STRATEGIES FOR SELECTING DROUGHT TOLERANT GERMPLASM IN FORAGE LEGUME SPECIES

Abstract

The growing demand throughout the world for good quality soils to expand more profitable productive systems (crops, fruits and vineyards) is displacing forage crop production to marginal environments that often have soils with low fertility, pH problems, poor drainage and subject to periods of drought. The situation is similar in Chile, but the problem is exacerbated by the effects of global climate changes, with an estimated decline in precipitation of 40 percent and an increase of 2-4oC in continental temperature by the end of this century. In this context grasses are increasingly being cultivated beyond their limit to adapt in areas where the ability to tolerate environmental stresses is an essential characteristic for success. The breeding of forage Lotus species and other perennial forage legumes has historically presented low rates of genetic progress because of their genetic complexity. The majority of forage legume species are polyploid, cross-pollinated and self-incompatible. These characteristics make it necessary to use plant-breeding methodologies that are inefficient and very time-consuming. The most popular selection strategies have been masal and recurrent phenotypic selection. Neither strategy considers progeny tests, because they are not efficient in the selection of characters of low inheritability, such as dry matter production. As well, commercial cultivars are the products of many genotypes that generate heterogeneous combinations, which hinders evaluation and prediction of genetic merits. Consequently, strategies are essential to improve our understanding of the genetic components that determine the expression of phenotypic traits of agronomic and adaptive interest. The objectives of this review are to describe the work carried out by the National Institute for Agricultural Research (INIA) of Chile, and the methodologies and results of its work in selecting naturalized populations of forage legume species to develop a broad genetic base for breeding.