Evaluation of the Potential for the Genetic Improvement of Salt Tolerance in Chile Pepper (Capsicum Annuum) Using Wild Germplasm and Cell Selection Procedures
At present, 1.4 million acres or 1.8% of New Mexico’s land area is being used for irrigated agriculture. However, further expansion is limited mainly by the lack of adequate fresh water supplies and few crops capable of utilizing the available brackish water. If existing crops of economic importance to New Mexico could be engineered to produce under culture with higher levels of salinity, the land area under cultivation could be significantly increased and water resources better utilized. Chile pepper, Capsicum annuum, is a vegetable crop of major importance to New Mexico’s economy. Results from experiments conducted during this project indicate that chile is very sensitive to the effects of saline irrigation. Salt concentrations as low as 775 PPM can reduce plant growth in commercial chile varieties now being grown in the state. Germination is severely inhibited at levels above 7000 PPM salt.
In screening diverse Capsicum germplasm we have discovered races that appear to germinate better at salt levels prohibitive to commerical varieties. These lines have been crossed to commercial cultivars for potential use in the New Mexico State University (NMSU) chile breeding program. In addition, a large collection of Mexican Capsicums has been obtained and partially increased. This material represents the largest collection of wild peppers with close affinity to the garden pepper, C. annuum. Preliminary screening for genetic variability using enzyme electrophoresis indicates that this material possesses a tremendous amount of genetic variation that may prove useful in the search for salt tolerance in pepper.
Repeatable methods for cloning chile plants by tissue culture have been developed that ultimately may lead to an in vitro cell selection procedure for obtaining salt tolerant pepper lines. The advantage of the cell selection procedure over classical hybridization approaches is that the cell-selected lines are derived from commercial cultivars. Thus, derived variants may be immediately useful as commercial cultivars. The response to salt stress of seedlings placed in tissue culture–but not cell or callus cultures–showed good correlation with the response of whole plants to salt stress. This in vitro seedling procedure is simple to apply and may have a role in a screening program. However, these results also suggest that in vitro selection may require organized as opposed to unorganized tissues to accomplish genetic improvement for salt tolerance in peppers.