What does the last para mean? please help
It means that there are some variety of plants which are resistant to diseases but does not produce the product in high amount. On the other hand, there are some varieties which have good yield but they easily get diseased. One good example of this is Parbhani kranti:-
There were two varieties of ladyfinger(Abelmoschus esculentus)
One variety is wild and is very good in disease resistant ability( it does not get easily affected by yellow mosaic virus-YMV) . The other variety has good production / yield but gets easily affected by the disease which is not desirable . So, the gene for disease resistance(against YMV) was taken and introduced into the high yield variety of Abelmoschus esculentus . This resulted in production of a hybrid variety called Parbhani kranti which had both, disease resistance and high yield.
There were two varieties of ladyfinger(Abelmoschus esculentus)
One variety is wild and is very good in disease resistant ability( it does not get easily affected by yellow mosaic virus-YMV) . The other variety has good production / yield but gets easily affected by the disease which is not desirable . So, the gene for disease resistance(against YMV) was taken and introduced into the high yield variety of Abelmoschus esculentus . This resulted in production of a hybrid variety called Parbhani kranti which had both, disease resistance and high yield.