Genetic variability in a Brazilian apple germplasm collection with low chilling requirements.

Livia Costa Mariano,Felipe Liss Zchonski,Paulo Roberto Da-Silva,Clandio Medeiros da Silva

doi:10.7717/peerj.6265

Livia Costa Mariano, Felipe Liss Zchonski + Show 2 more

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https://doi.org/10.7717/peerj.6265

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Abstract

The apple (Malus domestica Borkh) originally evolved to require temperatures below 7.2 °C for the induction of budding and flowering. In Brazil, breeders have overcome the climate barrier and developed the cultivars Anabela, Julieta, Carícia, and Eva, with low chilling requirements and good yield characteristics. These cultivars are grown in many warmer climate countries in South America, Africa, and the Middle East. The apple germplasm collection that originated these cultivars has several genotypes with pedigrees for a low chilling requirement. Knowledge of the variability and genetic relationships among these genotypes may be useful in the development of superior new cultivars. In this work, we first selected the best ISSR (inter-simple sequence repeat) primers for genetic studies in apple, and then we used the selected primers to evaluate the genetic variability of the apple germplasm collection at the Instituto Agronômico do Paraná. The evaluation of 42 ISSR primers in 10 apple genotypes allowed us to select the best nine primers based on the polymorphic information content (PIC) and resolving power (RP) indexes. The primer selection step was robust since the dendrogram obtained with the nine selected primers was the same as the one obtained using all 26 polymorphic primers. Primer selection using PIC and RP indexes allowed us to save about 60% of time and costs in the genetic variability study. The nine ISSR primers showed high levels of genetic variability in the 60 apple genotypes evaluated. The relevance of the primer selection step is discussed from the perspective of saving time and money in germplasm characterization. The high genetic variability and the genetic relationships among the genotypes are discussed from the perspective of the development of new apple cultivars, mainly aiming for a low chilling requirement that can better adapt to current climatic conditions or those that may arise with global warming.

Highlights

The apple (Malus domestica Borkh) is a species of the family Rosaceae, subfamily Pomoideae, which comprises 100 genera and around 2,000 species spread throughoutHow to cite this article Mariano LC, Zchonski FL, da Silva CM, Da-Silva PR. 2019
This work aimed to select, from among 42 ISSR primers, the most robust ones for genetic studies in apple, and to use them to resolve the genetic relationship between the apple genotypes of the Instituto Agronômico do Paraná (IAPAR) germplasm collection to assist in the selection of genotypes for future crosses in order to obtain new cultivars with low chilling requirements and good production and market characteristics
Of the 42 ISSR primers tested in 10 apple genotypes, 26 (61.90%) showed amplification with good fragment resolution (Table 2)

Summary

Introduction

The apple (Malus domestica Borkh) is a species of the family Rosaceae, subfamily Pomoideae, which comprises 100 genera and around 2,000 species spread throughoutHow to cite this article Mariano LC, Zchonski FL, da Silva CM, Da-Silva PR. 2019. The center of origin of the apple is Kazakhstan and Central Asia; the genus Malus primarily originated in Asia Minor, the Caucasus, Central Asia, the Indian Himalayas, Pakistan, and Western China, where there are at least 25 to 47 native Malus species (Yan et al, 2008; Folta & Gardiner, 2009; Hofer et al, 2014). The species is cultivated in subtropical regions with less rigorous winters (0 to 10 ◦C), and even in tropical climates, such as in Northeast Brazil (Pommer & Barbosa, 2009). In these regions, the apple shows problems with climatic adaptation (Lopes et al, 2012)

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