Principal Component and Cluster Analysis as a Tool in the Assessment of Tomato Hybrids and Cultivars

Determination of germplasm diversity and genetic relationships among breeding materials is an invaluable aid in crop improvement strategies. This study assessed the breeding value of tomato source material. Two commercial hybrids along with an experimental hybrid and four cultivars were assessed with cluster and principal component analyses based on morphophysiological data, yield and quality, stability of performance, heterosis, and combining abilities. The assessment of commercial hybrids revealed a related origin and subsequently does not support the identification of promising offspring in their crossing. The assessment of the cultivars discriminated them according to origin and evolutionary and selection effects. On the Principal Component 1, the largest group with positive loading included, yield components, heterosis, general and specific combining ability, whereas the largest negative loading was obtained by qualitative and descriptive traits. The Principal Component 2 revealed two smaller groups, a positive one with phenotypic traits and a negative one with tolerance to inbreeding. Stability of performance was loaded positively and/or negatively. In conclusion, combing ability, yield components, and heterosis provided a mechanism for ensuring continued improvement in plant selection programs

The efficiency of a breeding programme with progressively advanced targets applied in an elite cultivar of snap bean

The objective of this study was to assess the efficiency of a pedigree intra-cultivar selection, based on widely spaced individual plant performance, in a traditional snap bean (Phaseolus vulgaris L.) cultivar, aiming to restore or even improve the cultivar. The programme started with the target of earliness and yield stability, and was progressively advanced with the target of seed shape uniformity. Two parallel pathways were followed: under greenhouse conditions (four generations of selection) and under field conditions (two generations of selection). The average response to selection was 2·43–3·15 and 0·13–0·42 pods/plant per generation for earliness and yield, respectively. The coefficient of variability (CV) of earliness decreased from 81·33 to 39·43 % and from 61·31 to 42·51 % for greenhouse and field grown progenies, respectively. For yield, the CV showed a low decreasing rate, and was stabilized at the end-value of almost 28 %. The results were confirmed during two direct evaluation tests. Firstly, the evaluation of 21 families, as individual spaced plants, showed mean values for earliness of 18·99–22·94 pods/plant and for yield of 32·89–33·09 pods/plant. Secondly, the evaluation of improved selections from the greenhouse and the field and of the source cultivar, in a dense stand, showed that all the selections produced high and stable early fresh pod harvest even 53 days after planting, while the control was still at the vegetative phase. The yield of selected progenies was 219–242 % superior compared with source material. Also, seed stocks of all selections were of the normal long shape. Short-seed progenies were excluded from the breeding programme, since they lacked earliness and stability of performance. The results demonstrate conclusively that it is possible to simultaneously improve earliness and pod yield through diminishing plant-to-plant variability.</jats:p