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  • Author or Editor: Elmer E. EWing x
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Abstract

Following curing and a period of storage at 10°C, potato (Solanum tuberosum L.) tubers were stored for 4 to 5 weeks at 1° or 10° in controlled atmospheres consisting of either air, 2.5% O2 (balance N2), or N2. CO2 production of tubers stored in air at 10° was relatively constant. When tubers were stored in air at 1°, CO2 production initially was lower than at 10° in air. It then increased to a maximum after about 15 days and eventually declined again. Storage in 2.5% O2 or N2 prevented the increase in CO2 production that occurred after several days of storage in air at 1°. Malate and citrate were the only organic acids detected in significant amounts in juice extracted from tubers when experiments were terminated. Changes in citrate showed no consistent trends. Tubers stored in air at 1° had higher sucrose, fructose, glucose, and malate levels than tubers stored at 10°. Storage in N2 at 1° prevented the malate, sucrose, and reducing sugar increases. Storage in 2.5% O2 inhibited the malate, fructose, and glucose increases at 1° and reduced the sucrose content of ‘Monona’ and ‘Norchip’ cultivars, which accumulated large amounts of sucrose during storage in air at 1°. Sucrose content of ‘Kennebec’ was not affected by 2.5% O2. Storage in 2.5% O2 slowed the accumulation of fructose and glucose, but only ‘Monona’ and ‘Norchip’ yielded acceptable chips after storage in 2.5% O2 at 1°. All 3 cultivars yielded acceptably colored chips after storage in N2 at 1°, but the development of blackheart when tubers were returned to air makes N2 an unacceptable storage atmosphere at this temperature. Storage in N2 resulted in soft rot at 10°.

Open Access

Abstract

Cuttings of young potato plants (Solanum tuberosum L.) were used as a technique for evaluating the influence of temperature and photoperiod on the degree of tuber induction. Growth chambers were used to create four combinations of two air temperature regimes (“hot”, 30C day/25C night, or “cool”, 20C day/15C night) and two photoperiods (“long photoperiod”, 16 hr of light, or “short photoperiod”, 10 hr of light). The six cultivars and clones tested exhibited varying degrees of induction. Early maturing cultivars, such as ‘Norchip’ and ‘Cl-884’, were less affected by increased temperature with short photoperiod or by longer photoperiod under cool temperatures than were other cultivars. Raising the temperature under short photoperiod caused a reduction of about 50% in tuber dry weight from cuttings of the late-maturing ‘Katahdin’. Long photoperiod intensified the effects of higher temperature in reducing induction, especially with later-maturing cultivars such as ‘Katahdin’ and ‘Désirée’.

Open Access

Pea (Pisum sativum) dominant for the fundamental color gene A showed a high level of resistance to Globisporangium ultimum (formerly Pythium ultimum) seed rot. Reciprocal crosses demonstrated that, with our materials, such resistance was associated with the testa (seedcoat) phenotype but not the embryo phenotype. Dominance of A over a was complete for this trait. Neither wrinkled seed form (r) nor green cotyledons (i) diminished resistance when A was dominant, although both recessive alleles diminished resistance when seeds were borne on white-flowering (a) plants. The product of the A gene functions in the pathway leading to flavonoids, including proanthocyanidins (PAs) and anthocyanidins. We found that resistance to G. ultimum seed rot was closely associated with not only dominant A but also testa PAs and testa sclerenchyma. Even A testas that lacked anthocyanins but contained PAs and sclerenchyma showed a high level of seed rot resistance. Moreover, a mutation removing PAs and sclerenchyma in a narrow zone from the hilum to the radicle markedly increased susceptibility. The PAs in pea testas were predominantly prodelphinidins in seeds from purple-flowered plants (A B) and procyanidins from pink-flowered plants (A b). Compared with procyanidins, prodelphinidins have higher antioxidant activity but are more likely to sequester iron, a particular concern with dry pea. Although A B testas were more resistant than A b to seed rot, the difference seemed too slight to militate against growing pink-flowered pea. We stressed the need for more histological comparisons of A B and A b testas, and we indicated that genes and their phenotypic effects examined during the current study could be useful for modeling biosynthesis of PAs and related cell walls.

Open Access