Fernando López Anido

Heterotic patterns in hybrids involving cultivar-groups of summer squash, Cucurbita pepo L.

Heterotic response for total yield among five cultivar-groups of summer squash, Cocozelle, Vegetable Marrow, Zucchini, Crookneck and Straightneck, was studied in two sets of diallel crosses evaluated in two harvest seasons. Each diallel cross included two representatives of each the five cultivar-groups. Griffing and diallel GGE biplot (genotype main effect and interaction) analyses were carried out. The relative importance of the specific combining ability variance on total variance was greater than that reported earlier for intragroup crosses. Highly significant heterosis was manifested only in combinations of Crooknecks or Straightnecks crossed to Cocozelles, Vegetable Marrows or Zucchinis. GGE biplots showed a consistent arrangement where testers of ssp. texana interacted with cultivars of ssp. pepo and vice versa. We propose that the heterotic pattern of texana-pepo crosses could be potentially used to achieve increased yields in hybrids by introgressing one group into another in a manner that would maintain fruit attributes of the cultivar-group.

Early selection of elite plants in Asparagus

In order to establish an efficient selection criterion the variability in three asparagus populations was evaluated defining the most important yield components and analysing its evolution along three growing seasons. The yield components, coefficient of variation (CV) and the proportion of plants contributing to 80% of the total yield were estimated. The elite plants were selected by mean of total yield and clusters techniques. Multiple regression showed that spear number (SN) and spear weight (SW) were the most important yield components. In every population, total yield (TY) and SN showed the highest values of CV, independently of sex. 69% of the plants contributed to the 80% of the total yield in the first year while in the second and third year the contribution was 57%. At the end of the third year, 17 plants were selected by the average of the total yield and 43 by clusters. It is suggested to select for SW in the first year, reducing in 68% the experimental material. In the second year, the selection for SN would reduce to 5% the plants to evaluate for total yield in the third year. In this way the selected plants are the same but the number of plants to evaluate is dramatically reduced along the years, therefore facilitating the breeders work.

Evaluation of seven asparagus populations ( Asparagus officinalis L.)

The materials of asparagus (Asparagus officinalis L.) that growers have in use are imported by seed dealers and have been selected according to overseas markets requirements. With the aim of selecting proper parents to use in a breeding program, seven populations of Asparagus officinalis (P1 to P7), all rised as white asparagus, were tested during 1993 and 1994, at the Experimental Field of the Facultad de Ciencias Agrarias (Universidad Nacional de Rosario) placed in Zavalla, Santa Fe, Argentina. The evaluation was made on individual plant in a 40 days of harvest period. ANOVA and a cluster analysis were made. In order to improve total and marketable yield, P1, P2 and P3 should be used as females regarding that these ones also have high spear number. To improve spears weight and diameter as well as late production, P5 and P7 are recommended as males, but it should be considered that P5 has a better yield performance.

Caracteres agronómicos en el cultivo de espárrago de diferentes edades y manejos

Age and crop system effects on agronomic response were evaluated in 11 hybrids of Asparagus officinalis L. The experimental design was a complete randomized block with three replicates of 20 plants of 3 or 4 years old, conducted either in mounded soil over plants for blanched asparagus, or in raised beds without ridging for green asparagus. The highest mean values were obtained under the blanched production for days to harvest, market yield, total yield, spears number and the spear mean weight. However, under the green production, the rate of increment from first to second year was superior for market yield and total yield due to an augmented rate of increment of spears number. Type and year of production effects were similar for days to first harvest and spears mean weight, meanwhile days to 50% of sprout plot was affected mainly by the year of production.

Efecto de una generación de endocría sobre caracteres vegetativos y productivos en dos estructuras familiares de alcaucil

Globe artichoke (Cynara scolymus L.) is an allogamous species where vegetative propagated cultivars are not suitable for seed multiplication due to their high heterozigous condition. To obtain homogeneous materials, the inbreeding process is necessary. Inbred lines could be used as cultivars or in hybrid combinations. The effect of one generation of selfing over vegetative and productive traits were evaluated. The Genetic Determination Coefficient was estimated in two different family structures. Two sets of S1 families were originated: one from crosses between clones and the other through open pollination of the same clones. These assays were implanted in the field, in Zavalla, Argentina. The vegetative and reproductive characters were evaluated in a single plant. The importance of the starting material to obtain lines with adequate agronomic performance was demonstrated: S1 families originated from half-sib plants presented a strong endogamic depression in the majority of the traits in comparison to those obtained from full-sibs. Although all characters manifested endogamic depression after one generation of selfing, a genetic variability still remained among sets, among families and plants within families. As a consequence, it could be possible to select elite plants to continue the inbreeding process or to be vegetatively propagated as clones.

Response of Productive and Morphovegetative Traits of Globe Artichoke (Cynara cardunculus var. scolymus) to Mass Selection and Estimation of their Heritability

There have been few reports on genetic parameters or artificial selection for growth traits in globe artichoke (Cynara cardunculus var. scolymus), the study of the effect of one cycle of mass selection and realized heritability estimates would be valuable for planning breeding strategies in this species. A C0 segregating population was formed from the cross of two contrasting seed-grown cultivars, Imperial Star and Estrella del Sur FCA. Selected plants for productive traits were intercrossed to produce a C1 population. The C1 population along with the C0 population, both parents and the F1 were evaluated obtaining the response to selection and estimating realized heritability. Mass selection for increased yield and precocity was particularly successful, where for the first trait realized heritability reached 0.71 and 0.60 for the second one. For most traits, the observed values for realized heritability in the experiment (0.75, 0.61 and 0.52 for weight of the main head, marketable yield and length of the main head, respectively) indicate that a substantial part of the observed phenotypic variance is of additive nature. Therefore, in general, selection for these traits in seed-grown globe artichoke populations will be effective.

Multidisciplinary studies in Cucurbita maxima (squash) domestication

Plant domestication is a complex process in which natural and cultural factors play important roles delimiting evolutionary pathways of plants under cultivation. In order to deal with and understand the changes generated during this process, multi-disciplinary research is required, especially when a full picture of the domestication history of a taxon is to be assessed. We present here some advances in the study of Cucurbita maxima (squash) domestication from an integrated perspective, including experimental, morphometric and archaeobotanical approaches, which are discussed in the light of new data from physiological analyses. Modern material includes plants obtained from experimental fields, derived from crosses between domesticated (C. maxima ssp. maxima) and spontaneous/wild forms (C. maxima ssp. andreana), resulting in F1 and F2 generations. The archaeobotanical material includes remains recovered from sites in southern Peru and northwest Argentina ranging in date from 3,000 to 800 bp. Morphological and anatomical analyses were conducted on seeds, pericarps and peduncles (the stem of the flower or fruit) for reconstructing squash size and shape evolution under domestication. The results suggest the presence of hybrid forms, mainly from the earlier sites, but also from more recent ones. As expected, a linear evolutionary pathway was not found. Diversity and multiple crossings seem to have been a constant in squash cultivation over time, emphasising the role of gene flows between domestic and wild variants in the domestication process. Finally, we hypothesize the possible linkage between past gene flow and different dormancy patterns as part of management practices, allowing the maintenance of squash populations adapted to different environmental conditions.

Comparison of morphological and molecular data for pea (Pisum sativum) in low and high yielding environments.

Abstract Genotypes by year interactions are considered to be among the major factors limiting response to selection. The objectives of this study were to estimate the heritability via variance components and genotype × year interactions for different traits determining the consensus between morphological and molecular data under two environmental conditions. Forty pea accessions were evaluated during 2005, a year with no temperature or rainfall stress, and 2006, a stress year. Morphologic, productive, and sequence‐related amplified polymorphism (SRAP) data were collected. Phenotypic and genotypic variances were determined and heritability estimated. One hundred and sixty‐two polymorphic SRAP bands were scored. Regressions between morphological and SRAP data were conducted. In a stressful year the correlation between SRAP and morphological data was higher than in a non‐stressed season (r = 0.72 versus r = 0.55). The results suggest that exposure to combinations of environmental stresses may increase expression of genetic variability for productive traits.