Molecular and Genetic Characterization of Alfalfa Under Black Water Irrigation in Central Valley of Mexico.

Alfalfa is highly produced in Central Valley of Mexico, using different cultural activities. One of the most intensive practices has been the production of alfalfa using black wastewater coming from industries, buildings and houses in the metropolitan area of Mexico City, and it is used to irrigate 46750 ha only of alfalfa in the Mezquital Valley. Data are presented for the first alfalfa breeding program with black wastewater irrigation, including the genetic and molecular characterization of 73 adapted alfalfa genotypes and 253 ecotypes collected in the Mezquital Valley to identify germplasm widely adapted to soil and irrigation conditions; morphological characterization of adapted ecotypes to high content of Pb, Cr, Co, and detergent in soil and water; and estimation of genetic variance components for agronomic traits in HS families. 25 SSR pair primers to estimate genetic similarity among genotypes were used. Eleven harvests from October 2007 to November 2008 were done of the 73 alfalfa genotypes, and 16 morphological traits were recorded to construct a phylogenetic tree and estimate genetic distance among genotypes both morphological and molecular data. Half sib families (n=10) were derived of the twenty high yield cultivars, transplanted in June 2007 in a 10x15 rectangular lattice design with four replications, and nine harvests done to estimate heritability and genetic correlations among yield traits. Eventhough has been reported no differences among big set of M. sativa spp sativa genotypes, there was significant variation among alfalfa genotypes, with cultivars commonly used in the Mezquital Valley were intermediate to low yield; molecular data clearly differentiated alfalfa genotypes originally breed in Mexico from those selected oversea, suggesting that DNA markers can be used to discriminate alfalfa germplasm to introgress in highly adapted cultivars. However no association was identified between Pb, Cr, Co and detergent content, with those persistent genotypes that resulted in high tissue content of metals. Broad sense heritability on an HS family basis of DMP, DM ha and plant height were from intermediate to high. Phenotypic and genetic correlations of half sib families for all high yield cultivars between plant height and forage yield were 0.53 and 0.411 (p>0.001), and were consistent for every harvest, indicating that taller plants are more productive. These results indicate that selection of variables for the productivity could enable breeders to increase forage yield of alfalfa, both within and among populations, although it is recommend further investigation to identify genomic regions associated to toxic chemical components in black wastewater irrigation.