As the leaf area expansion and the foliar regression are governed by the sunflower water and N status, the interactions of these factors on leaf area index (LAI) and duration (LAD), and their relationships with yield components, are studied in a field experiment involving different soil depths, N fertilizations and irrigations and two hybrid cultivars. The plants were allowed to take up 100 to 470 kg-ha-1 N, and 200 to 700 mm of water; they were free of any diseases or lodging. Twenty-five typical plants per plot were tagged at the 12 leaves stage, and some of them were sampled at the stages: bud apparition, beginning and end of anthesis, and maturity, for measurements of dry matter and N content in leaves, stems and heads. Yields vary from about 1.5 to 4.5 tons -ha-1; N supply mainly affects the number of achenes per head and their protein contentl water has a strong effect on this number, on the average weight of achenes and on their oil percenlage. The LAD is chiefly dependant on the water regimen, with some modulation according to N availabilities. A LAI of about 2.5 is sufficient for the maximum growth of the shorlest hybrid, the taller one requiring roughly 4. From the stage of bud enlargcment, the numbcr of achenes is strongly correlated both with LAI and ttte N content in leaves and stems. The average weight of achenes is well-correlated with LAI beyond anthesis and then with the available water. N mainly determines the potential number of achenes at eârly stages, and wâter their setting and filling' with a predominant effect on LAI and LAD.

Element concentration and the organic matter synthesis were studied in five sunflower inbreds. Plant material was obtained from the Institute of Field and Vegetable Crops, Faculty of Agriculture, Novi Sad. The sunflower inbreds were characterized by the same growing season. The plants were grown by the method of water cultures using various concentrations of nutrient solution (1/8 and 1/2 strength of that described by Reid-York sewing as control (1), and 2 and 3 times higher than the control solution). Dry mass of above-ground part and root, as well as concentration of certain elements of mineral nutrition were examined. The results obtained show that dry mass of above-ground part and root depended upon inbred line and variant of mineral nutrition. On average, the highest dry masswas found in the inbred O-CMS-3l, the lowest in O-CMS-25 and O-CMS 41. Also, significant differences in concentration of the elements analyzed, depending on inbred line, were established. On average, the highest N concentration was recorded in the line O-CMS-31, the lowest in O-CMS-6, the lowest in O-CMS-21. Also, concentration of N, P, and K in plant tissue increased as concentration of all elements in nutrient solution increased.

Tlventy six sunflower (Helianthus annuus L.) cultivars were evaluated at National Agricultural Research Centre, Islamabad. The trial was planted on March 3, July 23, and February 5, during 1984, 1985 and 1986, respectively. Data on seed yield, days to flower initiation, days to flower completion, plant height, head diameter and days to maturity were recorded. Simple correlations between all traits were worked out and direct effects of agronomic characters on seed yield from path coefficient analysis were calculated. TWo hybrids, NS-Condor from Yugoslavia and IH-173 from Hungary,werehighyielding with average seed yield of 2374 and 2184 kg/ha, respectively. Days to flower initiation, days to flower completion and days to maturity ranged from 68,4 to 78.1,73.3 to 85.0 and 96.8 to 109.7, respectively. Cuhivars Thiumph 570, Peredovik (an open-pollinated) and Citosol-Fl, Citosol-4, and NS-Flowerwere taller than all otherentries. Hybrid NK-2l2wasmostconsistent for plant height and head diameter. All cultivars grew taller, took more days to flower and maturity and also gave higher yields in 1986 than both in 1984 and 1985. Variety x year interaction was highly significant for all the traits. Days to flower initiation, days to flower completion and days to maturitywere strongly and positively correlated with eâch other. Days to maturity showed significant and positive correlation with plant height. The only significant correlation with yield was that of head diameter. Direct effects from path coefficient analysis indicated that head diameter had a strong and positive direct correlation with seed yield while days to flower completion had a strong but negative correlation with seed yield.

The effects of four sowing dates (9th June, 23rd June, 12th July and 28th July) and six intra-row spacings (15, 20,25,30,35 and 40 cm) on sunflower performance were studied for two years in the Nigerian savanna. Sowing date was found to have significantly affected plant height at flowering in both yean. However, sowing date significantly affected grain yield in 1987 and the number of days to first flowering in 1988. Intra-row spacing significantly affected grain yield in both years and the number of days to first flowering in 1988. The interactions between the sowing dates and the intra-row spacings were significant for grain yield in 1987 and for plant height at flowering in 1988. sowing from the last week of June to the second week of July at intra-row spacings between 25 and 30 cm gave highest grain yietds.

Introduction, collection, preservation and evaluation of germplasm materials is absolutely necessary in any result-oriented breeding programme. Forthis reason, 34 sunflower hybrids introduced from three different countries have been evaluâted in the field for two consecutive years (1986 and 1987). The performance of the syn 1 (F1) relative to the syn 2 indicate a mean reduction in the syn 2 generation of 62, 48,3r and ?À per cent for seed yield, head diameter, plant height and number of leaves per plant, respectively. The use of synthetic cultivars and the method of their devlopment were discussed.

Attention of researchers and plant breeders was turned to Helianthus debilis debilis since 1985. This species seems to have taken part in allopolyploid differentiation of Helianthus genus. In order to get information on interspecific hybridization in the genus Helianthus we have studied four accessions, H. debilis debilis, H. annuus Ha 89mt. F1 hvbrid and F2 selfed line. Chromosome number analysis that revealed the occurrence of aneuploid chromosol me number was performed; in root and shoot tips. F the parents, the occurence of diptoid number is superior to thet in the hybrids. Microdensitometric analysis of nuclear DNA content of shoot and root apices showed variability in DNA values.

Orobanche cernuo Loefl. (O. cumana Wallr.; broomrape) is a troublesome parasitic weed of confectionery sunflower (Helianthus annuus L.). It is probably the most widespread species of of Orobanche spp., as it affects extensive areas of sunflower in Southern and Eastern Europe ancl Micldle East (Parker, 1936). In Spain this species was first detectcd in 1958 at Tbledo Province (Diaz-Celayeta,1974). Gonzalez-Torres, Jimenez Diaz and Melero-Vara (1982) reported the spreading of the infestation to Cuenca Province and to Fuente Piedra (Malaga Province). Recently O. cernua has also heavily infested another important confectionary sunflower area of about 20,000 ha at El Coronil (Sevilla Province) (Castejon, Romero-Munoz and Garcia-Torres, 1987). The area planted to confectionery sunflower has been drasticaly reducecl because of this parasite. O. cernua seeds are pear shaped and extremely small, from 250 to 390 um long and 150 to 240 um wide (Joel, 1987). The description of the surface characteristics of Orobanche spp. seeds is reported by Musselman and Mann (1976) and a key for their identification using these characteristics was developed by Joey (1987). The morphology of sunflower achenes is described by Knowles (1978), indicating the presence ofitraigtri hairs inclined outward or appressed in the pericarp or hull, and of an armor layer in some cultivars where the outer layer of cells developed in an unusual way, creating pointed cones or hooklets. Although some authors have previously suggested the possibility of O. cenua seed dispersal through sunflower achenes (Vranceanu, 1974) no dà1a have ever been reported to actually confirm it. The aim of this paper is to ieport stuclies that evidence ancl quantiff the dispersal of O. cernua through sunflower achenes.

Two NS-sunflower (Helianthus annuus L.) hybrids, differently resistant to Diaporthe / Phonopsis helianthi, and their parental lines were examined on the effect of ageing and position on leaf growth parameters and photosynthetic potential of leaves. It was found that both hybrids, NS-H-26 and NS-H-43, had higher rates of leaf appearance, leaf expansion and leaf area duration than their parental lines. Heterotic effect was especially noticeable in leaf area formation, in both hybrids. Most of the examined parameters point to the similarity between the hybrid NS-lt-26 and its female pârenr and between the hybrid NS-H-43 and its male parent. The hybrid NS-H-43 followed a patrern of the male parent RFIA-SNRF in photosynthetic potential of the examined leaves too.

OBTENCION DE CRUZAMIENTOS INTERESPECIFICOS Y CULTIVARES DE GIRASOL CON RESISTENCIA A: Puccinia Y Plasmopara helianthii Y OTPAS ENFERMEDADES

This research determined the percentage ofseed set and pollen tube growth in styles of six sunflower cultivars, under self-pollination conditions. Three days before anthesis, plants of the tested materiâl were bagged with paper bags to ensure selfp-ollination. The bagged plants were randomly divided in two equal groups. one was harvested after physiological maturity and seed set percentage was measured. From the other group, 48 hours after self-pollination, styles were removed and observed with microscope, in order to examine pollen tubes in the lower part. Results proved that strong relationship exists between sed set and penetrated styles percentage in the tested material. So, self-compatibility degree that is determined from seed set percentage under selfpollination, could also be determined by the percentage of penetrated styles from pollen tubes.

The bracteal leaf, the nearest "source" to the "pool" of grain, increases the photosynthetic area and efficiency of sunflower and its removal reduces the grain yield by 1.9-7.6% in an edible variety and by 1.8-5.1% in a high oil one. Except for the mechanical injury when the bracteal leaf is removed, the effects of pruning off the bracteal leaf on grain yield agreed with Pereita's (1978) results who stated that 5% of grain yield were supplied by the ten leaves located on the basal part of the sunflower stem. Measures should be tâken to promote and safeguard the growth of the bracteal leaf. Selection for the area of the bracteal leaf and gradient and size of flower disc should also be conducted in breeding programs. According to A.N.RYTAEB the area of the bracteal leaf is â quantitative trait which can be set as an objective and improved in a sunflower breeding program.

Thirteen exotic sunflower inbred lines and eight isolates of Macrophomina phaseolina were studied to observe the genotypic variation for resistance to charcoal rot. The results indicated that significant differences exist among inbred lines for all trâits waluated. Among charcoal rot isolates, significant differences were observed for head weight only. Three inbread lines, namely, HAR 1, HAR 2 and HAR 5 had maximum head diametér and differed significantly from other inbred lines. Among the inbreds, HAR 1 and HAR 2 had maxrmum head weight, greater number of achenes per head. Hence inbred lines HAR 1 and HAR 2 were resistant/tolerant across charcoal rot isolates while HA 822 was susceptible for disease development and two charcoal rot isolates (MP 9 and MP 21) were virulent affecting head weight.

The experiment object were 154 sunflower hybrids developed by research institutes and international breeding companies and intended for growing in the agroecotogical conditions of Europe, the Americas, Australia, Asia and Africa. The hybrids were tested for the following characters: plant height, head diameter, number of leaves and the sums of effective temperatures to budding, flowering and maturation. Statistical calcutations included the cluster analysis with the Euclidean distance treated as a metric distance. Despite a large variability in all the characters tested, the majority of the hybrids were grouped in two clusters. An exception in that sense were the sums of effective temperatures io maturity which were grouped in four out of the five clusters.

A complete set of diallel crosses between four inbred lines of sunflower has been used to study genetic variability of the following characters: duration of phenological phases, dry matter production in each phase considered, leaf area per plant, seed yield and harvest index. The results obtained indicate that, while the additive genetic component is consistent for the characters collected during the first phases of plant dwelopment, the unfixable component of variation is the major part of genetic variability for the characters collected at the end of the onthogenetic cycle, as seed yield and harvest index. The genetic correlations between seed yield and physiological characters as dry matter production and leaf area, are discussed in relation to the possibilitv of their use in sunflower breeding programs.

Las Variaciones en el rendimiento de grano y en el contenido y calidad del aceite de girasol, se atribuyen principalmente a lâ temperatura durante la etapa de floraci6n, formaci6n y llenado de grano. Para observar estos efectos en el periodo vegetativo mencionado se establecieron en 1987 doce fechas de siembra de abrit 14 a septiembre 18 a intervalos de 15 dias. El trabajo se realizd en el Campo Experimentâl de Rio Bravo (CERIB) en Tàmaulipas, México. La siembra se hizo en suelo arcillo-arenoso y bajo riego. Para cada fecha se utilizd una poblacidn de 50.000 plantas y 80 kg de nitrdgeno - por hectârea. Se efectuaron por fecha y por genotipo una serie de 10 cortes de capitulos iniciados al finalizar la floraci6n y posteriormente cada 5 dias. Se realizd el anâlisis de varianza para diâmetro de capitilo, peso de grano seco, - pesofuolumen, peso de 100 semillas, porcentaje de aceite y de los âcidos grasos oleico y linoleico, ademâs de sus correlaciones donde se incluy6 unidades calor (U.C.) y horas luz (H.L.) registradas en cada fecha. Las Resultados obtenidos mostraton que la madurez fisioldgica se alcanzd a los 25 dias después de finalizada la floracdn, donde se acumularon 605 U.C. y y 2a9 FI.L. en promedio en siembras de abril a julio 10 y 4?A U.C. y 251 tl.L. en siembras de Julio 23 a Septiembre 18. El peso volumétrico del grano mantuvo una correlaci6n alta y significativa con el porcentaje de aceite y con los âcidos grasos oleico y linoleico. La temperatura mantuvo una influencia marcada en la formaci6n de los dcidos grasos olcico y linoleico que correlacionaron alta y significativamente con unidades calor. El âciclo oleico predomind cuando se acumularon arriba de 590 unidattes calor; mientras que el 6cido linoleico super6 al âcido oleico al acumularse menos de 500 unidades calor en la etapa de fin de floraci6n a madurez fisioldsica.

The authors have studied the physiological life span of leaves in a confectionery sunflower variety 'Three Brows' and a corn hybrid 'Jing Hybrid Number' used as a check, with intention of establishing indicaton for control of leaf growth and prwenting a premature senescence of sunflower leaves. In the sunflower variety, the 35th leaf was found to have the longest physiological life span of 58.4 days; the 44th leaf had the longest life span after flowering, 45.8 days. The average period of physiological activity of leaves after the stage of flowering was 29.0 days, i.e., 62.5 % of the entire physiological lifetime. The respective figures for the corn hybrid were: the 15th leat - 94.9 days; the 20th leaf- 67.1 days; 53.2 days or 87.7%. It is pointed out that grain yield could be further increased by prolonging the physiological life span of leaves after the stage of flowering which would promote the process of grain filling, increase grain weight and decrease the percentage of hulls.

Callus formation could be induced from segments of different organs prepared from mature seeds or germinated seedlings of sunflower. In the latter case, callus formation was pronounced from hypocotyl and cotyledon segments, howwer, no plants could be regenerated from such calluses. on the contrary, multiple shoot formation was achieved froir mature embryo segments and callus induced on these fragments. Genotypic differences were obvious for all types of response. Shoots could be rooted and induced to dwelop complete plants which could be grown to maturity. As a major obstacle, excessive "prematuie flo*'eringn must be avoided in order to improve the efficiency of vegetative propagation in vitro.

In the experiments presented here initial steps for the development of successful microspore culture of sunflower have been carried out. Both division of uninucleate microspores and embryogenesis were achieved - although in low rates - with two of the four genotypes tested. Further studies with other genotypes, at varying flower bud stages, with different media compositions and culture condltioni will be necerrary in order to develop an efficient microspore culture technique applicable to sunflower breeding.

Altennria helianthificiens Simm., Wal. and Rob. was first determined in Yugoslavia in 1987, in the vicinity of Novi Sad and later on other locations. Disease symploms are manifested on sunflower leaf, stem and head. in the form of brown-red angular spots. In pure culture on PDA\ the fungus produces septated hyphae and multicellular condiophores with conidia.- Tle dimensions of conidia are 13.88-114.57 x 1.3g-11.0g *m (59.47-3.19 *m).- Tèmperatures between 0 antr 5ºC are minimum for [ungus developmenr, maximum ones are between 35 and 40ºC, whilc the and optimum is arouitl 15ºC. The temperatures 15, 20 and 30ºC are minimum, optimum and maximum, respectively, for fructification. The best mcdia for the development of mycelia were bean and cârrot media and carrot and prune media were best for conidia prduction. After two or three sowings on nutrient media, the fungus loses its ability of fructification (production of conidia). The incubation in greenhouse lasts for two dâys and after 10 days all plânts are dry. In field,l. helianthirtf;cierc was more pathogenic than A. helianthi but iess pathogenic than Phomopsis helianthi.-A. helianthinficiens overwinters in the form of mycelia on infected harvest residues and infected seeds, which are the maior sources of infection.