A trial was carried out in Mozambique in 1998-1999, with the aim to study the effect of three levels of maize-sunflower intercropping ratios (25:75, 50:50, 75:25) in comparison with the pure-stand crop of two sunflower and maize varieties. For both maize varieties yield per plant decreased in relation to density, being lowest in the pure-stand crop. This beaviour was partially true for sunflower. The intercropping 75:25 maize-sunflower ratio showed the highest seed yield per hectare (5195 kg ha-1) and the maize and sunflower LER coefficients suggested that maize is slightly dominant over sunflower in the mixture. The relative advantage of the two species in respect to the single crop stand was about 16 and 19%. However each species and variety reached its maximum yield per hectare when it was grown as pure stand crop (100%). On the other side, when yield is examined in terms of food energy (K-calories), given by maize grain and sunflower protein and oil per hectare, maize-sun flower 75:25 mixture ratio appears to be much more convenient and suitable for food supply even when compared with the maize pure crop stand. The increase in K-calories is 380 ha-1 and the better balance in carbohydrates, pro teins and lipids can assure sustainability to standard farm families as those living in Mozambique. Using sunflower oil, a quite good amount of unsaturated fatty acids and lyposoluble vitamins are also supplied in the diet of farming people.

Broadleaf weeds cause considerable yield losses to sunflower production in all regions of the world. Resistance to the imidazolinone herbicides, imazethapyr and imazamox, found in a population of wild sunflower, could have great value for controlling many broadleaf weeds. The herbicide resistance was successfully transferred from resistant wild sunflower plants to a cultivated sunflower inbred line, HA 425. The objective of this investigation was to determine the inheritance of resistance to the herbicide imazamox in HA 425. Segregation ratios of plants in F2 and testcross populations indicated that resistance was controlled by two genes, a major gene having a semi-dominant type of gene action (Imr1), and a second gene (Imr2) with a modifier effect when the major gene is present. Resistance in sunflower can only be achieved with homozygocity (Imr1, Imr1, Imr2, Imr2) of both resistance genes in an inbred line or in a hybrid. Completely resistant hybrids require having resist ance factors in both parents.

Six cytoplasmic male sterile lines used as females were crossed with four fertile lines used as males in a factorial design. The 24 F1 hybrids obtained were evaluated in vitro for their organogenesis ability from cotyledonary explants. The regeneration medium was MS supplemented with 200 mg/l of glutamine, 1 mg/l of indol-3-acetic acid and 2 mg/l of kinetin. The experimental design was a complete randomized block in 2 replications. General combining ability variances were significant for some of the in vitro traits, while the vari ance due to specific combining ability was nonsignificant in all cases. Some of these positive and negative values of general combining ability were significant for the studied traits. These results suggest the importance of the additive component in the genetic control of the studied in vitro traits.

The objective of this paper was to estimate the genetic and ecological vari ation as well as the stability of tuber yield per plant, tuber number per plant and tuber size of Jerusalem artichoke based on the results of a variety trial carried out with 20 different Jerusalem artichoke varieties during the period of 1994-2000. Significant genetic as well as ecologycal variation was observed for all of the traits studied. The most promissing varieties showing high tuber yield combined with high yield stability were “BT-4”, “Violet Rennes” and “UKR 4/ 82”. It is encouraging that the highest yielding varieties exibited a rather stable performance over environments.

The effect of gamma rays on meiosis in the M2 generation has been stud ied in sunflower (Helianthus annuus L.) variety Ekiz 1. Seeds were irradiated with gamma rays at 10, 20, 30, 40 and 50 kR doses. Radiation induced meotic abnormalities. The chromosomal aberrations included univalents, multiva lents and stickiness at diakinesis, laggards and stickiness at metaphase I, bridges and laggards at anaphase and telophase I-II, micronuclei at telophase II. The percentage frequencies of anomalies increased generally with the increasing dose of radiation.

In this study, mitotic effects of gamma rays on Ekiz 1 variety belonging to Helianthus annuus L. (2n= 34) in the M0 (first irradiated seeds), M1 and M2 generations have been investigated. Seeds (M0) were irradiated with gamma rays at 10, 20, 30, 40 and 50 kR doses. Percentage of total abnormalities in the M0, M1 and M2 generations increased parallel to the increasing dose of radiation. These abnormalites have been observed as C-metaphase, chromosome stickiness, laggards and bridges with or without fragment. Mitotic index (M.I.) in the M0, M1 and M2 generations has decreased parallel to the dose increase. When the generations are compared, both the amounts of decrease in mitotic index and in the percentage of mitotic abnormalities were mostly observed in M0.

A new Bacillus thuringiensis strain, 00-50-5, exhibited an unusually high activity against banded sunflower moth (BSM) Cochylis hospes, which is an economically important pest of cultivated sunflowers in North America. The strain was fermented with a modified commercial medium in a bioreactor. This was a successful trial for production of 00-50-5 on a larger scale. After fermentation, the yield of dried powder was 5.8 g/l broth. In the laboratory assays, the LC50 (lethal concentration required to kill 50% of targets) of the dried powder was 0.5 µg/ml 3 d after exposure against four instars of BSM. Some practically useful conditions and parameters for the fermentation oper ating procedure and methods for harvesting were determined.

Sunflower chlorotic mottle virus (SuCMoV) was detected in several sun flower (Helianthus annuus L.) growing areas, causing a disease characterized by systemic chlorotic mottling. Symptom severity depended on several factors, including the ontogenetic stage at which infections occur. The objective of this study was to determine the effects of artificial infections with SuCMoV at different ontogenetic stages on agronomic yield characters (plant height, stem and capitulum diameters, achene yield, seed width and length, weight of 1000 seeds and oil content). Sunflower seeds of commercial hybrids Dekalb 4030, Contiflor 3N, and ACA 884 were sown in a split plot design with four replications, which were mechanically inoculated with SuCMoV at four growth stages. A negative (non-inoculated) control was included in the experiment. Virus infection was detected by symptoms and by double antibody sandwich enzymelinked immunosorbent assay (DAS-ELISA). Virus infections at all stages significantly reduced plant height (16-39%), stem diameter (21-51%), capitulum diameter (27-57%), achene yield (58-87%), seed width (13 -15%), seed length (10-16%) and weight of 1000 seeds (26-28%) compared with healthy controls, independent of hybrid tested. Oil content determined by magnetic nuclear resonance showed no significant differences among treatments.

Five fungicides, namely Tecto, Benlate, Bayton, Topsin and Derosal, were evaluated for their effect on seed germination and control of major seed-borne pathogens of sunflower. Two sunflower cultivars, HO-1 and NK-212, naturally infected with important seed-borne fungi were treated with these fungicides at 1.5, 2.0, 2.5, 3.0 g/kg. All the fungicides under study controlled the seed-borne fungi and increased the germination of sunflower seed to various levels. Tecto and Benlate in both cultivars gave better performance in reducing the fungal population and increasing seed germination. Topsin and Derosal also reduced the fungal population at higher dosage but there was no considerable improvement in germination. The use of fungicides at 2.5 g/kg provided almost com plete elimination of fungi and 8-10 percent increase in seed germination as compared to the use of fungicides at 2 g/kg.

The broomrape genus (Orobanche L.) is characterized by pronounced biodiversity. Of its 99 species identified so far throughout the world, 26 have been found in Serbia. The species of the Orobanche genus are highly variable and include 56 varieties, 226 forms (a total of 308 taxons), and a number of physiological races adjusted to specific crops. Despite such high biodiversity, 8 species alone are important parasite species in cultivated crops (Orobanche cumana Wallr., O. ramosa L., O. nana Noë, O. muteli Sch., O. minor Sutt., O. lutea Baumg., O. aegyptiaca Pers. and O. crenata Forsk.). Orobanche cumana Wallr. (O. cernua Loefl.) is especially important as a parasite species in sunflower but it is also frequently found growing on the root of tomato, tobacco and some weed plants.

The objective of this work was to determine the number of reproductive structures in relation to the vascularization of sunflower capitulum in three sectors: outer, middle and center, and in four development stages: E2 (early floral button), E4 (late floral button), F3.2 (beginning flowering) and M0 (end flowering) according to the CETIOM code. Seeds of Dekalb G100 sunflower hybrid were sown at 72.000 pl/ha density and the capitula gathered at the indicated stages. At each stage, significant increases were noticed in the reproductive structures number from the outer sector to the center of capitulum. The number of vascular bundles per unit of surface showed a significant decrease from the outer sector to the center at E2 and E4 stages and a tendency to become stable at F3.2 and M0. The obtained values of surface covered by phloem per cm2 of capitulum, decreased remarkably from the outer sector to the center at E4 stage while at F3.2 and M0 minor but still important decreases were observed. The statistical analysis made on reproductive structures number in relation to vascular bundles number and surface covered by phloem showed low and insignificant correlations, respectively.

A field experiment was conducted at Gandhi Krishi Vignana Kendra, University of Agricultural Sciences, Bangalore to study the effect of irrigation regimens on the biomass accumulation, canopy development, light interception and radiation use efficiency of sunflower. The treatments includes irrigating the plants at 0.4, 0.6, 0.8 and 1.0 cumulative pan evaporation. The results indicated that the aboveground biomass, canopy development, radiation interception and radiation use efficiency were influenced favorably by the irrigation regimens. Irrespective of the irrigation regimen, the radiation use efficiency of sunflower increased from 15 DAS to 75 DAS and then tended to decline. The decrease in RUE after anthesis is coupled with decrease in leaf nitrogen content. In general the RUE of sunflower ranged from 0.49 g MJ-1 to 1.84 g MJ-1 at different growth stages. The light transmission within the canopy increased exponentially with plant height and the canopy extension coefficient is found to be 0.8.

During the rainy season of 1998, a field experiment was established in Cocula, Guerrero (hot subhumid climate, Awo) and in Montecillo, México (semiarid climate, BS1), to evaluate the effect of nitrogen (0, 10 and 20 g m-2) and environment on phenology, yield and its components, water use efficiency (WUE), and crop evapotranspiration (ETc) and heat units (HU) accumulated during the growth cycle of sunflower (Helianthus annuus L.) cv. Victoria. The crop was planted on June 1 at a density of 7.5 pl m-2 in both climates. In Cocula, maximum and minimum temperatures were more extreme and rainfall was more intense, while soil was poor in total nitrogen, compared with Montecillo. Crop growth, yield and its components, and water use efficiency were affected significantly by the environment, nitrogen and the interaction environ ment * nitrogen. The crop cycle in the hot environment was 36 days shorter, with a greater accumulation of HU and ETc. Yield and its components and water use efficiency were significantly higher in Cocula. Nitrogen positively affected the evaluated variables. The interactive effect of environment * nitrogen was observed clearly, since in Cocula there was response to the application of nitrogen in most of the variables evaluated, while in Montecillo there was not.

In arid and semi arid areas, water is the most limiting factor of crop pro -duction. Germination is susceptible to water shortage. Experimentation was undertaken to study the effect of water stress on germination of seeds of three sunflower genotypes (Oro 9, Mirasol and Albena). Six PEG 6000 osmotic constraints were tested (0, -0.4, -0.6, -1, -1.2 and -1.6 MPa). Results showed no significant difference between germination percent of the control and -0.4 MPa treatment and between -0.8, -1 and -1.2 MPa treatments. Germination percent was most reduced at -1.6 MPa (-65%). Mean germination duration was also affected and the highest value was obtained for -1.6 MPa (4.95 days, related to an increase of 185%). Differences between genotypes were significant in the treatment at -1 MPa.

An experiment has been carried out in order to study the behaviour under mineral deficiency of three sunflower genotypes, a population variety (Oro 9) and two hybrids (Mirasol and Albena). Sunflower seedlings were submitted to five treatments: N deficiency (N0), P deficiency (P0), K deficiency (K0), N and K deficiency (N0K0) and a control. Plants were harvested when they reached 3-4 true pairs of leaves. Growth parameters measured (height, total leaf area, root length, root and shoot dry mater) were all significantly reduced by mineral deficiency. Leaf area was most reduced by N0 (-61%) and P0 (-56%). Total dry matter was most affected by N0 (-63%) and by N0K0 (-66%). Genotype comparisons showed that Oro 9 had the highest shoot dry matter while Albena had the lowest root dry matter. Effect of mineral deficiency on content and partitioning of N, P, K, Ca and Na was significant and varied according to treatments and among plant parts. Shoot dry weight was significantly correlated with root N content (r2=0.81) and root K content (r2=-0.61) for N0 and K0.

A hydroponic study was conducted to evaluate the performance of five sunflower hybrids, i.e., PARSUN, SH-3322, XF-4623, SMH-9706 and XF 4619, at 0, 75 and 150 mM NaCl salinity in root medium. Sunflower (Helianthus annuus L.) seeds were germinated in moist quartz sand, twelve-day old seedlings were foam plugged in lids of plastic pots containing 2.5 l of continuosly aerated half-strength Hoagland’s nutrient solution. The experiment was organized in completely randomized design (CRD) using four replications. Sunflower growth deceased drastically with increasing concentration of NaCl in root medium. Sunflower hybrid XF-4619 registered maximum shoot and root fresh weight, stem diameter and leaf area. Furthermore XF-4619 exhibited the least decrease in these parameters under saline conditions. XF-4619 exhibited 14 and 53% decrease in shoot fresh weight, 11 and 35% decrease in root fresh weight, 6 and 34% decrease in stem length, 12 and 34% decrease in stem diameter, 10 and 40% decrease in leaf area, 2 and 31% decrease in root dry matter and 13 and 50% decrease in shoot dry matter yield at 75 and 150 mMNaCl, respectively, as compared with the control. Moreover, Ca and K were also efficiently taken up by XF-4619 in saline and non-saline root medium. This is indicative of it having better yield potential than the other commercial sunflower hybrids