The efficiency of seedling selection by visual preference in a potato breeding programme

Abstract

The efficiency of visual selection in a glasshouse of 1600 seedlings compared with visual selection in the field of the same clones is examined. Also the amount of agreement in assessment between four different potato breeders screening the same clones is investigated. Seedlings were grown from true seed in four-inch pots in a glasshouse and all the clones which produced tubers were grown in the field the following year. Clones which produced more than one tuber from a seedling were grown at two locations in the first clonal year. One of the sites used in the first clonal year is normally used for potato yield trials (i.e. a ware site) and the other is normally used for the production of healthy seed tubers (i.e. a seed site). In all three environments, the tubers produced from each plant were assessed by four breeders independently on a 1-9 scale of increasing attractiveness.From the data it was found that the repeatability of assessment between the glasshouse and the first clonal year was low in that the correlation between the average preference score of the four breeders in the glasshouse and each of the two first clonal year sites accounted for only 8-24 and 6-84% of the total variation. Many clones which had low scores in the glasshouse were subsequently given high scores in the first clonal year. It was therefore concluded that selection of seedlings was not very efficient. Although, in general, the weight of the tuber that was planted greatly influenced whether a clone was selected in the first clonal year, a large number of clones which produced only small tubers in the glasshouse were subsequently selected in the first clonal year.Within each environment the four breeders were either all selecting, or all rejecting, a much higher proportion of clones than would be expected if selection had been made completely at random. The breeders were in most agreement when assessing clones at the 'ware' site, and in most disagreement when assessing them grown in the glasshouse from true seed. Therefore the poor efficiency of selection of seedlings grown in the glasshouse was not, in the main, a result of a high error variance in visual assessment but rather due to poor association between the performance of seedlings and first clonal year plants.

The use of univariate cross prediction methods in the breeding of a clonally reproduced crop (Solanum tuberosum)

“…They were also the same crosses as reported by Brown et al (1984), , and . The crosses are identified by the codes Cl to C8.…”

“…The growing conditions and experimental designs used for the seedlings in the glasshouse (GH) and clones in the field for the first clonal year were given by Brown et aL (1984), while those for the second clonal year were given in . The details are thus only reported briefly here.…”

“…For a description of the Scottish Crop Research Institute (SCRI) potato breeding programme see Holden, 1977 andMackay, 1982. However, all the other problems of selection efficiency are still pertinent and studies have shown that such conventional phenotypic selection in the early generations is relatively ineffective (Brown, Caligari, Mackay and Swan, 1984;Brown, Caligari, Mackay and Swan, 1986). It would therefore seem appropriate to investigate cross prediction methods in potatoes, particularly as have reported that progeny means were repeatable over the early generations, even though the environments in which different generations were raised were as diverse as seedlings in small pots in a glasshouse to material grown in the field from tubers.…”

Expected response to early-generation selection for yield and tuber appearance traits in potatoes

“…The lower number of tubers, of smaller size, has been indicated as the main obstacle for the application of selection during seedling generation (BROWN et al, 1984;PINTO, 1999;GOPAL;MINOCHA, 1997). Recent studies have focused on the size of the containers where the seedling is grown, and for some traits, the containers should be larger than the usual 250 ml vases used in many potato improvement programs (VERÍSSIMO et al, 2012).…”

The use of multivariate cross prediction methods in the breeding of a clonally reproduced crop (Solanum tuberosum)

“…The growing conditions and experimental design used for the seedlings in the glasshouse, and the clones in the first clonal year were described by Brown, Caligari, Mackay and Swan (1984). Those for the second and third clonal generations were given by Brown et al, (1987 In each year, at each site, individual plots were harvested and taken into storage.…”