[Show abstract][Hide abstract] ABSTRACT: Molecular identification of the Phytophthora spp. affecting betelvine (Piper betel), brinjal (Solanum melongena), guava (Psidium guajava), roselle (Hibiscus subdariffa), black pepper (Piper nigrum), sesame (Sesamum indicum), taro (Colocasia esculenta), chilli (Capsicum annuum), pointed gourd (Trichosanthes dioica), papaya (Carica papaya) was performed through rDNA ITS-RFLP and also additionally by sequencing the Internal Transcriber spacer (ITS) ITS1 and ITS2 regions. Phytophthora nicotianae, Phytophthora capsici, Phytophthora colocasiae, Phytophthora melonis and Phytophthora palmivora isolates from these 10 different crops were accessioned and the ITS sequences were deposited in Genbank. ITS sequences for Phytophthora isolates from most of these crops are being reported here for the first time. In this study, a review of all earlier Indian reports based on morphology from the above crops and their molecular corroboration has been attempted. This study revealed that not only is P. nicotianae the most prevalent species but also there is the presence of both P. nicotianae and P. capsici, but not P. palmivora on betelvine; as well as possible first reports of P. nicotianae on pepper, P. capsici on chilli and P. palmivora on papaya from this vegetable growing Eastern region of the country. Mating type assays and RAPD markers were used to assess the genotypic diversity of the population. This detection of diversity is a first and critical step for helping to devise and adopt strategies for control and quarantine of these pathogens in this region.
Journal of Phytopathology 12/2009; 157:666-674. DOI:10.1111/j.1439-0434.2008.01537.x · 0.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Phytophthora, the oömycetous stramenopile protist, is one of the most destructive of plant pathogens, which abounds in tropics causing losses amounting to billions of dollars in S.E Asia. A cause for concern is that almost a third of the species has been reported from India alone.
Control strategies are presently dependent on chemicals but are increasingly failing to control the threat. Biological control methods though tried extensively are being met with variable success. Control with Trichoderma species though albeit successful, warrants intensive ecological investigation as it has been known to induce oospore in Phytophthora even when there is no physical contact between them. An additional constraint in the use of biocontrol agents is that they have to be region specific or alternatively should be able to adapt to the other ecological niche’s (which is rare) where they are to be used.
In the Indian context a successful biocontrol agent against multiple species of Phytophthora is not known till date. Here we present data regarding the in-vitro ability of a novel indigenous Pseudomonas aeruginosa strain having antagonistic activity against P.nicotianae, P.capsici, P.colocasiae and P.melonis for the first time in India and possibly globally.
[Show abstract][Hide abstract] ABSTRACT: Phytophthora, the stramenopile, oömycetous organism with about, 70 recognised species is one of the most destructive of plant pathogens affecting a wide host range consisting of economically important crops, fruits, trees, weeds and many undetermined hosts. The unique life cycle requirements of this pathogen predispose it to have a widespread occurrence in the wet tropical regions; as a result, almost a third of the Phytophthora species reported worldwide are from India. Though the study of Phytophthora is almost as old as the study of the discipline of plant pathology, identification and taxonomy of Phytophthora is still acknowledged to be ‘difficult’ primarily due to its morphological plasticity. Resulting misidentifications are a detriment both for control and clear scientific communication.
An attempt has been made therefore to identify and characterise the Phytophthora population prevalent on some of the common high value economically important crops grown in this region; brinjal, betel vine, guava, sesame, roselle, chilli, black pepper, pointed gourd and taro both through molecular methods like Restriction Fragment Length Polymorphism (RFLP) of the Internal Transcriber Spacer (ITS) region of rDNA, sequencing of the ITS region and also on morphological parameters. The Phytophthora species prevalent on these crops, which have been identified by the above mentioned molecular methods are P. melonis, P. nicotianae, P. colocasiae and P. capsici. Multiple occurrences of different Phytophthora species on a single crop have also been observed. Data on all of the above-mentioned aspects of the isolates, twenty-six in number, under accession at World Phytophthora Collection, (WPC), USA have been discussed
[Show abstract][Hide abstract] ABSTRACT: Pointed gourd is an important tropical high value vegetable crop, which is mainly affected by fruit and vine rot disease in field conditions. Causal organism of this devastating disease is Phytophthora melonis as revealed through morphological criteria as well as by molecular tools based on the restriction fragment length polymorphism (RFLP) of non-coding Internal Transcriber Spacer (ITS) region and ITS sequencing. Sequencing of ITS region of our Ph. melonis isolate has 100% similarity with the five isolates of GenBank including a Ph. sinensis. The pathogen, Ph. melonis, is a new report from India and as regards host ranges a possible new report globally.
[Show abstract][Hide abstract] ABSTRACT: Two cultivated indica rice Pankaj and Mahsuri susceptible to submergence were crossed with submergence tolerant semi wild FR-13A and wild O. rufipogon. FR- 13A had better submergence tolerance than rufipogon as revealed by submergence tolerance score. F1s of rufipogon exhibited higher cell abnormality in meiotic divisions and recorded high pollen sterility. F1s of Pankaj x FR-13A and Pankaj x rufipogon exhibited higher level of submergence tolerance indicating crosses involving Pankaj with either FR-13A or rufipogon appeared to be better cross combinations. This would suggest that gene/s responsible for submergence tolerance are expressed more efficiently against the genetic background of Pankaj. Androgenic dihaploids were raised through anther culture from F1s. Submergence tolerant androgenic dihaploid lines were identified through two passages of submergence tolerant screening test. They were evaluated for their seed protein polymorphism through SDS-PAGE as well for their esterase and peroxidase banding patterns. A general trend became evident where lower molecular wieght bands of either esterase or peroxidase as well seed protein similar to FR-13A and rufipogon were observed in submergence tolerant androgenic dihaploid lines. The dihaploid lines derived either from the crosses between Pankaj and FR-13A or between Pankaj and rufipogon displayed better survivability under submergence. Our results, therefore indicate that submergence tolerance favours the genetic background of Pankaj for its expression where FR-13A proves to be desirable donor for submergence trait.