Criteria for Judging Polyploidy 367 



lion of tetraploid tomatoes may be coarser, and for that reason the 

 polyploids are less desirable than the diploid. Many fruited plants 

 of horticultural importance show direct correlation between fruit size 

 and polyploidy within certain limits. A'aluable tetraploid varieties 

 of grapes are larger and superior to diploids. Tetraploid muskmelon 



TABLE 15.2 

 Seed Weights of Species and Allopolyploid Deriv.\tives of the Hexaploid 



Species of Bromus ( Ccratochloa ) 



Species of Polyploid 



B. catharticus 



B. catharticus 



B. catharticus 



B. haenkeanus 



B. haenkeanus 



B. stamineiis 



B. catharticus-haenkeanus . . . 

 B. catharticus-haenkeanus . . . 

 B. catharticus-haenkeanus . . . 

 B. haenkeanus-stamineus ... 

 D. haenkeanus-stamineus ... 

 B. haenkeanus-stamineus .... 



Strain 



Waite 



Berkeley 



San Antonio 



Carmel 



Sparks 



Berkeley 



Waite-Carmel 



Berkeley-Sparks 



San Antonio-Carmel 



Carmel-Berkeley 



Sparks-Berkeley 



San Antonio-Berkelev 



Weight of 

 200 Seeds 



[grams) 



3.1 



^ 



Increase 

 Over Arith- 

 metic Mean 

 Between Parts 



(per cent) 



52 

 17 

 25 

 41 

 75 

 64 



fruits were more promising than the diploids according to sampling 

 methods made in one sttidy. 



Pistillate flowers of tetraploids pollinated with pollen from diploid 

 strains may reduce the size of grain in such a plant as rye. Normally 

 these species are cross-fertilized, so planting side by side gives the 

 diploid pollinator an advantage over the slower-growing pollen from 

 tetraploid flowers." Yield is at once reduced. The effect of diploid 

 pollen upon fruit development in watermelon is quite the opposite. 

 The triploid plants must be interplanted with diploids to insure 

 pollination, for the diploid pollen stimulates parthenocarpic or seed- 

 less fruit formation. The number of fruits produced by triploids may 

 be double the number for a representative diploid. Yield trials 

 showed that this feature favors the polyploid. 



15.4: Physiological Differences 



Excellent reviews have been made to differentiate the diploid and 

 tetraploid plants.^-* An ever-increasing nuniber of autotetraploids 

 adds more material for such study, including physiology, incom- 

 patibility,-' •*» morphology, and anatomy. Final superiority of the 



