Papaya yellow leaf curl virus: A newly identified begomovirus infecting Carica papaya L. from the Indian Subcontinent

India is one of the world’s largest producers of papaya. Viruses, mainly begomoviruses and potyviruses, cause a significant loss in papaya production. The study described here has identified a new species of begomovirus and a new species of betasatellite infecting Carica papaya in India. The sequences of the begomovirus and betasatellite show 90.03% nucleotide sequence identity to an isolate of Radish leaf curl virus and 92.25% identity to an isolate of Tomato leaf curl betasatellite, respectively. Maximum likelihood phylogenetic tree of begomovirus sequence of isolate DP2 (KX353622) showed distant relationships with previously characterised begomoviruses. Recombination analysis proposed six recombination breakpoints in begomovirus genome with other geographical begomovirus isolates.     

Antibacterial activity of embelin

Embelin, a benzoquinone-derivative isolated from Embelia ribes, when tested for its antibacterial potential exhibited significant inhibition against five and moderate activity against three strains of the 12 bacteria tested.     

An analysis of the persistence and potency of film‐coated seed protectant as influenced by various storage parameters

BACKGROUND: An efficient delivery system for seed‐protectant chemicals is needed in light of several disadvantages of conventional seed treatment methods. This study evaluates the efficacy of film‐coat application in maintaining the persistence and potency of imidacloprid on Lycopersicon esculentum (L.) Mill. seeds after simultaneous storage under ambient and regulated environment in paper and aluminium packages. RESULTS: High‐performance liquid chromatography (HPLC) revealed 0.135 mg kg^?1 of herbage material to be the threshold value beyond which absolute control was obtained, and with film coating the latter was achieved even with half‐dosage seed treatment, irrespective of the storage condition. The technique provided early protection to the crop and also nullified the deleterious effects of ambient storage on the persistence and potency of the pesticide. CONCLUSION: Film coating enabled superior pesticide dosage as well as higher biological efficacy to be achieved. Hence, in addition to being an ecofriendly alternative, the technique would be a more economically viable option for storage of treated seeds. Copyright © 2009 Society of Chemical Industry     

Effect of in vitro propagation methods on field performance of two strawberry cultivars

Summary Strawberry cultivars, Redcoat and Veestar, propagated by meristem culture (MC), callus culture (CC) and direct shoot regeneration (DR) from leaf disks were compared for their vegetative and reproductive characters with standard runner (SR) propagated plants under field conditions. In the planting year, in vitro propagated plants of both cultivars had the same number of leaves as SR plants, but in vitro propagated Redcoat produced fewer stolons per plant than SR plants. However, in the following year, in vitro propagated mother plants of both cultivars had more leaves and higher runner production than SR mother plants. Flowering and fruiting behaviour of Veestar was not appreciably influenced by in vitro propagation methods. However, in vitro propagated plants of Redcoat flowered earlier and produced more flowers and fruits than SR plants, but still maintained normal berry weight. Among in vitro propagated plants, DR plants of Redcoat were the earliest to flower, whereas MC plants produced more flowers and fruits. The field performance of the first daughter plants derived from the in vitro propagated plants was consistent with their respective mother plants. Leaf shape of both cultivars was not altered by in vitro propagation. Phenotypic abnormalities were mainly confined to occurrence of yellow leaf variants in MC and CC plants and occasional appearance of plants with irregular flowering and growth habit among CC plants.NRCC No. 38004     

Variability in phytic acid content and protein digestibility of grain legumes

Several genotypes, number given within parenthesis, of chickpea, pigeonpea, urd bean, mung bean and soybean, differing in seed characteristics were analyzed for phytic acid, in vitro protein digestibility (IVPD), protein, total phosphorus, and seed size. Phytic acid contents and IVPD values differed significantly among and within these species. Phytic acid content (mg/g) was the highest in soybean (36.4) followed by urd bean (13.7), pigeonpea (12.7), mung bean (12.0) chickpea (9.6). On an average, phytic acid constituted 78.2 percent of the total phosphorus content and this percentage figure was the highest in soybean and the lowest in mung bean. In vitro protein digestibility (IVPD) of pigeonpea and chickpea genotypes varied from 60.4 to 74.4 percent and 65.3 to 79.4 percent, respectively. The IVPD values of genotypes of mung bean, urd bean and soybean ranged from 67.2 to 72.2 percent, 55.7 to 63.3 percent and 62.7 to 71.6 percent, respectively. There was a significant negative correlation between phytic acid and IVPD of these genotypes. Phytic acid was significantly and positively correlated with protein but the magnitude of correlation was very low in chickpea and pigeonpea. Results indicate that the genotypes of pulses with low phytic acid content could be identified and used in breeding program to improve their nutritive value and utilization.     

Effect of Plant Growth Regulators and Different Nitrogen Sources on Glutamate Dehydrogenase Activity

Radish (Raphanus sativus L.) seedlings, treated with various plant growth regulators (PGRs) [viz. kinetin (KiN), gibberellic acid (GA), and abscisic acid(ABA)] were exposed to different nitrogen (N) sources in light and dark condition, and aminative (NADH) and deaminative (NAD⁺) glutamate dehydrogenase (GDH) activities were measured in cotyledons. A differential effect of nitrogen sources, plant growth regulators, and light or dark condition was observed in all the treatments. The NAD‐GDH (deaminating) activity in radish seedlings was only about 10% of aminating activity (irrespective of the PGR treatment). Except with abscisic acid, in all other treatments, either NAD‐GDH or NADH‐GDH activities were more in dark than in light. The amination and deamination reactions also showed different ratios of activity under different N sources (KNO3, NH₄Cl and NH₄NO₃). These data suggest the presence of isoenzymes or conformers of GDH, specific for each tissue, whose activities vary depending on the physiological condition of the tissue. Different energy status of the seedlings during light or dark condition or with PGR treatments may affect the GDH activity differently.     

Influence of plant growth regulators on some enzymes of nitrogen assimilation in mustard seedlings

Effect of plant growth regulators (PGR) viz. gibberellic acid (GA), kinetin (KN), and abscissic acid (ABA) were investigated on growth and activities of nitrate reductase (NR) and glutamine synthetase (GS) in mustard (Brassica juncea) seedlings. All the PGRs tested promoted in vivo NR activity in cotyledons, but the magnitude differed with different treatments. Cytosolic GS in root and hypocotyl was promoted by GA treatment and inhibited by ABA and KN treatments although the latter showed slight promotion initially in hypocotyl; the trend was not clear in cotyledons. Determination of K_m value of GS extracted from 96‐h‐old cotyledons recorded lower K_m value in GA treatment (2.5 mM), while it increased in ABA treatment (4.35 mM), There was little change in K_m value in KN (3.03 mM) treatment. The kinetics of GS enzyme in cotyledons of different treatments showed marked variation in V_max . Both GA and ABA treatments inhibited GS activity while no significant effect by KN treatment was observed. It is argued that GA treatment inhibits chloroplastic GS (an enzyme which has higher K_m value), while ABA‐induced inhibition may not be specific to cytosolic or chloroplastic isoforms. Kinetin treatment was ineffective in promoting or inhibiting GS activity in cotyledons. The above conclusion is further supported by chloroplastic pigment data where inhibition is recorded in all the PGRs tested.     

Association mapping in rice: basic concepts and perspectives for molecular breeding

In the last decade, association mapping (AM) has become a well-established method to detect genes and quantitative trait loci (QTLs) associated with agronomically important traits. The identification of a large number of single nucleotide polymorphisms (SNPs) from genome sequencing and concurrent development of high-throughput genotyping platforms has led to AM being widely used for a range of crops. These technologies have been used in rice (Oryza sativa) to explore the abundant diversity and there is enormous potential to identify novel QTLs for traits of interest. Due to the availability of cost-effective high-throughput SNP genotyping methods and rapid developments in rice genomics, it is inevitable that these AM approaches will become more popular in the future, especially in the context of genome-wide association studies (GWASs). In this paper, we review the fundamental concepts, critical considerations and limitations of AM focusing on rice, and reiterate the importance of accurate phenotypic data. We also include a section about connecting GWAS to molecular breeding, covering practical consideration for breeders, which is required to use GWAS results in actual rice molecular breeding programs and which has not received adequate attention in the scientific literature.