Genotypic and environmental variation in protein content of field peas
Jermyn, William Alexander
The contributions of genotype, location, and year to variability in yield and protein content of field peas were estimated from a study of 25 genotypes grown at three locations in one year and 22 genotypes grown at one location for three years. Protein content was less variable than yield within and among locations and years. Protein content varied substantially with locations but only slightly with years. The relationship of protein content to several other plant traits was assessed. Protein content was not correlated with height, harvest index, seed weight, or days to flower. However, it was consistently negatively correlated with yield over locations, years and a wide range of genotypes. Coefficients of determination showed that between 6 and 66% of the observed variation in protein content over three experiments was associated with variation in yield. The negative relationship diminished among F2 populations. indicating that correlations between traits among heterogeneous populations may be misleading. Physiological explanations for the negative yield-protein content correlation were offered. Yield and protein yield were very highly correlated, whereas protein content and protein yield were unrelated. This indicates that improved protein productivity would come only from increased yield. Methionine content of field peas expressed as mg met/g meal and as mg met/g protein was low and the range was very narrow, indicating insufficient scope for improvement by breeding among the genotypes tested. Protein content was positively correlated with mg met/g meal but not correlated with mg met/g protein. Broad-sense and narrow-sense heritability estimates for protein content were low to moderate, and additive inheritance was indicated. Mg met/g protein was not heritable, indicating the need for an alternative approach to protein quality improvement. Reported differences between smooth-seeded and wrinkle-seeded genotypes were verified and a new one added. The gene for wrinkling caused a seed-weight reduction in wrinkle-seeded compared with smooth-seeded progeny of crosses' between parents of different seed shape, regardless of parental seed weight. The range in protein content among 1071 genotypes from the U.S.D.A. World Pea Collection was very narrow (22.6 to 30.9%), compared with the wide range in yield and very wide range in seed weight of the same genotypes.
DegreeDoctor of Philosophy (Ph.D.)
DepartmentAgricultural and Bioresource Engineering
SupervisorSlinkard, A. E.
Copyright DateAugust 1976