Latest Research News on Fruit Crops : Nov 2020
Comparative mapping and marker-assisted selection in Rosaceae fruit crops
The development of saturated linkage maps using transferable markers, restriction fragment length polymorphisms, and micro-satellites has provided a foundation for fruit tree genetics and breeding. A Prunus reference map with 562 such markers is available, and a further set of 13 maps constructed with a subset of these markers has allowed genome comparison among seven Prunus diploid (x = 8) species (almond, peach, apricot, cherry, Prunus ferganensis, Prunus davidiana, and Prunus cerasifera); marker colinearity was the rule with all of them. Preliminary results of the comparison between apple and Prunus maps suggest a high level of synteny between these two genera. Conserved genomic regions have also been detected between Prunus and Arabidopsis. By using the data from different linkage maps anchored with the reference Prunus map, it has been possible to establish, in a general map, the position of 28 major genes affecting agronomic characters found in different species. Markers tightly linked to the major genes responsible for the expression of important traits (disease/pest resistances, fruit/nut quality, self-incompatibility, etc.) have been developed in apple and Prunus and are currently in use for marker-assisted selection in breeding programs. Quantitative character dissection using linkage maps and candidate gene approaches has already started. Genomic tools such as the Prunus physical map, large EST collections in both Prunus and Malus, and the establishment of the map position of high numbers of ESTs are required for a better understanding of the Rosaceae genome and to foster additional research and applications on fruit tree genetics. 
Doubled haploid production in fruit crops
The interest of fruit breeders in haploids and doubled haploids (DH), lies in the possibility of shortening the time needed to produce homozygous lines compared to conventional breeding. Haplo-diploidization through gametic embryogenesis allows single-step development of complete homozygous lines from heterozygous parents. In a conventional breeding programme, a pure line is developed after several generations of selfing. With fruit crops, characterized by a long reproductive cycle, a high degree of heterozygosity, large size, and, sometimes, self-incompatibility, there is no way to obtain haploidization through conventional methods. This paper reviews the current status of research on doubled haploid production in the main fruit crops: Citrus, Malus domestica, Pyrus communis, Pyrus pyrifolia, Prunus persica, Prunus avium, Prunus domestica, Prunus armeniaca, Vitis vinifera, Actinidia deliciosa, Olea europaea, Morus alba, Actinidia deliziosa, [Musa balbisiana (BB)], Carica papaya, Annona squamosa, Feijoa sellowiana, Opuntia ficus-indica, Eriobotrya japonica. 
Integrated management of postharvest gray mold on fruit crops
Gray mold, incited by Botrytis cinerea, causes major postharvest losses in a wide range of crops. Some infections that occur in the field remain quiescent during the growing season and develop after harvest. The pathogen is also capable of infecting plant tissues through surface injuries inflicted during harvesting and subsequent handling; these develop during storage, even at 0 °C, and spread among products by aerial mycelial growth and conidia. The postharvest decay by this pathogen is controlled by a combination of preharvest and postharvest practices. To minimize postharvest gray mold, control programs rely mainly on applications of fungicides. However, mounting concerns of consumers and regulatory authorities about risks associated with chemical residues in food have led to imposition of strict regulations, the banning of use of certain chemical groups, and preferences by wholesaler, retailers and consumers to avoid chemically treated produce. These developments have driven the search for alternative management strategies that are effective and not reliant on conventional fungicide applications. In this review, conventional and alternative control strategies are discussed including their advantages and disadvantages. They include the use of conventional fungicides, biocontrol agents, physical treatments, natural antimicrobials, and disinfecting agents. Based on examples to control gray mold on specific crops, it is concluded that an integrated management program where adoption of a holistic approach is the key for meeting the challenge of minimizing postharvest losses caused by B. cinerea. To optimize the efficacy of treatments, it is essential to understand their mechanism of action as much as possible. Information about direct and indirect effects of each approach on the pathogen is also presented. 
Pre-harvest Factors Influencing the Postharvest Quality of Fruits: A Review
Fruits play a good role in nutritional security as well as generate high income to the growers. Pre-harvest factors have a great effect on postharvest quality of fruits. The combination of these factors includes genetic, environmental, cultural practices and physiological components. In this paper, we provide a review of studies on how pre-harvest factors influence the post quality of fruits. The influence of pre-harvest factors can be controlled by various cultural practices and high tech recent management practices. It was concluded by this study that understanding and managing pre-harvest factors properly will maintain the postharvest quality of fruits. 
Yield, Fruit Body Diameter and Cropping Duration of Oyster Mushroom (Pleurotus sajor caju) Grown on Different Grasses and Paddy Straw as Substrates
The present experiment aimed at finding the suitability of some grasses as cost effective alternative substrates, for cultivation of one species of oyster mushroom viz., Pleurotus sajor caju (Fr.) Singer in eastern India. Relative efficacy three grasses viz., kash grass (Saccharum spontaneum L.), sabai grass (Eulaliopsis binata C.E. Hubb (Retz.)) and lemon grass (Cymbopogon citrates Stapf.) was tested by using each of them either as whole substrate or in combination with the conventional substrate i.e., paddy straw in 3:1, 1:1, and 1:3 ratios. Results revealed that the maximum yield of mushroom was recorded under paddy straw with biological efficiency of 85.9%. However, no significant difference in yield was found when 25% or 50% of the conventional substrate (paddy straw) was replaced by lemon grass and sabai grass. The results indicated that grasses which are available in plenty in the forests and wastelands of lateritic uplands of eastern India can be utilized successfully as promising substrate for the commercial cultivation of Pleurotus sajor caju. 
 Dirlewanger, E., Graziano, E., Joobeur, T., Garriga-Calderé, F., Cosson, P., Howad, W. and Arús, P., 2004. Comparative mapping and marker-assisted selection in Rosaceae fruit crops. Proceedings of the national academy of sciences, 101(26), pp.9891-9896.
 Germana, M.A., 2006. Doubled haploid production in fruit crops. Plant Cell, Tissue and Organ Culture, 86(2), p.131.
 Romanazzi, G., Smilanick, J.L., Feliziani, E. and Droby, S., 2016. Integrated management of postharvest gray mold on fruit crops. Postharvest Biology and Technology, 113, pp.69-76.
 Tyagi, S., Sahay, S., Imran, M., Rashmi, K. and Mahesh, S. (2017) “Pre-harvest Factors Influencing the Postharvest Quality of Fruits: A Review”, Current Journal of Applied Science and Technology, 23(4), pp. 1-12. doi: 10.9734/CJAST/2017/32909.
 Rajak, S., Mahapatra, S. C. and Basu, M. (2011) “Yield, Fruit Body Diameter and Cropping Duration of Oyster Mushroom (Pleurotus sajor caju) Grown on Different Grasses and Paddy Straw as Substrates”, European Journal of Medicinal Plants, 1(1), pp. 10-17. doi: 10.9734/EJMP/2011/108.