like (DL) and non-defoliating (ND) pathotypes, respectively. This is the first record of the D-pathotype in Israel. The host range of representative isolates of each VCG-associated pathotype was investigated using a number of cultivated plants. Overall, the D isolates were more virulent than DL isolates on all tested host plants, but the order of hosts (from highly susceptible to resistant) was the same: okra (Hibiscus esculentus local cultivar), cotton (Gossypium hirsutum cv. Acala SJ2), watermelon (Citrullus lanatus cv. Crimson Sweet), safflower (Carthamus tinctorius cv. PI 251264), sunflower (Helianthus annuum cv. 2053), eggplant (Solanum melongena cv. Black Beauty), and tomato (Lycopersicon esculentum cv. Rehovot 13). The pattern of virulence of ND isolates differed from that of D and DL isolates, so that the former were highly virulent on eggplant but mildly virulent on cotton. Tomato was resistant to all cotton V. dahliae isolates tested. RAPD and specific PCR assays confirmed that the D isolates from Israel were similar to those originating from other countries.

A transgressive segregation factor (RKN2) in Gossypium barbadense for nematode resistance clusters with gene rkn1 in G. hirsutum

Host plant resistance is an important strategy for managing root-knot nematode (Meloidogyne incognita) in cotton (Gossypium L.). Here we report evidence for enhanced resistance in interspecific crosses resulting from transgressive segregation of clustered gene loci. Recently, a major gene, rkn1, on chromosome 11 for resistance to M. incognita in cv. Acala NemX was identified using an intraspecific G. hirsutum cross with susceptible cv. Acala SJ-2. Using interspecific crosses of Acala NemXxsusceptible G. barbadense cv. Pima S-7, F1, F2, F2:3, backcross, and testcross Acala NemXxF1 (Pima S-7xSJ-2), parental entries and populations were inoculated in greenhouse tests with M. incognita. Genetic analyses based on nematode-induced root galling and nematode egg production on roots, and molecular marker analysis of the segregating interspecific populations revealed that gene rkn1 interacted with a gene (designated as RKN2) in susceptible Pima S-7 to produce a highly resistant phenotype. RKN2 did not confer resistance in Pima S-7, but when combined with rkn1 (genotype Aa or aa), high levels of resistance were produced in the F1 and segregating F2, F3, and BC1F1 populations. One SSR marker MUCS088 was identified tightly linked to RKN2 within 4.4 cM in a NemXxF1 (Pima S-7xSJ-2) testcross population. Using mapped SSR markers and interspecific segregating populations, MUCS088 linked to the transgressive gene from the susceptible parent and was located in the vicinity of rkn1 on chromosome 11. Diverse genome analyses among A and D genome diploid and tetraploid cottons revealed that marker MUCS088 (165 and 167 bp) is derived from G. arboreum, A2 diploid genome. These results demonstrated that a highly susceptible parent contributed to nematode resistance via transgressive segregation. Derived highly resistant lines can be used as improved resistance sources in cotton breeding, and MUCS088 can be used to monitor RKN2 introgression in diverse populations. The close genomic location of the transgressive resistance determinants provides an important model system for studying transgressive segregation and epistasis in plants.

A Fusarium Wilt Resistance Gene in Gossypium barbadense and Its Effect on Root-Knot Nematode-Wilt Disease Complex

ABSTRACT Fusarium wilt, caused by the soilborne pathogen Fusarium oxysporum f. sp. vasinfectum race 1, is a vascular disease in cotton (Gossypium spp.), and is a component of a disease complex with root-knot nematodes (Meloidogyne incognita). Genetic analysis of two interspecific crosses (G. barbadense Pima S-7 x G. hirsutum Acala NemX and Pima S-7 x Acala SJ-2) showed that one major gene (designated Fov1) with allele dosage effect conferred resistance to F. oxysporum f. sp. vasinfectum race 1 in Pima S-7. Two amplified fragment length polymorphism (AFLP) markers were linked to Fov1 in Pima S-7, with genetic distance from the gene of 9.3 and 14.6 centimorgans. Less severe wilt symptoms in Acala NemX than Acala SJ-2 indicated that Acala NemX possesses one or more minor genes contributing to delay of wilt symptoms. Highly resistant plants in F(2) and F(3) (Pima S-7 x NemX) families indicated transgressive segregation effects of minor genes in Acala NemX combined with Fov1 from Pima S-7. The effects of wilt and nematode resistance on the nematode-wilt disease complex were assayed with two inoculation methods. In the presence of both pathogens, wilt damage measured as shoot and root weight reductions was greatest on wilt- and nematode-susceptible Acala SJ-2 and least in root-knot nematode-resistant and wilt-susceptible Acala NemX. Intermediate damage occurred in wilt-resistant and root-knot nematode-susceptible Pima S-7. The results indicated that nematode resistance was more effective than wilt resistance in suppressing wilt symptoms when either resistance was present alone. Nematode resistance combined with intermediate wilt resistance, as in the F(1) (Pima S-7 x NemX), was highly effective in protecting plants from root-knot nematodes and race 1 of Fusarium wilt as a disease complex.

First Record of Fusarium Wilt of Tobacco in Greece Imported as Seedborne Inoculum

Leaf yellowing and brown discoloration was observed in tobacco plants cv. Burley TN97 in tobacco fields of central Greece in 2002. Fusarium oxysporum f. sp. nicotianae was isolated from symptomatic plants and Koch's postulates were fulfilled. The pathogenicity of the isolated fungus was examined on five tobacco cultivars (Burley TN97, BurleyB21, VirginiaBE9, Virginia Niki and Anatolika KE26/2). The pathogen was present in tobacco seed batches imported in 2000 and 2001, which indicates that the infected seed is most probably the primary source of the disease in Greece. As Fusarium oxysporum f. sp. vasinfectum can also cause vascular wilt in tobacco, the hypothesis that the isolated F. oxysporum strain belongs to f. sp. vasinfectum was excluded by a pathogenicity test to cotton cv. Acala SJ-2. This is the first report of F. oxysporum f. sp. nicotianae in Greece and the second in the European Union, although the seedborne nature of the pathogen has not been previously reported in Europe.

Genetic and Virulence Diversity in Verticillium dahliae Populations Infecting Artichoke in Eastern-Central Spain

ABSTRACT Severe Verticillium dahliae attacks have occurred in artichoke crops in the Comunidad Valenciana region of eastern-central Spain since the late 1990s. Knowledge of genetic and virulence diversity in the pathogen population is a key factor for the management of the disease through disease risk assessment as well as development and use of resistant cultivars. V. dahliae isolates from artichoke (109 isolates) and cotton (three isolates) in that region were characterized by vegetative compatibility grouping (VCG), and specific polymerase chain reaction assays using three sets of primer pairs that differentiate the cotton-defoliating (D) and -nondefoliating (ND) V. dahliae pathotypes. In all, 35 and 39 V. dahliae isolates representative of the identified VCGs and geographic origins were tested for virulence to artichoke cvs. Nun 6374 and Nun 9444, and cotton cv. Acala SJ-2, respectively. Four VCGs were identified among 107 artichoke isolates, and 2 isolates were heterokaryon self-incompatible: VCG1A (one isolate), VCG2A (31 isolates), VCG2B (72 isolates), and VCG4B (three isolates). The three cotton isolates were VCG1A. Isolates in VCG2B were distributed across the region and were the most prevalent isolates in the northern part. Conversely, 83.9% of isolates in VCG2A were recovered from the southern part of the region. Two subgroups of isolates were identified in VCG2B based on heterokaryon compatibility with either international or local tester isolates, which further showed diversity in the amplification of 334- and 824-bp DNA fragments which are markers of the D and ND pathotypes, respectively. Virulence of isolates to artichoke and cotton correlated with VCG but the pattern of correlation varied with the host. VCG1A isolates from artichoke and cotton induced defoliation in cotton but not in artichoke. Collectively, isolates of VCG2B and VCG4B were the most virulent and isolates of VCG1A or HSI were the least virulent to artichoke; but isolates of VCG1A were more virulent to cotton than those of any other VCG. Also, molecular subgrouping in VCG2B determined by amplification of the 334- and 824-bp markers correlated with virulence of isolates to the two hosts tested.

Identification and mapping of microsatellite markers linked to a root-knot nematode resistance gene (rkn1) in Acala NemX cotton (Gossypium hirsutum L.)

Host-plant resistance is the most economic and effective strategy for root-knot nematode (RKN) Meloidogyne incognita control in cotton (Gossypium hirsutum L.). Molecular markers linked to resistance are important for incorporating resistance genes into elite cultivars. To screen for microsatellite markers (SSR) closely linked to RKN resistance in G. hirsutum cv. Acala NemX, F1, F2, BC1F1, and F2:7 recombinant inbred lines (RILs) from intraspecific crosses and an F2 from an interspecific cross with G. barbadense cv. Pima S-7 were used. Screening of 284 SSR markers, which cover all the known identified chromosomes and most linkage groups of cotton, was performed by bulked segregant analysis, revealing informative SSRs. The informative SSRs were then mapped on the above populations. One co-dominant SSR marker CIR316 was identified tightly linked to a major resistance gene (designated as rkn1), producing amplified DNA fragments of approximately 221 bp (CIR316a) and 210 bp (CIR316c) in Acala NemX and susceptible Acala SJ-2, respectively. The linkage between CIR316a marker and resistance gene rkn1 in Acala NemX had an estimated distance of 2.1-3.3 cM depending on the population used. Additional markers, including BNL1231 with loose linkage to rkn1 (map distance 25.1-27.4 cM), BNL1066, and CIR003 allowed the rkn1 gene to be mapped to cotton linkage group A03. This is the first report in cotton with a closely linked major gene locus determining nematode resistance, and informative SSRs may be used for marker-assisted selection.

Evaluation of Five Most Commonly Grown Cotton Cultivars (Gossypium hirsutum L.) Under Mediterranean Conditions: Productivity and Fibre Quality

AbstractStudies were conducted in four regions of central Greece (Larisa, Karditsa, Livadia, Thiva), to evaluate the productivity and fibre properties (fibre strength and fibre length) of the five most commonly grown cotton cultivars in these regions. The experiments lasted for 6 years (1995–2000). All the characteristics tested were strongly influenced by the factors ‘year’, ‘cultivar’ and ‘region’. Significant cultivar × region, year × cultivar, region × year and cultivar × region × year interactions occurred for all the characteristics studied. The cultivar Alegria had the highest seed‐cotton and lint yield, while Aria had the lowest ones. Both cultivars gave the highest mean lint percentage but the lowest mean boll weight (MBW). Alegria had the lowest fibre strength, while Aria had the highest. The Acala‐type cultivars, Acala SJ2 and Zeta 2, had intermediate seed‐cotton and lint yield, while Vered 171 had high seed‐cotton and satisfactory lint yield. The three cultivars mentioned above had the highest MBW and very good fibre strength. Positive correlation was observed between fibre strength and length. In spite of the fact that mean fibre length was statistically the same in all cultivars, it was influenced by the factor ‘year’, as a result of different weather conditions. The year 1996 was the most unfavourable one for seed‐cotton yield and MBW, because it was characterized by lower than average air temperatures and rather dry conditions for all study sites. The factor ‘region’, a combination of different climatic conditions and cultural practices, influenced significantly all the parameters studied.

Effectiveness of Entomopathogenic Nematodes in an Alginate Gel Formulation Against Lepidopterous Pests

An improved calcium alginate gel formulation was developed and tested as a carrier for entomopathogenic nematodes against Spodoptera littoralis and Helicoverpa armigera larvae. Mortality of 100% was caused in 4th instar larvae of the two insects by feeding them on 1000 infective juveniles (IJ) g -1 of Steinernema carpocapsae (ALL strain) in the gel for 24 h. Exposing 2nd to 5th instars of H. armigera and 3rd to 6th of S. littoralis to 500 IJ g -1 of S. carpocapsae (ALL strain) resulted in 70-100% larval mortality. Mature larvae were less susceptible to the nematodes. Mortality of larvae exposed to 500 IJg -1 of S. carpocapsae (ALL strain) ranged from about 45-55% at 4 h to 90-95% at 48 h. Fourth instar larvae fed for 24 h with 250 IJ g -1 of nematode strains in gel showed in S. littoralis ranges of susceptibility in the following descending order: S. feltiae (IS -7 strain) = S. carpocapsae (DT strain) = S. feltiae (IS-6 strain) > S. carpocapsae (Mexican strain) = S. carpocapsae (ALL strain) = Heterorhabditis bacteriophora (HP-88 strain) = H sp. (IS-5 strain) > S. riobravae (Texas strain); in H. armigera the rating was: S. feltiae (IS-7 strain) = H. bacteriophora (HP88 strain) > S. carpocapsae (ALL strain) = S. feltiae (IS-6 strain ) = Heterorhabditis sp. (IS5 strain) > S. carpocapsae (Mexican strain) > S. riobravae (Texas strain) . The number of nematodes per larval cadaver increased with mortality rates. In greenhouse tests at 28 - 2°C and 90% relative humidity, gel discs containing 500 IJ g -1 of nematodes were pinned to leaves of potted plants of cotton ( Gossypium hirsutum ) (Acala SJ2) and the plants were offered to S. littoralis larvae. Larval mortality of 89 - 12.7% was caused by S. feltiae (IS-7 strain) and most of the plant leaves were protected against the larvae by the nematodes. In the control, larval mortality was 3.3 - 0.05% and the plants were almost completely defoliated. Possibilities of using the gel-nematode formulation to protect sheltered crops against insect pests are discussed

Vegetative Compatibility Groups of Verticillium dahliae in Israel: Their Distribution and Association with Pathogenicity

A collection of 565 isolates of Verticillium dahliae, recovered between 1992 and 1997 from 13 host plant species and soil at 47 sites in Israel, was tested for vegetative compatibility using nitrate-nonutilizing (nit) mutants. Three vegetative compatibility groups (VCGs) were found and identified as VCG2A (28 isolates), VCG2B (158 isolates), and VCG4B (378 isolates) by using international reference strains. One isolate was heterokaryon self-incompatible. Of the VCG2B isolates, 92% were recovered from the northern part of Israel and 90% of VCG4B isolates were recovered from the south, with some overlap in the central region. Isolates of the minor group VCG2A were geographically scattered among the two major VCGs. Isolates of the same VCG resembled one another more than isolates from different VCGs based on colony and microsclerotial morphology, temperature responses, and, partially, pathogenicity. Different pathotypes were defined among 60 isolates tested, using cotton (cv. Acala SJ-2) and eggplant (cv. Black Beauty) as differentials. All isolates in VCG2A and 86% of the isolates in VCG4B, irrespective of their origin, induced weak to moderate symptoms on cotton and moderate to severe symptoms on eggplant and were similar to the previously described cotton nondefoliating patho-type. In contrast, all cotton isolates in VCG2B caused severe foliar symptoms, stunting, and often death, but little or no defoliation of inoculated cotton plants. These were defined as a cotton defoliating-like pathotype and induced only weak to moderate symptoms on eggplant. We concluded that vegetative compatibility grouping of V. dahliae in Israel is closely associated with specific pathogenicity and other phenotypic traits.

Cytochemistry of developing cotton fibers:: A hypothesized relationship between motes and non-dyeing fibers

Developing lint fibers from normally developing seeds and from motes of Upland cotton ( Gossypium hirsutum L. cv Acala SJ2 and cv Acala Maxxa) were compared with respect to cell wall cytochemistry. Fibers from motes (unfertilized ovules or aborted seeds) were used as a model for non-dyeing fibers, a contributor to poor quality textiles. Primary and secondary fiber walls were stained for pectin, cutin, suberin, callose, and cellulose. Up to 25 days post-anthesis (DPA), mote fibers had pectinaceous primary walls with a thin layer of cellulose, indistinguishable from primary walls of normally developing fibers. However, secondary walls in mote fibers had scanty, irregularly deposited cellulose, while secondary walls in normal fibers were well developed with thick cellulosic layers. At 29 DPA and at later stages of development, fibers on normal seeds had well-developed secondary walls, which were proportionally less developed on medium-sized and small motes. Nonetheless, fibers, which varied in diameter and cell wall thickness, were found on all normal seeds, on medium-sized and on small motes; most fiber cell walls were smaller in thickness at the chalazal than at the micropylar end. Regardless of their thickness, fibers on seeds and motes had cellulosic secondary cell walls. As most industrial dyes are specific for cellulose, the paucity of cellulose in mote fibers is consistent with the suggested causal relationship between lack of cellulose and the non-dyeing nature of some fibers. There were indications that immature fibers at the chalazal end of seeds may also contribute to dye imperfections in fabrics.

Dyeing Characteristics of Acala Cotton Seed Fibers

The dyeing characteristics of fibers from three Acala cotton varieties, i.e., Maxxa, SJ-2, and SJC-9, are investigated using direct and reactive dyestuffs along with the Goldthwait cotton maturity test. Dyed and less-dyed fibers are detached from the dyed seed fibers, separated, and characterized by seed fiber weight, single fiber strength, and color measurement. With Direct Blue 1, SJC-9 fibers are dyed to the darkest shade across all seed fiber weights, whereas the Maxxa fibers have the lightest shade. The SJC-9 seed fibers have the least amounts ( ~5%) of less-dyed fibers and the proportions of such fibers are independent of seed fiber weights. For the Maxxa and SJ-2 varieties, the proportions of less-dyed fibers decrease with increasing seed fiber weights. The proportions of less-dyed Maxxa and SJ-2 fibers are above 30% on seed fibers weighing less than 100 mg and are 10% or less on seeds weighing more than 150 mg. The SJ- 2 seed fibers contain higher proportions of less-dyed fibers, but their overall shades are deeper than the Maxxa fibers. For all three varieties, most less-dyed fibers are from the chalazal ends of the seeds of all seed fiber weights. Dyeing with Reactive Blue 19 results in the same proportions of less-dyed fibers on the Maxxa seed fibers as with Direct Blue 1. The Goldthwait cotton maturity test confirms the trend of decreasing amounts of less-dyed fibers with increasing seed fiber weight with both direct and reactive dyes. For all three varieties, the force to break is higher for the dyed fibers than the less-dyed fibers, confirming that less-dyed fibers have less developed cell wall structures.

On the correlation of primary root growth and tracheary element size and distance from the tip in cotton seedlings grown under salinity

Cotton seedlings ( Gossypium hirsutum L. cv. Acala SJ-2) were germinated and grown in vermiculite for 7 days, at 1–150 mM NaCl salinity. Primary root samples were harvested daily, root lengths measured and, after clearing and staining, the distance from the root tip to the closest protoxylem tracheary element (PTE) secondary cell wall depositions was determined. The length of control roots correlated with the PTE distance and the root elongation rate. Initially, as roots became longer, elongation rates increased and so did the distance for PTE secondary wall depositions. The highest elongation rates and the farthest PTE distances were reached for 75–125 mm long roots. Thereafter, as root length increased, the PTE distance and growth rates dropped gradually. A high linear correlation between the distance for PTE secondary wall depositions and the root growth rate was obtained for control plants (up to 200 mm long) over the experimental period. This correlation was weakened by rising salinity. At 150 mM NaCl no such correlation was found. Salinity resulted in PTE distances closer to the tip in roots of intermediate length (50–150 mm). In longer and in shorter roots, salinity did not affect the distance from the root tip for PTE secondary wall depositions. Vermiculite-grown seedlings, 4–11 days old, were used to assess the effects of 200 mM NaCl salinity on the development of metaxylem vessel members (MVMs). In macerated stele samples from regions close to the root base, the dimensions of MVMs were measured. High salinity resulted in reductions of both width and length of MVMs, and this inhibition increased with plant age. Large, central MVMs matured mostly earlier in control plants than in salt-stressed plants.

Salinity accelerates endodermal development and induces an exodermis in cotton seedling roots

The development of the endodermis was studied in 5- to 48-day-old cotton ( Gossypium hirsutum L., cv. Acala SJ-2) seedling roots grown in vermiculite at different NaCl salinity levels. Sensitive fluorochromes (berberine-aniline blue for Casparian bands, and fluorol yellow-aniline blue for suberin lamellae) were used to detect cell wall modifications. Endodermal cells progressed through several developmental stages. In the primary stage, endodermal Casparian bands appeared synchronously in the radial walls. Then, suberin lamellae were laid down asynchronously in all cell walls, but always first in endodermal cells in the phloem sectors. Passage cells without suberin lamellae were usually present in the endodermal layer opposite protoxylem poles. The positions relative to the root tip at which Casparian bands and suberin lamellae developed were dependent on plant age and primary root length for control and salt-stressed seedlings. Salinity induced those structures to mature closer to the root tip for plants up to 10 days old, whereas in older plants no differences between treatments were observed. Exposure to high salinity (200 mM NaCl) induced the formation of an exodermis with Casparian bands and suberin lamellae close to the root base and in the transition zone to the hypocotyl. The exodermis, which never developed in control roots, may play a role in protecting the root from water loss and/or leakage of solutes important for osmotic adjustment. An exodermis was detected in 5- to 28-day-old seedlings. Older plants (48 days), with advanced secondary growth in the root stele, did not differentiate an exodermis.