Maize
Genetics Cooperation Newsletter 80. 2006.
Institute of Genetics, Bulgarian Academy of Sciences
Plant
tissue culture techniques have been used as a complementary tool in plant
breeding improvement. Our aim was
to study this technique as a procedure for early prediction of heterosis in
sweet corn hybrid breeding programs.
The genetic potential of sweet corn for initiation and maintenance of
calli and regeneration of whole plants was investigated. A tissue culture experiment with mature
embryos was used to study the possibility for prediction of heterosis at early
stages of mature embryo growth. A
half diallel set of crosses was made among ten sweet corn inbred lines, and 45
F1 hybrids were obtained. The
kernels were divided into 2 groups for in vitro callus induction and for in
vivo measurement of some agronomic traits. The kernels in the first group were evaluated for callus
formation, and the growth rate of the calli obtained was measured. The potential for callus initiation was
investigated on N6 medium, supplemented with 4 mg/l dichlorophenyl
acetic acid (2,4-D), vitamins according to Murashige and Skoog, 150 mg/l asparagineasparagines,
30 g/l sucrose and 7 g/l agar.
Callus growth rate was estimated as an increase in the original fresh
weight of the calli for a period of 30 days.
In general, sweet corn lines and F1 hybrids may be derived in 3 groups. The first group comprised kernels was capable of initiating callus; the second group consisted of kernels capable of initiating calli, which can grow at different rates; and the kernels in the third group were able to initiate callus with morphological characteristics totally different from the others. The potential of this third cross to initiate callus was investigated on immature embryos under conditions described by Nedev et al. (MNL 75). The cross was competent at initiatng morphogenic callus, and in vitro organogenesis was obtained. A study on the utility of this cross in in vitro programmes for improving maize breeding processes is in progress.
The ten sweet corn lines investigated and their respective 45 F1 hybrids were grown at the Experimental Farm of the Institute of Genetics in Sofia. Fifteen competitive plants were taken for recording data for the following characters: ear length (cm), ear circumference (cm), number of rows/plant, number of kernels/row, plant height (cm), tassel height (cm), ear height (cm), number of internodes, and length and width of the ear leaf (cm). From all 45 F1 hybrids investigated, 10 indicated a high heterotic effect regarding the majority of the characteristics tested. All hybrids surpassed the parental lines in the parameters investigated.
The preliminary data show that there is a positive correlation
between the characteristics studied in vitro and in vivo.
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note:
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