Conventional Genetic Improvement

Conventional genetic improvement in musaceae. Treatment given to different varieties of crops . They depend on crosses between fertile female and male clones that produce viable pollen . Diploid genotypes and wild varieties produce more pollen than triploid and tetraploid clones.

Summary

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  • 1 Importance
  • 2 Plant breeding
    • 1 Banana and banana
  • 3 Diploid enhancement
  • 4 Triploid enhancement
  • 5 FHIA Achievements
    • 1 Honduras
    • 2 Cuba
  • 6 Source

Importance

The triploid nature and high degree of sterility make the genetic analysis of the banana difficult. The manipulation of the degree of ploidy (increase or decrease in the number of chromosomes) and the interspecific hybridization of plantain – banana have opened the way for genetic improvement and genomic study of this plant, which in turn will allow other manipulations. The interaction of the copy number of the black Sigatoka resistance allele and the fruit parthenocarpy gene, as well as its intralocus interaction and the degree of ploidy, are elements that have important effects on the characteristics of the bunches and fruits of these. hybrids.

Plant breeding

Banana and banana

It is highly restricted due to low seed production, especially in 3N x 2N type crossings. Thousands of pollinations are necessary to obtain progeny testing seeds that are large enough to guarantee success. Different methods of pollination and doses of triadimefon (bayleton) were evaluated in 1987. The possible influence of the age of male flowers on female fertilization was investigated, as well as the effect of climatic factors on seed production and it was concluded that:

  • It is not recommended to change the current pollination method used in the genetic program.
  • The use of triadimefon in the studied doses did not have a significant influence on the increase in seed production.
  • Male flowers work with equal efficiency, regardless of age.
  • Climatic factors did not show any correlation with the fertility of the female parents.

Diploid enhancement

The most important activity in the genetic improvement of bananas and plantains has always been the development of diploid hybrids with superior agronomic characteristics and resistant to diseases, these are the main source of genetic variability in the improvement of new commercial-type hybrids, since the Triploids that cross with them are fixed in their genetic makeup.

The diploid ‘SH-2095’ (AA) was chosen for the favorable, unprecedented characteristics of the cluster. This hybrid was derived from the cross of (Sinwobogi X Tjau Lagada) X (a wild Musa acuminata subspecies malaccensis X Goyud).

The only weakness of ‘SH-2095’ (AA) is its poor pollen production, limiting its usefulness as a male parent. This hybrid has a few seeds per pollinated bunch and cross pollinations have shown that the desired characteristics are easily transmitted to the progeny.

The development of the ‘SH-2095’ (AA) hybrid, which was the first diploid with exceptional cluster characteristics, has been the result of the exhaustive effort of different forms of genetic improvement. The ‘SH-2095’ (AA) was the only agronomically superior hybrid selected during the first 10 years of the FHIA program and is in the pedigree of most of the subsequent diploids that have been selected from the segregating populations.

The hybrid that required the second most intense pollination for its development was the ‘SH-3142’ (AA), which is the only hybrid resistant to nematodes. This was the only hybrid selected from the few seeds obtained after pollinating some 10,000 clusters of the almost sterile clone ‘Pisang Jary Buaya’ (AA), which is resistant to the borer nematode. In contrast to the ‘Pisag Jary Buaya’ (AA), the ‘SH-3142’ (AA) is easily usable as a paternal or maternal line in cross-pollinations.

The ‘Pisang Jary Buaya’ (AA) clone has outstanding agronomic characteristics as a natural diploid and is resistant to Radopholus similis (Wehunt and Edwards, 1978) but this banana contains little pollen and most of the pollinated clusters remain seedless. Extensive pollinations of the ‘Pisang Jary Buaya’ (AA) have been carried out which were necessary to obtain a few ‘seedlings’ of the hybrid, and the subsequent selection of the diploid ‘SH-3142’ (AA) as the only useful progeny of this series of crosses.

The development of ‘SH-3142’ (AA) is arguably the most significant achievement in the Honduran program. This diploid hybrid was resistant to Radopholus similis , presenting fertile pollen and seeds. The availability of this clone also provided genetic diversity in diploids with superior agronomic characteristics and it was anticipated that the use of this line in cross-pollinations would guarantee the qualities of the existing diploids.

The value of ‘SH-3142’ (AA) was shown when it was crossed with ‘Highgate’ (AAA), resulting in the tetraploid progeny ‘SH-3436’ (AAAA), which is the most prospective commercial hybrid developed by the Honduras FHIA program .

The agronomic excellence of diploids derived from ‘SH-3142’ (AA) is illustrated by the cluster characteristics of ‘SH-3362’ (AA). This diploid hybrid is from the cross between ‘SH-3142’ (AA) X ‘SH-3217’ (AA).

The ‘SH-3362’ (AA) is used as a progenitor of pollen in crosses with the ‘Higtgate’ (AAA) and other female fertile progenitors.

Triploid enhancement

The success of genetic improvement of any crop depends, among other factors, on the breadth of genetic variability available to the breeder. Genetic improvement of the viabanda plantain (AAB) and donkey plantain (ABB) has been a secondary object in conventional improvement programs. At the moment they are more extensive due to the threat caused by the appearance of the black Sigatoka, in a continuous way.

The key discovery in banana improvement was the finding that female bananas have seeds when pollinated. The female banana used in the FHIA program has the name ‘AVP-67’ (AAB), which can be used to synthesize new tetraploid hybrids, which can be evaluated as commercial.

The clones ‘Pelipita’ and ‘Saba’ (ABB), of high size, in the improvement of cooking bananas of small size have not produced anything promising. The interest in crossing these clones has been the increase in genetic diversity and the hope that the fruit developed from these crosses will remain with the same mealy consistency when ripe.

On the other hand, the success of a cross in the breeding program requires the production of true seeds as a result of sexual hybridization as a first step. This is considered the most difficult problem for genetic manipulation of Musa triploid cultivars .
True seeds in type AABs have been found with great variations among banana cultivars. The average range is from 1 to 20 seeds per bunch, although this range is influenced by the different seasons.

Bioversity believes that through collaboration and partnership development, the results and impact of ongoing research can be maximized. This collaborative approach consolidates inter-institutional efforts in genetic improvement of “Musa” and has culminated in the establishment of PRO-MUSA, a global program for Musa improvement .

Improvement of bananas involves the identification of useful genes in traditional cultivars or related wild species and the introduction of these characteristics in commercially acceptable varieties. This can be accomplished through conventional breeding using hybridization techniques, or through genetic transformation using techniques from cellular and molecular biology .

In order to complement traditional breeding methods, new genetic improvement methods based on Agrobacterium transformation of embryogenic cell suspensions and tissue cultures, among others , are currently being investigated .

Horn AAB banana is sterile. However, dipolid (AA) cross pollinations in fertile seed AAB and ABB types may offer possibilities for the improvement of new cooking bananas.

The most cultivated plantain in Central and South America is the Horn plantain (AAB), this clone is resistant to the common Sigatoka pathogen but is susceptible to the Black Sigatoka pathogen ( Mycosphaerella finjiensis ). The rapid spread of this disease threatens the continuity of production of this crop.

The hybrids ‘FHIA-20’, 21 and 22 are French type bananas with 8 to 10 hands / bunches compared to the False Horn, although their performance is greater due to their greater number of hands.
Banana breeding activities (AAB) have always been limited. Two hybrid bananas ‘FHIA-20’ (AAAB) and ‘FHIA-21’ (AAAB) have been evaluated in several countries after 25 years where the genetic improvement of the banana was widely considered impossible to achieve.

The plantain hybrids developed by the Banana and Plantain Program come mainly from three crosses.

Parents Progeny
AVP-67 (m) X ‘SH-3142’ (p) ‘FHIA-21 and’ FHIA-22 ‘
AVP-67 (m) X ‘SH-3437’ (p) ‘FHIA-04’, ‘FHIA-05’, ‘FHIA-16’, ‘FHIA-19’ and ‘FHIA-20’
‘Maqueño (m) X’ SH-3437 ‘(p) ‘FHIA-06’, ‘FHIA-07’, ‘FHIA-14’, ‘FHIA-15’

All are tertraploid hybrids of the AAAB type.
. The mother of the ‘FHIA-20’ and ‘FHIA-21’ was the same, AVP-67, French type, but the parents were two different enhanced elite diploids. The green life of the ‘FHIA-20’ and ‘FHIA-21’ is suitable for export and for local markets where there is refrigeration. These hybrids have lower dry matter content and less firmness.

The starch content of the hybrids and the False Horn seems to be similar in the green fruit but in the mature fruit of the hybrids it is lower, suggesting that the conversion to sugars is more complete in these, however the soluble solids content is higher in False Horn, a result contrary to what was expected.

FHIA achievements

Honduras

Dodds’ prediction over 60 years ago that superior quality diploids could be developed has now come true. The agronomically improved diplodes currently used extensively in various breeding programs are: ‘SH-3142’ (AA), as a source of resistance to borer nematode; ‘SH-3362’ (AA), with resistance to Race 4 of Panama Disease; ‘SH-3437’ (AA), as a source of resistance to black Sigatoka. These three diploids are themselves resistant to the most common race (Race 1) of Panama Disease. In addition to the ‘Gross Michel’ (AAA) variety, several other fertile triploid clones in different types of banana and plantain were later identified.

Cuba

In Cuba there is a significant number of areas dedicated to cultivating ‘FHIA-18’ (AAAB) under cultivation without chemical control of black Sigatoka. In addition to having a high level of disease tolerance, the ‘FHIA-18’ variety is also a borer nematode variety and is a sweet, acidulated dessert banana.

Banana hybrids types ‘FHIA-20’ and ‘FHIA-21’ have been grown commercially in several Latin American countries and have been shown to be twice as productive as the traditional Falso Cuerno variety banana.

The objective of any conventional breeding program is to develop hybrids of bananas and plantains resistant to the main pests and diseases of economic importance. Improved varieties are also intended to have the ability to thrive under adverse growing conditions. In this way, it seeks to reduce the dependence of these crops on agro-chemicals and contribute to the sustainable development of production. The banana breeding program was started by the United Fruit Co. in 1958. The FHIA has continued the banana work and started the banana work in 1984. Currently this program is a world leader in banana and plantain improvement. Its improved varieties are being commercially produced in several countries and evaluated in about 50 countries in Asia., Africa , Latin America and Oceania .

 

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