Forage potential of Urochloa genotypes by using leaf anatomy

Janaína Mauri,Gabrielle Avelar Silva,Vânia Helena Techio,Fausto Souza Sobrinho,Daniele Laís Pereira,Fabricio José Pereira,Lisete Chamma Davide

doi:10.1590/0103-8478cr20170266

Janaína Mauri, Gabrielle Avelar Silva + Show 5 more

Open Access

https://doi.org/10.1590/0103-8478cr20170266

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Abstract

ABSTRACT: The digestibility potential of leaves from forages depends on the amount of nutrition in their tissues, with low lignin deposition in the cell wall, mainly parenchyma and phloem. This research evaluated the leaf structure of different Urochloa genotypes and discussed its potential for evaluating digestibility. The cultivars U. brizantha, U. decumbens, U. ruziziensis and three clones of U. ruziziensis (1, 95 and 97), which are under development in breeding programs, were evaluated. Plants were grown under the recommended culture conditions for the Urochloa species. Plants were cut 60 days after sowing, and leaves were collected at 15 days of regrowth. Leaves were fixed in FAA 70 and further stored in 70% ethanol until being submitted to the usual microtechniques for the preparation of microscopy slides. The area of the tissues from the interveinal and midrib regions was measured using ImageJ software, and their proportions were calculated. In the interveinal region, the proportion of chlorophyll parenchyma was greater for U. decumbens and the Clone 1 genotypes. Urochloa brizantha and clones 95 and 97 showed a higher proportion of the vascular bundle compared to U. ruziziensis, U. decumbens and Clone 1. The proportion of the ground parenchyma in the midrib was greater in U. brizantha, Clone 95 and Clone 97. Thus, it can be concluded that the Clone 1 genotypes (from U. ruziziensis) showed leaf tissues (parenchyma and phloem) with higher digestibility potential; in addition, U. brizantha and U. decumbens showed a high percentage of xylem and sclerenchyma, which reduces their quality as forage.

Highlights

Urochloa is a genus that was previously named Brachiaria (SHIRASUNA, 2015) and includes forage species among those most used by livestock breeders in Brazil (VALLE et al, 2009; SOUZA SOBRINHO et al, 2009a)
It can be concluded that the Clone 1 genotypes showed leaf tissues with higher digestibility potential; in addition, U. brizantha and U. decumbens showed a high percentage of xylem and sclerenchyma, which reduces their quality as forage
The phloem proportion was higher in U. brizantha and Clone 1 compared to the other genotypes; the total phloem proportion was higher in U. brizantha

Summary

INTRODUCTION

Urochloa is a genus that was previously named Brachiaria (SHIRASUNA, 2015) and includes forage species among those most used by livestock breeders in Brazil (VALLE et al, 2009; SOUZA SOBRINHO et al, 2009a). Classical studies that investigated the digestibility of leaf tissues in the rumen solution itself have reported that the degradation of the tissues follows a specific sequence based on cell’s structure This sequence begins with the chlorophyll parenchyma, phloem, epidermis, bundle sheath parenchyma, and, as the least digestible tissues, the xylem and sclerenchyma (HANNA et al 1973; AKIN, 1989; BRITO et al, 1999; PACIULLO, 2002; PACIULLO et al, 2002). Including the plant anatomy in the studies for the breeding process of forages permits the selection of plants with higher digestibility and the potential to recover quicker in addition to avoiding the use of animals for in vivo investigations In this regard, the present work aimed to evaluate the leaf structure of different Urochloa genotypes and discuss their forage potential as related to their anatomical differences

MATERIALS AND METHODS

RESULTS AND DISCUSSION

CONCLUSION