Plant Genetics: Increasing Crop Yield

Potato protoplasts in crop improvement

Clonal populations regenerated from single-leaf cell protoplasts of the potato cultivar ;Russet Burbank' display a high frequency of variation for several horticultural and disease resistance characters. Observations over a period of three tuber generations suggest stable changes in tuber shape, yield, and maturity date, in photo-period requirements for flowering, and in plant morphology. Enhanced resistance to early blight (Alternaria solani) and late blight (Phytophthora infestans) diseases also regularly occurs within regenerated populations. These findings are discussed in the context of possible application to varietal improvement, particularly as they pertain to asexually propagated plants.

Herbicide-tolerant tobacco mutants selected in situ and recovered via regeneration from cell culture

The herbicides Bentazone and Phenmedipharm kill the leaves of intact tobacco plants but do not affect callus cultures. Tolerant mutants were isolated by treating leaves of previously γ-irradiated haploid plants with herbicide then excising and culturing the green herbicide-resistant cell clones on the otherwise yellowed leaves. Among plants subsequently regenerated were a total of ten stable independently isolated mutants. Sexual crosses show these ten represent four Bentazone and two Phenmedipharm loci; all mutants were recessive to wild type.

The opportunity for and significance of alteration of ribulose 1,5-bisphosphate carboxylase activities in crop production

Increased population and the dietary changes accompanying increased affluence are creating a need for a suggested doubling of world cereal grain production (a 3% per year compounding rate) and quadrupling of grain legume production (a 6% per year compounding rate) during this quarter century (1). CO2 enrichment of field-grown crops has demonstrated the possibility of enhancing RuBP carboxylase activity to achieve improved crop production; it increases the production of grain legumes by 50 to 100% and that of cereal grains, for which the studies are less complete, by perhaps 10 to 50%. Results of O2 alteration of growth-room legumes and cereal grains are consistent with the results of CO2 enrichment except for a second role of O2 in assimilate partitioning. It may be necessary to include other components of the system, e.g., additional soil fertility, especially for non-N2-fixing plants, to enable an improved RuBP carboxylase to increase production. No practical method--chemical, genetic, or physical--of improving RuBP carboxylase activity has been reported.