High value of coffee in international trade and domestic economies of the many producing countries is well known. It is also well known that most of world’s coffee is produced in the poor and under-developed countries. This is a beverage being consumed across the world for almost four centuries and most of the consumption is in the affluent western countries. Possibly, it is on account of these facts that very little effort is directed towards the pre-emptive breeding of this important crop plant to achieve resistance against various adversaries.
If we take a look at the history of the various diseases and pests of coffee, it becomes clear that these various adversaries became prominent in different crisis times. Like all other internationally traded commodities, coffee has also been passing through ‘boom and bust’ cycles, leading to financial crises in the lives of farmers producing this crop. When the price of coffee is very low in the markets, its direct impact is on the maintenance of coffee plantations that get neglected. This leads to the more severe occurrence of diseases, of which coffee leaf rust is the most prominent. Leaf rust is a defoliating disease that predisposes the coffee plant to many other adversaries that take advantage of the situation. Defoliation leads to debilitation of the plant as its photosynthetic and other biosynthetic processes carried out by leaves get compromised opening an advantageous situation for the adversaries. Evolution of new races of coffee leaf rust that can defeat the resistance achieved by incorporating newer genes is known to be considerably rapid.
All this is true in the context of Arabica coffee that is susceptible to the pests and diseases. We have known resistance to a variety of adversaries like nematodes, insects and diseases in the various species of the diploid gene pool of coffee. Diploid species like Robusta and Liberica were utilized in a modest way towards improving leaf rust resistance of the coffee plant and Arabica – Robusta hybrids are also known to possess some resistance to the nematodes. Also, it is known that several diploid species cross well with the lone tetraploid Arabica to yield moderately fertile hybrids. Also, it is known that diploid species of coffee naturally cross to give rise to natural interspecific hybrids. These innate potencies of the coffee plants should be exploited to transfer the requisite resistance to the species of choice to create germplasm that can be used in long term breeding exercises to evolve coffee plants resistant to the various adversaries.
This is a long term exercise in breeding that also demands special skills in cytogenetics and chromosome manipulation to achieve positive and stable results that benefit the coffee farmers over long periods of time. Conceptual background for this effort comes from the fact that diploid species of coffee naturally and freely cross among themselves and also with Arabica to yield fertile or moderately fertile hybrids. As explained in the concept paper posted a few days earlier, scientists at different coffee research stations in Africa as well as other countries where some species are available in the gene banks should create diploid-diploid and diploid-tetraploid interspecific hybrids that should be handled appropriately to evolve tetraploid Arabicoids that constitute novel germplasm for breeding Arabica coffee in the future, against a variety of adversaries like newer diseases, nematodes and possibly abiotic factors arising out of climate change.