First report of cotton leaf curl disease affecting chili peppers

Cotton leaf curl disease (CLCuD) is an important disorder of cotton in Pakistan and Western India and is associated with begomovirus species. A symptom modulating DNA satellite (CLCuD DNA b ) is also required to induce CLCuD (Briddon et al., 2001; Mansoor et al., 2003b). Recently a CLCuD begomovirus/DNA b complex that overcomes disease resistance in cotton has been found in Pakistan (Mansoor et al., 2003a). This prompted efforts to identify alternate host plants that may affect the epidemiology. A survey of cotton growing areas in 2002/2003 found typical CLCuD symptoms, leaf curling (LC) and vein thickening (VT), on chili pepper (Capsicum annum) (Figure 1).

Chili pepper production often overlaps with cotton in Pakistan and might serve as an important inoculum source. Chili peppers with LC have been shown to contain begomoviruses and a distinct DNA b has been isolated (Briddon et al., 2003). However, there are no reports of CLCuD affecting chili pepper. To assess CLCuD in chili pepper, plants with LC and VT were collected from the Vehari and Khanewal districts of Punjab province. To identify the begomoviruses present, total DNA was isolated from leaf samples, resolved in agarose gels and blotted on to nylon membranes. A sample from the Jhang district previously shown to contain chili leaf curl disease (ChLCD) DNA b was included. Blots were probed with a non-radioactive probe derived from Cotton leaf curl Multan virus (Briddon et al., 2001) and washed at low stringency. A positive signal was detected in all symptomatic chili pepper samples. PCR using primers CLCV1 [5'-CCGTGCTGCTGCCCCCATTGTCCGCGTCAC-3'] and CLCV2 [5'-CTGCCACAACCATGGATTCACGCACAGGG-3'], designed to conserved sequences of begomoviruses isolated from cotton and okra, produced products of the expected size from all symptomatic samples. DNA b was determined by PCR using a set of universal primers (Briddon et al., 2003). An amplicon of the expected size (approx. 1350 nucleotides) was produced in assays of all symptomatic samples. Southern blots of extracts from symptomatic chili peppers, probed with CLCuD DNA b and washed at high stringency yielded a strong signal in samples from Vehari and Khanewal districts but not from the Jhang District. The results confirm the presence of CLCuD DNA b in chili pepper. This is the first report of CLCuD in this crop.