Year : 2022, Volume : 12, Issue : 2
First page : ( 96) Last page : ( 104)
Print ISSN : 2229-3744. Online ISSN : 2250-0499. Published online : 2022  07.
Article DOI : 10.5958/2250-0499.2022.00058.1

Ascorbic acid content, pest-pathogen preference and their phenological association in chilli (Capsicum spp)

Edakkalathur Asish I^1*, Presannakumari KT¹, Minimol JS¹, Latha M², Pradeepkumar T¹

¹Department of Plant Breeding and Genetics, College of AgricultureKerala Agricultural University, Thrissur680656Kerala, India

²ICAR- National Bureau of Plant Genetic Resources, Regional StationThrissur680656Kerala, India

^*Email for correspondence: asish.ei@kau.in

Online Published on 07 May, 2022.

Received:  13  ,  2022; Accepted:  26  ,  2022.

Abstract

The landraces of Capsicum belonging to four major cultivated species, collected from various agro-ecological zones (AEZ) of Kerala were evaluated based on the ascorbic acid content and natural incidence of pests and diseases. Association of ascorbic acid was checked with 80 different characters comprising 40 qualitative and 32 quantitative characters, incidence of pest and diseases, species, horticultural type as well as AEZ differences. Association of bacterial wilt, dieback, mite, thrips and Spodoptera incidences with qualitative features was also evaluated. Species specific pigmentation and phenomics-based association patterns recorded in the present study will be helpful to sort out promising genotypes from a large pool of genetic resources and to fine tune selection criteria for ascorbic acid content and biotic resistance in chilli.

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Keywords

Ascorbic acid, Bacterial wilt, Mite, Thrips, Dieback, Spodoptera.

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Introduction

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Material and Methods

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RESULTS and Discussion

Ascorbic acid content and phenological association

Ascorbic acid content varied from 59.52 to 339.29 mg per 100 g of ripe fruit with a mean of 152.24 ± 4.22. Huge variability in ascorbic acid content is quite discernible as it is controlled by endogenous factors like genetic constitution (Chattopadhyay et al 2011, Litoriya et al 2014, Yatung et al 2014), feedback mechanism of genes (Alos et al 2013) as well as exogenous factors like drought (Kopta et al 2020), maturity, weather and post-harvest handling methods (Bhattacharya et al 2010). Landraces with green primary leaves, compact growth habit, non-pigmented calyx, green immature fruits and absence of petal spots were characterized with high ascorbic acid content (Table 1, Figs 1, 2). No significant variation was observed in ascorbic acid content with respect to difference in species, geographical origin as well as pest and disease incidence. The landraces with slow maturing nature as well as long fruits tended to have higher ascorbic acid levels (Table 2). Plant height, height to first bifurcation and stem diameter exhibited significant negative correlation with ascorbic acid content. Differentiation of ascorbic acid content with respect to fruit and leaf colouring pigments is in agreement with the work of Simonne et al (1997), Gadal et al (2003) and Patel et al (2015). Gonzalez-Lopez et al (2021) reported similarity of C annuum - C frutescens species as well as C chinense - C baccatum species in ascorbic acid with higher content in former group. They also observed significant differences in ascorbic acid content according to ecological-geographical origin of accessions. Kaur and Nayyar (2014) observed higher endogenous levels of ascorbic acid in stress-tolerant genotypes. The finding of positive association of ascorbic acid content and fruit length is in agreement with the work of Renthlei (1991), Manju and Sreelathakumary (2002) and Kumar et al (2003). However previous studies reported positive (Manju and Sreelathakumary 2002) as well as negative association (Sharma et al 2010) of ascorbic acid with plant height.

Phenological association of pest and disease preference

The landraces with purple leaves, nodal anthocyanin pigmentation and wrinkled fruit surface were less prone to bacterial wilt infection (Table 1). None of the landraces with purple leaves had bacterial wilt symptoms. Similarly landraces with wrinkled fruit surface were totally devoid of wilt symptom. Landraces with purple pigmentation were characterized with less incidence of mite infestation (Fig 3). Mite infestation had significant negative correlation with purple primary leaf, purple coloured filament and purple fruit colour at immature stage. Previous studies indicated influence of lot of biochemical features like tannins, phenols, chlorophyll, total sugars, protein content and mineral content in controlling mite incidence (Ahmed et al 2000, Rameash et al 2017, Latha and Hanumanthraya 2018). Landraces with purple pigmentation may be characterized with biochemical features that are less favourable to mite infestation. Incidence of thrips exhibited significant negative association with erect position of flowers, absence of fruit blossom end appendage, erect position of fruits and strong persistence of fruit pedicel with stem (Fig 4). Erect flower, erect fruit position and strong persistence of fruit pedicel on the stem are considered as wild features in chilli (Carvalho et al 2014). Hence it could be inferred that landraces retaining wild characters had deterrence to thrips infestation whereas those with more of domesticated characters were more prone to infestation.

Dieback incidence was found to be significantly low in landraces with sparse branching habit, green stem with purple stripes, dense stem pubescence, nodal anthocyanin pigmentation, sparse leaf pubescence, low leaf density, non-erect position of flower and fruit pedicel, white or purple corolla, non-white (green or purple) immature fruit colour, wrinkled fruit surface, low persistence of ripe fruit pedicel on the stem, low persistence of ripe fruit on the pedicel and truncate fruit shape at pedicel attachment. Present study revealed high vulnerability of C fruescens genotypes to dieback disease. Association of secondary features of C frutescens viz erect flower and fruit position, greenish yellow corolla, white immature fruit colour and semi-wrinkled fruit surface (Greenleaf 1986, Eshbaugh 2012) with dieback incidence may be due to high vulnerability of that species to dieback.

Spodoptera infestation was significantly lower in landraces with purple hypocotyl, deltoid or ovate leaf shape, entire calyx margin, greenish yellow corolla, yellow anther lobe, green or yellow filaments, non-elongate shaped fruits, non-pointed blossom end of fruit, fruit blossom end appendage, highly corrugated fruit cross section, wrinkled fruit surface, annular constriction at junction of pedicel and calyx, low persistence of ripe fruit pedicel on stem, brown seed colour and presence of more than two flowers per axil.

The present study revealed the low preference of Spodoptera towards C chinense types. Annular constriction is a key character of C chinense (Smith and Heiser 1957). Further, most of the cultivated types of C chinense are characterized by the presence of ovate leaves, entire calyx margin, highly corrugated fruits, wrinkled fruit surface and more than two flowers per axil. Negative association of these characters with Spodopera infestation may be due to deterrence of the pest to C chinense.

Among the cultivated species of the annuum complex, incidence of bacterial wilt and dieback was the highest in C frutescens. Bacterial wilt incidence and Spodoptera infestation were found to be the lowest in C chinense. C annuum landraces were characterized with lowest incidence of dieback symptoms and highest incidence of Spodoptera infestation. The report of absence of species specificity in bacterial wilt resistance through artificial inoculation study (Anusree 2020) is contrary to the results of the present investigations. In the present study, Ancho, Cayenne, Cuban and Wax groups were almost free from dieback incidence whereas Tabasco types were highly prone to disease. Landraces belonging to Ancho and Cherry groups were completely free from Spodoptera infestation.

Based on the phenological associations elucidated from the present study, correlated characters helpful for selection of genotypes with higher ascorbic acid and biotic tolerance were worked out (Table 3). This will be helpful for easy identification of desirable genotypes from a large group of germplasm. It will also enhance the accuracy of the selection programme during the field screening. Estimation of ascorbic acid is laborious, time consuming and one has to wait till fruit maturity. Further screening for pests and diseases needs specific climatic and environmental conditions. Under these circumstances, correlated characters which are less influenced by environment and easily identifiable at the seedling or vegetative stage will be advantageous.

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Conclusion

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Figures

Fig 1.: Box-plot elucidating association of ascorbic acid with primary leaf colour and immature fruit colour; twenty fifth percentile, median, seventy fifth percentile, range and outliers presented TopBack

Fig 2.: Box-plot elucidating association of ascorbic acid with primary leaf colour and immature fruit colour; twenty fifth percentile, median, seventy fifth percentile, range and outliers presented TopBack

Fig 3.: Natural incidence of mite across contrasting descriptor states in chilli TopBack

Fig 4.: Natural incidence of thrips across contrasting descriptor states in chilli TopBack

Tables