Seeds Of Cv Research Articles

First Report of Fusarium Wilt of Basil Caused by Fusarium oxysporum f. sp. basilici in Argentina

Annually, ~20 ha of sweet basil (Ocimum basilicum L.) are cultivated in greenhouses in the green belt area surrounding La Plata, Argentina, mainly for fresh consumption. In 2004 to 2007, basil plants of cv. Genovese showed wilt symptoms, necrosis of leaves and stems, asymmetrical growth, and discolored vascular tissue in greenhouses in La Plata. In 2007, the same symptoms were observed on plants of cv. Morada grown from seeds that were produced in Italy. Isolations were completed from root, crown, and stem sections of diseased plants of cv. Genovese from three greenhouses in 2004 to 2007, and from commercial seeds, stem sections, flowers, and seeds of diseased plants of cv. Morada in 2007. Seeds and portions of symptomatic tissues were surface-disinfested with 0.5% NaOCl for 1 min, rinsed in sterilized distilled water, air dried, and plated on 2% potato dextrose agar (PDA). Twenty-seven isolates were identified as Fusarium oxysporum Schltdl. based on morphological characteristics (4), and the species identification confirmed by PCR assay using a F. oxysporum f. sp. basilici-specific primer pair, Bik 1 and Bik 2 (1). Vegetative compatibility groups (VCGs) were determined for the 27 isolates through complementation of nitrate-nonutilizing mutants generated from these isolates (2) and paired with two Italian tester strains from an international collection (PVS-Fu 220 and PVS-Fu 125, provided by V. Balmas, Univeristà degli Studi di Sassari, Italy). All 27 isolates from Argentina belonged to VCG 0200. This is a unique VCG for F. oxysporum f. sp. basilici and has been identified in Israeli, American, and Italian isolates of the fungus (3). To fulfill Koch's postulates, pathogenicity tests were conducted with 12 isolates selected to reflect the multiple sources of fungal recovery, including root, crown, and stem sections, and leaves of diseased plants of cv. Genovese and commercial seeds, stem sections, flowers, and seeds of cv. Morada. Isolates were each grown on moistened (40% w/w), autoclaved, polished rice for 10 days, dried, and ground in a grinder. The number of CFU/g rice was determined by serial dilution plating onto PDA plates. The inoculum was added to autoclaved soil at 104 CFU/g dry soil. For each isolate, 8 healthy basil seedlings of each of cvs. Genovese and Morada were planted in pots, each containing 1 liter of inoculated soil. The control treatment consisted of 8 basil seedlings of each of the same cultivars planted in autoclaved soil mixed with sterilized, ground, polished rice. Plants were grown in a greenhouse with natural daylight for 45 to 50 days after inoculation. All inoculated plants showed the same symptoms described for the original basil plants. No symptoms were observed on the control plants. F. oxysporum f. sp. basilici was re-isolated from the vascular tissue of stems of symptomatic plants but not from control plants, and species identification confirmed by PCR assay as previously described. The presence of the pathogen was verified in the seed lot produced in Italy, suggesting that this could have been a source of inoculum that introduced the pathogen into La Plata, Argentina, as supported by the hypothesis that infested seed resulted in spread of a clonal population of F. oxysporum f. sp. basilici internationally (1). To our knowledge, this is the first report of F. oxysporum f. sp. basilici infecting sweet basil in Argentina.

Yariability of dry seed mycobiota of Pisum sativum

Mycobiota of dry pea seeds of cv. Ramir and line R 429/87 harvested at Radzików, Oleśnica Mała and Łagiewniki in 1991—93 was investigated. Among twenty species <i>Alternaria aliernata</i> and <i>Stemphylium botryosum</i> occurred commonly each year. <i>Mycosphaerella pinodes, Ascochyta pisi, Fusarium poae</i> and <i>Cladosporium herbarum</i> were noted on most of the tested seed samples. Percentage of sccee transmitting the fungi varied depending on locations, time and genotypes, being the lowest for Łagiewniki and in 1992. The year 1991 was the most favourable for seed mycobiota development, especially for pathogenic fungi.

The white-tip nematode, Aphelenchoides besseyi, exhibits an auxin-orientated behaviour affecting its migration and propagation

Aphelenchoides besseyiis an obligate parasite that often causes white-tip symptoms in rice plants. The nematode exhibits ectoparasitic behaviour with its infection rate matching the development of rice plants. Few studies have analysed howA. besseyimigration is influenced by chemical and host factors. Here, we focused on the effects of auxins on nematode migration and propagation. Exposure ofA. besseyito an auxin gradient created by a Pluronic F-127 gel resulted in nematode aggregation at the highest auxin concentration tested, 100 μm. Inoculation on the susceptible cv. Ningjing1 produced more nematodes than on the resistant rice cv. Tetep, which correlated with their endogenous auxin levels. Young panicles treated with 1-naphthaleneacetic acid produced more grains and nematodes, whereas plants treated with the auxin transport inhibitor, 2,3,5-triiodobenzoic acid, led to fewer nematodes in the seeds. In addition,A. besseyirarely migrated and multiplied in the plants of the male sterile rice cv. Zhenshan97A, which had insufficient auxin level in pollen and thus could not generate any grains in most panicles. However, large numbers of nematodes were observed in seeds of cv. Zhenshan97A that had received pollens from the maintainer cv. Zhenshan97B. The results indicate that auxin might play a key role in the migration and propagation ofA. besseyi.

Gibberellic Acid Sensitivity among Common Bean Cultivars (Phaseolus vulgaris L.)

To lower seed yield loss from directly harvested common bean or dry bean, height of the lower pod-bearing nodes needs to be raised. The objective of this greenhouse study was to stimulate lower stem elongation by gibberellic acid (GA3) of dry bean cultivars. Seeds of cv. Matterhorn, erect indeterminate Type II, and cv. Poncho, prostate indeterminate Type III, were dipped in GA3 at 62.5 to 16,000 ppm and planted. After 14 d, the height of the unifoliate and first trifoliate nodes showed maximum stimulation of stem elongation by 1000 ppm GA3 for ‘Poncho’ and by 2000 ppm for ‘Matterhorn’. Application of 1 mL of GA3 at 0.031 to 2048 ppm to newly expanded unifoliate leaves showed cultivar differences. Whereas ‘Matterhorn’ was promoted at 64 ppm and reached a maximum height by 512 ppm GA3, ‘Poncho’ was promoted at 0.25 ppm and reached a maximum height by 8 ppm GA3. Flowering of ‘Matterhorn’ was unaffected by GA3; flowering of ‘Poncho’ was completely inhibited by 128 ppm. The sensitivity difference of cultivars was verified with other cultivars. Type I cultivars, which are all determinate, showed a full range of GA3 sensitivity. Dry bean cultivars may be regrouped based on the GA3 dose to which they respond. Individual response to GA3 rates of dry bean cultivars needs to be predetermined using a short-term, 2–3 weeks, greenhouse bioassay before field use of GA3.

Shaping of the fungal communities isolated from yellow lupin seeds (Lupinus luteus L.) throughout storage time

The object of the experiment were seeds of two traditional cultivars of yellow lupin (Juno and Amulet) cultivated in 1999 in two crop-rotation with 20% and 33% yellow lupine contribution. The quantitative and qualitative composition of the fungal community colonizing the seeds were determined in the laboratory conditions after 0.5-, 1.5- and 2.5-year of storage time. In total 1077 fungal colonies were isolated from the lupin seeds. Fungi representing the species of <i>Penicillium</i> - 29.3%, <i>Alternaria alternata</i> - 26.7% and <i>Rhizopus nigricans</i> - 12.7% were isolated most widely. Among the fungi pathogenic to lupin, the species of <i>Colletotrichum gloeosporioides</i> (16.3% isolates) was dominant. The crop rotation with 20% lupin reduced the number of fungal colonies colonizing the seeds including the pathogens from the species of <i>C. gloeosporioides</i>. Seed disinfection decreased the total number of fungal colonies isolated from both cultivars. Higher number of <i>C. gloeosporioides</i> isolates was found in the combination with disinfected seeds. More fungal colonies were obtained from seeds of cv. Amulet than from those of cv. Juno. The storage duration had an effect on the population and the composition of species of fungi isolated from seeds of yellow lupine. With longer storage population of <i>Penicillium</i> spp. and <i>Rhizopus</i> spp. increased, whereas the population of <i>C. gloeosporioides</i> decreased.

Blackberry Seed Extracts and Isolated Polyphenolic Compounds Showing Protective Effect on Human Lymphocytes DNA

The tentative identification of seed extracts from 3 cultivars of blackberry (blackberry seed extracts [BSEs]) constituents was performed by LC/UV/MS technique. The identified compounds belonged to ellagitannins, galic acid derivatives, and ellagic acid derivatives. Two ellagitannins, Lambertianin C and Sanguiniin H-6, and an ellagic acid derivative, 4-α-L-arabinofuranosylellagic acid, were isolated using semipreparative High-performance liquid chromatography. The structure elucidations were based on high resolution-mass spectrometry and nuclear magnetic resonance studies. The BSEs and 3 isolated pure compounds were tested for in vitro protective effect on chromosome aberrations in peripheral human lymphocytes using cytochalasin-B blocked micronucleus (MN) assay. The frequency of MN was scored in binucleated cells, and nuclear proliferation index was calculated. Among the tested extracts, the seeds of cv. Thornfree at concentration of 1 μg/mL exhibit the most prominent effect decreasing the frequency of MN by 62.4%, when compared with the controls cell cultures. Antioxidant potential of pure ellagitannins cannot explain the strong effect of BSEs. The assumption was that better antioxidant effect of BSEs result from synergistic effects of individual compounds contained in the extracts and/or some minor components possessed strong activity. PraCTICAL APPLICATION: Our results provide evidence of protective effects of BSEs and isolated pure compounds on cytogenetic damages in human lymphocytes. Thus, BSEs could exert beneficial effects in quite a few diseases, because many of the biological actions have been attributed to their antioxidant properties.

Mutations modulate soluble carbohydrates composition in seeds of Lathyrus sativus L.

Seeds of <em>Lathyrus sativus</em> cv. Derek and Krab were used as biological material for induced mutagenesis. Three mutant lines were obtained from seeds of grass pea cv. Derek and 15 lines from mutagenised seeds of cv. Krab. Twelve ethanol-soluble carbohydrates were identified in the seeds. We have selected grass pea mutant lines with high oligosaccharides content (lines D4, K56, K25, and K7) and lines with low raffinose family oligosaccharides (RFO) content (lines K12, K29 and K13). Mutations changing the levels of RFO have not affected the contents of galactosyl cyclitols.

Condicionamento fisiológico de sementes de couve-flor

Esta pesquisa teve como objetivos definir o procedimento para o condicionamento fisiológico de sementes de couve-flor e verificar a influência do potencial fisiológico das sementes sobre os resultados desse tratamento. Seis lotes de sementes, três da cultivar Sharon e três da cultivar Teresópolis Gigante, foram submetidos ao hidrocondicionamento entre camadas de duas, quatro e seis folhas de papel toalha e ao osmocondicionamento entre camadas de quatro folhas de papel toalha umedecidas com solução de polietilenoglicol 6000 (potenciais de -0,1 e -0,2 MPa). Em todos os procedimentos os teores de água foram ajustados para 32 e 38%, para a cultivar Sharon, e 34 e 41% para a cultivar Teresópolis Gigante. Os efeitos dos tratamentos sobre a germinação e emergência das plântulas foram comparados à testemunha (sem condicionamento). O hidrocondicionamento entre quatro e seis folhas, até a obtenção dos teores de água mais elevados, beneficiou a velocidade de germinação (VG) e a de emergência de plântulas (VE), nas duas cultivares. Na cultivar Sharon a VG foi de 14,6 (testemunha) em comparação a 16,4 nas sementes hidrocondicionadas, para os lotes de maior e menor potencial fisiológico; paralelamente, os valores da VE aumentaram de 8,9 para 11,2 e de 7,8 para 11,6, nos lotes de menor potencial fisiológico. Para a cultivar Teresópolis Gigante, a VG e a VE foram favorecidas pelo hidrocondicionamento, independentemente do potencial fisiológico dos lotes (a VG aumentou de 16,4 para 21,4 e, a VE, de 9,5 para 13,5). Conclui-se que o hidrocondicionamento entre quatro e seis folhas de papel toalha, até a obtenção de teores de água próximos aos da emissão da raiz primária é favorável à velocidade de germinação e de emergência de plântulas em couve-flor e que o potencial fisológico inicial dos lotes pode influenciar a resposta ao condicionamento fisiológico, dependendo da cultivar ou histórico dos lotes.

THE INFLUENCE OF DIFFERENT SUBSTRATE COMPOSITION ON GROWTH PARAMETERS AND DRY MASS PARTITIONING OF CUCUMBER (CUCUMIS SATIVUM L.) SEEDLINGS

The influences of substrate composition on growth parameters and dry mass portioning of cucumber (Cucumis sativum L.) seedlings were estimated in an experiment conducted in a plastic greenhouse. Graded seeds of cv. Ekron F1, were individually seeded in foam trays filled with different substrates, namely peat compost (Klassmann product), vermin compost (locally produced) and a mixture (50 % to 50%) of peat compost and vermin compost. Plants were equally irrigated, but no additional nutrient elements were supplied during the experiment time. Roots, stems and leaf dry matter were weighted and stem length and plant leaf area was successfully measured after the first and the second true leafs were appeared. Based on that data, the relative growth rates (RGR) and its components; net assimilation rate (NAR) and leaf area ratio (LAR) were computed. The relative stem elongation rate (RSER), the relative leaf expansion rate (RLER), root to whole plant dry weight ratio (RWR), root to shoot dry weight ratio (RSR), and the respective fractions of roots, stems and leaf dry mass against total plant weight (RMF, SMF, LMF) were also calculated for each experimental plot. A significantly higher relative growth rate (RGR) was found for young seedlings grown in vermin compost compared to commercial peat compost. Though there was a difference on net assimilation rate (the physiological component of RGR), the increased growth rate was mostly due to differences found for leaf assimilation ratio (the morphological component of RGR). Higher dry matter per plant, higher relative stem elongation rate and higher relative leaf expansion rate were found for vermin compost, but no effect was found regarding dry mass partitioning of young cucumber seedlings.

Studies on genetic transformation of olive (Olea europaea L.) somatic embryos: I. Evaluation of different aminoglycoside antibiotics for nptII selection; II. Transient transformation via particle bombardment

As a first step to the establishment of a genetic transformation protocol for olive somatic embryos obtained from the seeds of cv. 'Picual', the efficiencies of different aminoglycoside antibiotics as selective agents to be used with the nptII marker gene, and the particle bombardment technique for transient transformation have been evaluated. Among the three antibiotics tested, paromomycin and kanamycin showed a similar inhibitory effect and, at 200 mg l -1 , both of them impaired callus growth after 8 weeks of culture. However, when isolated embryos were cultured in the presence of these antibiotics, a 20% of the embryos still remained viable at 400 mg l -1 . Neomycin was discarded as a selective agent since it showed only a mod- erate toxic effect. Contrary to solid medium, when olive callus was cultured in liquid medium supplemented with different paromomycin concentrations for 3 weeks, the callus growth was impaired at the lowest antibiotic concentration, 3 mg l -1 . Best conditions for transient transformation of olive callus using PDS-1000/He system were a 6 cm target distance and a 900 psi bombardment pressure. pCGUD1 plasmid, containing the gus gene under the control of sunflower ubiquitin promoter yielded a sig- nificantly higher number of gus expression areas per bombarded explant than pGUSINT or pJGUS5 plasmids, where the gus gene is driven by CaMV35S promoter or CaMV35S with enhancer, respectively. Almost 45% of bombarded explants showed gus expression 12 weeks after

N AND CA CONCENTRATION OF PRE TRANSPLANT NUTRIENT SOLUTION EFFECTS ON THE STAND ESTABLISHMENT RATE OF PEPPER (C. ANNUM. L) SEEDLINGS UNDER SALINE CONDITIONS

N AND CA CONCENTRATION OF PRE TRANSPLANT NUTRIENT SOLUTION EFFECTS ON THE STAND ESTABLISHMENT RATE OF PEPPER (C. ANNUM. L) SEEDLINGS UNDER SALINE CONDITIONS

Maternal Light Environment During Seed Development Affects Lettuce Seed Weight, Germinability, and Storability

Seed germinability and storability are important aspects of seed quality determined by the genotype and environment of seed development. Lettuce (Lactuca sativa L.) is produced commercially in most temperate and subtropical areas of the world. The objective of this study was to determine how photoperiod and light quality of the mother plant environment affects lettuce seed quality. Seeds of cv. Tango were produced in growth chambers under one of two treatments: a) short day (SD), consisting of 8 hours of fluorescent light (≈310 μmol·m−2·s−1) plus 16 hours of darkness daily, and b) long day (LD), consisting of 4 hours of incandescent light (≈21 μmol·m−2·s−1), 8 hours of fluorescent light, 4 hours of incandescent light, and 8 hours of darkness daily. The red to far-red ratio was ≈6.8 and 1.0 for the fluorescent and incandescent light, respectively. In both treatments, the temperature was 23 °C. The LD treatment produced significantly heavier seeds; however, germination at optimal conditions (20 °C-light) was similar for both treatments. Germinability (percentage and rates) at suboptimal conditions (30 °C, 20 °C with different external ABA concentrations, negative osmotic potentials, or dark) was higher for seeds produced under the LD treatment. On the other hand, seeds produced under the LD treatment presented better storability (evaluated by the accelerated aging test and standard germination after storage at 30 °C and 74% RH). The critical period for light environment effects was also studied. Seed weight patterns were determined early in seed development, during the first 6 days after flowering. Conversely, light environment effects on seed germinability and storability were determined at the end of seed development, after physiological maturity, which occurred by 11 days after flowering. These results show that lettuce seed germinability and storability may be modified by management of light conditions during seed production and provide useful information for seed producers, seed companies, and seed conservation institutions.

Avocado Dieback Caused by Neofusicoccum parvum in the Andalucia Region, Spain.

From 2002 to 2006, adult avocado trees, Persea americana Miller cv. Hass, located in the subtropical-fruit-producing area of Andalucia (southern Spain) developed symptoms of dieback characterized by death of twigs and branches in the tree canopy. Sections of surface-disinfested, necrotic branch tissues were plated on Difco potato dextrose agar (PDA) (Sparks, NV) and a Neofusicoccum-like fungus was isolated. On PDA, the isolates had white, appressed mycelium that turned dull gray as the colony aged, although conidia were not formed. Abundant pycnidia and conidia developed when isolates were cultured on 2% water agar with sterilized pine needles as substratum at 25°C under near-UV light for 2 weeks. Conidia were hyaline, unicellular, ellipsoid with an obtuse apex and subtruncate base, averaged 16.2 μm long by 5.8 μm wide and ranged from 12.0 to 20.0 by 4.0 to 8.0 μm, and becoming brown with one or two septa with age. Sequenced rDNA fragments (ITS1, 5.8S rDNA, and ITS2, amplified with ITS1 and ITS4 primers) of two avocado isolates were 100% homologous with Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers, & A.J.L. Phillips (1) (GenBank Accession Nos. AM410965 and AM410966). Morphological and molecular results confirmed this species as N. parvum, reported as the anamorph of Botryosphaeria parva (1). A pathogenicity test was conducted using two isolates on sets of five 2-year-old avocado plants produced from seeds of cv. Topa-Topa growing in 5-liter pots with soil. Unwounded and wounded plants were used for inoculations. Plants were wounded 2 to 3 cm below the apical tip with a lance (4 mm long and 1 mm deep). For inoculation, 4-mm 2-week-old PDA culture plugs were placed in contact with wounded tissues and covered with Parafilm. Five noninoculated plants treated similarly served as controls. Plants were maintained in the greenhouse with a temperature range of 18 to 26°C, and 1 month later, brown stem lesions, as much as 5 cm, originating from the inoculation site followed by dieback of branches were observed. Reisolations from necrotic branches were successful, and both isolates with identical morphology to those used for inoculations were recovered. Pathogenicity tests of seedlings using the same methods also caused stem lesions on unwounded plants and the pathogen was reisolated. To our knowledge, this is the first report of N. parvum causing dieback of avocado trees in Spain. Previously, B. parva has been reported causing stem-end rot of avocado fruit in New Zealand (2). In Spain, since diseased orchards are increasing rapidly, this pathogen could be efficiently distributed by pruning activities (tools and vegetal debris) as observed with other diseases (3). The presence of N. parvum in this subtropical area presents a serious disease problem not only to avocado but also to mango (Mangifera indica L.), which is another susceptible host (4).

Nematofauna fitopatogênica de sementes comerciais de forrageiras tropicais

O objetivo deste trabalho foi identificar e quantificar a nematofauna fitopatogênica de sementes de forrageiras, destinadas aos mercados interno e externo. Examinaram-se sementes de Brachiaria brizantha (cvs. Marandu e Xaraés), B. decumbens cv. Basilisk, Panicum maximum (cvs. Massai, Mombaça e Tanzânia) e Stylosanthes capitata e S. macrocephala, componentes da cultivar Estilosantes Campo Grande. As extrações foram realizadas por flotação centrífuga, em solução de sacarose com caulim. Nas gramíneas, encontraram-se os gêneros Aphelenchoides e Ditylenchus. O maior número de espécimes de Aphelenchoides spp. foi observado nas sementes de 'Marandu', e, em seguida, nas sementes de 'Xaraés', 'Basilisk' e 'Tanzânia'. Quanto à densidade populacional de Ditylenchus spp., os maiores valores foram observados nas sementes de 'Marandu', 'Xaraés' e 'Basilisk'. Os resultados sugerem que pelo menos duas espécies de Aphelenchoides e Ditylenchus estão associadas às sementes de gramíneas forrageiras, destinadas ao mercado interno. Fitonematóides não são detectados em sementes de 'Estilosantes Campo Grande', tampouco nas cultivares Marandu, Mombaça e Tanzânia, destinadas à exportação.

Comparison of the Phosphorus and Mineral Concentrations in Bran and Abraded Kernel Fractions of a Normal Barley (Hordeum vulgare) Cultivar versus Four Low Phytic Acid Isolines

Phytic acid consists of 65-80% of the total phosphorus (P) in cereal grains. Its salts are concentrated in the germ and aleurone layers, which are typically removed during milling. We hypothesize that concentrations of different types of P and minerals in milled products will be greatly altered in low phytic acid (lpa) barleys. Seeds of cv. Harrington (control) and four lpa isolines-lpa1-1, lpa2-1, lpa3-1, and M955-were abraded by a laboratory method into five surface layer and four remaining kernel fractions. Results show that phytic acid in the four lpa lines ranged from 75% to 5% of the control. The decrease in phytic acid P concentration was matched almost equally by an increase in inorganic P, so that the rest of P (the sum of all P-containing compounds other than phytic acid P and inorganic P) and total P levels remained relatively unchanged among the five genotypes. These trends were also observed for the processed fractions. The major mineral elements in barley seeds were P, K, Mg, S, and Ca, while minor ones were Fe, Zn, Mn, Cu, and Ba. All types of P and other minerals measured were generally concentrated in the outer layers of the grain. Although there were substantial differences in mineral contents of bran fractions among genotypes, the level of phytic acid P had little effect on mineral contents in whole or abraded kernels. One major exception was Fe, which had the highest level in all tissues of M955 genotype. The above findings were all confirmed by analyzing another set of barley samples grown in a different environment. Thus, in general, breeding lpa barleys does not lead to reduced mineral contents in whole grains or elevated mineral levels in milled products.

Differences in the Development of Lateral Roots among Several Cultivars in Japanese Radishes (Raphanus sativus L.) under Low Temperature Condition

Seeds of cv. T-340 were sown in the field on 10 March and 9 April 1997. The lateral root (LR) production was progressively intensified in early sown plot (ESP) instead of late (LSP). Plants in the ESP produced roots with small mean weights, diameter and length as compared with those in the LSP. Early-sown seedlings were subjected to low soil temperature conditions, below approximately 12°C during the first growth stage. In a second experiment, seeds of cvs. T-340 and T-396 were sown in 2 experimental plots: a control plot and a high soil temperature plot (HTP). The minimum soil temperatures in the control were often remained below 10°C for about 25 days after sowing, but the temperatures in the HTP kept above 15°C during the growth period. When grown under the control, larger number of thickened LRs was observed in roots of cv. T-340, but roots of cv. T-396 did not exhibit this disorder at any soil temperature plot. In both cvs., hinder root elongation was observed in the control as compared with the HTP. In a third experiment, varietal difference in the occurrence of LR in roots of cvs. Oshin, T-340, T-396 and Tenpou was compared. Although no correlation was observed between the different cvs. and root growth, active meristematic activity was observed in the pericycle region outside the protoxylem in roots of susceptible cvs. Oshin and T-340. Conversely, this meristematic activity remained low in roots of resilient cvs. T-396 and Tenpou. These observations led to the hypothesis that the obstruction of root elongation caused by low soil temperatures (below 12°C) during the first growth period often results in activation of the basal region of the LR meristem in susceptible cvs. prompting LR development. However, in resilient cvs., the LR seldom occur, even when root elongation is inhibited by low soil temperatures that normally decrease the meristematic activity of this region.

Mechanism of seed dormancy in eggplant (Solanum melongena L.)

Seed dormancy was observed in fresh seeds of eggplant cultivars, Arka Neelkant and Arka Keshav, derived from the same parentage. The germination of 2-month-old seeds of cv. Arka Keshav and Arka Neelkant was 0 and 2%, respectively, revealing the presence of dormancy. There was a gradual decline in the seed dormancy with the ageing of seeds under ambient conditions and complete breakdown of dormancy occurred after 12 months of storage. Abscisic acid (ABA) concentration in the 2-month-old seeds of dormant cv. Arka Neelkant and Arka Keshav was nearly 2-fold higher than the non-dormant cv. Manjarigota. ABA concentration in seeds declined considerably after 12 months of storage. Soaking of fresh seeds in GA3 (725 μM) solution for 3 and 24 hours was effective in removing seed dormancy in Arka Neelkant and Arka Keshav, respectively.

Calorimetric studies of quinoa ( Chenopodium quinoa Willd.) seed germination under saline stress conditions

Most crops in saline environments are negatively affected in their rate of growth. This effect is attributed either to osmotic causes or to ion toxicity depending on the plant species, salt composition and salt concentration. Species of the Chenopodiaceae family are considered to be resistant to this type of stress. Two cultivars of quinoa ( Chenopodium quinoa Willd.), an ancestral crop from the Andes of South America with a high nutritional value are evaluated for tolerance to saline stress by calorimetric experiments of seed germination carried out at 24.7 °C in NaCl, KCl, Na 2SO 4, K 2SO 4 and Na 2CO 3 solutions. Also, 0.1 mM HgCl 2 was used in combination with the salts to evaluate the possible existence of channels blocked by the mercurial reagent involved in the transport of ions. Results indicate that seeds of cv. Robura are less tolerant to saline stress than are seeds of cv. Sajama with a tolerance limit for seeds of the former cultivar of 100 mM NaCl. Above this concentration there is an apparent expression of proteins bearing –SH groups that block influx of NaCl, which are inhibited by 0.1 mM HgCl 2.

Lipid Peroxidation and Peroxide-Scavenging Enzymes in Cotton Seeds Under Natural Ageing

The present study was carried out to contribute to our knowledge of the mechanism of seed deterioration in two cotton (Gossypium hirsutum L.) cultivars (HS6 and H1098) during natural ageing. The seeds were sealed in polythene bags and stored at 25 ± 1 °C for 3, 6, 9, 12 and 18 months. In both the cultivars, germinability decreased whereas membrane deterioration assayed as electrical conductivity of the seed leachates increased with storage period. The decrease in germinability was well correlated with increased accumulation of H2O2 and malondialdehyde content. The activities of peroxidase, catalase, ascorbate peroxidase, glutathione reductase and superoxide dismutase decreased with ageing. Seeds of cv. H1098 were more susceptible to ageing than HS6.

First Report of Fusarium Wilt of Lettuce Caused by Fusarium oxysporum f. sp. lactucae in Arizona.

A new wilt and root rot disease was observed in 6 and 11 commercial fields of lettuce (Lactuca sativa) in western Arizona during the fall of 2001 and 2002, respectively. Distance between infested sites ranged from approximately 0.5 to 39 km. Five head lettuce cultivars as well as a red leaf lettuce cultivar were affected. Disease symptoms included yellowing and wilting of leaves, as well as stunting and plant death. The cortex of the crown and upper root of infected plants usually was decayed and reddish brown. Disease symptoms first appeared at the time of plant thinning and continued to develop up to plant maturity. Fusarium oxysporum was consistently isolated from symptomatic plant roots. Seeds of cv. Lighthouse were planted in nonsterile vermiculite within 3.0-cm-square × 7.0-cm-deep cells in a transplant tray and thinned to a single plant per cell. When the first true leaves were emerging, 10 individual seedlings were inoculated with a single-spore isolate of F. oxysporum recovered from diseased lettuce root cortex tissue. Inoculum was prepared by growing the fungus on potato dextrose agar in 100-mm-diameter × 15-mm-deep plastic petri dishes at 28°C with a 12-h photoperiod under fluorescent light. Once the fungus completely covered the agar surface, 50 ml of sterile distilled water was added to the dish, and the mycelia and conidia on the surface were scraped off the agar and suspended in the water. This fungal suspension was decanted, and a 2-ml aliquot containing 1.8 × 105 CFU was pipetted into the vermiculite near the stem of each lettuce seedling. Ten plants grown in noninfested vermiculite served as uninoculated controls. After inoculation, plants were maintained in a growth chamber at 28°C with a 12-h photoperiod under fluorescent light for 3 weeks. Symptoms of yellowing, wilt, vascular decay, and often plant death developed during the incubation period on all inoculated plants but not on control plants. Fusarium oxysporum was consistently reisolated from inoculated plants but not from uninoculated plants. The experiment was repeated and yielded the same results. A wilt and root rot disease of lettuce attributed to F. oxysporum f. sp. lactucae was first reported in Japan in 1967 (3) and subsequently in the United States (San Joaquin Valley of California) in 1993 (2), and Italy in 2002 (1). The researchers of the U.S. report did not cite the earlier work from Japan and described the pathogen as F. oxysporum f. sp. lactucum. The Arizona isolate used to demonstrate pathogenicity was of the same vegetative compatibility group as an isolate of the pathogen from lettuce in California reported in 1993. Several companies grow and harvest lettuce in Arizona and California. At the end of production and harvest in the fall, tractors, implements, and harvesting equipment are transported from the San Joaquin Valley in California to western Arizona. The similarity between the isolate of F. oxysporum f. sp. lactucae from western Arizona and the San Joaquin Valley of California suggest a possible introduction of the pathogen into Arizona from California, perhaps on soil adhering to farm equipment. To our knowledge, this is the first report of F. oxysporum f. sp. lactucae infecting lettuce in Arizona.