Mixed Model Analysis of Within-plant Variation of Fruit Weight with Implications for Sampling of Kiwifruit Vines

In relation to horticultural crops, for purposes of predictingmean plant attributes, there has recently been an interest inusing model based approaches such as kriging that account forspatial dependencies within a plant. These models assume stationarity,i.e. observed values for two fruit on a plant depend only ontheir physical separation and not on their location. However,in most situations systematic trends exist within a plant, andthese need to be included in formulating the spatial modelsfor studying within-plant variation patterns. We propose theuse of mixed models which can simultaneously model fixed andrandom effects as well as the underlying covariance structureon the residual variation. The method is illustrated by analysisof two data sets of kiwifruit fruit sizes. The results indicatesystematic trends in fruit size within a vine, due to the positionof cane along the cordon and the shoot position along the cane.There is also evidence of a positive correlated response (