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Lycopersicon pennellii accession LA 1277 was crossed to tomato (L. esculentum) and the F1 was backcrossed to tomato. Self-pollinated seed was saved from backcross plants and seedlings derived were inoculated with Fusarium oxysporum Schlecht f.sp. radicus-lycopersici Jarvis and Shoemaker, the causal agent of Fusarium crown and root rot (FCRR). Seed was saved from resistant plants that were self-pollinated and screened until homozygous resistance was verified five generations after the backcross. Three homozygous lines were crossed to Fla. 7547, a tomato breeding line susceptible to FCRR but resistant to Fusarium wilt races 1, 2, and 3. Subsequently, backcrosses were made to each parent and F2 seed were obtained. The three homozygous FCRR-resistant lines were also crossed to Ohio 89-1, which has a dominant gene for FCRR resistance presently being used in breeding programs. F2 seed were obtained from these crosses. These generations were inoculated with the FCRR pathogen. The resistant parents, F1, and backcross to the resistant parents were all healthy. The backcross to the susceptible parent and the F2 segregated healthy to susceptible plants in 1:1 and 3:1 ratios, respectively. Thus, the resistance from LA 1277 was inherited as a single dominant gene. This gene was different than the gene from Ohio 89-1 because susceptible segregants were detected in the F2 generation derived from the two resistant sources.

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Forty-two Lycopersicon pennellii Corr. D'Arcy accessions, from the Tomato Genetics Stock Center, were inoculated for resistance to Fusarium wilt race 3 at the 3-leaf and cotyledon stage. All were over 90% healthy when inoculated at the 3-leaf stage but had greater disease incidence at the cotyledon stage. Crosses were made between healthy plants within each accession. Using this seed, 39 accessions were 100% healthy and 3 were over 96% healthy when inoculated at either stage. Seventeen F1's with susceptible parents were tested for race 3 and all had over 80% healthy plants. Twenty-two accessions were tested for Fusarium wilt race 1 and race 2. For race 1, 21 were 100% healthy and 1 was 91% healthy, For race 2, 20 were 100% healthy, 1 was 96% healthy, and 1 was 75% healthy. Forty accessions were screened for Fusarium crown rot and Verticillium wilt. For crown rot, LA 1277, LA 1367, and LA 1657 were over 95% healthy, 6 other accessions were over 68% healthy and several others had over 50% healthy plants, All 40 were susceptible to Verticillium wilt race 1. L. pennellii appears to be a good source of resistance to Fusarium sp. but not to Verticillium wilt.

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Kentucky is one of seven states in the southeast evaluating 13 Asian pear cultivars for suitability to the region. The cultivars were planted on a (20′ × 10′) spacing in 1989 at three separate locations. Data on time of bloom, tree growth, fire blight susceptibility and fruit quality and yield were collected. This study demonstrates the variability seen in Asian pear cultivars in response to site. There was a significant site by cultivar interaction for fire blight. The Princeton site had significantly more fire blight than either Lexington or Quicksand. Four cultivars, Niitaka, Shin Li, Shinko and Shinseiki had low fire blight ratings which were not significantly different between the three sites. Asian pear growth rates were significantly different between the three sites, but cultivar growth rates were not. Tree growth rate showed a significant negative correlation to fire blight rating. That is infected trees did not grow much. Initial findings show Shinko, Shinseiki and Niitaka to have some tolerance to fire blight spread and to produce good yields of attractive fruit. However, Niitaka had a very tough skin with a tendency towards fruit cracking. The cultivar Shin Li which also had fire blight tolerance did not produce fruit or flowers.

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A `spray-inoculation seedling screening procedure was developed for detecting resistance to Xanthomonas campestris pv. vesicatoria (Doidge) Dye, causal agent of bacterial spot of tomato (Lycopersicon esculentum Mill.). Two-week-old transplants were preconditioned under 95% humidity for 16 hours before spray inoculation and then rated for bacterial spot 2 weeks later. Resistant plants could also be distinguished from susceptible genotypes using a modified bacterial speck [Pseudomonas syringae pv. tomato (Okabe) Young, Dye, and Wilkie] screening procedure (cotyledon-dip technique). When results of both screening methods were compared to field ratings from three previous seasons, significant correlations were more frequently observed for the spray-inoculation method. In Summer 1991, individual plants were evaluated by the spray-inoculation technique and then were placed in the field to determine susceptibility under field conditions. Correlations (r = 0.28 to 0.34) between spray-inoculation seedling screening ratings and field ratings, although low, were significant (P ≤ 0.0001). More than 90% of susceptible plants could be eliminated, saving labor, space, and time.

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Media and nutrient variables were investigated to develop methods of reducing the incidence and severity of fusarium crown rot incited by Fusarium oxysporum Schlecht. f. sp. radicis-lycopersici Jarvis & Shoemaker (FORL), a disease problem of current importance with tomato Lycopersicon esculentum Mill. Root-dip inoculated seedlings were transplanted into trays of a 1 Canadian peat: 1 vermiculite medium that had been prepared with factorial combinations of CaCO, (0.75 or 3.0 kg·m), Ca(NO) or (NH) SO (each at 225 mg N/liter), and NaCl at 0 or 2000 mg Na/liter as the experimental treatments. Crown rot was more severe with the lower CaCO rate, with (NH) SO, and supplemental NaCI. Data on fresh weight of seedlings expressed as percentage values relative to the noninoculated controls supported observations on disease severity.

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Tomato (Lycopersicon esculentum) line E427 has resistance genes to all three races of Fusarium oxysporum f.sp. lycopersici derived from L. pennellii accession LA 716 and L. pimpinellifolium accession PI 126915. To determine genes that confer resistance to specific races of fusarium wilt, line E427 was crossed to susceptible `Bonny Best' and then F2 and backcross (to `Bonny Best') seed were obtained. Self-pollinations resulted in 337 lines and progeny of each line was inoculated separately with fusarium wilt races 1, 2, or 3. Plants from lines whose segregation suggested recombination of resistance were self-pollinated and reinoculated until disease reactions were homozygous. Four lines were obtained with resistance to both races 2 and 3, but susceptible to race 1. These lines had the L. pennellii alleles at restriction fragment length polymorphism (RFLP) markers linked to I-3 on chromosome 7 and lacked L. pimpinellifolium alleles linked to I and I-2 on chromosome 11. Complementation (F2) data indicated race 2 resistance on chromosome 7 was controlled by a single dominant gene. Three lines were resistant to race 2, but susceptible to races 1 and 3. These lines had L. pimpinellifolium alleles at TG105 and flanking markers encompassing a 14.4 cM region indicating the presence of I-2, and no L. pennellii alleles at markers linked to I-3. Three lines were resistant to race 1, but susceptible to races 2 and 3. All three lines had L. pimpinellifolium alleles at TG523 confirming linkage to I on chromosome 11 and no L. pennellii alleles at markers tightly linked to I-3. However, one of the lines, 415, had L. pennellii alleles at CT113 on chromosome 7. This data along with F2 complementation data suggests the possible existence of a second race 1 resistant locus, I1, in this region. The four lines resistant to both races 2 and 3 were backcrossed again to `Bonny Best' and self-pollinated progeny from 174 plants were screened as described above. Two lines derived from different BC1S1 lines that were fusarium wilt race 3 resistant and susceptible to race 1 had intermediate resistance to race 2. These two lines did not have the L. pennellii alleles at TG183, TG174, and CT43 near the I-3 locus indicating crossovers in this region resulted in reduced race 2 resistance. Collectively, this is the first clear break in the fusarium wilt race 2 and race 1 resistance linkage on chromosome 11. It appears that the race 1 resistance derived from PI 126915 is controlled by the I gene. On chromosome 7, there was a break between the I-3 and I1 genes indicating I-3 does not confer race 1 resistance. The crossovers resulting in reduced resistance to race 2 could be within a complex I-3 locus or a tightly linked race 2 locus.

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Abstract

A model which predicts terminal and spur leaf emergence of sour cherry (Prunus cerasus L. cv. Montmorency) grown near East Lansing, Michigan was developed from biological and temperature observations made in orchards near Egg Harbor, Wisconsin. Leaf number of spur and terminal shoots was more highly correlated with degree-day accumulation at a base of 4°C starting April 19, than with time. Leaf number on individual shoots was linear with respect to degree-day accumulation; however, not all growth on an individual tree was synchronous, and the plot of average leaf number vs. time was slightly curvilinear. Terminal buds set about 350 and 850 degree-days after first leaf emergence for spur and terminal shoots, respectively, regardless of location. Leaf size increased linearly with degree-day accumulation until full leaf expansion. At maturity terminal leaves were about 50% larger in area than spur leaves. Foliage growth was greatest during stage I and early stage II of fruit growth, and may compete with the fruit for assimilates needed for growth.

Open Access

Abstract

‘Centennial’ and ‘L4-89’ cultivars of sweet potatoes grown in soil with a pH of 4.4–5.1 had a higher dry matter content than when grown in soil with a pH of 5.3–6.0 or 6.4–7.2. Soil pH had no influence on dry matter content of ‘L4-186’. Soil pH did influence firmness of the canned product; however, cultivar differences occurred. ‘L4-89’ when grown on soil with a pH of 4.4–5.1 had firmer roots than when grown at higher soil pH. Firmness of ‘L-186’ was not affected by soil pH. Roots from ‘Centennial’ grown at the higher soil pH in combination with fertilizer were softer after canning; however, without fertilizer, roots from the intermediate soil pH were the firmest. Carotenoid content (flesh color) of either fresh or processed roots was not affected by varying soil pH. Varying soil pH had a slight influence on fiber content of ‘Centennial’ but no effect on fiber content of ‘L4-89’ and ‘L4-186’. Protein content and splitting of canned roots were not greatly affected by varying the pH of the soil.

The addition of fertilizer to the soil pH plots resulted in a lowering of dry matter content and softer canned roots of ‘Centennial’; however, the reverse was true for ‘L4-89’.

Carotenoid content and splitting of canned roots were not affected by the addition of fertilizer to the soil pH plots. Fiber content was lowered in ‘Centennial’ (fresh wt. basis) and in ‘L4-186’ (dry wt. basis) by the addition of fertilizer to the soil. Roots grown in plots receiving fertilizer were higher in protein content than those grown without fertilization.

Open Access

Abstract

Twenty-two sweet potato (Ipomoea batatas (L.) Lam.) breeding lines and 19 open-pollinated offspring from each were used to estimate the heritabilities of 7 measures of soil insect injury. Four measures of injury by the wireworm, Diabrotica spp., and Systena spp. (WDS) complex and h2 (± SE) were: percentage of roots injured, 0.45 ± 0.12; holes per root, 0.32 ± 0.09; severity index, 0.37 ±0.11; and damage score, 0.39 ± 0.17. Two measures of injury by the sweetpotato flea beetle, Chaetocnema confinis Crotch, and h2 were: percentage of roots injured, 0.40 ± 0.07, and tunnels per root, 0.25 ± 0.08. The h2 of percentage of roots injured by all insects was 0.51 ± 0.12. The percentage measures were more easily obtained and were as effective as the other measures under the conditions of natural infestation that occurred in this test. Further advances in selection for high levels of resistance to soil insects are possible within the breeding materials tested.

Open Access