Genotypic and phenotypic diversity of triticale in relation to cell wall digestibility

Climate models predict higher average temperatures, and more frequent and severe drought spells in Europe. Triticale (× Triticosecale Wittmack) is one of the most promising alternative forage crops due to its high yield potential under dry growing conditions. However, its nutritive value for ruminants should be improved. Therefore, breeding triticale forage varieties with a high cell wall digestibility is an interesting strategy. The main objective of this PhD research was to get a better understanding of cell wall digestibility in triticale forage at both the phenotypic and genotypic level. To this purpose, a collection of 120 winter triticale genotypes of European and North American breeding origin was assembled. In this research, NIRS calibrations were successfully developed as tool to screen cell wall digestibility in triticale forage. When tested in field experiments, a large phenotypic and genotypic variability in cell wall digestibility among triticale genotypes harvested at the soft dough developmental stage was observed. Further, our phenotypic dataset was combined with genotypic data to perform a genome-wide association study. This study allowed to decipher the genetic architecture of cell wall digestibility in triticale and to identify phenotypic traits related to this trait. Moreover, the genomic regions identified in this doctoral research are of great value for breeders aiming to improve cell wall digestibility in triticale forage. Lastly, since triticale forage will be mostly fed as silage, the silage characteristics of soft dough triticale were studied. Our results showed that harvesting triticale at the soft dough stage guaranteed a good silage quality in terms of pH, fermentation losses, and aerobic stability

Composition and digestibility of whole plant triticale as affected by maturity stage and genotype

Maize is grown in monoculture on many dairy farms in NW Europe. Triticale for use as whole plant (WPT) may contribute to the diversification of crop rotation, resulting in a lower disease and weed pressure and higher yields. Moreover with climate changing to warmer and dryer summers, WPT offers an advantage compared with maize as it can be harvested before the summer heat. A six-year study was started to investigate the potential of WPT as alternative roughage crop for maize silage. An important objective is to study the factors affecting the digestibility of organic matter (OMd) and cell wall digestibility (NDFd). In a first field trial, 36 genotypes were harvested at 5 maturity stages and samples from these 180 WPT objects were scanned by NIRS. Based on spectral variation, 80 samples were selected to determine dry matter (DM), crude protein (CP), crude fat, crude ash, sugars, starch, NDF, ADF and ADL as well as cellulase OMd and rumen fluid NDFd. The DM content of the WPT for the 5 stages averaged 268, 285, 467, 508 and 574 g/kg, respectively. During maturing, sugar content decreased, whereas starch content increased with a clear shift from the second to the third stage. With advancing maturity there was a relative small decrease in NDF, CP and ash content. The NDFd seemed hardly affected by maturity stage with on average 53.9 and 55.4% for the first and fifth stage. On the other hand, mean OMd increased linearly with later harvesting and amounted to 63.8, 65.0, 67.9, 68.1 and 69.1%, respectively. In addition to the effect of maturity stage, there appeared a large variation among genotypes. For the last stage, OMd ranged between 67.3 and 73.2%. This variation opens perspectives to select for WPT with high nutritive value. The reference data from this first trial were used to develop NIRS calibrations in order to allow rapid feed evaluation throughout the study

In vitro digestibility as screening tool for improved forage quality in triticale

Context or Problem: Small grain forages are considered an alternative to maize, a globally important forage crop on dairy farms. Triticale is one of the most promising small grains to be cultivated as a source of forage. The inclusion of triticale in the crop rotation system can widen a narrow maize rotation, increase biodiversity, and improve the humus balance. However, successful implementation of the use of triticale forage depends largely on its forage quality, of which digestibility is the most important characteristic. Objective or Research Question: The main objectives of this study were to investigate the genetic variation for in vitro digestibility (IVD) on total plant and stem level in a diverse triticale collection and to identify traits that can assist breeders in selecting for improved IVD. Methods: The collection consisted of 120 winter triticale genotypes (103 varieties and 17 breeding lines) of North-American and European breeding origin. These genotypes were cultivated in micro plots in two consecutive growing seasons and harvested at the soft dough maturity stage (Z85, Zadoks scale). Forage quality traits were estimated on total plant and stem samples using near infrared spectroscopy (NIRS). Results: The dataset showed considerable genotypic variation (CV 3.9–10%) and broad-sense heritability values between 0.66 and 0.73 for total plant in vitro digestibility of organic matter (plant IVOMD), total plant in vitro digestibility of neutral detergent fibre (plant IVNDFD), and stem IVNDFD. Our results show that low total plant acid detergent fibre (ADFom) can be used as a selection criterion to improve plant IVOMD and plant IVNDFD. In turn, stem Klason lignin (KL) has the highest potential for improving stem IVNDFD. Multivariate analysis combining all traits investigated, revealed clustering according to North-American or European breeding origin. In general terms, the European genotypes have higher IVD than the North-American genotypes. Conclusions: In conclusion, high phenotypic diversity and high heritabilities were detected for triticale forage quality on total plant and stem level in a collection of European and North-American triticale. Implications or Significance: This study suggested the potential for improvement of triticale forage IVD, indicating total plant ADFom and stem KL might be relevant traits in triticale forage breeding. Promising genotypes with a good plant IVOMD and high forage yield are of relevance for future triticale forage breeding purposes