Boris Kraptchev

INDIRECT SHOOT ORGANOGENESIS OF EGGPLANT (SOLANUM MELONGENA L.)

A protocol for indirect shoot organogenesis of Solanum melongena ‘Larga Negra’ and ‘Black Beauty’ was established using hypocotyl and cotyledon derived calluses. The maximum morphogenic callus induction was observed from cultured cotyledons of 30-days old seedlings on Murashige and Skoog (MS) medium containing 2.0 mg/l α-naphthalene acetic acid and 0.5 mg/l 6-benzylaminopurine. The highest percentage of shoot regeneration and the highest mean number of shoots/callus were obtained on hormone-free MS medium. In terms of callus induction and subsequent plant regeneration, cotyledon explants were more responsive than hypocotyl explants. Regenerated shoots (2-3 cm) were rooted on MS hormone-free medium or medium containing 0.1 mg/l indole-3-butyric acid. About 90% of regenerated plantlets survived under field conditions after hardening in the glasshouse. Several somaclones exhibiting useful variation would to be proposed as initial plant material for eggplant breeding programs.

Utilization of related wild species (Echinacea purpurea) for genetic enhancement of cultivated sunflower (Helianthus annuus L.)

* Correspondence: bkraptchev@yahoo.com

Response of sunflower (Helianthus annuus L) genotypes to PEG-mediated water stress

Drought tolerance of two sunflower (Helianthus annuus L.) genotypes, cultivated cultivar 1114 and interspecific line H. annuus × H. mollis, was studied under laboratory conditions using PEG-6000. Four levels of osmotic stress (−0.4, −0.6, −0.8 and −1.0 MPa) were created and performances were monitored against a control. Physiological and biochemical stress determining parameters such as malondialdechyde (MDA), proline content, and hydrogen peroxide (H2O2) were compared between seedlings of both genotypes. The results indicated that both genotypes have similar responses at four osmotic potentials for all traits studied. All seedling growth parameters such as germination percentage, root length, shoot length, root and shoot dry weight decreased with increasing osmotic stress. MDA, proline, and H2O2 were found to be increased at different osmotic gradients in comparison to control. Cultivar 1114 was less affected than the interspecific line under these stress conditions. The data observed in the experiments revealed that perennial wild H. mollis can hardly be considered to be an excellent candidate of drought tolerance genes.

Micropropagation of six Paulownia genotypes through tissue culture

We investigated the effect of genotype and culture medium on the in vitro germination and development of plantlets from seeds of 6 different Paulownia genotypes (P. tomentosa, hybrid lines P. tomentosa × P. fortunei (Mega, Ganter and Caroline), P. elongata and hybrid line P. elongata × P. fortunei). Nodal and shoot tip explants were used for micropropagation of Paulownia genotypes by manipulating plant growth regulators. The highest germination percentage for all genotypes was obtained for seeds inoculated on medium supplemented with 50 mg*L GA3 (MSG2). On Thidiazuron containing media, the explants of hybrid line P. elongata × P. fortunei exhibited the highest frequency of axillary shoot proliferation following by P. tomentosa × P. fortunei. The results are discussed with the perspective of applying an improved protocol for in vitro seed germination and plantlet formation in several economically valuable Paulownia genotypes.

A compact sunflower line produced after cross Helianthus annuus x Verbesina encelioides

Intergeneric cross was made between the cultivated sunflower inbred line HA89 and an accession of wild Verbesina encelioides tolerant to drought and high temperature. The line was a BC2F5 progeny. The most remarkable feature of the plants was their compact architecture due to short petiole length and also, rather specific bright-yellow inflorescences. Similar plant architecture did not exist in either the wild or the cultivated parent. For sunflower, it is considered as a favourable and potentially useful adaptive trait. The line was multi-branched of medium type branching and possessed good agronomic characteristics. The overall characteristics of HA-VERBENC line make it a useful plant material for research on wide hybridization.

An intergeneric sunflower line produced after cross Helianthus annuus × Echinacea purpurea

One intergeneric hybrid line involving cultivated sunflower line HA89 and wild medicinal species Echinacea purpurea was developed through conventional cross. The line was a BC1F8 progeny. Morphological and biochemical studies were conducted to establish its hybridism. The most remarkable feature of the plants was greatly reduced number of leaves and stature, resulting in a semi-dwarf growth habit. All the hybrid plants, though morphologically distinct, were intermediate phenotypically between its parents with a stronger resemblance to Helianthus annuus with respect to whole habit. The line was non-branched (monocephalic) without anthocyanin pigmentation and possessed good agronomic characteristics. Biochemical analysis of the HAEPLNL hybrid line revealed that the total phenolic content was under-expressed while the flavonoids and the water soluble antioxidant capacity were over-expressed as compared to both parents. The overall characteristics of HAEPLNL line make it a useful plant material for research on wide hybridization.