MSc

Cowpea (Vigna unguiculata (L.) Walp) is an annual leguminous vegetable crop.
It is grown throughout india for its tender green pods used as vegetable. Green cowpea
seeds are boiled as a fresh vegetable or may be canned or frozen. The beans are
nutritious and provide complementary proteins to cereals diets.
Seedlings like cowpea, cucurbits having lanky growth growing in polyhouses is an
undesirable quality, especially in plugs intended for mechanized planting and long
distance transport. Seed treatment with growth retardants is an effective method for
controlling seedling height .However limited studies have been conducted in vegetable
crops
The present study was undertaken with the objectives of controlling seedling height of
vegetable cowpea and to assess the field performance of treated seedlings. The
experiment was conducted at the Centre for Hi-Tech Horticulture and Precision
farming, Vellanikkara KAU, Thrissur during the year 2020-2021
In seedling stage, highest germination was recorded in control treatment on 5th and 10th
days after sowing (89%) and (91%) respectively in Vellayani Jyothika. Minimum
germination percentage was recorded in Paclobutrazol @ 200 ppm on 5th and 10th day
after sowing (64.3%) and (66.0%) respectively in cowpea genotype Vellayani Jyothika.
Significantly lower germination percentage was recorded in treatments receiving
Paclobutrazol @ 200 ppm on 5th and 10th day after sowing (70.0%) (72%) in the
genotype Kashi Kanchan. In both the genotypes there were no significant difference
between the treatments on 15th days after sowing. Paclobutrazol treatment took more
number of days for emergence of seedling up to the first node compared to control
treatment ie Paclobutrazol @ 200 ppm (8.13) and (8.00) respectively in both the
genotypes.
Highest shoot length was recorded in control treatment on 5th, 10th and 15 th days
after germination in both the genotypes. Significantly lower shoot length was recorded
in treatments receiving Paclobutrazol @ 200 ppm irrespective of the number of days
after germination. Growth retardants in general reduce root growth, shoot weight and
root weight of the seedlings. In both the genotypes (Vellayani Jyothika and Kashi
Kanchan) significantly lower root length, shoot weight and root weight was obtained in
Paclobutrazol treatments compared to non-treated control. Height of seedling up to the
first node was directly linked to shoot length. In both the genotypes of the cowpea
significantly lower shoot length was recorded in treatments receiving Paclobutrazol @
200 ppm (4.09) and (4.03) respectively. Paclobutrazol treated seedlings had dark green
leaves when compared to other growth regulator and control treatments on 5th ,10th and
15th days after germination. In both the cowpea genotypes, when compared to other
growth retardant and control treatments highest stem girth of the seedlings was recorded
in treatments receiving Paclobutrazol @ 200 ppm on 5th (3.19 mm) 10th (3.45mm) and
15th (3.7mm) in Vellayani Jyothika and on 5th (3.3mm ) 10th (3.4mm) and 15th (3.8mm)
in Kashi Kanchan. There were no significant difference between the treatments on 5th
(2) and 15th days (7-8) after germination in both the genotypes. The total chlorophyll
content and carotenoid content was recorded highest in treatments receiving
Paclobutrazol treatments on seedling stage. Minimum auxin content and gibberellic
acid contents were observed in Paclobutrazol treatments.
In the field experiment, in both the cowpea genotypes, plant growth regulator
Ethrel recorded maximum plant height where as in Vellayani Jyothika minimum plant
height was recorded in Cycocel@ 50 ppm (112.40 cm) .In Kashi Kanchan lowest plant
height was recorded in Paclobutrazol @ 200 ppm (33.06 cm) in Kashi Kanchan. In
vellayani Jyothika highest internodal length was recorded in Ethrel @100 ppm (3.13
cm) and Ethrel @50 ppm (3.04 cm). Minimum was recorded in Paclobutrazol@ 200
ppm (2.63 cm). In the genotype Kashi Kanchan maximum internodal length was
recorded in Ethrel@ 200 ppm (3.34 cm) and minimum was recorded in Cycocel @ 100
ppm (2.53cm). Highest number of primary branches was recorded in treatments
receiving Paclobutrazol @ 200 ppm which was on par with Paclobutrazol @ 100 ppm
compared to control in Vellayani Jyothika. In Kashi Kanchan there were no significant
differences found between the treatments. Growth retardants had significant effect on
the viz days to first flowering, days to first harvest and crop duration. Early flowering
results in early harvesting of pods. Plant growth retardant Cycocel @ 200 ppm (41day)
and Cycocel @ 25 ppm (36.80 days) recorded earliest flowering in the field in both the
genotypes. In both the genotypes delayed flowering and maximum crop duration was
recorded in Paclobutrazol treatments. Pod length and pod girth are related with pod
weight. Ethrel treatment had highest pod length and pod girth compared to control .The
higher number of flowers, pod girth and pod length contributed to production of more
number of pods which in turn resulted in higher yield per plant. In both the cowpea
genotypes, highest number of pods per plant and yield per plant was recorded in Ethrel
treatments (Ethrel 100 ppm) in Vellayani Jyothika followed by Paclobutrazol treatment
(Paclobutrazol 100 ppm) where as in Kashi Kanchan Paclobutrazol 100 ppm was on
par with Ethrel 100 ppm. From the above study it could be concluded that,
Paclobutrazol 100 ppm seed treatment was effective in controlling seedling height as
well to obtain good yield in vegetable cowpea.