Eight staked, determinate tomato (Lycopersicon esculentum Mill.) cultivars were harvested when green (before breaker stage) or when pink (breaker stage and riper) in two replicated field studies. In general, total yield and average fruit size were reduced when fruit were harvested at the green stage. Harvest maturity had only a small effect on occurrence of most fruit defects, except fruit cracking, which was more severe for pink than for green fruit in the early season experiment. Although total yields for pink harvested fruit were higher than for green harvested fruit in the early season study, the high incidence of fruit crack in pink fruit resulted in similar yields of U.S. combination grade (U.S. no. 1 and U.S. no. 2) fruit for both treatments. Because the largest fruit often bring a premium price, harvesting fruit when pink probably will result in a higher price per kilogram than harvesting fruit when green. Fruit harvested green, however, are generally firmer, more crack resistant, and require fewer harvests than fruit harvested pink.
Jeanine M. Davis and Randolph G. Gardner
Richard H. Ozminkowski Jr., Robert H. Moll, and Randolph G. Gardner
Allan F. Nash and Randolph G. Gardner
Early blight resistance was estimated in field plots for parents and F1, F2, and backcross progenies of crosses with NC EBR-1, a line derived from Lycopersicon hirsutum P.I. 126445. Areas under the disease progress curve (AUDPC) showed that resistance from NC EBR-1 was heritable and quantitative in nature. generation means in two families were intermediate to those of NC EBR-1 and susceptible parents. The distribution of AUDPC means for the different generations in both families indicated the presence of epistasis or gene linkage. Lack of fitness tests for curve-linearity confirmed this in one family. A, B, and C scaling tests showed similar results. A joint three-factor model and subsequently a six-factor model displayed the presence of epistasis in both families. Ignoring epistatic effects, narrow-sense heritability (h2) was 0.49 in one family and 0.40 in the other. By regressing F3 progeny AUDPC means on selected F2 plant values, h2 was 0.25 and 0.17, respectively.
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.
Richard H. Ozminkowski Jr., Randolph G. Gardner, Warren R. Henderson, and Robert H. Moll
Two inbred lines of fresh-market tomato (Lycopersicon esculentum Mill.), NC 20G-1 and NC 53G-1, both exhibiting prostrate growth habit (PGH), were crossed with the upright growth habit cultivar Piedmont and advanced to the F2 generation. Plants of each F2 population were grown without plant support on black plastic and subjectively rated in field plots for PGH. Extreme upright and prostrate plants were chosen from each F2 population for harvest. Mean comparisons between plants of extreme upright and prostrate habit showed increased total and marketable yields from plants with a prostrate habit. Decay and groundscarring of fruit were less in prostrate than in normally upright plants; the percentage of misshapen fruit was similar in both. The PGH character may be useful in increasing total and marketable yield of ground-culture tomatoes.
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.
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.
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.
Allan F. Nash, Randolph G. Gardner, and Warren R. Henderson
Eight stamenless tomato mutants (Lycopersicon esculentum Mill.) were intercrossed in a half-diallel design to determine allelic relationships. Two allelic series were represented among the mutants. One series included sl, sl 2 , sl 5, cs, and fl. The 2nd series included bn, sl?, and pms. No allelic interactions occurred between members of the 2 series. Fruit and seed set resulting from cross-pollinations varied greatly among the mutants. The stamenless types, with the exception of sl 2, do not appear to be promising for use in producing hybrid tomato seed because of poor fruit and seed set.
Randolph G. Gardner, James N. Cummins, and Herb S. Aldwinckle
Reactions of 122 apple clones, representing 26 pure and hybrid species of Malus, to Erwinia amylovora (Burrill) Winslow et al. were evaluated in the greenhouse, orchard, and field nursery. Vigorously growing shoots, 7 to 9 weeks old, were tip inoculated by injecting a 24-hour broth culture of a highly pathogenic isolate of E. amylovora. Lesion development, measured 5 to 7 weeks after inoculation, was expressed as a percentage of the current season’s shoot length killed by fire blight. Inter- and intraspecific variation in resistance, similar to that reported for Pyrus, was observed. The highest level of resistance, typified by a small necrotic lesion 2-3 mm in diameter around the inoculation point, occurred in small-fruited selections derived from Asiatic species. Few selections of the cultivated apple, Malus pumila Mill., were resistant. Fire blight ratings were assigned the clones based on their potentials as parents for breeding apple rootstocks.