Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/15/2000
Publication Date: N/A
Citation: Interpretive Summary: Digestibility is a key factor in determining the total nutritive value that can be obtained from forages by ruminants. Digestibility is strongly influenced by total fiber and lignin content of the plant material. It is valuable to have alternative genetic resources with improved digestibility in order to improve the total nutritive value of silage corn. We evaluated fiber and digestibility characteristics of a lax leaf mutant of corn, identified by their bent leaves. Lax leaf plants had lower levels of fiber and lignin and higher digestiblitities than normal corn. A genetic analysis was undertaken to determine the genetic control of the lax leaf character and to determine if the lax leaf trait was related to nutritive value traits. In other words would selection for increased "laxness" in corn plants lead to increased nutritive value? This work showed that greater laxness was actually associated with lower nutritive value within this population of corn. Therefore, selection for "laxness" does not improve nutritive value. However, the original lax leaf line can be a good source for improved nutritive value and may be incorporated into existing lines to improve corn for higher silage quality.
Technical Abstract: Forage nutritive value is an important criterion for maize (Zea mays L.) harvested as silage. A study was conducted to characterize the cell wall composition of the lax leaf line. Lax leaf and "normal" maize inbreds were evaluated for cell wall composition traits in five tissues from the ear node and the internode above it. Acid (ADF) and neutral detergent fiber (NDF) and 48-hr in vitro true digestibility (IVTD) were predicted using near infrared sprectrophotometry (NIRS). Lax leaf inbred tissues had lower levels of ADF, NDF, lignin, and xylose, and were more digestible than tissues from the inbreds representing 'normal' maize. To determine the genotypic relation between the lax leaf character and nutritive value a recombinant inbred mapping population was developed. Plant samples from each recombinant inbred line were evaluated for ADF, NDF, acid detergent lignin and IVTD of dry matter using NIRS. Laxness was measured by counting broken leaves on plants. AFLP and SSR markers were used to identify linkage groups associated with the lax leaf character, digestibility, and fiber content. Contrary to expectations, greater laxness was associated with lower nutritive value in this population. The lax leaf parent allele was associated with increased nutritive value in linkage groups unassociated with the lax leaf character. While the lax leaf line may be a good source for alleles for improved nutritive value, selection for laxness will not likely be accompanied by improvement in forage quality.