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Joseph M. Kemble, Jeanine M. Davis, Randolph G. Gardner, and Douglas C. Sanders

The influence of flat cell volume (cavity containing growing medium) on transplant growth and development of NC 13G-1, a compact-growth-habit, fresh-market tomato (Lycopersicon esculentum Mill.) breeding line, was compared to that of a normal growth habit line, NC 8288. Transplants of each line were produced in four cell volumes (3.3, 27, 37.1, and 80cm3) for 5 weeks, evaluated and then transplanted to larger containers, and grown until anthesis. During the first 5 weeks after seeding, plant dry weight did not differ between the lines; however, plant height of NC 13G-1 was ≈60% of the height of NC 8288. For both lines, number of days from sowing to anthesis decreased as root cell volumes increased. For space-efficient production of large quantities of compact-growth-habit tomato transplants, flats with root cell volumes as small as 27 and 37 cm3 can be used without greatly delaying anthesis.

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Joseph M. Kemble, Jeanine M. Davis, Randolph G. Gardner, and Douglas C. Sanders

Compact-growth-habit (CGH) tomatoes (Lycopersicon esculentum Mill.) do not require the pruning, staking, and tying required for many fresh-market tomato cultivars. In 1990, 5-week-old transplants of the CGH tomato breeding line NC 13G-1 were grown in single rows with in-row spacings of 31, 46, 61, and 76 cm and in double rows with in-row spacings of 31 and 46 cm. NC 13G-1 produced high early and total season marketable yields when grown in either double-row treatment compared to any single-row treatment. In 1991 and 1992, 4- and 5-week-old NC 13G-1 transplants were produced in five root cell volumes (8.6, 13.6, 27.0, 37.1, and 80.0 cm3), transplanted into double rows with an in-row spacing of 46 cm, and evaluated for yield. Five-week-old transplants produced in 37.1- and 80-cm3 cells flowered sooner after transplanting and produced higher early season yields than 4-week-old transplants produced in the three smaller cells. Midseason yields increased quadratically and late-season yields decreased quadratically as root cell volume increased. Total season marketable yields did not differ among treatments. In 1991, production costs were influenced by root cell volume, but not in 1992. In 1992, net returns for the four smallest cell volumes were similar, and lower than for transplants grown in the largest cell volume. In both years, highest net returns were achieved with transplants produced in 37.1-cm3 cells. Considering the estimated 1992 net returns of $17,000/ha, production of CGH tomatoes may provide an alternative for staked-tomato growers concerned with labor availability and production costs, even though marketable yield from NC 13G-1 was lower than with a conventional cultivar under the standard system.

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Douglas C. Sanders, Jennifer D. Cure, Pamela M. Deyton, and Randolph G. Gardner

Amount of vascular development (veininess) is an important quality factor for processing wholepack tomatoes. The influences of nutrient and soil moisture stress on the amount of vascular development in `Chico III', `Dorchester', and `Roma' tomato fruit were studied. Fruit subjected to nutrient stress showed the highest amount of veininess. Fruit exposed to moisture stress after initial fruit set did not differ from controls in amount of veininess. Amount of vascularization did not differ among cultivars. A method for quantifying veininess was developed and compared with a traditional subjective rating scale. There was a high correlation (r2 = 0.77) between the subjective rating and quantitative measurement of veininess.

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Richard H. Ozminkowski Jr., Randolph G. Gardner, Robert H. Moll, and Warren R. Henderson

Prostrate growth habit (PGH) in tomato (Lycopersicon esculentum Mill.) lines derived from breeding material developed at the Agriculture Canada Research Station, Beaverlodge, Alberta, was the subject of a quantitative inheritance study. Plants with PGH have an increased lateral branch angle, relative to upright plants, and crown-set fruit supported above the soil surface making hand harvest easier. Genetic parameters were estimated in two families (20G and 53G), each containing PGH and upright-habit parental lines, F1, F2, and backcrosses to each parent. Field-grown plants were subjectively rated twice during the growing season. Broad-sense heritability of PGH in family 20G was estimated to be 0.65 and 0.71 for ratings of plant growth habit 6 and 9 weeks after transplanting, respectively, and 0.71 and 0.68 for those of family 53G. Narrow-sense heritability was estimated to be 0.83 and 1.05 for the two ratings in the 20G family and 0.77 and 0.78 in the 53G family. F1 and F2 means were not different from mid-parent values. The genetic variance was entirely additive and expression was influenced by the environment. The data did not support the hypothesis that PGH was controlled by a single gene.

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Matthew D. Robbins, Mohammed A.T. Masud, Dilip R. Panthee, Randolph G. Gardner, David M. Francis, and Mikel R. Stevens

Tomato spotted wilt virus (TSWV) and Phytophthora infestans (late blight) in tomato (Solanum lycopersicum) have a worldwide distribution and are known to cause substantial disease damage. Sw-5 (derived from S. peruvianum) and Ph-3 (derived from S. pimpinellifolium) are, respectively, TSWV and late blight resistance genes. These two genes are linked (within 5 cM on several maps) in repulsion phase near the telomere of the long arm on chromosome 9. The tomato lines NC592 (Ph-3) and NC946 (Sw-5) were crossed to develop an F2 population and subsequent inbred generations. Marker-assisted selection (MAS) using three polymerase chain reaction-based codominant markers (TG328, TG591, and SCAR421) was used in F2 progeny with the goal of selecting for homozygous coupling-phase recombinant lines. From 1152 F2 plants, 11 were identified with potential recombination events between Ph-3 and Sw-5; of those, three were male sterile (ms-10). F3 progeny were generated from the remaining eight F2 recombinants, and resistance to both pathogens, or Ph-3 and Sw-5 in coupling phase, was confirmed in three of those. Recombination was suppressed fivefold in our F2 population to 1.11 cM between genes when compared with published maps of the same region. However, MAS was an efficient tool for selecting the desirable recombination events for these two pathogen resistance genes.