Associations among forage quality traits, vigor, and disease resistance inalfalfa

Major objectives for alfalfa (Medicago sativa L.) breeding include improvin g forage quality and levels of disease resistance. Little is known about th e associations between forage quality characteristics, including pectin (th e main component of neutral detergent-soluble fiber [NDSF]), and disease re sistance and vigor in alfalfa. Our objectives were to determine, in two alf alfa populations, the (i) correlations among NDSF and other forage quality traits; (ii) correlations of forage quality traits with plant persistence, vigor, and levels of resistance to diseases; and (iii) heritabilities and e xpected gains from selection for the aforementioned traits. Simple, phenoty pic, and additive genetic correlation coefficients were estimated from half -sib (HS) progeny tests of two alfalfa populations (NY9505 and NY9515). In both populations, NDSF was negatively correlated with acid detergent fiber (ADF), lignin, and neutral detergent fiber (NDF), and positively correlated with true in vitro dry matter digestibility (IVDMD). Vigor was positively correlated with ADF, lignin, and NDF, and negatively correlated with IVDMD and crude protein (CP) only in. NY9515. Of 144 correlation coefficients com puted between forage quality traits and resistances to five major alfalfa d iseases, only six were significant, and they were low in magnitude (-0.22 /- 0.11 to 0.30 +/- 0.14). In an alfalfa improvement program, selection for forage quality is not expected to indirectly affect levels of disease resi stance, but it may reduce vigor.