Field performance and cytology of protoplast-derived rice (Oryza sativa): high yield and low degree of variation of four japonica cultivars

Characteristics of genetic variation in the progenies of protoplast-derived plants of rice, Oryza sativa cv Nipponbare

Genetic variation in protoplast-derived rice (Oryza sativa L.) plants was characterized using first and second generation selfed progenies. A total of 133 regenerated plants were obtained from ten protoplasts of the japonica rice cultivar Nipponbare. Sixty two regenerated plants which set enough seeds for the subsequent field tests at the next generation and were derived from five protoplasts were selected, and their selfed seeds were used as the first selfed-seed progeny (Pt(1) generation). Fifteen plants were selected from each of the 15 Pt(1) lines, and their selfed seeds were used for tests at the Pt(2) generation. Thirty seven Pt(1) lines (60%) segregated plants with detrimental mutant characters of yellowgreen phenotype, dwarf stature, dense and short panicle, or low seed fertility. According to the segregation patterns in the lines having mutated plants among those originated from the same protoplasts, the stages of mutation induction were estimated. Additionally, five quantitative traits were changed in almost all Pt(1) and Pt(2) lines. Varied quantitative traits of heading date, number of spikelets per panicle, and seed fertility, were in a heterozygous state. However, culm and panicle lengths showed high uniformity, whereas reduced culm and panicle lengths were caused by mutational changes in polygenes and/or multiple genes.

Field performance of anther-culture-derived lines from F1 crosses of Indica rices under saline and nonsaline conditions

Field experiments were conducted to evaluate and compare the yield and agronomic characteristics of anther-culture-derived (AC) lines in rice and the parents under saline and nonsaline soil conditions. The yield stability of two entries was also evaluated by comparing their performance under two distinct nonsaline soil environments. The test entries were planted in randomized complete block design with four replications at each test location. Data were collected on grain yield, yield components, and agronomic characteristics. This study demonstrates that through anther culture, it is possible to produce homozygous diploid lines in a short time. The possibility of regenerating recombinants with desirable characteristics such as good plant type and salinity tolerance, higher yield, and increased resistance to pests and diseases from both the parents is high.

Molecular changes in protoplast-derived rice plants

To determine whether regeneration of rice plants from protoplast culture induces DNA polymorphisms, progeny plants from direct regenerants of such cultures were examined for restriction fragment length polymorphisms (RFLP analysis). Significantly increased levels of DNA polymorphism were found compared with those in non-tissue culture control plants. Analysis with gene sequences representative of different functional domains, revealed that such polymorphisms are apparently widespread and not associated with any particular region. Analysis by comparative digestion with both methylation-sensitive and insensitive restriction enzymes revealed that methylation changes cannot be regarded as a major factor in the induction of these DNA polymorphisms.

Regeneration of haploid and dihaploid plants from protoplasts of supersweet (sh2sh2) corn

Plants were regenerated from maize (Zea mays L.) protoplasts isolated from embryogenic cell suspensions. The donor maize suspension cultures were established from friable callus initiated from microspores of a commercial supersweet hybrid (sh2sh2). The frequency of cell colony formation was higher when protoplasts were cultured on feeder layers of maize cells as compared with a liquid thin layer method. It was demonstrated that haploid and dihaploid soil-grown plants can be regenerated from maize protoplasts isolated from haploid cell cultures.

Plant regeneration from protoplasts of indica rice: genotypic differences in culture response

Fourteen varieties of indica rice (Oryza saliva L.) were examined for their capacity for plant regeneration from protoplasts using the nurse culture methods developed for japonica rice. Calli induced from germinating seeds were grouped into two types: type I, white and compact; type II, yellow and friable. In four varieties producing type II callus, colony formation (2%-4.5%) and plant regeneration (2%-35%) were observed. The inability to develop suspension cultures was a major obstacle in regenerating plants from protoplasts of the remaining rice varieties studied.

Initiation of morphogenic cell-suspension and protoplast cultures of barley (Hordeum vulgare L.)

Cell-suspension cultures were initiated from embryogenic calli of various barley cultivars. Seven fast-growing suspension lines were obtained from four different cultivars (cvs. Dissa, Emir, Golden Promise and Igri). Two of these cell suspensions showed morphogenic capacity. From a cell suspension of cv. Dissa, albino plantlets were regenerated when aggregates were cultured on solid medium. Aggregates of cv. Igri usually stopped differentiation at the globular stage, but occasionally formed scutellum-like structures. Five suspension lines were used for protoplast isolation and culture. Dividing protoplasts were obtained from all lines, but with cv. Igri a few divisions only and no further development were observed. Protoplasts from the various lines differed in the time of first division (2-14 d), division frequency (0.09-70.9%) and efficiency of colony formation (0.09-7.3%). Protoplasts isolated from the morphogenic cell suspension of cv. Dissa developed compact calli which sporadically regenerated albino plantlets.