Biochemical changes in fenugreek due to powdery mildew (Erysiphe polygoni DC.) and its management
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Date
2022
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Abstract
Fenugreek (Trigonella foenum-graecum L.) is one of the important
and oldest spice and medicinal crops and is cultivated throughout India. It
is attacked by many diseases, however, powdery mildew incited by
Erysiphe polygoni DC. is a major constraint in cultivation of fenugreek.
Powdery mildew disease appeared during the end of January and
persisted till the maturity of the crop. Symptoms were observed as white
floury patches on leaves, tendrils, stem and pods whereas cleistothecia
appeared late in the season seen as black specks immersed in mycelial
mat. Microscopic observation revealed that conidia were barrel in shape
and formed singly and in chains. Conidiophores were septate that were
straight to sub-straight with 4 to 5 cells.
Thirty six genotypes and varieties were screened under natural
condition to find out the source of resistance against the disease. It was
found that HM 444 and UM 411 showed resistant reaction with percent
disease intensity (PDI) of 9.66 and 10.27 respectively. The remaining nine
were rated as moderately resistant, thirteen as moderately susceptible
and twelve as susceptible.Biochemical studies on thirty six genotypes and varieties were
undertaken twice, once before the disease occurrence and then after the
disease occurrence. It was found that total phenol, peroxidase (PO) and
polyphenol oxidase (PPO) content in plants increased in all the genotypes
after the disease appearance and the amount of these components were
higher in resistant ones and comparatively lower in susceptible ones.
Chlorophyll content of all the lines decreased after the disease
appearance and was greater in resistant lines than susceptible lines.
Correlation between biochemical components and percent disease
intensity was worked out. Phenol showed negative significant correlation (-
0.958) (-0.864) in both healthy and infected leaves with PDI, the enzyme
peroxidase showed negative significant correlation (-0.929) (-0.847) in
both healthy and infected leaves with PDI, the enzyme PPO showed
negative significant correlation (-0.892) (-0.837) in both healthy and
infected leaves with PDI and chlorophyll also showed negative significant
correlation (-0.758) (-0.892) with PDI.
Six treatments were evaluated along with one untreated control in
three replications. Among them, two sprays of panchgavya 5% recorded
minimum percent disease intensity of 30.66 with yield 13.47 q/ha.
Field evaluation of six systemic acquired resistance elicitors with
one unsprayed control in three replications were undertaken. The crop
was sprayed at 45 days after sowing and it was found that salicylic acid
200 ppm resulted in minimum percent disease intensity of 21.18 and yield
of 16.07 q/ha.
Six fungicides with one treatment of water spray and untreated
control in three replications were carried out twice where hexaconazole
5% SC at 0.1% recorded minimum percent disease intensity of 11.63 and
with higher yield of 20.65 q/ha. ICBR for fungicides were calculated and
hexaconazole showed maximum ratio of 1: 37.91