Question

1. Consider two hypothetical ranches owned by the same family. One ranch is on the Texas Gulf coast and the other is in the Texas Hill Country. They have Simmental and Simbrah cattle on both ranches. The foundation cattle on both of the ranches came from the same source and the bulls that they have bought for the two ranches have always come from the same sources. On both ranches, the Simmental and the Simbrah cattle receive the same management. Of course, the calf crop percentage weaned on both ranches varies some from year to year in both herds. However, on the Gulf Coast ranch, the Simbrah herd consistently has a higher calf crop percentage weaned than the Simmental herd. The average across years is about 83% in the Simbrah herd and 74% in the Simmental herd. On the Hill Country ranch, the calf crop percentage weaned is about 86% in both herds, when averaged across years. Using this hypothetical example to illustrate your discussion, discuss genotype - environment interactions.

Answer 1

GENOTYPE - ENVIRONMENT INTERACTION - This occurs whenever the phenotype won't be equal to genotypic value and environmental value.That is, P<or > (6 + E) - In this type of interaction, the ranking order of the genotypes will be different in different environments that is, the best genotype in one environment won't be the best in another environment. - In this interaction, the relative performance of the breeds in two environments will be different. That is the phenomenon of breeds – environment interaction is reflected by the differential expression of different breeds over environments -The Simbrah herd has higher calf crop percentage compared to the Simmental herd in gulf coast although both herds has got same performance in hill country ranch. - Therefore each herds has got its own specific adaptability for which the GⓇE interaction is responsible. - If there isn't any interaction the best herd in one environment will be the best in all. - then, P = G+E+ IGE. - In gulf coast ranch, Simmental herd are inferior to the Simbrah herd. - A linear additive relationship is observed- The phenotypic values of two the two herds are either increased or decreased in the changed environment in equal amount and the change is in the same direction, hence no change in rank order is also observed. Gulf coast ranch Simbrah herd Difference in production Hill country ranch Simmental herd