Divergência genética em progênies de abacaxizeiro e seleção de clones superiores resistentes a fusariose

Abstract

The pineapple tree has great economic and social importance in the world, being cultivated in around 90 countries. Brazil is the fourth largest producer, behind Costa Rica, Indonesia and the Philippines. The ‘Pérola’ cultivar predominates in Brazilian pineapple cultivation, even though it is susceptible to fusariosis, as well as the MD-2 and Smooth Cayenne cultivars, which dominate the international market. Almost all Brazilian production is sold in the domestic market in natural form. This predominance of the ‘Pérola’ pineapple is due to the plant’s wide adaptability and high rusticity, subject to climatic and soil conditions, completely different from Brazil. Although the ‘Pérola’ pineapple is widely accepted by the national consumer, its physical characteristics and fruit quality are unattractive and do not appeal to the international market, resulting in its negligible export. The conical shape of the fruit, greenish skin, creamywhite color of the pulp and high susceptibility to translucency at the point of harvest do not meet the preferences of the foreign market. Despite the availability of cultivars with genetic resistance to fusariosis and smooth leaves, such as 'BRS Imperial' and 'BRS Vitória', they do not show good adaptation to the different cropping systems and soil and climate conditions in Brazil. Therefore, regional development and local adaptation of new cultivars resistant to fusariosis and that bring together the best agronomic and quality characteristics of the fruit for the different segments and niches of the fresh market become essential to the sustainability of Brazilian pineapple farming. This work aimed to: study the genetic divergence (Ward-MLM) of pineapple progenies (Ananas comosus var. comosus) to identify parents within heterotic groups with greater potential for hybridization; select superior clones with resistance to fusariosis and adapted to the edaphoclimatic conditions of the northern region of the State of Mato Grosso via predicted genotypic values (REML/BLUP) and selection index; and evaluate the agronomic performance of promising clones resistant to fusariosis, developed and selected by the Genetic Improvement Program of the State University of Mato Grosso for commercial launch purposes. Of the three chapters developed, the first and second evaluated 91 clones, resulting from crosses: ‘IAC Fantástico’ x ‘Jupi’; ‘BRS Imperial’ x ‘Pérola’; ‘BRS Imperial’ x ‘Smoth Cayenne’; and ‘BRS Vitória’ x ‘Smoth Cayenne’. In chapter one, 42 characters (qualitative, quantitative and chemical characteristics of the fruit) were evaluated using the Ward-MLM procedure in the SAS program to quantify genetic divergence. In chapter two, 13 morphoagronomic descriptors were used to estimate genetic parameters and select superior clones, via REML/BLUP, with three different indices and weights. Genetic resistance to fusariosis was evaluated in the selected clones using the technique of inoculating the suspension of Fusarium guttiforme at the base of the seedlings, with the clones subsequently classified as resistant and susceptible. Estimates of gains through selection were obtained based on selection of 22.2%, with 20 promising clones selected. Chapter three presents the morphoagronomic evaluation of seven clones resistant to fusariosis in addition to six commercial cultivars. As a result, in chapter one, genetic variability was observed between pineapple genotypes for morphoagronomic variables, forming three groups. Individuals in group III had the highest averages for fruit mass with and without crown, length and average fruit diameter. On the other hand, groups I and II presented the lowest averages and were similar to each other, differing in the weight and length of the crown and in the ratio. The greatest distance was observed between groups II and III, therefore, it is recommended to cross the best individuals from these groups in order to explore the heterotic effect and expand the existing genetic variability. Therefore, the Ward-MLM method in distinguishing groups demonstrated that the simultaneous analysis of qualitative and quantitative data is viable and can allow greater efficiency in understanding the divergence between genotypes. In chapter two, significant differences are presented for most variables between clones, with high genetic variability between them. The clones showed better fruit quality, such as greater fruit mass and total soluble solids content, as well as fruit shape and pulp color expected by the consumer. In chapter three, the most promising resistant clones were Unemat 10, 31, 71 and 103, which should continue in Unemat's genetic improvement program, with the potential for commercial launch as new cultivars, as they were superior to commercial cultivars, with greater mass and fruit length. They also presented a high content of total soluble solids, creamy-white to yellow pulp color, and conical and cylindrical fruit shape. Finally, it was possible to infer the genetic divergence between the clones through the Ward-MLM grouping, where it was possible to predict some crossings between individuals from different groups. The selection of superior clones using the Smith & Hazel selection index provided an increase in important characteristics, allowing the selection of seven promising clones with better fruit quality, without thorns and resistant to fusariosis. The morphoagronomic evaluation of the selected clones showed the potential of each one. Four of the seven selected presented the greatest number of characteristics combined, both physical and chemical, and will undergo new tests for the commercial launch of cultivars.