Graduate Thesis Or Dissertation

Yield component and growth analysis of strawberries

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  • Two studies were initiated in June of 1981 in order to gain greater understanding of the growth and fruiting habits of field grown strawberries in Oregon's Willamette Valley. Yield component analysis of 'Benton', Oregon's leading cultivar and an advanced breeding selection, 'OR-US 4356' was conducted during the first (1981) and second (1982) fruiting years. In each season, the two genotypes produced essentially the same yields/plant, averaging 0.82 kg in 1981 and 0.94 kg in 1982. 'Benton' produced 25-30% more crowns/plant than 'OR-US 4356'. 'Benton' had fewed trusses/crown in 1981 (0.93 vs. 1.47) but in 1982 their numbers were the same (1.5). 'OR-US 4356' had about 60% higher numbers of fruit/truss in each season. However, 'Benton' averaged 75% greater mean berry weight than 'OR-US 4356'. There was no significant difference in total achenes/berry between genotypes (202 in 1981 and 239 in 1982). Larger fruit had a greater number of achenes and linear regressions of berry weight versus achenes/berry were significant different between genotypes in each season. 'Benton' had less achenes/gram fresh weight of berry (24 vs. 34) and achenes/cm2 (10.6 vs. 14.0) than 'OR-US 4356'. This indicates that 'OR-US 4356' fell short of its yield potential due to its inability to reach maximum berry expansion. Frequent sampling and functional growth analysis were used to quantify growth of field grown strawberry plants ('OR-US 4681') during the summer of establishment and through flowering and fruiting the next spring. Plant dry weight and leaf area increased rapidly during mid-summer, but thereafter gains slowed and finally ceased in October. This was reflected in the absolute growth rate (AGR) which peaked at 1 g dry matter/day near September 1, then fell to zero by early October. Over this period, weekly mean temperature, solar radiation, and daylength decreased by 37%, 47% and 35% respectively. Relative growth rate (RGR) declined steadily from a high of 44 mg/g/day at the end of June. Unit leaf rate (ULR) showed a similar pattern, starting at 9 g/m2/day. During the following April through June, both plant dry weight and leaf area increased at exponential rates. The growth environment improved during this period and the AGR increased continuously but RGR remained constant at 19 mg/g/day. The rate of dry matter accumulation in fruit was exponential, whereas that in leaf lamina and stems (crowns plus petioles) showed linear increases. Because of fruiting, a much smaller proportion of dry matter was partitioned to leaves than during plant establishment. However, ULR rose from 5.5 to 6.5 g/m2/day, indicating that dry matter production was relatively constant during flower and fruit production.
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