MSc

A field experiment entitled “Variability in ginger (Zingiber officinale Rosc.) for yield and resistance to rhizome rot” was conducted at Department of Plantation Crops and Spices, College of Agriculture, Vellayani during 2017-2019 with the objective to evaluate ginger genotypes for yield and resistance/tolerance to rhizome rot.
The study on variability in ginger (Zingiber officinale Rosc.) for yield and resistance to rhizome rot was conducted as two experiments (i) Collection of ginger genotypes and analysis for genetic variability and yield (ii) Screening of ginger genotypes against rhizome rot under natural condition. Twenty genotypes of ginger collected from different regions of Kerala and a control variety Aswathy were planted in Instructional Farm, College of Agriculture, Vellayani in a randomized block design with four replications. Qualitative characterization of the genotypes was carried out based on DUS guidelines. Plant growth habit of collected genotypes included erect and semi-erect types. All the genotypes were short type (height<100cm) with short leaf length (<25cm), medium leaf width (2.5-3.5cm) having few (<10) and medium (10-15) shoots. The intensity of shoot colour noticed was green and dark green while that of leaf were light green, green and dark green. The leaf petiole length was short (<0.5cm) for all the genotypes except T17 (Kalliyur). Spikes were formed only in three genotypes of which two had crimson bract tip and other had yellowish white tip. Rhizome thickness was thin (<2cm) for all genotypes except T11 (Kazhakootam) with medium (2-3cm) thickness with straight, curved and zigzagged rhizome shape. Greyish yellow rhizome skin colour was predominant while the flesh colour were light yellowish grey, greyish yellow and yellow.
The collected genotypes sprouted from 7 days after planting and continued upto 20 days after planting. Plant height was significantly superior for T12 (Irinjalakkuda) while the number of tillers and dry matter content was significantly higher for T11 (Kazhakootam) at 7 MAP. Leaf area for T8 (Karunagapally) was 48.2 cm2 which was








significantly higher and on par with T12 (Irinjalakkuda) which had 47.96 cm2 at 7 MAP. Rhizome spread (13.91 cm), rhizome thickness (2.02 cm) fresh weight per plant (0.150 kg plant-1) fresh weight per plot (2.33kg plot-1), dry weight per plant (0.031kg plant-1), dry weight per plot (0.475kg plot-1) and harvest index (0.60) were significantly higher for T11 (Kazhakootam). Dry recovery, starch content and oleoresin were significantly superior for T12 (Irinjalakkuda). Crude fibre content of T16 (Pozhuthana) was significantly higher (5.75 %) while the essential oil content (2.42 %) was significantly higher inT20 (Thalavur).
Significant variation existed among the genotypes for characters such as plant height, number of tillers, leaf area, rhizome spread, rhizome thickness and oleoresin. Phenotypic coefficient of variation (PCV) was a little bit higher than the genotypic coefficient of variation (GCV) indicating that environment played very little role in the expression of the characters. Crude fibre registered highest GCV (44.36) and PCV (44.84). High heritability coupled with high genetic advance was observed for rhizome yield, oleoresin, phenol, crude fibre, rhizome thickness and essential oil. Yield per plant was found to be significantly and positively correlated with plant height, number of tillers, leaf area, rhizome spread, rhizome thickness and oleoresin content. Path analysis revealed that leaf area, number of tillers and rhizome spread had maximum positive direct effect on yield per plant.
Ginger genotypes screened against rhizome rot using cultures of Pythium aphanidermatum under natural condition revealed increased phenol, polyphenyl oxidase, lipoxygenase and phenylalanine ammonia lyase activity in all genotypes after inoculation. Peroxidase activity was higher for genotypes of lower disease severity while it decreased for genotypes with higher disease severity. The percentage disease incidence and disease severity were significantly lower for T1 (Mananthavady) and was on par with T12 (Irinjalakkuda). Soil temperature ranged from 25.3ºC to 29.7ºC while maximum temperature varied from 29.2ºC to 32.4ºC, minimum temperature from








24.9ºC to 26ºC, relative humidity from 93% to 98 % and rainfall from 2.5cm to 28.3cm during the period of symptom development.
The ginger genotypes evaluated revealed higher yield for T11 (Kazhakootam) followed by T15 (Nedumkandam) which produced 65.27 and 20.87 percent yield increase over control. Quality parameters such as starch, oleoresin and dry recovery was significantly superior for T12 (Irinjalakkuda) suggesting the suitability of the genotype for dry ginger. Screening the ginger genotypes for rhizome rot under natural condition, revealed less disease severity in T1 (Mananthavady) and T12 (Irinjalakkuda). The genotype T11 (Kazhakootam) developed from the present study can thus be used for further evaluation for green ginger production, and T12 (Irinjalakkuda) for dry ginger production and resistance/tolerance to rhizome rot.