There is a need for identifying chili cultivars with stable amounts of capsaicinoids so that the amount of pungency in the final product can be controlled. Therefore, six cultivars were evaluated for yield and capsaicinoid contents across six environments, four in Thailand and two in Bhutan, ranging from 200 to 1,630 m above mean sea level. Combined analyses showed significant differences among cultivars, environments, and for cultivar by environment interactions for fruit yields, individual capsaicinoid and total capsaicinoid contents. A large proportion (46.1 %) of variation on yield was attributed to environments; however, for total capsaicinoid contents, genotype effect accounted for 74.2 % of variation. Variation due to environment was 5.8 %, while for cultivar by environment interaction was 15.8 %. Cultivar Dallay khorsaney had high capsaicin, dihydrocapsaicin and total capsaicinoids but was very sensitive to environmental changes, and therefore good for specific adaptation. Cultivar KKU-P-11003 with total capsaicinoid contents of 78,721 Scoville heat unit was stable for dry fruit yield, capsaicin, dihydrocapsaicin, and total capsaicinoids with regression coefficients b = 1.06, 1.06, 0.78, and 0.96 respectively. Therefore, KKU-P-11003 was considered suitable for diverse environments. In addition, this result indicates that it is possible to select stable cultivar for capsaicinoid contents.

Chili peppers (Capsicum annuum L.) are an economically important crop worldwide. Pepper yellow leaf curl Thailand virus (PepYLCTHV), a Begomovirus causing yellow leaf mosaic disease of chili pepper, has been reported to incur 95% economic loss under epiphytotic conditions. Thirty-one chili genotypes were screened for resistance to PepYLCTHV disease through inoculation using 10–15 viruliferous whiteflies per plant. We purified two resistant lines (PEP6 and PEP12) through four generations of selfing and selection. At 28 days after inoculations, two chili genotypes (PEP6 and PEP12) had low disease severity and percentage of disease incidence (DI) compared to four susceptible checks, viz., Yodsonkeam80, Homsupan, Huareau12, and Pong Charian, which had a disease severity score of 5 with 100% DI. Thirty initial plants of PEP6 showed an average disease severity of 3.64 with 69.33% DI, and PEP12 showed an average disease severity of 3.83 with 77.67% DI. From these populations, we selected nine highly resistant plant of PEP6 and seven plants of PEP12 having a disease severity of 0 through pure-line selection for four selfing generations. The ratio of resistance (R) to susceptibility (S) consequently decreased. In PEP6, the ratio decreased from 1R:2S to 1R:1S, while in PEP12 the ratio decreased from 1R:3S to 1R:1S. These lines have potential for release as resistant lines for improving chili pepper resistance to PepYLCTHV and for developing makers associated with the resistant trait.

Chili peppers (Capsicum annuum L.) are economically important crop worldwide. Pepper yellow leaf cure Thailand virus (PepYLCTHV), a Begomovirus causing yellow leaf mosaic disease of chili pepper has been reported to damage 95% economic loss under favorable epidemic conditions. Thirty-one chili genotypes were screened for resistance to PepYLCTHV disease through challenge inoculation using 10-15 viruliferous whiteflies per plant. We purified two resistant lines (PEP6 and PEP12) through four generations of selfing and selection through challenged inoculations. At the 28 days after inoculations two chili genotypes showed symptoms less based on disease severity and percentage of disease incidence of 30 plants PEP6 showed a disease severity 3.64 with 69.33 % DI and PEP12 showed a disease severity 3.83 with 77.67 % DI. PEP6 and PEP12 were selected for pure-line development for four cycles.Both varieties showed an increase in percentage of the resistant plant 12.78 % and 16.77 %, respectively. These lines have potential for release as resistant lines for improvement chili pepper resistance to PepYLCTHV and for developing maker associated with the resistant trait.