Host-specific pathogenicity and genome differences between inbred strains of meloidogyne hapla
Answers
Answered by
0
Five isolates of M. hapla originating from the Netherlands and California were inbred by sequential transfer of single egg masses to produce six strains. Cytological examination showed that oocytes of these strains underwent meiosis and had n = 16 chromosomes. Strains were tested for ability to infect and to develop on several hosts by in vitro assays. The two strains from California infected tomato roots at a higher rate than those from the Netherlands, but no difference among strains was seen for ability to develop on tomato with or without the resistance gene Mi-1. All strains developed on the common bean cultivar Kentucky Wonder, but strains differed in ability to develop on the nematode-resistant cultivar NemaSnap. Strain-specific differences were also seen in ability to infect and to develop on Solanum bulbocastanumclone SB-22. Strain VW13, derived from nematodes treated with the mutagen EMS, was defective in ability to infect tomato and potato roots in vitro. Comparison of DNA using AFLP markers showed an average of 4% of the bands were polymorphic across the six strains, but no correlation was observed between the geographical origin or virulence and DNA polymorphism pattern.
Keywords: AFLP, Northern root-knot nematode, Meloidogyne hapla, pathogenicity, virulence
Root-knot nematode species can have wide host ranges, but there are within-species differences in host range and in virulence on varieties of a host species (Roberts, 1995). Little is known about the genes in the nematode that account for these differences, in part due to the lack of a tractable genetic system to investigate their inheritance. Three of the most damaging root-knot nematode species, Meloidogyne incognita, M. javanica, and M. arenaria, reproduce by obligate mitotic parthenogenesis and are not amenable to genetic analysis. However, while cytological Race B isolates of M. hapla also reproduce by mitotic parthenogenesis, Race A isolates of this species undergo meiosis and reproduce by facultative meiotic parthenogenesis (Triantaphyllou, 1966, 1985). In this form of reproduction, oocytes undergo meiotic reduction to form a diploid nucleus and diploid polar body. The second meiotic division of the nucleus is arrested at telophase. If the female has been fertilized, nuclear division will be completed, and the sperm will fuse with the haploid egg pronucleus to form a zygote. In the absence of fertilization, the meiosis II products will fuse to restore the somatic chromosome number (Van der Beek et al., 1998). The reproductive mode of M. hapla Race A suggests that it should be possible to carry out genetic crosses and to analyze segregation of pathogenicity and virulence differences.
Although M. hapla reproduces on tomato, potato, carrots, alfalfa, onion, and many other crops, causing considerable economic damage (Mitkowski and Abawi, 2000), isolates of this species differ in host range and pathogenicity (Griffin and McKenry, 1989; Riggs, 1991; Djian-Caporalino et al., 1999). Isolates from the Netherlands have been found to differ in ability to reproduce on the wild potato species Solanum bulbocastanum(Janssen et al., 1997). In another example, isolates of M. hapla were found to differ in virulence on the common bean (Phaseolus vulgaris) cultivar NemaSnap, which carries a single, dominant gene for M. haplaresistance (Chen and Roberts, 2003a). In this case, there is genetic evidence that avirulence in the nematode segregates as a single, dominant locus (Chen and Roberts, 2003b). Although the tomato geneMi-1 confers resistance to M. incognita, M. arenaria, M. javanica, and potato aphid Macrosiphum euphorbiae (Williamson, 1998), it has been found to be ineffective against M. hapla (Brown et al., 1997;Williamson, 1998).
In this study, we produce and characterize six inbred strains of M. hapla originating from isolates obtained from the Netherlands and from California for cytological race, chromosome number, and DNA polymorphisms. For each strain, we compared ability to infect and develop on specific hosts using an in vitro assay system and investigated the relationship of DNA markers to pathogenicity and geographical origin.
Hope it helps plz mark it brainliest plz plz
Keywords: AFLP, Northern root-knot nematode, Meloidogyne hapla, pathogenicity, virulence
Root-knot nematode species can have wide host ranges, but there are within-species differences in host range and in virulence on varieties of a host species (Roberts, 1995). Little is known about the genes in the nematode that account for these differences, in part due to the lack of a tractable genetic system to investigate their inheritance. Three of the most damaging root-knot nematode species, Meloidogyne incognita, M. javanica, and M. arenaria, reproduce by obligate mitotic parthenogenesis and are not amenable to genetic analysis. However, while cytological Race B isolates of M. hapla also reproduce by mitotic parthenogenesis, Race A isolates of this species undergo meiosis and reproduce by facultative meiotic parthenogenesis (Triantaphyllou, 1966, 1985). In this form of reproduction, oocytes undergo meiotic reduction to form a diploid nucleus and diploid polar body. The second meiotic division of the nucleus is arrested at telophase. If the female has been fertilized, nuclear division will be completed, and the sperm will fuse with the haploid egg pronucleus to form a zygote. In the absence of fertilization, the meiosis II products will fuse to restore the somatic chromosome number (Van der Beek et al., 1998). The reproductive mode of M. hapla Race A suggests that it should be possible to carry out genetic crosses and to analyze segregation of pathogenicity and virulence differences.
Although M. hapla reproduces on tomato, potato, carrots, alfalfa, onion, and many other crops, causing considerable economic damage (Mitkowski and Abawi, 2000), isolates of this species differ in host range and pathogenicity (Griffin and McKenry, 1989; Riggs, 1991; Djian-Caporalino et al., 1999). Isolates from the Netherlands have been found to differ in ability to reproduce on the wild potato species Solanum bulbocastanum(Janssen et al., 1997). In another example, isolates of M. hapla were found to differ in virulence on the common bean (Phaseolus vulgaris) cultivar NemaSnap, which carries a single, dominant gene for M. haplaresistance (Chen and Roberts, 2003a). In this case, there is genetic evidence that avirulence in the nematode segregates as a single, dominant locus (Chen and Roberts, 2003b). Although the tomato geneMi-1 confers resistance to M. incognita, M. arenaria, M. javanica, and potato aphid Macrosiphum euphorbiae (Williamson, 1998), it has been found to be ineffective against M. hapla (Brown et al., 1997;Williamson, 1998).
In this study, we produce and characterize six inbred strains of M. hapla originating from isolates obtained from the Netherlands and from California for cytological race, chromosome number, and DNA polymorphisms. For each strain, we compared ability to infect and develop on specific hosts using an in vitro assay system and investigated the relationship of DNA markers to pathogenicity and geographical origin.
Hope it helps plz mark it brainliest plz plz
Similar questions