A half diallel including 11 parents was conducted under high temp. conditions in Florida and low temp. conditions in Israel. Blossom scar (BS) size was measured relative to the fruit size for 20 mature fruits per plot. Griffing's analysis showed that both GCA and SCA effects were highly significant at both locations (p< 0.0001). Analysis according to Hayman indicated no epistatic effects. In both environments, additive and dominant gene action was significant (p < 0.0005), although the additive gene effects were most important. Averaged over all loci, the incomplete dominance was in the direction of small BS. Narrow sense heritability estimates were 0.62 and 0.57 for Florida and Israel, respectively. Combined analysis showed that the genetic system was unstable over the 2 environments, as both additive and dominant gene effects interacted significantly with environment (p < 0.0001). The implication for breeding programs is that hybrid performance should be tested at several locations to insure stability of small BS.
J. H. M. Barten, J. W. Scott, J. Elkind, and N. Kedar
J. McFerran, M. J. Goode, S. J. Scott, and F. W. Montgomery
‘Ozark Pink’ VF is an indeterminate, pink-fruited tomato (Lycopersicon esculentum Mill.) developed at the Univ. of Arkansas to replace ‘Traveler 76’ (2), which is susceptible to verticillium wilt. ‘Ozark Pink’ provides the excellent flavor quality of traditional Arkansas pink tomatoes with improved fruit size and disease resistance over ‘Traveler 76’. Fruits also are larger and firmer than ‘VF Pink’ (3), which was grown primarily in southeastern Arkansas. ‘Ozark Pink’ is adapted to stake culture and vine-ripe harvest for local market, shipping short distances and for home gardens throughout Arkansas and the Ozark Mountain area. Pink cultivars remain the most popular type sold as bedding plants and at roadside stands in Arkansas, although part of the commercial acreage now grows red-fruited cultivars.
J.H.M. Barten, J.W. Scott, N. Kedar, and Y. Elkind
To identify the stage of flower development sensitive to low temperature-induced rough blossom-end scarring (RBS) in tomato (Lycopersicon esculentum Mill.), short-term low-temperature treatments (1, 3, and 5 days continuously at 10C or 6, 9, and 12 days at 18/10C day/night) were applied to young, flowering plants and to plants at the six-leaf stage. Flowers were tagged at anthesis over 4 weeks and the growth stage of the flowers at the beginning of the treatments was determined in days relative to anthesis. The blossom-end scar index (BSI), a measure for blossom-end scar size relative to fruit size, and number of locules were recorded for mature fruits. In three experiments, 5 days at 10C or 6 days at 18/10C, applied during early flower differentiation, induced RBS in mature fruits. For each of the three cultivars tested `Horizon', Waker', and `Solar Set'), flower buds were most sensitive from 26 to 19 days before anthesis. In this experiment, RBS induction was not caused by an increase in the average number of locules per fruit. A short period of sensitivity during very early flower development explains the variation in RBS among seasons and within plants encountered in field situations. This study also presents a standard induction technique for further investigation of physiological and morphological backgrounds of the disorder and possible genotype screening.
J.W. Scott, J.B. Jones, G.C. Somodi, and R.E. Stall
Tomato (Lycopersicon esculentum Mill.) accessions were tested for hypersensitivity and rated for resistance following field inoculation with tomato race 3 (T3) of the bacterial spot pathogen Xanthomonas campestris pv. vesicatoria (Doidge) Dye (Xcv) in 1992 and 1993. Hawaii 7981, PI 126932, PI 128216, and selections of the latter two expressed hypersensitivity. Hawaii 7981, only tested in the field in 1993, was nearly symptomless and developed significantly less disease than any other accession. PI 128216 had a level of disease similar to susceptible `Solar Set' when tested in 1993. However, a selection from it (PI 126218-S) was significantly more resistant than `Solar Set' in both years. Although PI 126932 had a level of disease similar to `Solar Set' in both years, a selection from it (PI 126932-1-2) was significantly more resistant than `Solar Set' in 1993. Other accessions without hypersensitive responses but more resistant than `Solar Set' for two seasons were PI 114490, PI 126428, PI 340905-S, and PI 155372. Hawaii 7975 was significantly more resistant than `Solar Set' in the one season it was tested.
S.M. Smith, J.W. Scott, J.A. Bartz, and S.A. Sargent
Fresh market tomatoes (Solanum lycopersicum L.) handled through dump tanks and flumes at packinghouses can absorb water via stem scar tissues. This water uptake can lead to internalization of various hazardous bacteria, including Erwinia carotovora (Jones), the causal agent of bacterial soft rot. Studies were conducted to determine if the interval between harvest and water immersion affected water uptake for ‘Florida 47’ and ‘Sebring’, cultivars with high and low water uptake, respectively. Fruit were held for 2, 8, 14, and 26 hours after harvest for the fall season and 2, 4, 6, 8, and 14 hours for the following spring season before water immersion. Mature green fruit were weighed, submerged in water for 2 min and then reweighed to determine water uptake. During the submergence, air pressure was applied such that the fruit were exposed to a static water-head equivalent to 1.3 m. In the fall season ‘Sebring’ fruit absorbed significantly less water than ‘Florida 47’ fruit at 8 and 26 hours after harvest. In the spring season fruit of ‘Sebring’ absorbed significantly less water than ‘Florida 47’ at all times after harvest, confirming results of previous studies. In the fall season, the time interval between harvest and treatment did not affect water uptake for either cultivar. By contrast, in the spring season fruit absorbed significantly greater amounts of water at 2 hours as compared with 4, 6, 8, and 14 hours after harvest, whereas similar amounts of water were absorbed at 4–14 hours after harvest. Therefore, to minimize the tendency of fruit to absorb water, packinghouse managers should hold freshly harvested fruit for at least 4 hours before immersing them in the dump tank.
J.W. Scott, J.B. Jones, G. Cameron Somodi, and R.E. Stall
Resistant Hawaii 7981 (P1) was crossed with susceptible Fla. 7060 (P2), and F1, BCP1, BCP2, and F2 generations were obtained. Hypersensitive reactions (Hr) were measured 24 and 48 hours after inoculation in growth chambers at 24 and 30C. At 30C, there was no Hr. At 24C and 24 hours, 100% of Hawaii 7981 plants, 54.2% of BCP1 plants, and 21.7% of F2 plants had Hr. At 24C and 48 hours, 100% of Hawaii 7981, the F1, and BCP1 plants; 50% of BCP2 plants; and 73.3% of F2 plants had Hr. Other plants were inoculated and rated for race T3 in the field. Disease for each generation was significantly different (P < 0.05) and their order from most to least resistant was P1, BCP1, F1, F2, BCP2, and P2. The F1s were distributed between the parents with slight overlaps. BC plants had bimodal peaks similar to the F1 and their respective parents. The F2 had three peaks corresponding to P1, F1, and P2. The data suggest Hr and field resistance are controlled by the same incompletely dominant gene.
J.W. Scott, D.M. Francis, S.A. Miller, G.C. Somodi, and J.B. Jones
Crosses were made between tomato (Lycopersicon esculentum Mill.) inbreds susceptible to races T2 and T3 of bacterial spot (Xanthomonas vesicatoria and Xanthomonas campestris pv. vesicatoria, respectively) and accession PI 114490 with resistance to races T1, T2, and T3. Resistance to race T2 was analyzed using the parents, F1, and F2 generations from one of the crosses. The F1 was intermediate between the parents for disease severity suggesting additive gene action. The segregation of F2 progeny fit a two-locus model (χ2 = 0.96, P = 0.9-0.5) where four resistance alleles are required for a high resistance level, two or three resistance alleles provide intermediate resistance, and zero or one resistance allele results in susceptibility. The narrow sense heritability of resistance to T2 strains was estimated to be 0.37 ± 0.1 based on F2 to F3 parent-offspring regression. A second cross was developed into an inbred backcross (IBC) population to facilitate multilocation replicated testing with multiple races. Segregation for T2 resistance in the inbred backcross population also suggested control was by two loci, lending support to the two-locus model hypothesized based on the F2 segregation. To determine if the same loci conferred resistance to the other races, selections for race T2 resistance were made in the F2 and F3 generations and for race T3 resistance in the F2 through F4 generations. Six T3 selections (F5), 13 T2 selections (F4's that diverged from seven F2 selections), and control lines were then evaluated for disease severity to races T1, T2, and T3 over two seasons. Linear correlations were used to estimate the efficiency of selecting for resistance to multiple races based on a disease nursery inoculated with a single race. Race T1 and race T2 disease severities were correlated (r ≥ 0.80, P< 0.001) within and between years while neither was correlated to race T3 either year. These results suggest that selecting for race T2 resistance in progeny derived from crosses to PI 114490 would be an effective strategy to obtain resistance to both race T1 and T2 in the populations tested. In contrast, selection for race T3 or T2 will be less likely to result in lines with resistance to the other race. PI 114490 had less resistance to T3 than to T2 or T1. Independent segregation of T2 and T3 resistance from the IBC population derived from PI 114490 suggests that T3 resistance is not controlled by the same genes as T2 resistance, supporting the linear correlation data.
J.W. Scott, J.B. Jones, G.C. Somodi, D.O. Chellemi, and S.M. Olson
J. W. Scott, G. Cameron Somodi, and J. B. Jones
Tomato (Lycopersicon esculentum Mill.) accession PI 270248 (‘Sugar’) had high levels of resistance to bacterial spot [incited by Xanthomonas campestris pv. vesicatoria (Doidge) Dye] on fruit, but foliage was susceptible. Hawaii 7998 (H7998) was highly resistant to foliar infection, but was intermediate in resistance to fruit infection. Fruit spot on hybrids between ‘Sugar’ and H7998 was usually intermediate to the parents. Occasionally, disease incidence of hybrids was not statistically different from one or both parents, but tended to resemble ‘Sugar’ more closely than H7998. There were no significant differences between reciprocal hybrids, indicating a lack of cytoplasmic inheritance. Under low disease incidence, hybrids between ‘Sugar’ and ‘Walter’ (susceptible to bacterial spot on fruit and foliage) had fruit spot incidence similar to ‘Sugar’ and significantly less than ‘Walter’. Thus, there was a high level of dominance for resistance to bacterial spot on fruit.
J. Rudich, L. R. Baker, J. W. Scott, and H. M. Sell
Effects of 4 daylength and temperature combinations on sex expression and growth of androecious (allmale) cucumber (Cucumis sativus L.) were studied. Three of 4 androecious lines were stable for male expression under all 4 combinations. However, low temperature and short days promoted femaleness in one line causing monoecious expression.
Ethylene production by androecious was compared to that of monoecious, andromonoecious, hermaphroditic and gynoecious phenotypes. Low ethylene evolution was associated with plants of androecious and monoecious phenotypes as compared to more female phenotypes. Furthermore, ethylene production by androecious plants remained low and constant throughout 30 days of growth, but a small peak in ethylene production by monoecious plants was noted. This small peak may be associated with the initiation of female flowers in monoecious phenotypes.