Habanero pepper (Capsicum chinense Jacq.) is a very important crop in Mexico and demand for it is increasing in national and international markets. The habanero pepper produced on the Yucatan Peninsula is considered of superior quality to that grown in the rest of the world as a result of its shelf life and pungency. Despite its importance, little research has been done on cultivation conditions that may affect its productivity and fruit quality. The effect of N or K fertilization on habanero pepper development and fruit pungency was evaluated. Plants under fertilization stress (control) had high capsaicin content. Nitrogen fertilization significantly increased plant growth and fruit while maintaining high capsaicin levels. Optimum response was produced with 15 mm urea as the N source. Potassium fertilization had no positive effects on growth or productivity. The N treatments modified endogenous K levels in the pepper plants and vice versa. The K : N ratio (specifically in leaves and roots) varied between treatments with values greater than 1 in the K treatments, near 0.5 in the control, and less than 0.5 in the N treatments. This parameter may be an important indicator of habanero pepper productivity and requires study under different fertilization regimes.

Under the assayed conditions, nitrate content in the placenta affects capsaicin synthesis.

The pungency of chili peppers is conferred by compounds called capsaicinoids that are produced only in the fruits of the Capsicum genus. Accumulation of capsaicinoids in these fruits may be affected by environmental conditions such as water and nutrient stresses, although these effects may vary even among genotypes within a species. The Habanero pepper (Capsicum chinense Jacq.), grown in the Yucatán, is in especially high demand as a result of its unique flavor, aroma, and pungency and is the second most important commercial crop in the state after the tomato. Although the Habanero pepper is a significant economic resource for the region, few studies have investigated the effects of abiotic stresses on capsaicinoid production. In this study, the effects of water stress on plant growth, capsaicinoid accumulation, and capsaicin synthase activity were evaluated. Habanero pepper plants under water stress had a lower height, root dry weight, and root/shoot relation than control plants, which were irrigated daily. However, fruit growth and production were unaffected by water stress. Capsaicin and dihydrocapsaicin concentrations increased in fruits of stressed plants compared with control plants, and this effect was correlated with fruit age. However, capsaicin synthase activity was reduced in response to water stress, and this effect depended on both stress severity and fruit age. These results provide new information on the regulation of capsaicinoid metabolism in response to abiotic stress from the fruit of a highly pungent chili pepper.

We sprayed defence-related plant growth regulators (salicylic acid, methyl jasmonate and ethephon) on one-month-old Habanero pepper seedlings cultivated in vitro. Twenty-four hours later, we inoculated the seedlings with a virulent strain of Phytophthora capsici and periodically evaluated the disease symptoms. At the concentrations used, neither salicylic acid nor methyl jasmonate generated a protective effect in the seedlings, which died less than 10 days post inoculation. However, the treatment with 5 mM ethephon delayed or prevented disease symptoms in 30% of the seedlings. Interestingly, blocking the ethylene receptor with a previous application of 300 μM silver nitrate impeded the protective effects of ethephon. This result demonstrated that the plant resistance response required the perception of ethylene. Analysis of transcript populations in ethephon-treated seedlings revealed a direct correlation between survival and the accumulation of PR1, a gene marker of the systemic acquired resistance (SAR). Although the ethephon treatment also modified transcript levels of the plant defensin PDF1.2, a marker of the induced systemic resistance (ISR), in this case the accumulation also occurred when the ethylene receptor was blocked, suggesting a non-specific effect. The ethephon treatment did not modify the expression of NPR1 (a key transcriptional regulator of plant defence). Interestingly, transgenic pepper seedlings overexpressing endogenous PR10 or esterase genes, which are induced by the ET treatment, completely resisted the infection, which corroborated the importance of these genes in the defence response. Our results suggest that ethylene induced a systemic defence response in susceptible seedlings, possibly in an NPR1-independent pathway.

Knowledge of the reproductive biology of a species is fundamental in order to develop an efficient program of genetic improvement by hybridization. The viability of the pollen, anther dehiscence, receptivity of the stigma and the anthesis of 12 improved lines of Habanero pepper were studied to develop a cross-breeding program. Among the results, the greatest number of flowers in anthesis was quantified at 8:00 a.m. for most genotypes. The dehiscence of the anther differed significantly in stages evaluated, observing in flower buds 100% of the closed anthers. The receptivity was positive in all the stages evaluated (before, during and after anthesis) and in all the genotypes, the most outstanding being the genotype AKN-08, which presented 100% of receptivity in the three stages evaluated. The viability of the pollen varied among the different conservation times evaluated (0, 24 and 48 h) while the highest percentage of viability (80%) and the largest number of seeds per fruit (56) were obtained when recently collected pollen was used (0 time). These results will have an important repercussion on the improvement of the Habanero pepper by increasing the efficiency of the programs to obtain hybrids and/or improved varieties.