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  • Author or Editor: M. A. Stevens x
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Abstract

The soluble solids content of ripe fruit of tomato (Lycopersicon esculeutum mill.) is positively associated with starch content early in fruit development. When 14C-sucrose or 14C-glucose were injected, the young fruits of the breeding line LA 1563 contained greater amounts of 14C in starch than those of the cultivars ‘UC 82B’. This, and the larger pool of hexoses in young fruits of ‘UC 82B’, implies that difference in starch synthesis is a primary factor affecting starch levels. The differences between 2 genotypes for fruit respiration and their ability to take up sucrose from an agar medium suggest that starch accumulation is a result of greater sink activity.

Open Access

Abstract

Threshing of large numbers of seed samples encountered in bean breeding programs has been a difficult problem to solve satisfactorily. In many cases, threshing has been done by hand with the aid of a small blower. Actual seed recovery is relatively efficient but it is painfully slow and tedious. With this method one person can normally thresh 10 to 15 small samples per hour.

Open Access

The regulation of anther dehiscence by relative humidity (RH) was assessed for detached anthers and detached whole flowers from a limited selection of apricot (Prunus armeniaca L.), peach [P. persica (L.) Batsch], and almond [P. dulcis (Mill.) D.A. Webb, syn. P. amygdalus Batsch; P. communis (L.) Arcangeli, non Huds.] genotypes, as well as an almond X peach F2 progeny. Dehiscence was evaluated at 33, 64, 87, 93 and 97% RH for detached anthers, and at 33, 64 and 97% RH for whole detached flowers. Anther dehiscence was suppressed with increasing RH for all genotypes. Apricot anthers showed the greatest dehiscence at low RH and measurable dehiscence at high RH even when detached. Anther dehiscence in almond appeared more suppressed than in apricot at all RH levels tested, being completely suppressed by high RH in detached anthers. Peach genotypes exhibited the full range of variability between apricot and almond patterns. Evidence for transgressive segregation of RH-controlled anther dehiscence was observed in the occurrence of cleistogamy in an almond × peach F2 progeny. Rates of anther dehiscence were approximately linear with change in RH in detached anthers but exhibited a more buffered, step-wise response when detached whole flowers were tested. Results are consistent with field observations, and highlight the low but measurable risk of cleistogamy in these species, as well as opportunities to modify the breeding systems and crossing environments to facilitate controlled hybridization, and to reduce pollination vulnerability to adverse environments.

Free access
Authors: and

Abstract

Evaluation of progeny populations from crosses between tomato accessions (Lycopersicon spp.) with high and low alkaloid levels indicated that variation in α-tomatine content is controlled by the segregation of 2 co-dominant alleles at a single locus.

Open Access
Authors: and

Abstract

When larvae of Heliothis zea (Boddie) were caged on fruits of varying developmental ages from 3 accessions of Lycopersicon, the length of the larval stage and mortality were positively correlated with fruit α-tomatine content. Larval growth rates and adult weights of H. zea were found to be inversely correlated with fruit alkaloid content. Growth and survival of caged Spodoptera exigua (Hubner) were not related to the levels of tomatine in the fruit. However, a highly significant correlation exists between fruit cuticular toughness and S. exigua mortality. Compared to the processing tomato line VF145B-7879, lower H. zea and S. exigua survival rates were observed when the larvae were reared on the tougher, higher-alkaloid fruits of L. esculentum var. cerasiforme and L. pimpinellifolium accessions. These results indicate a possibility of enhancing cultivar resistance to these insect pests through the development of tough-fruited, high-α-tomatine genotypes.

Open Access

Abstract

15N-labeled potassium nitrate was applied in a foliar spray to French prune/Marianna 2624 trees (Prunus domestica L.), and the nitrogen absorbed by the leaves was quantified. Nitrogen derived from a single foliar spray averaged 3% of total leaf nitrogen. L77, a non-ionic organosilicone surfactant which lowers surface tensions of aqueous solutions sufficiently for stomatal penetration, significantly enhanced the rate of NO3 absorption and increased incorporation of foliar-derived nitrogen into alcohol insoluble macromolecules. This enhancement was not apparent when labeled NO3 was applied with Regulaid, a carbohydrate-based non-ionic surfactant. About 25% of the foliar-derived N was apparently transported from leaves within 3 days when the stomatal penetrant was employed. No transport was evident in the absence of the penetrant.

Open Access

Abstract

Twenty-seven accessions from 6 species of the genus Lycopersicon and 1 accession of Solanum pennellii were surveyed for content of the glycoalkaloid, α-to-matine. Significant variation in alkaloid content was found to exist among the accessions. L. esculentum cultivars were found to contain much lower concentrations of α-tomatine than accessions of L. esculentum var. cerasiforme, L. pimpinellifolium, and the L. peruvianum accession, LA 462.

Open Access

Low-vigor seeds of black-eyed Susan (Rudbeckia fulgida Ait.) primed in aerated -1.3 MPa KNO3 for 7 days at 30C in darkness had double the total germination percentage at 30C and one-half the mean time of germination as nonprimed seeds. Priming the seeds in polyethylene glycol rather than KNO3 generally resulted in lower total germination percentage and longer mean time of germination. Osmotic priming increased total germination percentage and germination rate of seeds germinated at 21.9 to 32.2C, but the priming benefit on total germination percentage was greater at ≤27.6C. Total germination percentage of primed and nonprimed seeds was highest at 28.8 to 32.2C.

Free access

Germination trials of three seedlots were conducted over a temperature gradient for 14 days to determine the optimal germination temperature for the Black-eyed Susan (Rudbeckia fulgida Ait.). The optimal germination temperature for R. fulgida seeds was 30 ± 1C. All three seedlots began germination (radicle emergence) on the second day at 30.2C. By day four, all seedlots sur-passed 50% germination, with three seedlots germinating 53%, 52%, and 73%. Mean germination percentages were higher between 28.3 and 32.6C than at temperatures above or below this range. Significantly higher germination percentages and enhanced germination rates attained at the elevated temperatures may save time, cut production costs, and decrease exposure to detrimental pre-emergent pathogenic fungi.

Full access

The effects of low and high crop loads in 2002 on floral development (Summer 2002), pistil size at anthesis (Spring 2003), and subsequent season fruit size at maturity (Summer 2003) were studied. Trees were all thinned to the same crop load in 2003. Three peach cultivars (Elegant Lady, O'Henry and Fairtime) with different ripening times (mid-July, mid-August, and early-September, respectively) were used to assess the effects of current season crop on floral development for the subsequent season. Based on previous literature, we reasoned that the maximum competition for carbohydrates between maturing fruit and developing buds is likely to occur at fruit maturity, especially under heavy crop loads. In 2003, individual fruit were harvested and weighed at maturity. In all three cultivars, a heavy crop load reduced the percentage of floral buds initiated and delayed floral differentiation. A heavy crop load also reduced pistil size at anthesis and fruit size at maturity in the subsequent season. These data support the practice of vigorous pruning to annually renew fruiting wood in peach to minimize the influence of crop in the previous season on the subsequent season's fruit and maintain large fruit sizes.

Free access