Mosbah M. Kushad

Active oxygen-scavenging enzymes activities in developing apple flowers and fruits

The activities of active oxygen-scavenging enzymes, superoxide dismutase, catalase and peroxidase were evaluated during apple (Malus domestica Borkh cv. Red Spur Delicious) flower bud and fruit development. In dormant buds, superoxide dismutase, peroxidase and catalase activities were initially low, then increased sharply (2- to 5-fold) during bud swelling. With onset of bud break and during fruit development, superoxide dismutase and peroxidase activities decreased by 5- to 8-fold, while catalase activity remained relatively high throughout flower bud development and during early stages of fruit growth, before declining at full fruit development. A second increase in peroxidase activity occurred at full fruit development. In immature and mature fruits, superoxide dismutase activity was detected only in the peel, but not in cortex (flesh) or in seed tissue. Peroxidase activity was highest in peel, low in cortex and absent in seed tissue. Catalase activity was highest in seed, followed by peel, and cortex. Soluble protein levels in the seed were 7- and 12-fold higher than in the peel and cortex, respectively. Changes in the activities of these enzymes were related to growth and development of apple flower and fruit.

Influence of different drying methods on carotenoids and capsaicinoids of paprika (Cv., Jalapeno).

Influence of Refractance Window™ Drying (RWD), a novel contact drying method, on carotenoids, capsaicinoids, Retinol Activity Equivalent (RAE) and Scoville Heat Unit (SHU) of paprika (Cv., Jalapeno) was investigated in comparison with freeze drying (FD), oven drying (OD), and natural convective drying (NCD) methods. Eight carotenoids (capsanthin, capsorubin, capsolutein, β-carotene, β-cryptoxanthin, mutatoxanthin, violaxanthin and zeaxanthin) and five capsaicinoid analogues (capsaicin, dihydrocapsaicin, homodihydrocapsaicin, isodihydrocapsaicin, nordihydrocapsaicin) were identified in paprika. All these components were significantly (P<0.05) decreased by the RWD, FD and OD methods. However, due to ongoing synthesis, the NCD method resulted in higher carotenoids, except violaxanthin and mutatoxanthin, and capsaicinoids content than those of the others, even puree. Mutatoxanthin, naturally occurring pigment in red pepper, could only be detected in FD paprika. The highest RAE and SHU values, which were derived from the data of carotenoids and capsaicinoids, respectively, were also determined in NCD paprika.

Genetic Diversity and Characterization of a Core Collection of Malus Germplasm Using Simple Sequence Repeats (SSRs)

Simple sequence repeats (SSRs) were used to assess genetic diversity and study genetic relatedness in a large collection of Malus germplasm. A total of 164 accessions from the Malus core collection, maintained at the University of Illinois, were genotyped using apple SSR markers. Each of the accessions was genotyped using a single robust SSR marker from each of the 17 different linkage groups in Malus. Data were subjected to principal component analysis, and a dendrogram was constructed to establish genetic relatedness. As expected, this diverse core collection showed high allelic diversity; moreover, this allelic diversity was higher than that previously reported. Cluster analysis revealed the presence of four distinct clusters of accessions in this collection.

Methyl Jasmonate and 1-Methylcyclopropene Treatment Effects on Quinone Reductase Inducing Activity and Post-Harvest Quality of Broccoli

Effect of pre-harvest methyl jasmonate (MeJA) and post-harvest 1-methylcyclopropene (1-MCP) treatments on broccoli floret glucosinolate (GS) concentrations and quinone reductase (QR, an in vitro anti-cancer biomarker) inducing activity were evaluated two days prior to harvest, at harvest and at 10, 20, and 30 days of post-harvest storage at 4 °C. MeJA treatments four days prior to harvest of broccoli heads was observed to significantly increase floret ethylene biosynthesis resulting in chlorophyll catabolism during post-harvest storage and reduced product quality. Post-harvest treatment with 1-methylcyclopropene (1-MCP), which competitively binds to protein ethylene receptors, maintained post-harvest floret chlorophyll concentrations and product visual quality in both control and MeJA-treated broccoli. Transcript abundance of BoPPH, a gene which is responsible for the synthesis of pheophytinase, the primary enzyme associated with chlorophyll catabolism in broccoli, was reduced by 1-MCP treatment and showed a significant, negative correlation with floret chlorophyll concentrations. The GS, glucobrassicin, neoglucobrassicin, and gluconasturtiin were significantly increased by MeJA treatments. The products of some of the GS from endogenous myrosinase hydrolysis [sulforaphane (SF), neoascorbigen (NeoASG), N-methoxyindole-3-carbinol (NI3C), and phenethyl isothiocyanate (PEITC)] were also quantified and found to be significantly correlated with QR. Sulforaphane, the isothiocyanate hydrolysis product of the GS glucoraphanin, was found to be the most potent QR induction agent. Increased sulforaphane formation from the hydrolysis of glucoraphanin was associated with up-regulated gene expression of myrosinase (BoMyo) and the myrosinase enzyme co-factor gene, epithiospecifier modifier1 (BoESM1). This study demonstrates the combined treatment of MeJA and 1-MCP increased QR activity without post-harvest quality loss.

Fruit Quality Traits Have Played Critical Roles in Domestication of the Apple

With its long history of cultivation, the domesticated apple, Malus × domestica Borkh., is an excellent model for studying domestication in long‐lived perennial plants. As apples have been transported from their center of origin in the Tian Shan region in central Asia and moved along the famous Silk Road trading path, they have undergone selection for distinct phenotypic traits. In this study, a high‐throughput single nucleotide polymorphism (SNP) genotyping assay is used to investigate relationships of Malus species, draw inferences on the domestication history, identify traits critical for domestication, and assess potential genetic loci under selection. A total of 160 Malus accessions, including wild species, old and new apple cultivars, and advanced selections, were genotyped. Of 1536 SNPs from GoldenGate oligonucleotide pool assays (OPAs), 901 SNPs fulfilled filtering criteria. A principal component analysis (PCA) revealed that most M. × domestica accessions grouped together. A total of 67 loci, including 13 genomic SNPs and 54 genic SNPs, have been identified as potential targets for selection during evolution of the apple genome from its wild progenitor M. sieversii. Genes introgressed from local wild species into M. × domestica are associated with adaptation to local environments, while genes for fruit quality traits are derived from M. sieversii.

Correlation of Quinone Reductase Activity and Allyl Isothiocyanate Formation Among Different Genotypes and Grades of Horseradish Roots

Horseradish (Armoracia rusticana) is a perennial crop and its ground root tissue is used in condiments because of the pungency of the glucosinolate (GS)-hydrolysis products allyl isothiocyanate (AITC) and phenethyl isothiocyanate (PEITC) derived from sinigrin and gluconasturtiin, respectively. Horseradish roots are sold in three grades: U.S. Fancy, U.S. No. 1, and U.S. No. 2 according to the USDA standards. These grading standards are primarily based on root diameter and length. There is little information on whether root grades vary in their phytochemical content or potential health promoting properties. This study measured GS, GS-hydrolysis products, potential anticancer activity (as quinone reductase inducing activity), total phenolic content, and antioxidant activities from different grades of horseradish accessions. U.S. Fancy showed significantly higher sinigrin and AITC concentrations than U.S. No. 1 ,whereas U.S. No. 1 showed significantly higher concentrations of 1-cyano 2,3-epithiopropane, the epithionitrile hydrolysis product of sinigrin, and significantly higher total phenolic concentrations than U.S. Fancy.

Nitrogen and Tillage Effects on the Fruit Quality and Yield of Four Tomato Cultivars

ABSTRACT The type of tillage system used and the rate of nitrogen fertilizer applied may affect fruit quality and total fruit yield of tomato (Lycopersicon esculentum Mill.). The treatments were either conventional tillage or rye (Secale cereale L.) mulch with or without 50 kg·ha−1 N. In both tillage systems, the application of 50 kg·ha−1 of N reduced the concentric cracking of tomato fruit, except for ‘UC82’ in conventional tillage and ‘Cherry Express II’ in rye mulch. When harvested at the same stage of maturity, chroma and hue along with acetic and citric acid concentrations of fruit were not affected by tillage system or N treatment. Fruit yields ranged from 34.0 to 60.6 Mg·ha−1. Total yield of ‘UC82’ was not affected by cropping system. Depending on the year, total yields of ‘Mountain Supreme’, ‘Pik Red’, and ‘Cherry Express II’ were reduced in the rye mulch. Although rye mulch had a minimal effect on fruit quality, the delay in fruit maturity and resultant lower total yields will limit acceptance of the system. Later applications of fertilizer or combining rye with plastic mulches might overcome these limitations.

Influence of 1-Methylcyclopropene Treatment on Postharvest Quality of Four Scab (Venturia inaequalis)-Resistant Apple Cultivars

Scab (Venturia inaequalis) is a very serious disease for apples causing up to 80% of loss in yield but there are only a few studies on postharvest quality of scab-resistant cultivars. In this study we evaluated the effect of 1-methylcyclopropene (1-MCP) on fruit quality, total phenolic content, and antioxidant capacity after storage of four scab-resistant cultivars and compared to a standard cultivar, “Golden Delicious.” In general, ethylene production and respiration rates significantly differed among cultivars, between control and 1-MCP-treated fruits, and between storage duration regimes. 1-MCP treatment retarded fruit softening and lowered juice pH but storage effect on soluble solids and acidity depended on cultivar and 1-MCP treatment. Total phenolic content was significantly affected by storage duration and 1-MCP treatment. Antioxidant capacity of the four scab-resistant cultivars was either similar to or significantly higher than that of “Golden Delicious” with the 1-MCP-treated fruits having significantly higher antioxidant capacity than the nontreated fruits after storage. Our results clearly show that the quality of four scab-resistant cultivars was comparable to that of “Golden Delicious” and 1-MCP effect differed among cultivars. These differences need to be considered in developing storage regime to minimize quality deterioration during long-term storage.

Effects of Ethylene on the Production of Female Flowers by “Burpless Hybrid” Cucumber (Cucumis Sativus L.) In Vitro

ABSTRACT To investigate the role of ethylene in sex expression by cucumber (Cucumis sativus L.) in vitro, whole seeds of ‘Burpless Hybrid’ were explanted onto modified Murashige and Skoog (MS, 1962) medium supplemented with various concentrations of Ethephon (2-Chloroethyl phosphonic acid, Ethrel®), an ethylene releasing compound (0.0, 1.0, 2.0, 5.0, and 10.0 mg/l). Exogenous Ethephon significantly increased the incidence of female flowers and reduced the number of male flowers, especially at 10.0 mg/l (8.5 female flowers/tube vs.0.0 female flowers/tube for control). Control expiants (0.0 mg/l Ethephon) produced only male flowers (2.8 male flowers/tube). This information will be useful for researchers interested in studying flower induction, development, and sex regulation in vitro.