Muhanad Akash

Identification of candidate markers associated with agronomic traits in rice using discriminant analysis

Plant genetic mapping strategies routinely utilize marker genotype frequencies obtained from progeny of controlled crosses to declare presence of a quantitative trait locus (QTL) on previously constructed linkage maps. We have evaluated the potential of discriminant analysis (DA), a multivariate statistical procedure, to detect candidate markers associated with agronomic traits among inbred lines of rice (Oryza sativa L.). A total of 218 lines originating from the US and Asia were planted in field plots near Alvin, Texas, in 1996 and 1997. Agronomic data were collected for 12 economically important traits, and DNA profiles of each inbred line were produced using 60 SSR and 114 RFLP markers. Model-based methods revealed population structure among the lines. Marker alleles associated with all traits were identified by DA at high levels of correct percent classification within subpopulations and across all lines. Associated marker alleles pointed to the same and different regions on the rice genetic map when compared to previous QTL mapping experiments. Results from this study suggest that candidate markers associated with agronomic traits can be readily detected among inbred lines of rice using DA combined with other methods described in this report.

GROWTH, NUTRIENT ACQUISITION, AND PHYSIOLOGICAL RESPONSES OF HYDROPONIC GROWN TOMATO TO SODIUM CHLORIDE SALT INDUCED STRESS

□ Growth and nutrient acquisition of tomato (Lycopersicon esculentum L.) cv ‘Amani’ were studied under induced salt stress in Hoaglands solution. The plants were treated for 37 days with salinity induced by incorporating different concentrations [0.0 (control), 50, 100, 150, or 200 mM] of sodium chloride (NaCl) to the nutrient solution. Slight reduction was obtained in growth represented by (shoot length and number, leaf number, and dry weight) when seedlings were directly exposed to NaCl stress from 0.0 to 100 mM. At higher concentrations (150 or 200 mM), growth parameters were adversely affected and seedlings died thereafter. Elevated salinity significantly reduced crude protein and fiber in shoots and roots. Tomato shoot and root contents of potassium (K), iron (Fe), and ash were reduced significantly in response to increased levels of salinity. Tissue contents of sodium (Na) and chloride (Cl) increased with elevated salinity treatments.

Constant and Alternating Temperature Effects on Seed Germination Potential in Artemisia annua L

Artemisinin is a sesquiterpene lactone with a peroxide bridge, and it is a natural anti-malarial drug obtained from Artemisia annua L. High germination percentages and rates are essential for commercial growers of this species to justify buying premium-priced seed to ensure high performance of their crop. The objective of our research was to determine the seed germination potential of A. annua variety ‘CIM-Arogya.’ An experiment was conducted using three constant (15°C, 20°C, and 25°C) and three alternating (20/15°C, 25/15°C, and 20/25°C) temperature regimes. Seed germination was evaluated in Petri dishes lined with filter paper under daily 16 h light and 8 h dark photoperiod. The highest estimates of mean percentage germination (82.0) and germination energy (20.5) were observed at 15°C, followed by 20/15°C (74.5% germination and 18.6% germination energy). Further, the 3 to 5-day period after seed sowing was ideal for the first germination count, and the 7 to 8-day period after sowing was best for final germination count. Day 7 was best for final germination determination at both constant and alternating temperature regimes. Thus, growers should sow seeds when the mean temperature is 15–20°C for about 7 days.

Molecular and Field Comparison of Selected Barley Cultivars for Drought Tolerance

A field experiment was conducted using five most-planted barley (Hordeum vulgare L.) cultivars in Jordan — a country with 90% of its total land area receiving an annual rainfall of less than 200 mm. The objective of this study was to determine the response of these five cultivars evaluated under drought-stressed (DS) and non-stressed (NS) environments and to investigate polymorphism of 10 candidate genes for drought response. Drought susceptibility index (DSI) was used to rank cultivars according to their performance. Biological and grain yield for all cultivars was lower in DS compared with NS. Reduction in biological yield caused by drought stress ranged from 19% for ‘Mutah’ to 45% for ‘Rum’ cultivar. The least affected by drought stress was ‘Mutah’ with 13% percent reduction (PR) in grain yield. DSI for grain yield ranged from 0.33 for ‘Mutah’ to 1.41 for ‘Rum’. Depending on PR and DSI for biological and grain yield, ‘Mutah’ was the most tolerant cultivar. However, no clear differences were detected among cultivars for the tested genes. The use of this tolerant and improved genotype should be maximized in breeding and genetic studies to identify, map, and pyramid new drought-tolerance genes and to enhance sustainable farming systems.

In vitro response of two citrus rootstocks to salt stress.

The in vitro response of two citrus rootstocks (sour orange, Citrus aurantium L. and Volkamer lemon, Citrus volkameriana Ten. & Pasq.) to two types of salts (NaCl and CaCl2) of different concentrations (0, 50, 100, 150, 200, or 300 mM) was investigated. Results showed that increasing NaCl level in the growth medium led to increased Na and Cl accumulation and decreased Ca concentrations in plant tissue. Increasing CaCl2 levels in the growth medium led to increased Ca accumulation and decreased Na concentrations in plant tissue. Plant K concentrations decreased with increased salinity level in the media. In general, increased salinity level in growth medium, using NaCl, CaCl2, or a combination of the two, led to reduced plant growth (leaf number, plant length, fresh weight, dry weight, and increased plant leaf damage) in Volkamer lemon and sour orange after two months in culture.

Effect of Stabilized Rice Bran Fractions on the Formation of Rice Flour Pasting Properties

ABSTRACT Rice flour composition played a key role in determining the changes in pasting properties of rice flour. The influence of incorporating defatted rice bran (DFRB), rice bran fiber (RBF), rice bran protein (RBP), and stabilized rice bran (SRB) fractions on the mechanism of rice flour pasting viscosities was investigated. Pasting properties of long- and medium-grain rice flour substituted with 5, 10, 15, 20, and 100% bran fractions resulted in a significant decrease (P < 0.05) in rice flour pasting property values. Flour substituted with RBP had the lowest pasting property measurements compared with other fractions, and the greater the percentage substituted, the lower the pasting property values. DFRB and RBF were least affected properties when used as a replacement. Results were attributed to the contribution of rice starch in the mechanism of rice paste formation, in which decreasing starch in a rice flour sample, as a result of substituting with fractions of SRB, may have resulted in faster swel...

Genetic and Phenotypic Variation Among Faba Bean Landraces and Cultivars

Landraces of crops can contain phenotypic and genotypic variability that can be exploited so that new lines can be developed. The phenotypic and genotypic variability among 11 Jordanian faba bean (Vicia faba L.) landraces and five imported cultivars were studied. Yield and 12 yield components and yield-related traits were evaluated at two locations. Analysis indicated significant variability among germplasm for all characters and among locations for 10 characters, in which final plant height, pods/plant, and seeds/pod were not significant. Genetic variability and relationships among germplasm were established using 12 single sequence repeat (SSR) primer pairs. Eleven primers were particularly efficient in amplification of banding patterns among germplasm. The overall polymorphic percentage for the 31 loci generated by 11 SSR markers was 84%. This was sufficient to estimate genetic variation among faba bean germplasm. The unweighted pair group method with arithmetic average ordered germplasm into three groups based on a Dice similarity coefficient of 0.71, range 0.7 to 0.89. Clustering based on phenotypical traits indicated five smaller groups that were consistent with the three larger SSR-based groups. These landraces can be used for future faba bean breeding programs and derivation of new plant lines.

Cryopreservation and Genetic Stability Assessment of Threatened Medicinal Plant ( Ziziphoratenuior L. ) Grown Wild in Jordan

Ziziphora tenuior L. is one of the important medicinal plants that belong to the Lamiaceae family. It is a rare species with a promising medicinal potential and grows wild in the southern part of Jordan. Unfortunately, this plant might be totally extinct from the wild due to over-exploitation. Two cryopreservation techniques (encapsulation-dehydration and encapsulationvitrification) were applied for in vitro conservation of this valuable medicinal plant, and after that the explants were tested for their genetic stability using Amplified Fragment Length Polymorphism (AFLP) technique. In the encapsulation-dehydration experiment, the results revealed that 40% of the cryopreserved shoot tips survived when they were dehydrated chemically on 0.75 M sucrose in MS supplemented media for one day and exposed to air dehydration for 6 hrs. Moreover, the best recovery rate (20%) was obtained when either 0.5 M or 0.75 M sucrose MS supplemented media were used as preculture media for the shoot tips for one day, followed by air dehydration for 4 or 6 hrs. Meanwhile, in the encapsulation -vitrification experiment, the highest survival (37.5%) and recovery (10%) percentages of the cryopreserved shoot tips were obtained when the encapsulated shoot tips were pretreated for 60 min. with the loading solution before being exposed to PVS2 vitrification solution and LN. AFLP technique had clearly showed that, there were no genetic variations between the shoot tips of Ziziphora tenuior L., before and after cryopreservation.

Onion Seed Germination as Affected by Temperature and Light

Producers need to know whether the germination rate will produce sufficient numbers of seedlings needed for field production of onion (Allium cepa L.). The influence of temperature (5.0, 7.5, 10, 15, 20, 25, 30, 35, or 40°C) and continuous light or continuous dark was tested for effects on percentage germination of normal, abnormal, or diseased seed; production of normal seedlings; and percentage of ungerminated solid and soft seeds of onion. Temperatures from 7.5 to 30°C generally assured a high germination percentage and a high percentage of normal seedlings. The most rapid germination occurred at 25°C in the dark. At 5, 35, and 40°C normal germination was only about 10%. The model from the Weibull function indicated that temperature influenced the time between the beginning of imbibition to germination. Onion seed exposed to temperatures between 10 and 30°C under field conditions could produce a high germination percentage, which should lead to development of normal seedlings.

Marker-assisted pyramiding of four QTL/genes for Asian rust (Phakopsora pachyrhizi) resistance in soybean

ABSTRACT Gene pyramiding (assembling multiple desirable genes into a single genotype) via conventional methods to combat Asian rust resistance in soybean (Glycine max (L.) Merrill) and developing soybean varieties with durable resistance to this disease continues to be a challenge. Therefore, our objectives were to pyramid four Asian rust (caused by Phakopsora pachyrhizi) resistance (Rpp) genes, viz., Rpp1, Rpp2, Rpp3, and Rpp4 from their respective donors, PI200492 (Komata), PI230971, PI462312 (Ankur), and PI459025 (Bing Nan). Two single crosses (PI200492 × PI230971; PI462312 × PI459025) and a double-cross [(PI200492 × PI230971) × (PI462312 × PI459025)] were made for present study. The scoring of parents and crosses was done according to a 0–9 grading scale, where 0 = 0% disease intensity (absolutely resistant), 1 = 1% disease intensity (highly resistant), 3 = 1.1–10% disease intensity (moderately resistant), 5 = 10.1–25% disease intensity (moderately susceptible), 7 = 25.1–50% disease intensity (susceptible), and 9 = more than 50% disease intensity (highly susceptible). Out of four parents used, Rpp1 gene-donor plant introduction (PI)200492 (Komata) was immune to rust, with a disease grade of 0.92. Rpp2 and Rpp4 gene donors, PI230971 and [PI459025 (Bing Nan)], had reddish-brown (RB) lesions. Rpp3 gene-donor PI462312 (Ankur) showed a few, highly localized patches of tan lesions; however, it was not as susceptible as the susceptible check JS335. In cross-A (PI200492 × PI230971), all the F1s were rust resistant, whereas in the F2, 93.9% (845 plants) were either immune (11.0%, 99 plants) showing no infection or had RB lesions (82.9%, 746 plants) with resistant reaction and the remainder 6.1% (55 plants) had susceptible reaction. In cross-B (PI462312 × PI459025), 80.8% (63 plants) of the F1 had RB lesions and resistant reaction, whereas 19.2% (15 plants) had susceptible reaction. In its F2 population, 24.2% (217 plants) were susceptible. In cross-C [(PI200492 × PI230971) × (PI462312 × PI459025)], i.e., double-cross hybrid (DCH), 85.5% (77 plants) were either immune or had RB lesions, whereas the rest of the plants 14.5% (13 plants) showed susceptible reaction. Based on parental survey, four simple sequence repeat primers were short-listed for amplification of individual rust-resistance gene-specific markers in ten plants of each cross, viz., Satt191-210bp (Rpp1 gene), Sat_361-245bp (Rpp2 gene), Satt263-195bp (Rpp3 gene), and Rpp4TM-128bp (Rpp4 gene). In the single-cross hybrid (SCH)-A (PI200492 × PI230971), six plants had both Rpp1 and Rpp2 genes, whereas in another SCH-B (PI462312 × PI459025), seven plants had both Rpp3 and Rpp4 genes. In DCH [(PI200492 × PI230971) × (PI462312 × PI459025)], a single plant had all four Rpp genes, five plants had two Rpp genes, whereas a single susceptible plant had only Rpp3 gene. The homozygous rust-resistant segregants from these crosses can be used for improving rust resistance of otherwise adapted, high-yielding soybean genotypes.