Squash Genotypes Research Articles

Evaluating the Growth, Yield, and Resilience of F1, F2, and Open-Pollinated Squash Varieties: A Comparative Study

In our country, malnutrition poses a severe challenge due to the limited production of nutritious food. Developing disease and pest-resistant varieties such as squash is crucial to tackle this issue. A recent study conducted in Can-ayan, Malaybalay City, Bukidnon, from July to October 2019, explored the growth and yield performance of different squash varieties (OP, F1, F2). The research aimed to understand the variations in yield, horticultural and reproductive characteristics, inbreeding depression, and profitability of growing diverse squash genotypes. The results, obtained through a Randomized Complete Block Design with five treatments, highlighted significant differences in traits among the genotypes. Notably, inbreeding depression was observed in marketable fruit production and yield. The analysis revealed varying traits across genotypes, with Gracia hybrid emerging as the most profitable choice, showing positive returns on investment. This study sheds light on the importance of developing resilient crop varieties like squash to address malnutrition challenges effectively.

Evaluation of Summer Squash Genotypes (Cucurbita pepo L.) under Tropical Conditions

The investigation was carried out in a farmer’s field Sorakalnatham, Natrampalli taluk, Tirupattur district, Tamil Nadu during 2022. The experimental design used was randomized block layout with three replications and twenty genotypes. In results indicate the genotype were significantly differed in growth and yield attributes. According to the grand mean data, the CP 13 genotype of summer squash showed the best performance in the tropical condition. Significantly greater than the grand mean in the growth attributes viz., plant height (66.54 cm), least value was recorded in days taken for fifty per cent female flowering (40.54 days). The yield attributes was maximum than grand mean in term of single fruit weight (1200.18 g), number of fruits plant-1 (4.75), fruit yield plant-1 (5.64 kg).

Morphological Characterization and Selection in Some Summer Squash (Cucurbita pepo L.) Genotypes

This study was carried out to determine stage progression and specific plant and fruit characteristics in purposefully created summer squash genotypes. In this study, which was carried out in 2019, 59 squash genotypes were assessed with 24 morphological measurements and observations involving plant and fruit characteristics, and one-generation advancement was achieved. Cluster and PCA were implemented to determine the relationship between genotypes determined at the end of single plant selection. A dendrogram was constructed to assess the morphological similarities between the genotypes. In this respect, four main groups and 12 subgroups were determined in the cluster analysis performed among squash genotypes based on 24 morphological variables, while the 10 PC axis explained 94.3% of the total variation in the PCA. When the variance values of the principal component axis were examined, it was seen that the first principal component axis explained 28.8% of the total variation, the second principal component axis explained 26% of the variation, and the third principal component axis explained 11.2% of the total variation. Principal component analyses revealed that (i) 66% of the qualitative (neck in unripe fruit, curving of the neck in unripe fruit, mottling in unripe fruit, and type of mottling in unripe fruit) variation was explained by the first three components. At the end of the study, the phenotypic diversity that exists in this core collection provides valuable information to improve agronomic traits in the summer squash breeding program.

Mutagenic effect of ultraviolet rays on sex expression in summer squash genotypes

The present study aimed to induce genetic variations within the control of sex expression in summer squash using ultraviolet rays (UV) as a physical source of mutations in plants. Because the sex expression in summer squash is fundamentally controlled mainly by genetics and partially by the environment. Therefore, this study tries to increase floral differentiation of female flowers, as well as decrease male flowers developed per plant, because summer squash usually exhibit more male flowers and lower female flowers. This will cause decreases in fruits yield per plant. This study was designed in a randomized complete block design with a factorial investigation. It was included four genotypes of summer squash subjected to four exposure periods of UV rays, with three repetitions for each experimental unit. The results showed that genotype number four increased the features of female flowers by 28% and 14% at 4 and 8 minutes of exposure period, respectively. The 12 – minute exposure period significantly increased floral differentiation among all genotypes toward male flowers developed per plant. Meanwhile, genotype number two enhanced floral differentiation toward female flowers by 14% at 8 minutes of exposure period, indicating that these few periods of exposure to UV irradiation may be responsible for induced benefit mutations in cucurbits affected on sex expression, as it induced high number of female flowers. The results indicated that UV irradiation had a direct role in promoting floral differentiation as it inducement higher female flowers in some genotypes leading to improve floral characteristics, as a consequence increased fruits yield per plant.

Assessing the genetic diversity of squash (Cucurbita pepo L.) genotypes based on agro-morphological traits and genetic analysis

An experiment was conducted to estimate the genetic variability of 15 indigenous and exotic squash genotypes assessing 18 quantitative and 8 qualitative traits. Results showed that the accessions have high variability in qualitative traits like fruit size, fruit shape, fruit skin colour,lustre and fruit productivity, which allowed selection for considerable gains in these characteristics. The quantitative traits such as fruits yield per plant, fruit weight, length, diameter and total yield per hectare showed the greater phenotypic coefficient of variation (PCV) along with higher heritability which can helps to identify desirable genotypes. The obtained significant and positive correlation between fruit yield with number of leaves, nodes, fruit length, weight and number could assist in selection to improve this crop. Cluster analysis resulted in the formation of 4 groups, confirming the genetic variability among the studied genotypes. Eventually, the attained PCA analysis result revealed that the number of fruits per plant, fruit yield per plant, fruit length and days to first female flowering are the most discriminating traits which are accelerating the variability in squash genotypes. On the basis of the yield and its attributing traits, First Runner is the best genotype suited in this environment.

Cucurbit Powdery Mildew: First Insights for the Identification of the Causal Agent and Screening for Resistance of Squash Genotypes (Cucurbita moschata (Duchesne ex Lam.) Duchesne ex Poir.) in Mendoza, Argentina.

The cucurbit powdery mildew (CPM) caused by different fungal species is a major concern for cucurbit crops around the world. In Argentina CPM constitutes the most common and damaging disease for cucurbits, especially for squash crops (Cucurbita moschata). The present study displays initial insights into the knowledge of the disease in western Argentina, including the determination of the prevalent species causing CPM, as well as the evaluation of the resistance of squash cultivars and breeding lines. Fungal colonies were isolated from samples collected in Mendoza province, Argentina. A field trial was also performed to assess the resistance of five squash accessions, including commercial cultivars and breeding lines. The severity of CPM was analyzed and epidemiological models were built based on empirical data. The morphological determinations and analysis with specific molecular markers confirmed Podosphaera xanthi as the prevalent causal agent of CPM in Mendoza. The results od the field trial showed differences in the resistance trait among the squash accessions. The advanced breeding line BL717/1 showed promising results as source of CPM resistance for the future development of open pollinated resistant cultivars, a crucial tool for an integrative control of the disease.

Nitelikli Yazlık Kabak (Cucurbita pepo L.) Genotiplerinde Işınlanmış Polen Tekniği ile Dihaploidizasyon

Summer squash (Cucurbita pepo L.) is one of the important vegetable species preferred by the people of Turkey in terms of their nutritional value. F1 hybrid summer squash varieties are widely used both in the open field and protected cultivation. The majority of these varieties come from abroad, and our dependence on abroad continues. In this study, the effectiveness of the dihaploidization method, which has an important place in variety breeding studies, was investigated to reduce our import dependency and to produce new F1 hybrid varieties that are high yielded, quality, resistant to diseases and pests. In this context, 14 summer squash genotypes were used as plant material. Dihaploidization studies were carried out using the irradiated pollen technique. In total, 165 flowers were pollinated and 64 fruits, 7034 seeds, 521 embryos, and 144 plants were obtained. 111 pants were successfully acclimatized and cultivated in controlled conditions. As a result of ploidy analysis, 28 plants were haploid (2n=x=20), 77 were diploid (2n=2x=40) and 6 were mixoploid (containing diploid and haploid cells). Haploid plants were doubled with 1% olchicines treatment, grown in the greenhouse, selfed, and seeds were obtained.

Assessment of Genetic Diversity in Summer Squash Genotypes Using some Yield Traits and DNA Markers Analysis under Sinai Conditions

Fourteen summer squash genotypes were used to assess their genetic diversity and relationships using some yield traits (Fruit length, fruit diameter, fruit shape index, average fruit weight, No of fruits/plant, fruit yield, and total soluble solids %) and DNA markers (Random Amplified Polymorphic DNA, inter-simple sequence repeat, Start Codon Targeted polymorphism) analyses. Two open field trials were executed at two locations, i.e., El-Arish (L1) and Ras Sidr (L2) in the North and South Sinai-Egypt, respectively. Significant differences were observed between both locations and indicated the superiority of (L1) than (L2) in all studied traits, while the interaction between genotype and location was significant for all studied traits. The location had a major effect on the relative genotypic potential of these traits, in which the genotype × location interaction was highly significant. SQ6genotype ranked as the first in the fruit yield/plant and SQ2 for fruit diameter followed by SQ7and SQ2 for fruit shape as well as SQ13and SQ12for the number of fruits/plant in L1 and L2 locations, respectively. Additionally, high polymorphism percentage (P %) was detected using RAPD (85%), ISSR (79.25%) and SCoT (69.44). Among the 15 studied primers, OP-B17 showed the maximum P% (100%) followed by primer OP-C17 (90.9 %) which also scored the highest values for polymorphism information content, effective multiplex ratio, and marker index. In addition, OP-K01 represented the maximum value of resolving power (12.56), indicated that these primers were highly informative. Intriguingly, 55 positive and two unique negative bands were amplified, out of which (33) bands were generated by RAPD followed by SCoT (15) and ISSR (9). In this regard, OP-C17 and SQ1 genotype produced the highest number of unique marker18 and 11amplicon, respectively. Moreover, the maximum similarity was found between SQ 11 and SQ 12 indicating that both genotypes were the most similar. Cluster and PCA analysis using RAPD, ISSR, and SCoT data grouped the 14 squash genotypes into four, three and two distinct clusters, respectively. Generally, the yield traits alongside molecular results showed significant information that may be utilized to sort and relationship between the studied summer squash genotypes under different conditions

Use of Non-Destructive Measurements to Identify Cucurbit Species (Cucurbita maxima and Cucurbita moschata) Tolerant to Waterlogged Conditions.

Limited information is available regarding the physiology of squash plants grown under waterlogging stress. The objectives of this study were to investigate the growth and physiological performances of three cucurbit species, Cucurbita maxima cultivar (cv.) OK-101 (OK) and Cucurbita moschata cv. Early Price (EP) and Strong Man (SM), in response to waterlogging conditions, and to develop a precise, integrated, and quantitative non-destructive measurement of squash genotypes under stress. All tested plants were grown in a growth chamber under optimal irrigation and growth conditions for a month, and the pot plants were then subjected to non-waterlogging (control) and waterlogging treatments for periods of 1, 3, 7, and 13 days (d), followed by a 3-d post-waterlogging recovery period after water drainage. Plants with phenotypes, such as fresh weight (FW), dry weight (DW), and dry matter (DM) of shoots and roots, and various physiological systems, including relative water content (RWC), soil and plant analysis development (SPAD) chlorophyll meter, ratio of variable/maximal fluorescence (Fv/Fm), quantum photosynthetic yield (YII), normalized difference vegetation index (NDVI), and photochemical reflectance index (PRI) values, responded differently to waterlogging stress in accordance with the duration of the stress period and subsequent recovery period. When plants were treated with stress for 13 d, all plants exhibited harmful effects to their leaves compared with the control, but EP squash grew better than SM and OK squashes and exhibited stronger tolerance to waterlogging and showed less injury. Changes in the fresh weight, dry weight, and dry matter of shoots and roots indicated that OK plants suffered more severely than EP plants at the 3-d drainage period. The values of RWC, SPAD, Fv/Fm, YII, NDVI, and PRI in both SM and OK plants remarkably decreased at waterlogging at the 13-d time point compared with controls under identical time periods. However, the increased levels of SPAD, Fv/Fm, YII, NDVI, and PRI observed on 7 d or 13 d of waterlogging afforded the EP plant leaf with improved waterlogged tolerance. Significant and positive correlations were observed among NDVI and PRI with SPAD, Fv/Fm, and YII, indicating that these photosynthetic indices can be useful for developing non-destructive estimations of chlorophyll content in squashes when screening for waterlogging-tolerant plants, for establishing development practices for their cultivation in fields, and for enhanced cultivation during waterlogging in frequently flooded areas.

Selecting squash (Cucurbita sp.) introductions by seed nutritional quality and seed meal

Squash (Cucurbita sp.) is widely used in Colombia as both food and animal feed. However, its seeds are discarded. This study aimed to identify squash genotypes with a high nutritional value in the whole seed meal (WSM) and defatted seed meal (DSM) within a group of 19 introductions (14 of Cucurbita moschata and 5 of C. sororia). For WSM, 70% of the introductions presented above-average values for extract (36.9%) and crude protein (26.34%); the fiber values were 20.34% neutral detergent fiber (NDF) and 13% acid detergent fiber (ADF). For DSM, 57% of the introductions presented above-average crude protein (43.5%) and 52% above-average crude energy values (4078 cal g-1). Based on the relative feed value (RFV), introductions 1229, 1200, 1201, 1219 and 1206 were selected for WSM, and 1206 1229, 932, 1200, 786 and 954 were selected for DSM. In the selected C. moschata introductions, parents with general and specific combining abilities for ether extract and crude protein in WSM or high RFV in DSM should be identified. C. soraria introductions 1202 and 954 should be used in crosses that aim to obtain F2 segregants for seeds with a high oil content and high RFV in DSM.

Response of Certian Vegetable Genotypes to the Root Knot Nematode, Meloidogyne incognita

Resistance evaluation of 60 vegetable cultivars and hybrids of Eggplant, Pepper, Tomato, Cantaloupe, Cucumber and squash were tested against Root-knot nematodes (RKN) Meloidogyne incognita. Among Eggplant genotypes, Arosy1 recorded the lowest reproduction rate (15.1) while the highest population was possessed by kaser abiad (41.1). Pepper genotypes, in general, were less susceptible to RKN compared with Eggplants and Tomatoes, the reproduction rate varied between 3.5 (Romey) to 8.9 (P77). All Tomato genotypes were highly susceptible to RKN infection, Super strain B was the most susceptible cultivar because the nematode success to multiply 38.3 times, the lowest reproduction rate (13.3) registered by 820 and Castel rock (11.6 & 11.8 respectively). Similarly, all cucurbitaceous plants found to be susceptible to RKN infection. Among Cantaloupe genotypes, Alhana possessed the highest reproduction rate (15.8), while Galia 3 recorded the lowest reproduction (7.2). Within Cucumber genotypes, the minimum reproduction rate (6.2) was observed on Almanar, but the maximum population was possessed by Aliaa (13.8). Squash genotypes viz. Sama recorded the lowest reproduction rate (4.8) and the greatest population (10.1) was possessed by Dahab. Plant growth in most cases negatively reacted with nematode infection and the differences between infected and healthy plant was unobvious in many cases. To recommend the less susceptible genotypes as a tool for managing nematode strategy, further experiments are needed in the field for using these selected genotypes, also insertion these genotypes in breeding program for improving their characters specially resistance to nematode.

Tolerance of Varieties and Hybrid of Pumpkin and Squash to Salt Stress

Irrigated agriculture in arid and semi-arid regions is a practice encouraged to maximize food production, however these regions hesitate a qualitative shortage of water resources, often being necessary the use of saline water, affecting soil and sensitive plants to saline stress. So this study aimed to evaluate emergence, growth, phytomass accumulation and tolerance of the Tetsukabuto hybrid and varieties of pumpkin and squash under salt stress. The experiment was carried out in protected environment (greenhouse), located in the municipality of Pombal, Paraíba, Brazil. Treatments were arranged in completely randomized experimental design with four replicates, in a 5 × 3 factorial scheme, relative to five levels of irrigation water salinity and three genotypes of pumpkin and squash. Pumpkin and squash seedlings were grown on trays of 30 cells with capacity for 0.1 dm3 of substrate, during the first 20 days after sowing, and were monitored for emergence, initial growth, dry matter accumulation and tolerance to salinity. Increment in irrigation water salinity reduces emergence and initial growth of the pumpkin and squash genotypes. The genotypes G2 - ‘Squash cv. Coroa’ and G3 - Tetsukabuto hybrid are more tolerant to salinity than G1 - ‘Pumpkin cv. Jacarezinho’ in the initial growth stage.

Inheritance analysis and identification of SNP markers associated with ZYMV resistance in Cucurbita pepo

Cucurbit crops are economically important worldwide. One of the most serious threats to cucurbit production is Zucchini yellow mosaic virus (ZYMV). Several resistant accessions were identified in Cucurbita moschata and their resistance was introgressed into Cucurbita pepo. However, the mode of inheritance of ZYMV resistance in C. pepo presents a great challenge to attempts at introgressing resistance into elite germplasm. The main goal of this work was to analyze the inheritance of ZYMV resistance and to identify markers associated with genes conferring resistance. An Illumina GoldenGate assay allowed us to assess polymorphism among nine squash genotypes and to discover six polymorphic single-nucleotide polymorphisms (SNPs) between two near-isogenic lines, “True French” (susceptible to ZYMV) and Accession 381e (resistant to ZYMV). Two F2 and three BC1 populations obtained from crossing the ZYMV-resistant Accession 381e with two susceptible ones, the zucchini True French and the cocozelle “San Pasquale,” were assayed for ZYMV resistance. Molecular analysis revealed an approximately 90% association between SNP1 and resistance, which was confirmed using High Resolution Melt (HRM) and a CAPS marker. Co-segregation up to 72% in populations segregating for resistance was observed for two other SNP markers that could be potentially linked to genes involved in resistance expression. A functional prediction of proteins involved in the resistance response was performed on genome scaffolds containing the three SNPs of interest. Indeed, 16 full-length pathogen recognition genes (PRGs) were identified around the three SNP markers. In particular, we discovered that two nucleotide-binding site leucine-rich repeat (NBS-LRR) protein-encoding genes were located near the SNP1 marker. The investigation of ZYMV resistance in squash populations and the genomic analysis performed in this work could be useful for better directing the introgression of disease resistance into elite C. pepo germplasm.

Physical and chemical characterization in fruit from 22 summer squash (Cucurbita pepo L.) cultivars

Physical and chemical characters of 22 summer squash genotypes (traditional and commercial cultivars) were evaluated in fruit using correlation and principal component analysis. External and internal fruit quality was assessed by standard parameters (fruit weight and dimensions, firmness, color, dry matter, soluble solids, pH, total acidity) and nutritional quality (individual and total carotenoid content) in fruit epicarp and mesocarp. Some of the cultivars showed distinctive and interesting characters in mesocarp, such as high soluble solid (4.7 °Brix: Cu-8 traditional cultivar), dry matter (6.6 g 100 g−1: Cu-36 commercial cultivar), β-carotene (45 mg kg−1 dry matter: Cu-11 traditional cultivar) and total carotenoid contents (371 mg kg−1 dry matter: Cu-29 commercial cultivar). Moderate and significant positive relation was found between epicarp and mesocarp color parameter (b*) with lutein and total carotenoid contents in mesocarp (r > 0.52***), suggesting that indirect selection for high carotenoid content will be successful. Multivariable analysis allowed the grouping of variables, the most important being the a* and b* parameters (in epicarp and mesocarp), dry matter, soluble solid, total acidity, lutein, β-carotene and total carotenoid contents (in epicarp). Some cultivars may serve as a source of desirable genes to develop improved varieties that respond to the new needs of the market.

Genetic Diversity and Relationship in Squash Using Morphological, Chemical and Molecular Analyses

Germplasm characterization is an important link between the conservation and utilization of plant genetic resources. A collection of thirteen summer, spaghetti and acorn squash ( Cucurbita pepo L .) and one winter squash ( Cucurbita moschata L .) germplasm accessions were screened using morphological (leaf area, fruit weight, fruit length, fruit firmness), chemical [Soluble Solids Content (S.S.C.), ascorbic acid] and molecular [Random Amplified Polymorphic DNA (RAPD)] analyses. A wide range of variability among genotypes was recorded for morphological and chemical characteristics. The percentages of variation were 217%, 532%, 175%, 166%, 148%, 520% for leaf area, fruit length, fruit weight, fruit firmness, S.S.C, ascorbic acid content, respectively. Both significant positive and negative correlations have been found between the morphological and chemical characteristics. The RAPD analysis produced 209 DNA fragments with 100% polymorphism in two or more squash genotypes while none of the fragments showed monomorphic behavior among squash genotypes. At a similarity level of 82% the genotypes were divided into two clusters. The first cluster consisted of eight genotypes (PI 506466- PI 292014- PI 518688- PI 615119- PI 136448- Butternut- Copi- Eskandrani). The second cluster contained only two genotypes (Yellow Crookneck and Shamamy). When the cluster analysis of RAPD patterns was associated with morphological and chemical evaluation of squash genotypes used in this study, there was a notable degree of agreement. The RAPD-PCR was found to be suitable for use with squash due to its ability to discriminate between genotypes and determine their genetic relationship. Results obtained in this investigation provide clear evidence that there is a considerable variation among summer squash genotypes. Present results support the development of breeding programs in squash since high genetic variability in its accessions and landraces has been found.

Atratividade para adultos e preferência para oviposição de Bemisia tabaci (Genn.) biótipo B (Hemiptera: Aleyrodidae) em genótipos de Cucurbita spp

The objective was to evaluate the oviposition preference and attractiveness of squash genotypes (Cucurbita spp.) to Bemisia tabaci biotype B. For bioassays, B. tabaci rearing biotype B was kept under greenhouse conditions. Twenty genotypes of Cucurbita spp. (‘Alicia AF 9354’, ‘Aline AF 9353’, ‘Golden Delight’, ‘Nova Caravela’, ‘Menina Morena’, ‘Novita’, ‘AF-6741’, ‘Atlas’, ‘Bárbara 305’, ‘Menina Brasileira’, ‘Caserta’, ‘Itapuã 301’, ‘Tâmara’, ‘Samira’, ‘Canhão Seca Gigante’, ‘Exposição’, ‘Novita Plus’, ‘Daiane’, ‘Formosa’, ‘Sandy’) were evaluated in trials (attractiveness and oviposition choice), under laboratory and greenhouse. The attractiveness (adults/cm2) was assessed et 12, 24, 48 and 72 hours after release. After 72 hours leaves were collected for counting the number of eggs (free choice). The area of the sheets were measured to obtain the number of eggs/cm2 number of adults and / cm 2. The attractiveness index s (AI) and oviposition preference index (OPI) were calculated, and the genotype ‘Novita’ was adopted as the standard susceptible. The genotype ‘Golden Delight’ was the most attractive to adults of B. tabaci biotype B. ‘Sandy’ ‘Daiane’ and ‘Formosa’ showed low attractiveness and ‘Golden Delight’ was the most atractive to B. tabaci biotype B adults. ‘Sandy’, ‘Exposição’, ‘Daiane’, ‘Atlas’, ‘Tamara’ and ‘Formosa’ expressed no preference for free choise assay. According to the attractiveness index (AI) the genotype ‘Golden Delight’ was the most attractive to adults of B. tabaci biotype B, and between repellents stood out ‘Sandy’, ‘Daiane’, ‘Formosa’, ‘Novita Plus’, ‘Atlas’, ‘Bárbara 305’, ‘Canhão Seca Gigante’ and ‘Menina Brasileira’. The genotypes ‘Nova Caravela’, ‘Golden Delight’, ‘Aline AF 9353’ and ‘Samira’ are considered by stimulating oviposition preference index (OPI), while the genotypes ‘Sandy’, ‘Exposição’, ‘Daiane’ , ‘Atlas’, ‘Tâmara’, ‘Formosa’, ‘Menina Morena’ and ‘Itapuã 301’ were considered deterrents.

The role of ethylene and brassinosteroids in the control of sex expression and flower development in Cucurbita pepo

In this paper we compare the sensitivity of different squash genotypes to ethylene and brassinosteroids by studying the effects of different ethylene and brassinosteroid treatments on the sexual expression and flower development of different C. pepo genotypes: Bolognese (Bog) and Vegetable Spaghetti (Veg), two contrasting lines for ethylene production and sensitivity, as well as Cora, a standard commercial hybrid. Results have demonstrated that ethylene has a much greater effect on sexual expression and flower development in C. pepo than brassinosteroids. Ethephon increases the number of female flowers per plant and reduces the first male phase of development, while treatments with the ethylene inhibitors AVG and STS reduce the number of female flowers per plant and expand the first male phase of development. The differential response observed between genotypes appears to be related to ethylene production and sensitivity. Bog, which produces more ethylene and is more sensitive to this hormone, responded much better to AVG and STS, reducing the number of female flowers per plant, while Veg, which is characterised by lower production of and sensitivity to ethylene, responded better to ethephon by reducing the first male phase of development and increasing the number of female flowers per plant. The differential abortion of female and male flowers in ethephon, AVG and STS treatments, as well as the occurrence of bisexual flowers in the AVG and STS treated plants of the more ethylene sensitive genotypes, demonstrate that ethylene is also involved in the development of female flowers. Female flower buds require a minimal level of ethylene not only to complete their development and maturation without a premature abortion, but also to arrest the development of stamens in the third whorl and to promote the appropriate growth of the carpels. On the contrary, the role of brassinosteroids in the sexual expression of C. pepo was not so evident. The application of brassinazole, an inhibitor of brassinosteroid biosynthesis slightly changes the production of ethylene in the three analysed genotypes, but those changes have little effect on their sexual phenotypes, and they do not alter the development of the unisexual flowers.

Resistência de genótipos de abobrinha a Bemisia tabaci (Genn.) biótipo B (Hemiptera: Aleyrodidae)

Field assays were performed to evaluate the attractiveness and the non-preference of whitefly Bemisia tabaci (Genn.) biotype B for oviposition on squash genotypes (Cucurbita pepo) and to observe the susceptibility of genotypes (Novita, Sandy, Caserta Cac Melhorada, Novita Plus, Samira, Bianca, AF-2858 and Caserta TS) to silverleaf symptoms. The Sandy genotype was the least attractive to whitefly, while Novita Plus, AF-2858 and Samira were the most attractive. The Caserta Cac Melhorada genotype was the least preferred for oviposition. The Sandy and AF-2858 genotypes were the most productive, with the highest mean of fruits produced. The lowest silverleaf symptoms index was observed for the Sandy and Caserta Cac Melhorada genotypes.

Atratividade e preferência para oviposição de Trialeurodes vaporariorum em genótipos de aboboreira

O comportamento de 13 genótipos de aboboreira foi avaliado em relação à atratividade para adultos e à preferência para oviposição da mosca-branca Trialeurodes vaporariorum (West.) (Hemiptera: Aleyrodidae) em testes com e sem chance de escolha, em campo e em casa de vegetação. Os experimentos foram conduzidos com plantas de aboboreira em fase vegetativa, infestadas naturalmente no campo (atratividade para adultos e oviposição com chance de escolha) e artificialmente em casa de vegetação (oviposição sem chance de escolha). Dentre as aboboreiras tipo moita, o híbrido Arlika apresentou a menor atratividade para adultos e, entre os genótipos de crescimento rasteiro, não houve diferença em relação à atratividade. Quanto à preferência para oviposição em teste de livre escolha, 'Arlika', no grupo de moita, e 'Atlas', 'Sandy', 'Bárbara', 'Baianinha' e 'Caravela', no grupo das rasteiras, apresentaram os menores índices de oviposição, que se confirmaram no teste sem chance de escolha, indicando que a menor preferência para oviposição de T. vaporariorum nesses genótipos é estável.

Atratividade e Consumo Foliar por Adultos de Diabrotica speciosa (Germ.) (Coleoptera: Chrysomelidae) em Diferentes Genótipos de Abóbora

Alguns crisomelídeos atacam a abóbora desde a germinação até a colheita, destruindo folhas e causando danos característicos. Com o objetivo de selecionar genótipos de abóbora menos preferidos para alimentação por Diabrotica speciosa (Germar), realizaram-se ensaios, em condições de casa-de-vegetação e de laboratório, utilizando-se plântulas e discos foliares. Inicialmente avaliou-se a atratividade de 33 genótipos de abóbora Cucurbita moschata e um genótipo comercial de moranga C. maxima (Exposição), utilizado como genótipo suscetível padrão. Visando observar o consumo realizado em plântulas, efetuaram-se testes com e sem chance de escolha com oito genótipos selecionados a partir do ensaio de atratividade. Em placas de Petri, foram realizados testes de atratividade e consumo, com e sem chance de escolha, utilizando-se discos foliares de oito materiais. O índice de atratividade apontou o genótipo BRA003531 como o mais atrativo em relação ao padrão comercial (genótipo Exposição). Em teste de consumo com chance de escolha, utilizando-se plântulas, o genótipo BRA014869 foi o mais preferido para alimentação por adultos de D. speciosa, embora somente diferisse estatísticamente do genótipo BRA015059. BRA014958 revelou-se o mais consumido em teste sem chance de escolha com plântulas e em teste com chance de escolha utilizando-se discos foliares; em testes com discos foliares sem escolha, entretanto não se observaram diferenças entre os genótipos. Em geral todos os genótipos revelaram-se igualmente suscetíveis ao padrão Exposição, não tendo sido detectada a ocorrência de resistência do tipo não-preferência para alimentação.