Opportunities for marker-assisted selection (MAS) to improve the feed quality of crop residues in pearl millet and sorghum

Abstract

Cereal crop residues (straw, chaff, etc.) are important components of maintenance rations for ruminant livestock in many parts of the world. They are especially important in smallholder crop-livestock production systems in the sub-humid, semi-arid, and arid tropics and subtropics where most of the world's poorest livestock producers and consumers are found. Taking as examples tropically adapted cereals in the crop improvement mandate of the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), namely pearl millet [Pennisetum glaucum (L.) R. Br.] and sorghum [Sorghum bicolor (L.) Moench], this paper explores opportunities for using marker-assisted crop breeding methods to improve the quality and quantity of cereal crop residues for use as ruminant livestock feedstuffs. In the case of pearl millet, ICRISAT has been heavily involved with several UK-based collaborating research institutes, in development and initial application of the molecular genetic tools for markerassisted breeding. We have obtained some useful experience in quantitative trait loci (QTL) mapping and marker-assisted selection (MAS) for stover yield, foliar disease resistance, and in vitro estimates of the nutritive value of various stover fractions for ruminants. In sorghum, ICRISAT has focused on initiating a large-scale high-throughput marker-assisted backcrossing program for the stay-green component of terminal drought tolerance-a trait that is likely to be associated not only with more stable grain and stover yield, but which is also expected to contribute to maintenance of ruminant nutritional value of stover produced under drought stress conditions. Conventional and marker-assisted breeding for foliar disease resistance is recommended for dual-purpose cereal improvement, or indeed for improvement of the nutritional value of residues for any crop in which these are used as feedstuffs for ruminant livestock. Practical problems faced and proposed ways of dealing with these are discussed.

Modelling the effect of plant water use traits on yield and stay-green expression in sorghum

“…Thomas and Howarth 2000;Cha et al 2002)), there are basically two parallel streams of hypotheses explaining the maintenance of green leaves under water stress, one of which deals with the enhanced use of available N (Rajcan and Tollenaar 1999;Borrell and Hammer 2000;Borrell et al 2001;Bertheloot et al 2008;van Oosterom et al 2010b) and another one favouring an improved plant water use status Vadez et al 2011Vadez et al , 2014. Several quantitative trait loci (QTLs) contributing to stay-green phenotype expression under drought (Stages 1-4, Stages A and B) have been validated across different research groups (Tuinstra et al 1996(Tuinstra et al , 1997(Tuinstra et al , 1998Crasta et al 1999;Subudhi et al 2000;Tao et al 2000;Xu et al 2000;Kebede et al 2001;Sanchez et al 2002;Haussmann et al 2002;Hash et al 2003;Harris et al 2007). Introgressing stay-green QTLs into two senescent parental lines (R16, S35) from the staygreen donor B35 produced lines showing differences in several traits related to the plant water budget (e.g.…”

Construction of Genetic Linkage Map and QTL Analysis of Sink-Size Traits in Pearl Millet (Pennisetum glaucum)

“…This, in turn, requires an appropriate mapping population. In pearl millet, several F 2:3 and F 2:4 mapping populations have been developed from diverse inbred lines of Asian, American, and African origin [7] and genomic positions of QTLs were mapped for disease resistance [8][9][10][11][12][13][14], abiotic stress tolerance [6,10,[15][16][17][18], phenology [19,20], grain and stover yield, and quality components [16,18,[20][21][22][23]. However, panicle and grain size, though being major determinants of grain yield in pearl millet, have been sparingly subjected to QTL analysis.…”

Stay-green expression in early generation sorghum [Sorghum bicolor (L.) Moench] QTL introgression lines

“…The trait is likely to be more easily manipulated using a marker-assisted breeding approach, using as selection criteria speciWc alleles at molecular loci linked to genomic regions contributing to the stay-green trait (i.e., quantitative trait loci = QTLs), identiWed in carefully managed, replicated, multi-environment tests. The work of diVerent groups has led to a better understanding of the inheritance of stay-green (Walulu et al 1994;van Oosterom et al 1996;Tuinstra et al 1997), to the mapping of QTLs associated with postXowering drought tolerance in sorghum (Tuinstra et al 1996(Tuinstra et al , 1998Crasta et al 1999;Tao et al 2000;Xu et al 2000b;Subudhi et al 2000;Kebede et al 2001;Sanchez et al 2002;Haussmann et al 2002) and identiWcation of markers linked to these QTLs (Hash et al 2003;Harris et al 2007).…”