Eradication of taro viruses from seedlings via seed rescue culture coupled with thermotherapy

In order to investigate appropriate methodologies for producing virus-free taro plants, Papua New Guinea semi-wild taro (SWT), which had been grown in a field germplasm collection of 437 cultivars and exhibited high degree of field resistance to leaf blight and high susceptibility to taro viral diseases, was used as a mother source of seeds. Natural flowering was common, to varying degree, among all cultivars. All SWT plants examined produced 4-5 flower heads per plant with an average of 15,000 potentially viable seeds per head. Seeds were grown aseptically in vitro via a seed rescue culture (SRC) technique and further maintained in an insect-proof greenhouse for a period of 8 months and regularly inspected. Plants regenerated from seeds treated at 60 C for 120 min and at 55 C for 120 min remained free of all taro viral disease symptoms. Both treatments, however, significantly reduced germination from 92.16% to 42.24% and 62.28% respectively. Six other treatments, although all reduced symptoms below those of the untreated control, failed to various degrees to eradicate the symptoms. In addition to morphological and physiological variability among seedlings, the plants showed a range of susceptibility to leaf blight. The importance of using thermotherapy with the SRC technique in taro germplasm conservation, breeding and quarantine is highlighted.Afin qu'on puisse mener a terme les methodologies appropriees pour cultiver les choux caraibes, les choux caraibes a croissance demi-spontanee de Papua New Guinea (swt), dont la variete avait ete cultivee sur un champ de collection du plasme germinatifet ayant aussi 437 varietes et dont la resistance est tres elevee a la brulure des feuilles et aussi la sensibilite egalement elevee aux maladies virales, la variete etait utilisee comme source principale de multiplication de semences. La floraison naturelle etait habituelle, mais aux degre variants, parmi les varietes. Toutes les varietes examinees on produit 4 a 5 boutons a fleurs par plante avec une moyenne de 15,000 graines, d'une potentialite viable par bouton a fleurs . Les semences ont ete cultivees aseptiquement in vitro en utilisant une technique de conservation de semences, qui ont ete ensuite, conservees dans les serres anti-parasitaires pour une periode de 8 mois et sous la surveillance reguliere. Les plantes regenerees des semences traitees a 60 C et 55 C respectivemment pour une duree de 120 min ont demeure saines des symptomes des maladies virales de chou caraibe. Les deux traitements, par contre, ont reduit, d'une maniere considerable, leur faculte germinative de 92.16% a 42.24% et 62.28% respectivemment. Malgre quils aient pu reduire les symptomes des maladies aux niveaux plus bas que les echantillons moins non traites, les experiences menees sur six autres traitements, n'ont pas reussi a eliminer, aux degres variants, les symptomes des maladies. En plus de la variabilite morphologique et physiologique parmi les semis, les plantes ont demontre une sensibilite variante a la maladie des brulures des feulles. L'importance d'utiliser la thermotherapie avec la technique (SRC) dans la conservation du plasmegerminatif, la selection et l'etablissement des qarantaines est mis au point

Seed Rescue Culture: A technique for the Regeneration of Taro ( Colocasia esculenta )

In Papua New Guinea, twelve local taro cultivars were used to establish an initial breeding population from naturally flowering plants. Flowering rate varied significantly among cultivars, ranging from 0-5 flower heads per plant. Selected plants were transplanted and placed randomly in a separate plot to allow cross-pollination and production of fertile seeds to generate genetic variability and new recombinations in taro. At maturity, each flower head produced 400-500 seeds. The seeds did not grow in soil. However, embryos were rescued and grown aseptically via in vitro seed rescue culture (SRC) technique. Regenerated plantlets were free of contaminants and expressed a wide range of morphological and physiological variability. The SRC technique may be used for safer and convenient international exchange of taro germplasm and to widen the genetic diversity in taro breeding. The process encourages the initiation of a breeding programme involving hybridization of local exotic cultivars to generate improved cultivars of taro

Atividade isoenzimática em plantas de trigo infectadas com o vírus SBWMV Isoenzymatic activity in wheat plants infected by virus SBWMV

O objetivo deste trabalho foi elucidar a atividade e a expressão isoenzimática das esterases, das peroxidases e das aspartato aminotransferases em função da infecção de plantas de trigo pelo Soil-borne wheat mosaic virus (SBWMV). Foram analisadas, aos 45 dias após a emergência, quatro cultivares e uma linhagem de trigo, com diferentes níveis de resistência ao SBWMV: BRS Guabiju, BRS 194, BRS 179, BR 23 e PF 980524. De modo geral, ocorreram diferenças qualitativas e quantitativas intra e interpopulacional, quando comparadas plantas assintomáticas e sintomáticas ao SBWMV. Para o sistema esterase, nove padrões de bandas foram determinados e para peroxidase e aspartato aminotransferase foram detectados três padrões de bandas, para ambas as condições. Padrões eletroforéticos foram observados para plantas infectadas, quando comparadas com as não infectadas, destacando-se a atividade da esterase, o que permitiu identificar com maior precisão o estado metabólico e diferenciado das células.<br>The aim of this work was to elucidate the effect of the Soil-borne wheat mosaic virus (SBWMV) on the activity and on the isoenzymatic expression of esterases, peroxidases, and aspartate aminotranferases in wheat plants. Biochemical analyses were carried out for four cultivars and one line of wheat, 45 days after emergence with different levels of resistance to SBWMV: BRS Guabiju, BRS 194, BRS 179, BR 23 and PF 980524. In general, intra and interpopulation differences in quality and quantity were detected, when comparing plants with and without symptoms of SBWMV. Nine band patterns were determined in both situations for esterase. To peroxidase and aspartato aminotransferase, three band patterns were detected for both conditions. Eletrophoretic patterns of SBWMV infected plants were observed, when compared with noninfected ones, notably for esterase, which provides a more precise identification of cell metabolic condition