The effects of different factors were investigated in the process of isolated microspore culture of Zea mays L., Using donor plants grown in standard conditions and an efficient isolation technology, homogeneous populations of viable microspores at specific developmental stages were obtained and tested in culture. The cytological evolution of the microspores during the first week of culture was monitored using a DNA-specific fluorochrome. It was found that developmental stages of microspores, number of days of pretreatment at 7°C of the tassel, and culture density greatly influenced the number of microspore-derived embryos. Optimal conditions required for embryo and plant production are described.

Optimization of maize microspore isolation and culture conditions for reliable plant regeneration

The components of plant tissue culture media II. Organic additions, osmotic and pH effects, and support systems

Cereal microspore culture

In earlier works, the author reviewed and emphasized the importance of the in vitro induction of haploids (Reinert and Bajaj 1977; Bajaj 1983 a). During the last decade tremendous progress has been made in this area. The frequency of androgenesis has been increased, work extended successfully to a number of agricultural crops, and new cultivars have been released. This warrants the need to put this information and literature together.

In Vitro Production of Haploids and Their Use in Cell Genetics and Plant Breeding

Androgenesis in flowering plants is a unique biological process. It provides an understanding of the biological basis of single -cell microspore embryogenesis to the production of a dihaploid plant. This system provides an u nparalleled opportunity to shorten the breeding cycle and fix agronomic traits in the homozygous state, such as recessive genes for disease resistance. The most desirable dihaploid variation in all the m ajor crops including rice, wheat, barley, maize, rape, cotton, sunflower, coffee, etc. has already been developed and uti lized in modern crop breeding. Many known and a few unknown factors are involved in such development. A few noteworthy factors are donor plants, genotypic variation, media composition, and handling of cu ltures, which may have a greater influence on the response of androgenesis. A further opportunity has arisen to use a pollen-specific gene, promoter and transgenic dihaploid (homozygous), gene expression, proteomics, translational regulation and post-translational modification of genes to widen the scope of crop improvement. The homozygous (isogenic) lines will provide unique genetic material for mapping populations for use in functional genomics and molecular breeding.

Androgenic haploids: Factors controlling development and its application in crop improvement

Pollen calli and plantlets of Hordeum vulgare cv. ‘Sabarlis’ were obtained through direct pollen culture without pretreatment of spikes or preculture of anthers. Isolated immature pollen grains were cultured first in a 0.3 M mannitol solution or a C1 basal medium (Chen et al. 1979) supplemented with 0.3 M mannitol but without sucrose for 5–7 days, then transferred into a C1 medium containing 6% sucrose, 3 mM glutamine and 5 mM m-inositol. After a 3 week culture period small pollen calli derived from the pollen grains were transferred into a growth medium comprising C1 basal medium supplemented with 250 mg/1 lactalbumin hydrolysate and 0.5 mg/1 kinetin. For shoot regeneration, vigorously growing calli were transferred onto agarsolidified MS medium (Murashige and Skoog 1962) containing 3% sucrose, 2 mg/1 benzyladenine and 0.5 mg/1 indole-3-acetic acid. The ratio of green plants to albino was approximately 1∶2.2.

M. Kyo

Papers

Callus formation and plant regeneration through direct culture of isolated pollen of Hordeum vulgare cv. ‘Sabarlis’