Allelic variations in aroma gene in cultivated rice varieties

Germplasm is a valuable source of genetic diversity that supports crop improvement efforts in any breeding programme but it must first be fully characterised for economically valuable traits before it can be effectively utilised. In rice ( Oryza sativa ), the development of new varieties with improved aroma requires correct phenotyping and prior knowledge of the available genes and alleles governing the aroma trait in the gene pool. Correct phenotyping and genotyping can be achieved using sensory methods and functional markers associated with polymorphisms that define the aroma genes. The objective of this study was to evaluate the aroma status of rice accessions and to assess for the various alleles of badh2 gene using functional markers. A total of 56 rice accessions were evaluated at National Crops Resources Research Institute (NaCRRI) in Uganda for their aroma using sensory methods and a molecular marker to differentiate between aromatic and non- aromatic accessions. The aromatic accessions were then evaluated for variations within the betaine aldehyde dehydrogenase2 (badh2) gene responsible for aroma in rice using functional markers. Sensory evaluation of aroma identified 23 accessions to be aromatic; while 33 were non-aromatic. Molecular results identified 20 accessions as aromatic; while 36 accessions were non-aromatic. Functional marker analysis indicated the presence of badh2-E7 allele in 20 aromatic accessions within this collection that could be employed in the breeding programme for the rice aromatic trait.Le germoplasme est une source pr\ue9cieuse de diversit\ue9 g\ue9n\ue9tique qui soutient les efforts d\u2019am\ue9lioration des cultures dans tout programme de s\ue9lection, mais il doit d\u2019abord \ueatre enti\ue8rement caract\ue9ris\ue9 pour ses traits \ue9conomiquement pr\ue9cieux avant de pouvoir \ueatre utilis\ue9 efficacement. Dans le riz ( Oryza sativa ), le d\ue9veloppement de nouvelles vari\ue9t\ue9s avec un ar\uf4me am\ue9lior\ue9 n\ue9cessite un ph\ue9notypage correct et une connaissance pr\ue9alable des g\ue8nes et all\ue8les disponibles r\ue9gissant le caract\ue8re aromatique dans le pool g\ue9n\ue9tique. Un ph\ue9notypage et un g\ue9notypage corrects peuvent \ueatre obtenus en utilisant des m\ue9thodes sensorielles et des marqueurs fonctionnels associ\ue9s \ue0 des polymorphismes qui d\ue9finissent les g\ue8nes aromatiques. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer le statut aromatique des accessions de riz et d\u2019\ue9valuer les diff\ue9rents all\ue8les du g\ue8ne badh2 \ue0 l\u2019aide de marqueurs fonctionnels. Un total de 56 accessions de riz ont \ue9t\ue9 \ue9valu\ue9es au National Crops Resources Research Institute (NaCRRI) en Ouganda pour leur ar\uf4me en utilisant des m\ue9thodes sensorielles et un marqueur mol\ue9culaire pour diff\ue9rencier les accessions aromatiques et non aromatiques. Les accessions aromatiques ont ensuite \ue9t\ue9 \ue9valu\ue9es pour les variations au sein du g\ue8ne de la b\ue9ta\uefne ald\ue9hyde d\ue9shydrog\ue9nase2 (badh2) responsable de l\u2019ar\uf4me du riz \ue0 l\u2019aide de marqueurs fonctionnels. L\u2019\ue9valuation sensorielle de l\u2019ar\uf4me a identifi\ue9 23 accessions comme aromatiques; tandis que 33 \ue9taient non aromatiques. Les r\ue9sultats mol\ue9culaires ont identifi\ue9 20 accessions comme aromatiques; tandis que 36 accessions n\u2019\ue9taient pas aromatiques. L\u2019analyse des marqueurs fonctionnels a indiqu\ue9 la pr\ue9sence d\u2019all\ue8les badh2-E7 dans 20 accessions aromatiques de cette collection qui pourraient \ueatre utilis\ue9es dans le programme de s\ue9lection pour le trait aromatique du riz

Breeding banana (Musa spp.) for drought tolerance: A review

Drought is a major abiotic stress affecting banana production worldwide, leading to yield losses of up to 65%. Consequently, numerous efforts to understand and mitigate drought effects that include developing tolerant crop varieties are ongoing in several banana breeding programmes. The breeding efforts, however, have been greatly slowed down by inherent banana problems (polyploidy and male or female sterility) and complexity of drought tolerance (reportedly controlled by several genes). This review summarizes the pertinent research findings on water requirements of banana for its proper growth and productivity, symptoms of drought‐sensitive varieties and field management strategies to cope with drought stress. The coping strategies deployed by resistant cultivars include high assimilation rates and water retention capacity as well as minor losses in leaf area and gaseous exchange. Reduced bunch weight, leaf chlorosis, wilting and strangled birth are underlined to be directly associated with drought susceptibility. Integration of conventional, molecular breeding and biotechnological tools as well as exploitation of the existing banana genetic diversity presents a huge opportunity for successful banana improvement