Search Results

You are looking at 1 - 10 of 22 items for

  • Author or Editor: A. Hernandez x
Clear All Modify Search

Foundation sweetpotato [Ipomoea batatas (L.) Lam] seedstock has been produced annually at the Sweet Potato Research Station since 1949. Breeder seedstock is selected from superior hills and used for the following year's foundation seedstock. Fields are intensely monitored after planting until harvest to remove off-type plants, mutations, etc. Seedstock is harvested from August through October, stored, graded, and repacked beginning in late January, and then made available to the growers during the early spring.

Full access

A distinct type of postharvest skin browning on apple (Malus domestica Borkh.) fruit called “stain” is a frequent disorder in ‘Fuji’ grown under high light and elevated temperatures. Symptoms typically develop only on sun-exposed sections of the fruit regardless of the presence of sunburn symptoms, and sometimes only in the margins of this area. The role of different antioxidant systems in tissue exposed to different levels of sunlight and having different degrees of sun injury were investigated during cold storage [1 °C, >90% (relative humidity) RH]. Ascorbic acid (AsA) and glutathione (GSH) concentrations, AsA–GSH recycling enzyme activities and gene expression, and flavonoids and carotenoid concentrations were determined every 30 days. “Stain” incidence increased with sun exposure and sunburn level. Both shaded and exposed fruit peel without sunburn symptoms had the highest AsA content. The AsA–GSH recycling enzyme activities and gene expression levels had no clear relationship with sun exposure during cold storage. Chlorophyll a (chl a) and chlorophyll b (chl b) levels diminished over time and were higher in tissue without any type of sun injury. In contrast, carotenoid levels increased as sun injury incidence increased and remained relatively stable during storage. Total phenolics and quercetin glycoside levels changed coincidently during storage. Results indicate that the AsA–GSH cycle does not have a clear role in “stain” development. Nevertheless, reduced ascorbate levels may reduce the capacity to prevent oxidative stress–provoked damage which may, in turn, result in oxidation of quercetin glycosides, which would then lead to skin browning.

Free access

The phytotoxic effects on the physiology of chili (Capsicum annum L. cv. Ancho San Luis) caused by four different insecticides were evaluated. Three commercial mixes (methyl azinfos, methyl parathion CE720, and metamidophos 600 LM), and an active ingredient alone (methamidophos) were assayed; water was used as the control. The main goal was to evaluate the insecticide effects on chili using four different doses; the mean dose, recommended on the label of the product (R), a half one (1/2R), 1.5 times (1.5R) and twice the recommended dose (2R). Three frequencies of application were applied; once a week, twice a week, and once every other week, for 6 weeks from the beginning of flowering. Phytotoxicity was evaluated measuring the response of some physiological traits, Chlorophyll Fluorescence (CF), Leaf Temperature (LT), Transpiration (Tr), and Stomatal Resistance (SR). CF was measured by means of a portable chorophyll fluorscence meter; LT, Tr, and SR were measured using a LI-Cor Porometer. The doses and frequencies used are all common in commercial chili fields in Mexico. Results showed that phytotoxicity caused by insecticides can be an important damage factor to the plants, something that can cause reduction of yields. CF was shown to be the most sensitive variable to evaluate the phytotoxicity caused by insecticides. Fruit malformation was observed in all treatments. Chlorophyll content was reduced up to 25%, on average. The phosphorate insecticides affected the physiological parameters more drastically than the others. Results evidence the irreversible crop damage caused by excessive insecticide applications.

Free access

The standard strawberry (Fragaria ×ananassa) production system in Florida uses bare-root transplants with three to five leaves; however, commercial transplants are typically variable in size. The objective of this experiment was to study the effects of transplant crown diameter on the subsequent performance of three short-day strawberry cultivars under central Florida conditions. Trials were carried out during the 2012–13 and 2013–14 growing seasons with six treatments resulting from the combination of three cultivars and two crown diameter categories. Transplants of ‘Florida Radiance’, ‘Strawberry Festival’, and WinterStar™ were sorted into two initial crown diameter size ranges: <10 mm and >10 mm. Treatments were established in a split-plot design with cultivars as the main plot and four replications. Dry plant biomass was collected at 6 weeks after transplant (WAT). Canopy diameter and crown diameter were measured at 6 and 18 WAT and fruit harvest started at 8 WAT. There were no interactions between cultivar and initial crown diameter for any of the measured variables. For early yield, larger crowns led to 46% (3.5 Mg·ha−1) and 38% (3.9 Mg·ha−1) higher early yield than smaller crowns in 2012–13 and 2013–14, respectively. Crown diameters >10 mm also resulted in 18% (23.5 Mg·ha−1) and 27% (17.4 Mg·ha−1) higher total yields in 2012–13 and 2013–14, respectively.

Free access

Two key fruit qualities in Capsicum annuum are fruit pungency and color. We characterize 13 New Mexican landraces for fruit quality traits at both the chemical level measuring the capsaicinoids, dihydrocapsaicin, and capsaicin as well as five carotenoids, β-carotene, β-cryptoxanthin, zeaxanthin, violaxanthin, and capsanthin, and at the genetic level sequencing two genes in these landraces, Kas I, a capsaicinoid pathway gene, and Ccs, a carotenoid pathway gene. All of the landraces had unusually high levels of dihydrocapsaicin in comparison with capsaicin levels. The levels of the most abundant red pigment, capsanthin, ranged between 468 and 1007 μg·g−1 dry weight fruit in field-grown fruit, whereas levels of β-carotene were more similar in the landraces (13 to 22 μg·g−1 dry weight fruit). Twelve different Kas I alleles were found in the landraces, which predicted six novel KAS proteins in these landraces. Seven alleles of Ccs were found, which predicted three novel CCS proteins. These results demonstrate that the landraces under cultivation in small farms and pueblos in northern New Mexico are sources of important genetic diversity for Capsicum crops.

Free access

External, middle and inner scales in parent bulbs were studied to evaluate bulblet differentiation in Lilium longiflorum Thunb. during scale propagation at 25 °C. A 13-stage developmental process describes different steps including preprimordial, primordial, and bulblet formation. For all scales, preprimordial and primordial stages occurred within the first 4 days. The differentiation process depended on parent scale position. Most bulblets arising from external scales developed three true scales after 30 days while bulblets from middle scales formed four true scales. Homogeneity in the morphology of the parent scales, only shown in the middle ones, was associated with a rapid change in developmental stage for the population of bulblets. Inner scales showed few bulblets with three and four true scales, the rest remaining at earlier developmental stages. Bulblet production decreased from external to internal scales: 2.6, 2.2, and 1.2 bulblets per scale, respectively, and showed a positive correlation with the scale base width. Maximum scale weight and surface area and maximum bulblet fresh and dry weight occurred in the middle scales. We conclude that middle scales are the ideal starting material for experimental uses involving scaling propagation. For production purposes, the external scales, in addition to the middle scales, must also be included for propagation.

Free access

During three consecutive years of field experiments, three crop-covering treatments [noncovered (C), perforated polyethylene (PO, 500 holes/m2), and a nonwoven polypropylene (AO) sheet] were used to create different environmental conditions for growth of `Nagaoka 50' chinese cabbage [Brassica rapa L. (Pekinensis Group)]. The PO and AO treatments reduced solar irradiance and increased air and root temperatures compared to C plants. Plants were sampled five times each year from transplanting to harvest, and fresh and dry weights, yield at harvest, leaf pH, citric and ascorbic acid concentrations, and cell-wall fractions were determined. The PO floating row cover was the most beneficial for yield and chemical composition of chinese cabbage of the early spring crop in southern Spain, where environmental conditions during an unfavorable season can injure sensitive crops.

Free access

Genetic linkage map is being constructed for watermelon based on a testcross population and an F2 population. The testcross map comprises 262 markers (RAPD, ISSR, AFLP, SSR and ASRP markers) and covers 1,350 cM. The map comprises 11 large linkage groups (50.7–155.2 cM), 5 medium-size linkage groups (37.5–46.2 cM), and 16 small linkage groups (4.2–31.4 cM). Most AFLP markers are clustered on two linkage regions, while all other marker types are randomly dispersed on the genome. Many of the markers in this study are skewed from the classical (Mendelian) segregation ratio of1:1 in the testcross or the 3:1 ratio in the F2 population. Although the skewed segregation, marker order appeared to be consistent in linkage groups of the testcross and F2 population. A cDNA library was constructed using RNA isolated from watermelon flesh 1 week (rapid cell division stage), 2 weeks (cell growth and storage deposition stage, 4 weeks (maturation stage), and 5 weeks (postmaturation stage) post pollination. Over 1,020 cDNA clones were sequenced, and were analyzed using the Basic Local Alignment Search Tool (BLAST). The sequenced cDNA clones were designated as expressed sequenced tag (EST) markers and will be used in mapping analysis of watermelon genome.

Free access

Endophytic fungi are increasingly studied for their ability to enhance plant performance in field crops, yet there are few equivalent studies in floricultural crops. Given the economic importance of these crops and pressures faced by growers to produce plants of high aesthetic quality, we surveyed the natural occurrence of foliar fungal endophytes in Knock Out® roses to identify candidate beneficial isolates. We also tested the effects of entomopathogenic fungal inocula on marigold and zinnia plant growth using different application approaches. Our survey of Knock Out® rose foliage collected from five sites within central Texas revealed at least 24 different fungal genera and 30 probable species, including some isolates providing plant stress tolerance and pathogens or antagonists of insects and nematode pests. The effects of entomopathogen inocula on plant growth varied with host plant (marigold vs. zinnia) and inoculation method (soil drench vs. seed soak). Plant responses were complex, but inoculation with Isaria fumosorosea Wize tended to have a negative effect on plant performance characteristics whereas Beauveria bassiana (Bals.-Criv.) Vuill. tended to have positive effects. When applied to marigold as a seedcoating, I. fumosorosea reduced germination, seedling fresh weight, and produced seedlings with a less compact form. By contrast, seeds inoculated with B. bassiana required less time to germinate, had higher germination rates, and increased the plant compactness. These results show that the impact of fungal entomopathogens applied as endophytes depends on the specific fungi-plant combination being examined. The effect of plant inoculation with entomopathogenic fungi within a pest management context requires further evaluation.

Free access