Twenty-one new sources of CMS were produced using interspecific hybridization, experimental mutagenesis and spontaneous expression of male sterility in sunflower. For all CMS sources, fertility restorers have been discovered.

All CMS are a result of cytoplasmic mutation. It is theorized that transformation of the mitochondrial genes controlling the pollen production is envoked by the influence of a single command from the cell nucleus to the mitochondria. The transformation appears to be irreversable. Commands for pollen production could be only accepted by the mitochondrial genes in case of existence of a fertility restoring gene in the cell nucleus of sterile cytoplasm

Intergeneric hybridization between the cultivated sunflower H. annuus L. and 19 related genera of Compositae (Asteraceae) was investigated. Putative hybrids were obtained from twelve cross combinations. The general cross compatibility level and morphological characteristics of Fis were examined. In spite of the genetic distance between H. annuus and the wild species of genera from the Compositae, intergeneric hybridization appears promising as a breeding method for transferring wild germplasm for agronomic purposes. The data presented provide knowledge about the genetic properties of the species and will be useful for future improvement of the cultivated sunflower.

The objective was to determine the additive and dominance genetic variances and the broad- and narrow sense heritabilities of eleven traits in sunflower hybrids obtained from drought tolerant inbred lines. There were 32 hybrids that were evaluated in irrigation, drought and rainfed conditions. The N.C Design II was used for environments, male and female factors. Additive variance was more important than the dominance variance for the traits affecting the reproductive period, stem dry weight, total dry weight, and head weight. Dominance variance was more important for the days to beginning of flowering, days to end of flowering, days to physiological maturity, reproductive index, plant height, leaf dry weight and achene yield. All traits reached the limit of selection in consequence to their very low genetic variance, and the level of endogamy of the lines was adequate to test them in hybrid combinations. The very low narrow sense heritability values observed in all traits reflected the low proportion of total genetic variance and the varied environmental conditions. The traits with lowest heritabilities were those related to the reproductive ability, while the traits with higher heritabilities were those associated with biomass production and distribution. The usefulness of the line-hybrid correlations to select lines per se depended of the amount of the additive variance, the control of environment and the distribution of genetic variances among the female and male lines.

Eight sunflower inbred lines and 15 F1 hybrids (line x tester) have been analyzed for correlations between several yield components (oil yield, protein yield, kernel yield, grain yield, dry mass of the aboveground plant parts, leaf area and harvest index). The path coefficient analysis was employed to partition the direct and indirect effects of the studied characteristics on oil yield per plant. Highly significant positive correlations were found between oil yield on one side and all the characters under study on the other. Protein yield exhibited a highly significant positive direct effect on oil yield. Grain yield and kernel yield had positive direct effects on oil yield per plant, whereas the dry matter mass of the vegetative plant part, harvest index and leaf area had negative direct effects on oil yield.

Seeds of the sunflower variety 'Surya' were irradiated with 4 doses of gamma rays. Effects of gamma rays on the induction of plant injury and morphological mutations were studied. Increasing doses of gamma rays increased the plant injury in the M1 generation. Two sectorial male sterile chimera were found in the M1 generation. In the M2 generation, 27 morphological mutants were isolated. Among them, 3 each were for chlorophyll and stem, 9 for leaf, 8 for capitulum and 4 for seed coat colour. Some of the mutants possessed more than one mutated character. Mutations like yellow leaf vein, fasciation, wrinkled leaf, zigzag stem, zigzag ray florets, stigma emergence and brown patch mutants are novel characteristics. Among the 4 doses of gamma rays, 200 Gy was the most effective dose for induction of mutation in sunflower.

An investigation was undertaken to study the cytomorphology of the interspecific hybrid H. annuus var. Morden x H. argophyllus along with the parents. The hybrid showed considerable vigour for plant height and stem girth. The hybrid was intermediate for seed size and test weight and exhibited reduced pollen and seed fertility. The chromosome pairing was normal in the parents while one chain or ring quadrivalent was observed in the hybrid in most of the meiotic cells scored in diakinesis / metaphase I, suggesting that the species H. annuus and H. argophyllus differ by one reciprocal translocation. The mean chiasmata frequency in the hybrid was 20.94 per cell and 1.22 per bivalent, while for H. annuus and H. argophyllus the values were 22.76, 22.16 per cell and 1.33, 1.33 per bivalent, respectively.

A rapid production of doubled haploid lines in the cultivated sunflower (H. annuus L.) is already possible by means of irradiated pollen - induced parthenogenesis (Todorova et al., 1997). The genetic constitution of donor parents is one of the significant factors for the successful induction of parthenogenetic embryos. The effect of pollen donor was examined in eighty- eight combinations, involving 10 donor parents, a pollen mixture of them and two mother genotypes.

Pollen was treated with gamma-irradiation doses of 600 Gy and 900 Gy. In total, 705 embryos were cultivated, giving rise to 205 plants that reached maturity. After selfing, 104 plants produced seeds, while the others were sterile. Sixty-five agronomically useful doubled haploid lines were selected.

The ploidy level of all the regenerants was flow-cytometrically evaluated. Best results were achieved by the use of the pollen donor Z-8-A.

The mixed pollen, followed by two pollen donor lines yielded also very high numbers of parthenogenetic embryos, i.e., plants

Competitive ability of pollen parents involving ten restorers, three maintainer lines and thirty hybrids were studied at gametophytic and sporophytic level. Three pollen parents (R X-13, R IV-83 and R-857) recorded more than 80 percent pollen germination and more than 50 um pollen tube length ten minutes after incubation in pollen germination media. This indicated differential reaction in pollen viability of the parents at the gametophytic level. This was reflected in high self-fertility percentage in the hybrids involving these three pollen parents at the sporophytic level. Identification of competitive pollen parents at the gametophytic level and its utilization in developing pollen mixture hybrids in lieu of hybrid mixtures is of practical significance in getting higher yields in sunflower.

A complete set of diallel cross experiments was conducted involving six sunflower (Helianthus annuus L.) inbred lines under non-saline and saline soil conditions during 1992-1994. The inbreds were selected on the basis of their salt tolerance and included two salt tolerant, two moderately tolerant and two salt sensitive lines. The experiments, which included the parents and their F1 and F2 generations under non-saline and saline soil conditions, were repeated in subsequent years. It was observed that additive and non-additive gene effects were frequent over the environments. Cytoplasmic inheritance was more pronounced under saline than under non-saline conditions. The performance of inbreds and their combinations was variable under the different environments. GIMSUN-856 invariably exhibited high general combining ability in both, non-saline and saline sotls. Similarly, the reciprocal combination GIMSUN-790 x GIMSUN-630 remained immutable under different soil conditions. Direct crosses between moderately tolerant and sensitive lines were promising under saline conditions and so were reciprocal crosses between moderately tolerant and tolerant lines. Direct and reciprocal crosses showed more promise under non-saline and saline soils, respectively. It appeared that salt tolerance potential was contributed more by the male than by the female parent.

Protoplasts isolated from hypocotyls and leaves of two genotypes of the cultivated sunflower and from stems and leaves of Helianthus maximiliani were cultured in the presence of different concentrations of oxalic acid, putative toxin of Sclerotinia sclerotiorum. Their viability was determined by staining with fluorescein diacetate during five days. Statistical analysis showed that there was significant difference in reaction to oxalic acid between the genotypes as well as between different organs of the same genotype. Protoplasts of H. maximiliant were found to be more resistant to stress with oxalic acid than protoplasts isolated from the two genotypes of the cultivated sunflower which is in accordance with the results obtained in field conditions. Differential reaction of protoplasts isolated from different plant organs to oxalic acid indicates that this method could be used for screening for resistance to different forms of Sclerotinia.

Phomopsis heltanthi Munt. Cvet. et al. has become one of the economically most important diseases of sunflower. To study the different resistance factors in leaf and stem, 29 inbred lines and 100 hybrids from a factorial cross of these lines were investigated. Observations across two environments with artificial leaf infection and in one environment with natural infection were conducted in 1998. Petiole score was taken as an indicator for leaf resistance after artificial infection. Diseased stems were used as a measure of stem resistance after natural infection. No correlation was found between resistance in the leaf and stem. Resistance against Phomopsis in both tissues was mainly controlled by additive gene action. Heterosis was not important. While stem resistance of hybrids seems to be predictable from their parents, a low correlation was found between line per se performance and general combining ability (GCA) effects for leaf resistance.

Albugo tragopogonis is associated with leaf spots, petiole greying and grey stem spot of sunflower. With this study, the fungus is also associated with heads of sunflower. In addition to oospores of A. tragopogonis that formed on involucral bracts and the base of receptacles, sexual structures were also produced at the base of floral disks. In these instances, aospores were observed in disk bracts, receptacles and in the pericarp of seeds, but not in disk flowers and pappuses. These infections appeared to take place in the absence of stromata, The incidence of seed transmission of A. tragopogonis is expected to be low.

Broomrape (Orobanche cernua Loefl./Orobanche cumana Wallr.) is counted among the most detrimental parasites of sunflowers. The occurrence of a new race, race E, in Yugoslavia has moved sunflower breeders to try to develop hybrids resistant to the new race. Tests in infected fields and in a quarantine chamber in a greenhouse have produced genotypes possessing Or5 gene, such as lines L-414, Bt analogue 2, Bt analogue 3, etc. There has been good agreement between the results obtained outdoors and indoors.

A study has been carried out in the greenhouse in order to establish correlations between seed and field infection intensities and to determine disease tolerance limits. It was observed that the pre- and post-emergence mortality of seedlings increased as the seed infection increased. On the other hand, yield and seed mass decreased with the increase in seed infection. Seed infection levels of 5 to 10 percent due to M. phaseolina and A. alternata showed no significant effect on yield performance in relation to the control (healthy seeds). It was concluded that with infection levels from 10 to 5 percent due to A. alternata and M. phaseolina, sunflower seed can be sown safely without seed treatment. This finding may be helpful in reducing the cost of seed and health hazards involved in indiscriminate use of chemicals.

Of the thirty-two seed diffusates tested, ten were found to be effective against the seed-borne fungi of sunflower namely Alternaria alternata, Emericellopsis terricola, Fussarium solani, Macrophomina phaseolina and Stemphyllum helianthi. Out of these ten, six seed diffusates, those of Anethum graveolens, Azadirachta indica, Canabis sativa, Coriandrum sativum, Melia azedarach and Memordica charantia, inhibited the growth higher in all fungi under test in the concentrations of 0.5 and 1.0 percent. Results of the present study indicate that seed diffusates could substitute costly chemical in controlling the seed-borne diseases.

Sunflower (Heltanthus annuus L.) can be affected by leaf blight and stem spot disease caused by Alternaria helianthi. Genotypes with genetic resistance to this disease are highly desirable for reducing yield losses. The reaction of 28 sunflower genotypes to Alternaria leaf spot disease was evaluated in the state of Paraná, Brazil, during the 1995-96 and 1996-97 growing seasons. Disease occurrence, under natural conditions, was evaluated at the flowering stage with reference to a diagrammatic scale of severity, varying from 0 to 5 according to the area of diseased leaf tissue. High Alternaria disease intensity was observed in eight field trials. The genotypes Contiflor 3, Contiflor 15 and Cargill 9401 showed an intermediate level of resistance to the Alternaria disease.

During summer 1997, a wilt disease of sunflower (Helianthus annuus L.) was observed in the experimental field at NARC, Islamabad. The diseased plants exhibited symptoms of wilt with dull yellowing of leaves at flowering. Large areas on the leaves first turned dull light green, usually starting at the apex and leaf margins and extending inward, and then became necrotic. Severely infected plants were stunted, with small heads. The causal agent was isolated and, based on the characteristics morphological features, identified as Phialophora asteris f. sp. helianthi. This is the first report of the disease on sunflowers in Pakistan.