Beneficial exploitation of additive genetic effects to improve yield potential per plant in maize

The effect of inbreeding on yield potential per plant and the load of deleterious genes in maize ( Zea mays L.) were studied. Twelve recycled hybrids obtained though inbreeding and selection on the basis line performance per se , along with their original hybrid PR 3183 and the check hybrid B73×Mo17, were tested in a R28 honeycomb trial under very low density (0.74 plants/m 2 ). Inbreeding depression was related with reduced yield potential per plant and increased CV of individual plant yield (estimated in F 1 and F 3 ), as well as with increased heterosis. The recycled hybrids were found to have improved yield potential per plant in both F 1 and F 3 , lower CV values in F 3 , and lower inbreeding depression. Results were indicative of the effective exploitation of the additive genetic effects, which reduced the load of deleterious genes, and produced less heterozygous hybrids that were characterized by improved yield potential per plant

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