MSc

Piriformospora indica is a novel, and adaptable root endophyte which colonizes
a wide range of plant species. The colonisation of P. indica in the roots results in
improved plant performance including seed germination, seedling development, early
blooming, improved fruiting, increase in secondary metabolites as well as resistance to
biotic and abiotic stress. Watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) is
one of the most important crops coming under the family Cucurbitaceae. It is rich in
vitamins and minerals, nutritional components and other polyphenolic components.
About 93 per cent of the fruit contains water. However, there is no report on the
association of P. indica with watermelon. Considering the several benefits of the fungus
for crop production, the present investigation entitled “Influence of Piriformospora
indica on the growth, yield and quality of watermelon (Citrullus lanatus (Thunb.)
Matsum. & Nakai) was conducted out at the Department of Vegetable Science, College
of Agriculture, Kerala Agricultural University, Vellanikkara, during December-April
2020-2021.
Four different watermelon varieties viz., Swarna, Shonima, Sugarbaby, and
Durgapur Lal were used in the experiment, both with and without P. indica -
colonisation. It was conducted as two experiments (Influence of P. indica on seed
germination and seedling growth and Influence of P. indica on yield and quality of
watermelon). Analysis variance revealed significant differences among most of the
characters studied.
In the evaluation of the influence of P. indica on seed germination and seedling
growth, except days taken to germination and germination percentage all the other
parameters like root length, shoot length, fresh and dry weight of root and shoot and
phytohormones were highly variable with respect to P. indica colonisation. P. indicacolonized Swarna and Shonima possessed the longest shoot and root (10.63 and 19.53
cm respectively). P. indica colonized Shonima had the heaviest fresh root weight (0.12
g) and the highest dried root weight (0.007g) whereas fungal inoculated Sugarbaby had
the highest fresh and dry shoot weights (0.96 g and 0.06 g, respectively). The presence
of chlamydospores in the stained root bits after 10 days of germination interpreted the
presence of fungus which was absent in the non-colonized plants. P. indica colonized
Shonima had the greatest levels of auxin and Gibberellic acid (22.53 µg /g and 0.19 µg
/g, respectively).
Similarly, the effect of colonisation was highly significant with respect to days
to the first female flower, the node number of the first female flower, the number of
flowers, the number of fruits per plant, average fruit weight, fruit girth, rind thickness,
no of seeds per fruit, yield per plant, TSS, lycopene, beta carotene, citrulline and pest
and diseases. P. indica colonized Durgapur Lal took the fewest days to first female
flower (24.46). P. indica colonized Swarna (5.26) was the earliest in the node number
of the first female flower. The highest number of fruits was observed in P. indicacolonized Shonima (6.40) whereas the highest yield per plant (10.33 kg), TSS (11.770
B) and the number of seeds (862.33) were seen in P. indica colonized Sugarbaby.
Lycopene and beta carotene were highest in P. indica-colonized Shonima (5.43 mg/g
and 0.65 mg/g respectively). Citrulline content was higher in P. indica colonized
Swarna (2266.00 ppm). Under field conditions, P. indica colonisation reduced the
prevalence and severity of pests and diseases. Moreover, it showed a marked decline in
the severity of the Bud necrosis virus and the least affected was the P. indica colonized
plants (33.33%). It also reduced some physiological disorders like white heart.
Correlation analysis revealed that the shoot length of plants indicated a
significant and positive correlation for auxin (0.56). The number of female flowers
exhibited a significant positive correlation with Gibberellic acid (0.81). The percentage
disease index displayed a profound and significant negative correlation with yield per
plant (-0.80). The number of seeds of seeded varieties had a strong positive correlation
(0.94) with fruit girth.
Thus, the present study reveals that P. indica is most effective for promoting the
growth, yield and quality parameters of watermelon. The study also revealed that the
fungus is very efficient in managing pests and diseases. Hence there is a vast scope for
further improvement of watermelon through P. indica inoculation.