Symptoms of piper yellow mottle virus in black pepper as influenced by temperature and relative humidity

Abstract

Masking of symptoms in winter and their re-appearance in black pepper (Piper nigrum L.) infected with piper yellow mottle virus (PYMoV) in summer is common, especially on new flushes that appear after pre-monsoon showers. Plants of nineteen cultivars of black pepper infected with PYMoV but without any visible symptoms were grown in a polyhouse under natural conditions and in a greenhouse under controlled conditions from January 2019 to January 2020. The number of plants expressing symptoms in the polyhouse increased gradually from 1% during the 3rd standard meteorological week (SMW) (16 January) to 41% during the 21st SMW (22 May), when the afternoon temperature was 30-40 °C and relative humidity (RH) was 75-93%, but began declining thereafter until the 53rd SMW (1 January), when the afternoon temperature was 30-36 °C and RH was 65-86%. The proportion of plants expressing symptoms varied with the cultivar. However, in the greenhouse, in which temperature and RH were maintained at approximately 26 °C and 80%, respectively, not more than 2% of the plants expressed symptoms. The number of symptomatic plants was positively correlated to maximum temperature (T Max) and maximum relative humidity (RH Max) in the afternoon. Based on this observation, a model for predicting the percentage of symptomatic plants was developed using stepwise regression analysis. Plants at the two sites did not differ significantly in the concentration of virus (virus titre) but differed significantly in the content of total carbohydrates, lipid peroxidase, and phenols.

Supplementary information: The online version contains supplementary material available at 10.1007/s13337-021-00686-3.

Keywords: Biochemical assays; Real-time reverse transcription-polymerase chain reaction; Standard meteorological week (SMW); Virus titre.

Fig. 1

Symptoms of piper yellow mottle virus on black pepper plants grown in a polyhouse (under natural conditions). a asymptomatic (apparently healthy) plants, b, c mild and moderate yellow mottling, d, e mottling and leaf deformation, f, g severely infected plants, h close-up view of a severely infected plant

Fig. 2

Percentage of disease incidence in selected cultivars of black pepper grown in a polyhouse (under natural conditions) from the 1st to the 53rd standard meteorological week (SMW). Average afternoon temperature (Avg A Temp) and afternoon relative humidity (Avg A RH) recorded at 2.30 p.m. in each SMW in the polyhouse are also shown. ACE (Arka Coorg Excel), Giri (IISR-Girimunda), ME (IISR-Malabar Excel), Shakthi (IISR-Shakthi), P-2 to P-9 (Panniyur-2 to Panniyur-9), Pourna (Pournami), Srekra (Sreekara), Subha (Subhakara)

Fig. 3

Normalized plot fit model. a High disease incidence (DI), b medium DI, and c low DI of piper yellow mottle virus (PYMoV) in different cultivars of black pepper as predicted by the model