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D.J. Wolyn

Fern vigor indices and estimates of percent marketable yield (PMY) were used to determine alternative measures of asparagus (Asparagus officinalis L.) marketable yield. Total yield was highly correlated (0.75 ≤ r ≤ 0.91), and marketable yield was not correlated with fern vigor indices. The products of fern vigor indices and seasonal PMYs were highly predictive of marketable yield (r 20.95). When the products of each daily PMY estimate and fern vigor index for the same season were determined, then averaged over years, <30% of correlations with marketable yield were ≥0.90, and r values varied considerably during the season. The products, averaged for 2 years, of fern vigor index and mean PMY estimated from combinations of three harvest dates during the season, except from the first harvest week, were associated with marketable yield. For the 40 3-day average estimates of PMY examined, 95% of Pearson correlation coefficients were ≥0.90 and all were ≥0.88. Thus, fern vigor index and PMY estimates from three harvest dates may be used to predict temperate zone marketable yield, decreasing labor requirements for yield trials, and facilitating evaluation of many experimental hybrids.

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Lorenzo León, Luis M. Martín, and Luis Rallo

Thirteen characters were evaluated over four years in progenies from a diallel cross among the olive (Olea europaea L.) cultivars `Arbequina', `Frantoio', and `Picual' to determine if phenotypic correlations existed between these characters. Yield per tree, ripening date, oil yield components and fatty acid composition were recorded annually once seedlings began to flower and produce fruit. Significant correlations were found between several characters including oil yield components and fatty acids composition. Lower correlation coefficients were obtained between ripening date and oil and oleic acid content. Generally, yield was not correlated with the other characters evaluated. Principal components analysis confirmed the main correlations among characters and showed them to be independent of the parents used.

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Paul G. Thompson, J. C. Schneider, Boyett Graves, and B. K. Kim

Twenty-four half-sib sweetpotato families were field tested for freedom from injury by sweetpotato weevil and other soil inhabiting, injurious insects (WDS). Three pairs of adult male and female weevils were applied to the crown of each plant at the beginning of storage root enlargement. Naturally occurring numbers of WDS were high enough for considerable injury from those insects. WDS injury free roots ranged from 19% in Centennial, the suceptible control, to 57% in Regal, the resistant control. The highest family mean for percent non-injured by WDS was 55%. Weevil injury free roots ranged from 67% in Centennial to 90% in Regal with 3 families producing mean weevil non-injured roots of 89%. The genetic correlation between weevil injury free and WDS injury free roots was 0.69 ± 0.28. That estimate is preliminary and based on data from one environment. Evaluations will be repeated in 1994 for estimates of GXE to derive genetic correlation estimates with less environmental interactions.

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C.A. Weber, W.B. Sherman, and G.A. Moore

Segregating F2 peach populations in the Univ. of Florida breeding program were analyzed to determine linkage relationships among five qualitative traits: flower type, Sh/sh, flesh type, M/m; flesh color, Y/y; leaf gland type, E/e; and pubescence, G/g. Independent segregation was confirmed between flesh color and leaf gland type, between pubescence and flesh color, and between flower type and pubescence. Previously undocumented independent segregation was found between leaf gland type and flesh type and between pubescence and leaf gland type in our populations. The relationship between these latter characteristics should be investigated in other breeding populations. No correlation was found between fruit development period and flesh type. Also, no correlation was found between chilling requirement and flesh type.

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Peter Cousins

The grapevine shoot has a zone in which leaf-opposed clusters are found at the nodes. Beyond the cluster zone, leaf-opposed tendrils are borne at the nodes in a patterned distribution. Cluster number is a primary yield component and selection programs for increasing yield in grapevine frequently consider cluster number. However, selection for increased cluster number requires direct observation, which is only possible once the vine matures. Clusters and tendrils are developmentally related, so it may be that tendril density (tendrils per node) reflects cluster number. In contrast to cluster number, tendril density can be observed on plants of all ages. The hypothesis that tendril density is related to cluster number was tested here. Cluster numbers and tendril density were assessed on 10 primary shoots each of 180 grapevine (Vitis) accessions. The accessions analyzed are cultivars and wild species collections held in the United States National Plant Germplasm System. The correlation coefficient of the number of clusters and tendril density was calculated using the means of 10 observations per accession. Tendril density was determined by calculating the mean number of tendrils per node in the nodes beyond the cluster zone. Cluster number and tendril density were positively correlated; the correlation coefficient was 0.35. This implies that vines with more tendrils per node also tend to have more clusters. The positive correlation of cluster number and tendril density has implications for grapevine improvement, pointing to the possibility of indirect selection for higher cluster number through selection for higher tendril density. Correlation between juvenile tendril density and mature cluster number is yet to be tested.

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Ali Akbar Ghasemi Soloklui, Ali Gharaghani, Nnadozie Oraguzie, Saeid Eshghi, and Mohammadreza Vazifeshenas

of this study were to 1) determine the chilling and heat requirements for breaking of bud dormancy in 20 Iranian pomegranate cultivars; 2) examine the correlations of chilling and heat requirements with tree and fruit characteristics; and 3) evaluate

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Peter Cousins*

The grapevine shoot consists of nodes without clusters (inflorescences) basal to a zone in which leaf-opposed clusters are found at the nodes. Beyond the cluster zone leaf-opposed tendrils are borne at the nodes. The numbers and possible relationship of basal nodes and clusters are important in grapevine breeding and improvement. Basal node number influences cluster placement within the canopy, which relates to light penetration to the fruit and fruit maturation and to application of cultural practices, including harvest and cluster treatments. Cluster number is a primary yield component. Basal node and clusters numbers were counted on ten primary shoots each of forty grapevine (Vitis) accessions. The accessions analyzed are cultivars and wild species collections held in the United States National Plant Germplasm System. The correlation coefficient of the number of basal nodes and number of clusters was calculated using the means of the ten observations per accession. Basal node and clusters numbers were negatively correlated; the correlation coefficient was -0.763, which is significant (P <0.001). The negative correlation of basal node and cluster number has implications for grapevine improvement.

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Samuel Contreras and Margarita Barros

The main objective of this study was to evaluate some of the available seed vigor tests to predict lettuce (Lactuca sativa L.) seedling emergence. Eight lettuce seed lots were evaluated by the following laboratory vigor tests: germination (GT); accelerated aging (AA); saturated salt accelerated aging (SSAA); conductivity (EC); and seed vigor imaging system (SVIS). Also evaluated were the percentage (EP) and speed (ES) of the seed lots' emergence under three conditions: seedling trays (ST) filled with a mixture of peat (80%) and perlite (20%); boxes with a clay loam soil (BS); and boxes with a mixture of clay loam soil (66%) and sand [34% (BSS)]. Correlation coefficients among the laboratory and emergence test results were calculated and significant differences were found. The correlation coefficients between EC results and each emergence parameter were nonsignificant, while AA results were only significantly correlated with the emergence percentage for BSS. GT values and emergence results were significantly correlated in all cases. SSAA results were equally or more positively correlated than GT results with the EP and, for the three sowing conditions, they were more correlated with the ES than GT values. Vigor index results from the SVIS were significantly correlated with both emergence parameters, and its correlation with emergence on ST (EP and ES) was greater than GT values. The results of this study showed that SSAA and SVIS were the best laboratory tests for lettuce seed vigor evaluation, especially for seed lots to be used for plug seedling production.

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Valdomiro A.B. de Souza, David H. Byrne, and Jeremy F. Taylor

Heritability estimates are useful to predict genetic progress among offspring when the parents are selected on their performance, but they also provide information about major changes in the amount and nature of genetic variability through generations. Genetic and phenotypic correlations, on the other hand, are useful for better planning of selection programs. In this research, seedlings of 39 families resulting from crosses among 27 peach [Prunus persica (L.) Batsch] cultivars and selections were evaluated for date of full bloom (DFB), date of ripening (DR), fruit period development (FDP), flower density (FD), node density (ND), fruit density (FRD), fruit weight (WT), soluble solids content (SS), apical protuberance (TIP), red skin color (BLUSH), and shape (SH) in 1993 and 1994. The data were analyzed using the mixed linear model. The best linear unbiased prediction (BLUP) was used to estimate fixed effects and predict breeding values (BV). Restricted maximum likelihood (REML) was used to estimate variance components, and a multiple-trait model to estimate genetic and phenotypic covariances between traits. The data indicates high heritability for DFB, DR, FDP, and BLUSH, intermediate heritability for WT, TIP, and SH, and low heritability for FD, ND, FRD, and SS. They also indicate year effect as a major environmental component affecting seedling performance. High correlation estimates were found between some traits, but further analysis is needed to determine their significance.

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Robert E. Rouse

The Minolta chlorophyll meter SPAD-502 (Minolta Camera Company, 101 Williams Drive, NJ 07446, USA) has been found to be a quick, accurate, simple, and nondestructive way to determine chlorophyll content in citrus leaves and a standard curve had been developed. The SPAD-502 chlorophyll meter was used to measure chlorophyll content in citrus leaves of ten varieties on three rootstocks. Leaf mineral analysis was then determined on these leaves for N, P, K, Mg, Mn, Zn, Fe, Cu and Ca. Correlation r values were generally low and not significant for most nutrient elements but were highest for Fe and Ca. The relationship of leaf nutrient levels and chlorophyll meter readings are not understood. The usefulness of the SPAD chlorophyll meter for determining mineral content in citrus leaves is not yet known.