The sunflower moth, Homoeosoma electellum (Hulst), is a major pest of sunflower (Helianthus annuus L.) mainly in the central and southern United States. The sunflower moth is most commonly controlled with pesticides. Resistant plants would provide an environmentally friendly approach to controlling this pest. Evaluation of 680 cultivated sunflower accessions in the U.S. National Plant Germplasm System's sunflower (Helianthus spp.) collection at the North Central Regional Plant Introduction Station, Ames, IA, USA. revealed 51 accessions resistant to sunflower moth feeding. A 1-3-5-7-9 rating scale is presented to compare accessions damaged by the pest. The proceeding evaluation data were entered into the Germplasm Resources Information Network (GRIN) and made available to researchers worldwide.

A breeding population of Nysius inconspicuus Distant., a pest of sunflower, was recorded for the first time in Pakistan. Duration of its growth stages, population build up during May and June and economic losses in sunflower were studied at National Agricultural Research Centre, Islamabad, during spring 1992. The development of N. inconspicuus Distant. was studied on sunflower florets and heads at an average temperature of 30.65℃ under laboratory conditions. Although nymphs did not survive on florets, their survival on sunflower heads was 60% in the first 20 days of development. The insect laid 12 eggs per female in captivity. The average incubation period and the nymphal duration was 5 and 20 days, respectively. The adults lived for 15 days. Thus the total life-span was 40 days. The pest appeared at seed formation stage and reached up to 58 individuals per sunflower head during the season. In a pot experiment 50 or more bugs per head caused about 26% losses in yield and 2% in oil content.

Twenty-two wild Helianthus species and eight interspecific hybrids were evaluated for resistance to the leaf spot disease coused by Alternaria helianthi. Cultural characteristics of the fungal pathogen at temperature range of 20-30℃ and on medium with different carbohydrates were also studied. Colony growth of Alternaria helianthi was maximum on sunflower leaf extract medium (SLEM) devoid of carbohydrates while the maximum spore concentration with the largest conidiophore length (154.9 um) was obtained on SLEM with 2% sucrose. Temperature had significant effect on the colony growth but had no influence on the spore concentration and spore size. A simple, rapid and reliable laboratory technique using detached leaves for screening germplasm against Alternaria leaf spot has been developed to assist the field-based selection for resistant types. Significant differences were detected between various species for their reaction to Alternaria as measured by the percentage of leaf area infected. All diploid annuals and their hybrids were found highly susceptible. Maximum resistance was conferred by H. mollis, H. maximiliani, H. divaricatus, H. pauciflorus, H. tuberosus, H. resinosus and H. simulans. Field evaluation under artificial epiphytotic conditions revealed a close agreement in the reaction of the wild sunflowers to A. helianthi under both laboratory and field conditions.

Isolates of Puccinia helianthi Schw. collected during 1996-1997 were assessed for virulence on a set of Canadian and USA differential lines. All isolates were identified as race 4. In this work, as the sexual phase of the fungus was not found, inoculum introduction was hypothesized. Preliminary observations on field crops suggested that the South African varieties are less susceptible to P. helianthi than the domestic material.

Although sunflower cultivation has been recently reintroduced in Mozambique, previous work regarding diseases distribution, incidence and severity is not complete. In this work the first systematic survey of the diseases in Mozambique was made. Results showed that the most important pathogens are Puccinia helianthi followed by Alternaria helianthi. Alternaria alternata and Sclerotium bataticola.

Nous avons étudié le comportement de 12 espéces de Helianthus et de 5 hybrides interspécifiques a des infections artificielles de Sclerotinia sclerotiorum sur feuille. Leur comportement est comparé a la teneur en dérivés caféoylquiniques (CQ) présente dans ces mémes organes. L'objet de ce travail est dune part de savoir s'il est possible d'utiliser le dosage des CQ comme critére de sélection pour la résistance sur feuille et d’autre part d’estimer la variabilité génétique d'espéces sauvages de tournesol, pour ce critére. Une variabilité importante parmi les populations sauvages est mise en évidence pour l'ensemble des caractéristiques étudiées. Cependant, l'absence de forte corrélation entre les teneurs des différents CQ et la réaction des individus au test pathologique (vitesse de croissance du champignon in situ) ne permet pas d'envisager l'utilisation de ce critére dans les programmes de sélection. Le possible réle de ces composés phénoliques dans la résistance de Helianthus spp.a S. sclerotiorum est discuté.

Attempts have been made to find a suitable medium for mass multiplication of Alternaria helianthi, a slow-growing fungus on potato dextrose agar. The present study revealed that natural media are better for growth and sporulation than synthetic and semi-synthetic media. For easy isolation of the fungus from diseased specimens, sunflower leaf plated on water agar and sunflower stem bits were found to be good medium sources. Sunflower leaf agar with 200g of sunflower leaves per litre of medium without dextrose was found to be an excellent medium for mass multiplication of Alternaria helianthi followed by oatmeal agar and Czapek's agar medium. Colony characters varied on different media tested and formation of microcyclic conidia was observed on parent conidia in the media which contained sucrose as a carbohydrate source.

Pathogenicity of twenty fungi isolated from sunflower seed intended for sowing. was tested on three sunflower cultivars (Ho-1, SMH-13, Suncome-110) seedlings and plants by appropriate recommended methods for different fungi under test and Kock's postulate's proved. Out of the twenty fungi studied, 15 fungi. Alternaria alternata. A. helianthi, A. zinniae, Curvularia lunata. Fusarium culmorum. F. moniliforme, F. semitectum, F. oxysporum. F. soloni. Macrophomina phaseolina, Myrothecium roridum. Phoma oleracea, Phomopsis helianthi. Stemphylium healianthi and Verticillium dehliae were found to be pathogenic on sunflower. Of the sunflower cultivars used in the pathogenicity test. Ho-1 was found most susceptible to the pathogens whereas Suncome-110 showed variable trend to different pathogens. Fusarium culmorum, F. moniliforme and F. semitectum were found to be less agressive as compared with F. solani and F. oxysporum.

Eleven naturally infected and four uninfected sunflower seed samples were used to study their oil content and fatty acid profile. It was observed that oil content showed decreasing trend due to a number of various types of seed mycoflora. The study of fatty acids profile showed that saturated fatty acid (palmitic and stearic acid) concentration increased and unsaturated decreased due to high infection level and number of seed mycoflora in all sunflower cultivars in relation to the control (healthy seed)

An investigation was undertaken to assess the magnitude and direction of combining ability of six cytoplasmic male sterile lines and twelve fertility restorer lines in sunflower. The study revealed that the parental lines RHA-99RTNBr. RHA-284. RHA-299 and CMS-302 possessed genes for earliness. The hybrid CMS-852 x RHA-99RTNBr was found to be the best combination for days to 50 per cent flowering. The lines CMS-207 and CMS-852 and the testers RHA-6D-5-3-6 and RHA-214Br appear to transmit genes for higher seed yield and hence they are suggested for utilization in hybridization programme to obtain better yields. The hybrids CMS-302 x RHA-273 and CMS-234 x RHA-284 were found to be the best combinations for seed yield and oil content, respectively. All the characters were found to be under control of both additive and non-additive gene action with the predomiance of the latter.

Generation mean analysis of eight quantitative traits: days to 50 percent flowering, plant height. stem diameter, head diameter, percent seed set, seed yield/plant. 100 seed weight and oil content in sunflower revealed that all are predominantly under the control of dominant gene effect. Also, digenic epistatic genetic effect were also found to be important in the inheritance of these traits. Therefore, appropriate breeding methods such as reciprocal recurrent selection and biparental mating methods would be needed to improve these traits.

An investigation was carried out at the University of Agricultural Sciences. G.K.V.K. Campus. Bangalore, India, to determine the possible limits to parental divergence for the occurrence of heterosis in sunflower. Seven inbred lines were used to synthesize twenty-eight hybrids following diallel mating design. The magnitude of heterosis in these crosses and the magnitude of the divergence between the parents of the corresponding crosses were estimated. The study revealed sufficient evidence for the limits to the parental divergence to realize high frequency of heterotic crosses with high magnitude. Chances of occurrence of heterosis are higher when the parents are chosen to have their divergence between (m-s) and (m+s) compared with the crosses between the parents whose divergence fall outside this limit. The study also indicated a poor correspondence between the magnitude of heterosis and the genetic divergence.

Numerous genetic studies have indicated the instability of the high oleic characteristic in sunflower. A high-oleic sunflower mutant was obtained using a dimethyl sulfate chemical treatment. There are several hypotheses about the number and action of genes that control high oleic acid content in sunflower oil. Since most mutations cause changes at the chromosome level, a cytogenetic study (analyses of meiosis and pollen viability) was undertaken to analyze a normal line, an isogenic mutant line and their F1 hybrid. The results of the cytogenetic analyses showed no change in either the number or the structure of chromosomes in the mutant and the F| hybrid in relation to the inbred line. It was concluded that there were no chromosome aberrations such as heterozygous translocation or inversion. Histological analyses showed no difference in the content of the spongy and palisade parenchyma tissues of the cotyledons in the normal line, the mutant and their F1 hybrid.

Tissue culture techniques were standardized for mass multiplication and maintenance of 18 Helianthus species using shoot apices and nodal explants from mature field grown plants. Meristematic explants were cultured on Murashige and Skoog's (MS) medium supplemented with varying concentrations of kinetin and benzyladenine (BA). Irrespective of the plant habit and ploidy, medium supplemented with 0.5 mg/l benzyladenine was found best for obtaining good axillary proliferation with less vitrification. Shoots from the multiplication medium were directly acclimatized bypassing the labour-intensive rooting stage. Plantlets thus obtained were successfully established in the field with a frequency of 66.5 to 100% and grown to maturity.

Sixty-six families of sunflower were ivestigated for their genetic response under two different sowing dates al the School of Biological Sciences. University of Birmingham. England. The results showed significant differences for flowering time, height at flowering and area of head set with seed in both sowings. However. more significant genetic variations were detected in normal sowing compared with late sowing.

Significant effect of genotype x sowing interaction on the family performance suggested that a good agreement exists between family means across sowing for all the traits. A low magnitude of corelations, however, indicated that low genetic variation exists among families.

Negative correlations between H6 and flowering time revealed that early flowering and short plants flower earlier than slow growing plants. Critical association between flowering time and Sclerotinia infection, an epidemic disease of sunflower in EC countries, further evidence that early flowering and short plants are attacked more than tall and late flowering families. Thus, normal sowing during the first fortnight of May is the optimum time for obtaining good yield because it attained maturity before the onset of severe wet weather in September.

Sunflower plants (Helianthus annuus L. cv. NK-265) were grown hydroponically in half strength Hoagland nutrient solution (pH 5.7) to study the response of plant parts to graded levels of S (0, 10, 20. 30. 40 and 50 ug ml-1) in triplicate. Twelve-day old seedlings were transplanted. The harvests took place on the 29th and 36th day after transplanting. After harvesting, plant parts were separated into leaf, stem and root. Plant parts were dried in an oven at 70+2℃ after recording fresh weight. The samples were digested in HNO3 and HCIO4 and S was estimated. The application of 20 ug S ml^-1 significantly increased the root and shoot length. The relative growth rate (RGR) of plants grown in 20 ug S ml^-1 was 0.26 mg mg-^1 day^-1 as compared with 0. 188 mg mg^-1 day^-1 in case of the control. Similarly sulphur was much more efficiently used by plants grown in 20 ug S ml" than in the other treatments. Sulphur uptake in developing leaves (DL), expanded leaves (EL) and old leaves (OL) was curvilinearly correlated with the S applied. Sulphur uptake was increased by 40 and 480%, in DL and EL, respectively, when plants were grown in 20 ug S ml^-1. As the S application increased beyond 20 ug ml^-1, the uptake declined. Developing. older and expanded leaves responded clearly to the applied S. Roots acted as a supplier from the source to sink, stem responded lesser than leaves. As the metabolic activities are higher in expanded leaves, they showed a clear response.

Immature zygotic embryos from nine inbred lines of sunflower (Helian-thus annuus L.) were used as a donor material for the induction of direct organogenesis and somatic embryogenesis. A portion of the embryos was treated with Cs 137 gamma radiation before plating, at doses of 5. 10 and 15 Gy.

Three induction media were used in the experiments - AO by Freyssinet and Freyssinet (1988). El (modified AO medium) and TPM by Wilcox et al.

The regeneration was strongly increased with the dose of 5 Gy in line Z-8-A in the medium AO. followed by the dose of 10 Gy in the lines 1395 Rf in AO and RNA-801 in El. For the three media and all genotypes the dose of 5 Gy in the medium AO appear to be most appropriate for increasing the frequency of plant regeneration.