This paper presents a method of genotypic stability analysis for regional variety trials. Based on the principle of structural relationship analysis, the genotype‐environment interaction effect of a variety is partitioned into two components. They are the linear response to environmental effects, which is measured by a statistic α̂, and the deviation from the linear response, which is measured by another statistic λ̂ A perfectly stable variety has (α, λ)=(‐1, 1) and a variety with average stability has (α, λ) = (0, 1).Seedlings in three series of potato maincrop regional trials were analyzed for the genotypic stability of their marketable tuber yields. The results showed that the highest yielders were unstable, while the seedlings with average stability had about the same yielding ability as the check varieties.

Histone acetylation is involved in the regulation of gene expression in plants and eukaryotes. Histone deacetylases (HDACs) are enzymes that catalyze the removal of acetyl groups from histones, which is associated with the repression of gene expression. To study the role of histone acetylation in the regulation of gene expression during seed germination, trichostatin A (TSA), a specific inhibitor of histone deacetylase, was used to treat imbibing Arabidopsis thaliana seeds. GeneChip arrays were used to show that TSA induces up-regulation of 45 genes and down-regulation of 27 genes during seed germination. Eight TSA-up-regulated genes were selected for further analysis - RAB18, RD29B, ATEM1, HSP70 and four late embryogenesis abundant protein genes (LEA). A gene expression time course shows that these eight genes are expressed at high levels in the dry seed and repressed upon seed imbibition at an exponential rate. In the presence of TSA, the onset of repression of the eight genes is not affected but the final level of repressed expression is elevated. Chromatin immunoprecipitation and HDAC assays show that there is a transient histone deacetylation event during seed germination at 1 day after imbibition, which serves as a key developmental signal that affects the repression of the eight genes.

In this work, we report cloning of two full-length 1-aminocyclopropane-1-carboxylate oxidase (ACO) cDNAs (ACO1 and ACO2) from potato (Solanum tuberosum) and their expression in potato tissues. The sequence data indicate that the two cDNAs share a high degree of homology with each other, and with known ACO genes from other plant species, including monocots and dicots. However, these potato genes lack homology at the 5' and 3' ends, despite similarities in their open reading frames and encoded amino acids. Phylogenetic analysis places them in two subfamilies of ACOs. The genes are tissue specific: expression is high in leaves and low in roots and tubers. In sprouts and tubers, ACO1 is induced by heat (40 degrees C) and cold (0 degrees C) stresses, whereas ACO2 is induced only by cold (0 degrees C). ACO1 is markedly induced in leaves by wounding, soil-flooding, and exogenous application of 1-aminocyclopropane-1-carboxylic acid (ACC). In contrast, ACO2 induction is lower under these treatments. ACO1 and ACO2 are regulated very differently in potato leaves with respect to senescence. ACO2 expression is unaffected by senescence, whereas that of ACO1 is closely related to the age and senescence in both attached and detached leaves. Exogenous ACC not only induces ACO1, but also accelerates leaf senescence. ACO1 transcripts are induced significantly in leaves, stems, and tubers in the Potato virus A (PVA)-resistant potato cultivar Shepody when graft inoculated with PVA.

No abstract

The differential tolerance to moisture stress among potato (Solanum tuberosum L.) genotypes may be associated with differences in sensitivity during the ontogeny of yield development. This study was undertaken to determine the effect of a wide range of moisture stresses on the yield and components of yield of eight genotypes (‘Acadia Russet’, ‘Bintje’, ‘Jemseg’, ‘Kennebec’, ‘Raritan’, ‘Russet Burbank’, ‘Sable’, and ’Shepody’). The genotypes were subjected to three levels of soil moisture tension in 1983 (−30, −60, and −90 kPa) and four in 1984 (−30, −60, −90, and −120 kPa) at Vauxhall, Alberta on a Cavendish sandy loam (Brown Chernozemic) (fine‐loamy, mixed, frigid Ultic Haploxeralf). A mathematical model based on the method of path analysis was used to study the relationship between the components of yield and the overall response of the final tuber yield to moisture stress. Moisture stress treatments caused marked (P < 0.01) reductions in marketable yield, tuber number per stem and average tuber weight. Mainstem number was not affected. The genotypes ✕ stress interaction was significant (P < 0.05) in an analysis of variation (ANOVA) carried out over 2 yr. While analysis of the yield data using the model demonstrated that in general genotypes are very sensitive to moisture stress at both tuber initiation and at the tuber sizing growth stages, the greatest variability amongst genotypes in response to stress occurred at tuber sizing. Shepody, Russet Burbank, and Sable showed a strong sensitivity to stress in the tuber initiation phase while Jemseg, Acadia Russet, and Kennebec were more sensitive at tuber sizing. The study demonstrates differences in the structure of the response of the genotypes to moisture stress, measured in terms of the components of tuber yield, and indicates the importance of this information to ensure efficient moisture management.