Results that, none of the carrot cultivar was

Results and Discussion

The
main edible part of the carrot is fresh taproot; so the foremost emphasis of
our investigation is to produce healthy and good quality carrot as well as to
control the root-knot nematode, M.
incognita using eco-friendly tactics. The results proclaimed that all the
tested cultivars of carrot behaved differently to nematode infestation i.e.
root-knot index, eggmasses/root, eggs/eggmass, nematode population and
reproduction factor (Table 4). The carrot cultivars are categorized on the
basis of root-knot index (Table 2). The results also revealed that, none of the
carrot cultivar was found to be highy resistant or immune against the root-knot
nematode, M. incognita. However, the
cultivar Golden Rosy was observed with least root-knot index (1.2) which
indicates the resistant reaction (fig. 4). Maximum root-knot index (5.0) was
recorded in cultivar Kamini indicating the greatest nematode attack was
experienced by it (Fig. 6). The cultivar Kamboj, Surbhi, Super Red and Pearl
Red were found moderately susceptible (MS); Rose Red, Noorie, Lali, Sindhuri,
and Selection 80 were found susceptible (S) to root-knot nematode. Two
cultivars Red King and Desi Red with root-knot indices (1.8 and 2.0) displayed moderately
resistant (MR) reaction against the nematode (Table 4 and Fig. 5). The
variations in the severity of gall formation in different cultivars may be due
to the number of nematodes penetrated
into the roots and their stabilization. It is evident from the finding that the
resistance or susceptibility of cultivars to root-knot nematodes denoted by the
presence or absence of galls on roots of tomato plants. However, significant
differences in the number of galls represent the levels of susceptibility (Castagnone-Sereno,
2006; Jaiteh et al., 2012). The reduced
rates of nematode reproduction, egg masses and consequently, low nematode
population densities than that of a susceptible one demonstrated the resistance
in host plants against nematodes (Khan, 1994; Ansari et al., 2018). Another salient property of resistance to root-knot
nematode is the impact on galls development commonly linked to compatible
interactions of nematode-host plants (Garcia et al., 1996). Resistance
during screening experiments can only be evaluated by development of galls in
most susceptible plants infested with root-knot nematodes (Fassuliotis,
1979). Hirunsalee et al., (1995) observed that gall formation
and nematode multiplication on the roots of plant were supported by susceptible
and tolerant cultivars while inhibition was observed in resistant ones.

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In
addition to galls, the nematode also provoked a significant increase in the
incidence of other undesirable characteristics on the infected carrots. The
most prominent was sudden and localized constrictions with twisting and
distortion in carrot. The second is the emergence of thumb-like branch of roots
or forked roots (Fig. 3 and 4). The highly susceptible cultivar showed maximum
forking as it exhibit highest susceptibility to M. incognita followed by susceptible cultivars (Fig. 3). Whereas
least forking was displayed by the moderately resistant cultivars as they experienced
comparatively less nematode attack (Fig. 3, 4 and 5). However, forking,
galling, twisting and cracking type symptoms were completely unseen in the
resistant cultivar (Fig. 5). The forking, twisting and cracking completely
damage and distorted the roots in terms of their shape, length, weight and
appearance (Fig. 3, 4 and 6). Besides the above symptoms, the formation of root
hairs (Fig. 5) also affects the root length of cultivars (Fig. 5). Comparatively larger number of
eggmasses was obtained from the carrot cultivars; Noorie, Lali, Sindhuri, and
Selection 80 (Table 4). From the roots of highly susceptible cultivar Kamini
highest number of eggmasses was recorded (Table 4) which revealed that maximum
number of juveniles penetrated the roots and completed their life cycles in a
successful manner. On the other hand, cultivar Golden Rosy allowed only a
limited number of juveniles of M.
incognita to penetrate the roots, leading to maturity as it is confirmed by
number of eggmasses and reproduction factor. Similarly the maximum eggs were
recorded on highly susceptible cultivar roots compared with the susceptible,
moderately susceptible, moderately resistant and/or resistant cultivars.
Formation of galls over the roots of susceptible cultivar is the primary
symptom of root-knot nematode infection. According to Cousins and
Walker (1998) root-knot nematode eggs developed poorly on resistant cultivars
compared to susceptible ones. Also,
the authors reported that total number of eggs represents the population of
nematodes that reached reproductive maturity, and therefore provide one measure
of resistance. Screening of individual seedlings for nematode resistance helps
in elimination of susceptible plants prior to field plantation which results in
the conservation of breeders’ nursery stocks.

It was investigated
from this study that, the highly susceptible cultivar (Kamini) recorded with
the highest nematode population/250 g soil which was significantly different
from all the cultivars studied in
the pots and uninoculated control (Table 4). Nematode population density
can be ascribed to the disease severity and size of the root-knot galls which
varies among the different tested cultivars. The increased population density and
size of the root galls might be due to penetration of large number of nematodes
favored by the highly susceptible cultivar and finally stabilized them to form
the giant cells. Similarly, Huang
(1986) reported that resistance is associated to reduced rate of nematode
penetration, development, egg formation and enhanced plant growth which ultimately
results in a low nematode population density with the fact that a few nematodes
could completed their life cycle. According to El-Sherif et al., 2007, roots of susceptible
cultivars are found to be more prone to root-knot nematode activities and
encourage reproduction and survival of juveniles. Therefore, more juveniles
were observed on susceptible cultivars compared to the resistant ones. The host
type is also a key factor in the
development of J2s (Davide, 1980). The potential development of juveniles was
observed on susceptible host whereas in resistant hosts the development can be inhibited
(Nelson et al., 1990).

Resistance and susceptibility of hosts to
phytopathogenic nematodes affects the reproductive capacity of nematodes
(Trudgill, 1991). The present reports showed significant differences in
reproduction factors of M. incognita
on all the carrot cultivars. The analysis of host status in 

Results and Discussion

The
main edible part of the carrot is fresh taproot; so the foremost emphasis of
our investigation is to produce healthy and good quality carrot as well as to
control the root-knot nematode, M.
incognita using eco-friendly tactics. The results proclaimed that all the
tested cultivars of carrot behaved differently to nematode infestation i.e.
root-knot index, eggmasses/root, eggs/eggmass, nematode population and
reproduction factor (Table 4). The carrot cultivars are categorized on the
basis of root-knot index (Table 2). The results also revealed that, none of the
carrot cultivar was found to be highy resistant or immune against the root-knot
nematode, M. incognita. However, the
cultivar Golden Rosy was observed with least root-knot index (1.2) which
indicates the resistant reaction (fig. 4). Maximum root-knot index (5.0) was
recorded in cultivar Kamini indicating the greatest nematode attack was
experienced by it (Fig. 6). The cultivar Kamboj, Surbhi, Super Red and Pearl
Red were found moderately susceptible (MS); Rose Red, Noorie, Lali, Sindhuri,
and Selection 80 were found susceptible (S) to root-knot nematode. Two
cultivars Red King and Desi Red with root-knot indices (1.8 and 2.0) displayed moderately
resistant (MR) reaction against the nematode (Table 4 and Fig. 5). The
variations in the severity of gall formation in different cultivars may be due
to the number of nematodes penetrated
into the roots and their stabilization. It is evident from the finding that the
resistance or susceptibility of cultivars to root-knot nematodes denoted by the
presence or absence of galls on roots of tomato plants. However, significant
differences in the number of galls represent the levels of susceptibility (Castagnone-Sereno,
2006; Jaiteh et al., 2012). The reduced
rates of nematode reproduction, egg masses and consequently, low nematode
population densities than that of a susceptible one demonstrated the resistance
in host plants against nematodes (Khan, 1994; Ansari et al., 2018). Another salient property of resistance to root-knot
nematode is the impact on galls development commonly linked to compatible
interactions of nematode-host plants (Garcia et al., 1996). Resistance
during screening experiments can only be evaluated by development of galls in
most susceptible plants infested with root-knot nematodes (Fassuliotis,
1979). Hirunsalee et al., (1995) observed that gall formation
and nematode multiplication on the roots of plant were supported by susceptible
and tolerant cultivars while inhibition was observed in resistant ones.

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For You For Only $13.90/page!


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In
addition to galls, the nematode also provoked a significant increase in the
incidence of other undesirable characteristics on the infected carrots. The
most prominent was sudden and localized constrictions with twisting and
distortion in carrot. The second is the emergence of thumb-like branch of roots
or forked roots (Fig. 3 and 4). The highly susceptible cultivar showed maximum
forking as it exhibit highest susceptibility to M. incognita followed by susceptible cultivars (Fig. 3). Whereas
least forking was displayed by the moderately resistant cultivars as they experienced
comparatively less nematode attack (Fig. 3, 4 and 5). However, forking,
galling, twisting and cracking type symptoms were completely unseen in the
resistant cultivar (Fig. 5). The forking, twisting and cracking completely
damage and distorted the roots in terms of their shape, length, weight and
appearance (Fig. 3, 4 and 6). Besides the above symptoms, the formation of root
hairs (Fig. 5) also affects the root length of cultivars (Fig. 5). Comparatively larger number of
eggmasses was obtained from the carrot cultivars; Noorie, Lali, Sindhuri, and
Selection 80 (Table 4). From the roots of highly susceptible cultivar Kamini
highest number of eggmasses was recorded (Table 4) which revealed that maximum
number of juveniles penetrated the roots and completed their life cycles in a
successful manner. On the other hand, cultivar Golden Rosy allowed only a
limited number of juveniles of M.
incognita to penetrate the roots, leading to maturity as it is confirmed by
number of eggmasses and reproduction factor. Similarly the maximum eggs were
recorded on highly susceptible cultivar roots compared with the susceptible,
moderately susceptible, moderately resistant and/or resistant cultivars.
Formation of galls over the roots of susceptible cultivar is the primary
symptom of root-knot nematode infection. According to Cousins and
Walker (1998) root-knot nematode eggs developed poorly on resistant cultivars
compared to susceptible ones. Also,
the authors reported that total number of eggs represents the population of
nematodes that reached reproductive maturity, and therefore provide one measure
of resistance. Screening of individual seedlings for nematode resistance helps
in elimination of susceptible plants prior to field plantation which results in
the conservation of breeders’ nursery stocks.

It was investigated
from this study that, the highly susceptible cultivar (Kamini) recorded with
the highest nematode population/250 g soil which was significantly different
from all the cultivars studied in
the pots and uninoculated control (Table 4). Nematode population density
can be ascribed to the disease severity and size of the root-knot galls which
varies among the different tested cultivars. The increased population density and
size of the root galls might be due to penetration of large number of nematodes
favored by the highly susceptible cultivar and finally stabilized them to form
the giant cells. Similarly, Huang
(1986) reported that resistance is associated to reduced rate of nematode
penetration, development, egg formation and enhanced plant growth which ultimately
results in a low nematode population density with the fact that a few nematodes
could completed their life cycle. According to El-Sherif et al., 2007, roots of susceptible
cultivars are found to be more prone to root-knot nematode activities and
encourage reproduction and survival of juveniles. Therefore, more juveniles
were observed on susceptible cultivars compared to the resistant ones. The host
type is also a key factor in the
development of J2s (Davide, 1980). The potential development of juveniles was
observed on susceptible host whereas in resistant hosts the development can be inhibited
(Nelson et al., 1990).

Resistance and susceptibility of hosts to
phytopathogenic nematodes affects the reproductive capacity of nematodes
(Trudgill, 1991). The present reports showed significant differences in
reproduction factors of M. incognita
on all the carrot cultivars. The analysis of host status in 

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