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Abstract
H. L. de Vilmorin, in 1900, wrote “selection is the surest and most powerful instrument that man possesses for the modification of living organisms”. This early estimate of selection’s importance would probably be accurate today. While many techniques have since been developed as effective tools for the plant breeder-irradiation, colchicine, tissue cluture-his reward more frequently comes from selection pressure applied to population variation, natural or created.
Abstract
‘Emerald’ asparagus (Asparagus officinalis L.) is a new cultivar well-adapted to northern states. It is intended for fresh market use, where the bright green spears provide an attractive alternative to typical asparagus showing anthocyanin at both spear base and tip. Quality appears to be equal to that of commonly used ‘Mary Washington’ and ‘Viking’, but winter survival and yield in young plantings have been superior.
Abstract
Progenies of 25 sib matings among 5 staminate and 5 pistillate green-stemmed parents of asparagus (Asparagus officinalis L.) were classified by stem color. Subsequently, purple offspring of these crosses were mated to single staminate or pistillate plants, and green offspring were mated to staminate and pistillate plants of the purple cultivar ‘Viking’. Chi Square tests supported a mechanism of inheritance based upon interaction between 2 linked genes. One dominant gene I apparently inhibits expression of dominant P (purple stem). Linkage of between 30% and 40% crossover units is suggested by observed ratios.
Abstract
Single seed descent (SSD) produced generally inferior fruit size, earliness and total yield among progenies as compared with pedigree (PED) selection alone and single seed descent following one cycle of pedigree selection (PDSD). The latter two systems were essentially equal in performance, but the PDSD system provided increased efficiency of time and space. Progeny tests in 1976 generally reflected the superiority that had been selected in 1975, regardless of selection system. In each system, acceptable performance was attained in at least one line. The data suggest, however, that chances of recovering high-performance lines are reduced in SSD as compared to PED or PDSD.
Abstract
Crosses between 6 inbreds of tomato (Lycopersicon esculentum Mill.) and each of 2 hybrid testers, and progenies derived from them by single seed descent (SSD), were grown in replicated trials in 1980 and 1981. Early yield, total yield, and fruit size means of the inbred parents were found to be correlated with estimates of general combining ability (GCA); strong relationships also were found among midparent, GCA, and testcross means and means of SSD derived lines. These relationships were especially evident for fruit size, a trait of moderately high heritability. GCA was correlated with progeny segregation for fruit size and for early yield; but only for fruit size was a significant correlation found between testcross segregation and similar data for SSD progenies.
Abstract
Coefficients of determination (CD) for the association of dates of first flower and first ripe fruit in tomato (Lycopersicon esculentum Mill.) were affected by the management system in which plants were grown. In a 2-year experiment, CD values increased when plants were grown using black polyethylene mulch and slitted polyethylene row covers. This increase was maximized using transplants. Row covers left over the plants beyond the date of first flower tended to reduce CD values, but this reduction was not a result of flower abortion. Row covers appear useful in northern areas to facilitate selection of early flowering lines.
Abstract
Bare ground (BG), black polyethylene mulch (ML), and polyester row covers with mulch (MRC), combined with three planting densities, provided increasing levels of cropping intensity to study phenotypic response. Four tomato (Lycopersicon esculentum Mill) phenotypes, ‘Sub Arctic Maxi’ (SAM), ‘New Yorker’ (NY), UNH-328 (328), and ‘Westover’ (WVR) represented combinations of small and large plant size and early and late maturity. Early and total yield responses to planting density were linear whether in ML, MRC, or BG treatments, and each phenotype also showed predominantly linear yield increases with increasing density. These linear increases were enhanced in SAM by ML and MRC, but the same mulch and row cover treatments tended to reduce the density response in other phenotypes. The difference was believed to relate to flowering pattern and time relative to vegetative development. Within MRC, compact plants were the most responsive to density in total, but not in early, yield. The predominant effect of ML and MRC was to improve earliness, with each treatment contributing an increment increase in early yield. However, the performance of one phenotype (328) was unchanged by ML or MRC, perhaps reflecting inherent stability.
Abstract
Three varieties, ‘Red Top’, ‘Fireball’ and ‘Valiant,’ and their hybrids were grown in a split-plot design of mixed and pure populations at high and low population densities. The frequencies with which varieties or hybrids were selected for earliness and fruit size within high density (1 ft in-row spacing) and low density (3 ft in-row spacing) plots when genotypes were mixed did not differ significantly. Selections for concentrated ripening within the 2 densities were significantly different. The mean response of hybrids to density change was not significant. The mean response of inbreds to density change was significantly different for earliness and fruit size. Fruit size of the inbreds was also affected by competition when grown in mixed stands.
Abstract
Enzyme heterogeneity in relatively pure extracts has been demonstrated for many plants (44), particularly through the application of gel electrophoresis techniques. Isoenzyme heterogeneity was discerned first in esterase and lactate dehydrogenase (27), and implications of this heterogeneity have excited interest in many areas of the biological sciences. We will discuss in this paper some areas in the horticultural sciences in which protein electrophoresis appears to have significant practical and basic research applications.
Abstract
Ten enzymes of asparagus (Asparagus officinalis L.) were examined on both starch and Polyacrylamide gels to identify polymorphic loci useful as genetic markers. Two polymorphic loci were discovered, one a root peroxidase (PER-1) and the other a stem shikimic acid dehydrogenase (skd-1). Electrophoretic analysis of 17 totipotent calli derived from anthers that were heterozygous for PER-1 showed 14 to be heterozygous somatic clones and three to be homozygous doubled haploids. The procedure described represents a significant improvement in efficiency over the current method of sexing and progeny testing for the recovery of gametic genotypes from asparagus anther culture.