The estimates reported in Table 10.2 are important to economic interpretation subject to two conditions. First, the trait value is confined to achievements where there is real insect or disease stress. Thus traits are not valuable over all rice acreage. Second, trait values are 'additive' in that a variety may incorporate more than one trait and each trait will contribute to yields.
Perhaps the simplest calculation utilizing both of these conditions is to compute the value of traits in India by multiplying mean values (from Table 10.1) by trait values (from Table 10.2), dropping negative trait values. This is an estimate of the specific values of these traits actually realized in India by the mid-
1980s or so. They are underestimates of the full value of these traits because of incomplete adoption and incomplete breeding processes.
These calculations for the district data show only a 2% yield gain for disease resistance and 3% yield gain for insect resistance. The state varietal estimate, on the other hand, shows a 4.5% yield gain from disease resistance and a 6.9% yield gain from insect resistance.
The nature of the data suggests that the state estimate is a more reasonable one than that computed from the district data. Adoption of varieties incorporating these traits is quite low (Table 10.1) with only a few traits covering 20% of the area at the mean of the data set. By 1992 these adoption levels are higher by a factor of 1.5-2.
We would thus consider it a reasonable (and conservative) estimate that conventional breeding for disease resistance has produced a 2-5% yield gain in India. Conventional breeding for insect resistance has produced a 3-7% yield gain in India. Further, conventional breeding efforts are likely to increase these levels further - perhaps doubling them in another 20 years.
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