MSc

The study entitled “Seed pre-treatment with endospore-forming rhizobacteria in
Kiriyathu (Andrographis paniculata (Burm. f.) Wall. ex. Nees) for enhancing growth
and quality” was carried out at the Department of Plantation, Spices, Medicinal and
Aromatic Crops, College of Agriculture, Vellayani, Thiruvananthapuram, Kerala
during 2021-2023 with the objectives to evaluate the effect of seed treatment with
endospore-forming rhizobacteria on seed storage; seed germination; growth promotion
and secondary metabolites production in Kiriyathu.
The seed of A. paniculata variety Anand Kalmegh 1 (AK-1) was pre-treated with
bacterial cultures viz., B. pumilus VLY 17 (T1), B. amyloliquefaciens VLY 24 (T2), B.
velezensis PCSE 10 (T3) and bacterial consortium [B. pumilus VLY17+ B.
amyloliquefaciens VLY 24+ B. velezensis PCSE 10] (T4) at 1014 cfu mL-1. Seed without
bacterial pre-treatment was served as the control (T5). The treated seeds were evaluated
during seed storage for bacterial survival. Moreover, the pre-treated seeds were
evaluated for seed germination characteristics and planted in polybags for assessing
growth and quality.
All bacteria species as well as its combination found to survive in the pre-treated
seed up to six months after storage. The bacterial count was found to be highest for B.
pumilus VLY 17 during 6 MAS (6.66 log cfu g-1).
Germination characteristics of bacteria pre-treated seed were found to be superior
than the control seed. The Kiriyathu seed pre-treated with B. pumilus VLY 17 exhibited
the highest germination percentage (85.00 %), survival percentage (85.00 %),
germination index (2.60), shoot length (6.54 cm), root length (5.04 cm), seed vigour
index (926.60), allometric index (0.77) and lower mean germination time (3.30 days).
Seed pre-treatment with bacteria showed significant improvement in plant growth
characteristics viz., morphological, phenological and yield parameters during harvest at
120 DAS compared to the control. B. pumilus VLY 17 pre-treated seed recorded the
highest plant height (83.03 cm), number of branches (33.42), number of nodes (472.44),
number of flowers (104.00), shoot weight (fresh-120.27 g, dry-38.81 g), whole plant
weight (fresh -138.21 g, dry -43.02 g), root length (29.29 cm), seed yield (3.43 g) and
thousand seed weight (2.22 g). Also, B. pumilus VLY 17 pre-treatment took lesser days
to flower initiation (95.88 days), days to fruit set (16.06 days) and days to fruit maturity
(28.25 days) as well as the highest number of fruits (309.44) and fruit weight (fresh
13.54 g). Highest root dry weight (4.01 g) and fruit dry weight (3.95 g) were in
combination treatment and B. velezensis PCSE 10 respectively. Seed pre-treatment
showed no significant difference for stem girth, root fresh weight and root volume of
Kiriyathu plants.
Phytochemicals viz., total alkaloids, total flavonoid content, total phenol content,
total saponins and cardiac glycosides were found to be superior in Kiriyathu herbage
(ethanolic extract) of bacteria pre-treated seed than the control. B. velezensis PCSE 10
pre-treatment recorded highest total alkaloid content, 78.47 µg AE mg-1 whereas highest
flavonoid (37.62 µg QE mg-1) and phenol content (349.92 µg GAE mg-1) were observed
by B. pumilus VLY 17 treatment. Total saponins content (140.45 µg DE mg-1) was
found highest in bacterial combination while the highest cardiac glycosides (169.33 µg
DE mg-1) were present in B. amyloliquefaciens VLY 24 treatment.
Pharmacological properties of the Kiriyathu herbage ethanolic extract viz., in vitro
antioxidant activity and cytotoxicity against liver cancer cell line (HepG2) were highest
in B. pumilus VLY 17 seed pre-treatment, 94.00 % DPPH free radicle inhibition and
IC50 value, 50.09 µg mL-1 respectively.
Kiriyathu seed could be pre-treated with B. pumilus VLY 17 as a liquid spray at
1014 cfu mL-1 concentration for ensuring enhanced seed germination, plant growth,
phytochemical quality and in vitro pharmacological properties. The bacteria survival
in the pre-treated seed is ensured up to six months after storage under ambient
condition.